Adult rats were subjected to chronic treatment with the cannabinoid agonist, Delta9-tetrahydrocannabinol, or with vehicle, and their brains used to analyze the contents of serotonin (<em>5HT</em>) and of its intraneuronal metabolite, 5-hydroxyindolacetic acid (5HIAA). <em>5HT</em> and 5HIAA contents were not affected by chronic cannabinoid administration in most of the brain regions analyzed. We found a marked increase in <em>5HT</em> contents in the frontal cortex that was accompanied by no changes in 5HIAA contents. This originated a decrease in 5HIAA/<em>5HT</em> ratio, which suggests a possible reduction in the activity of serotoninergic terminals reaching this cortical area. This effect was not seen after an acute injection of this cannabinoid. The relevance of these observations was that they occurred in a region where changes in serotoninergic transmission have been implicated in the development of depression; therefore, our data support the theory that the cannabinoid system might be a potential target for the treatment of this neuropsychiatric disease.

An immunohistochemical technique for simultaneously visualizing two different antigens has been used to investigate the presence of the acidic dipeptide, N-acetyl-aspartyl-glutamate (NAAG), in cholinergic, noradrenergic-adrenergic, and serotonergic neurons within CNS. The brain slices were processed sequentially with purified antisera against NAAG and then monoclonal antibody against choline acetyltransferase (ChAT), a marker for cholinergic neurons, or antiserum against dopamine-beta-hydroxylase (DBH), a marker of noradrenergic-adrenergic neurons, or antiserum against serotonin (<em>5HT</em>). Both antigens were revealed by the peroxidase reaction but with different chromogens, which are easily distinguishable. An intense double staining of NAAG-like immunoreactivity (NAAG-LI) and ChAT was observed in the motoneurons of the spinal cord as well as in the several motor components of cranial nerve nuclei including facial, ambiguus, and trigeminal nuclei. A partial colocalization of NAAG-LI and ChAT was evident in the perikarya of the basal forebrain cholinergic system, whereas cholinergic neurons of the medial septum exhibited only sporadic staining for NAAG-LI. A complete coexistence of NAAG-LI and DBH was observed in the locus coeruleus. Most of the other noradrenergic and adrenergic cell groups of the medulla region exhibited substantial co-localization with the exception of the A2 cell group, which was virtually devoid of NAAG-LI. In the dorsal raphe, only a low percentage of serotonergic neurons stained for NAAG-LI. The co-existence of NAAG-LI and serotonin was more evident in the neurons of the median raphe, although the majority of cells failed to show double staining.(ABSTRACT TRUNCATED AT 250 WORDS)

BACKGROUND

Among serotonin receptors, 5-HT(1A) receptors are implicated in the regulation of central serotoninergic tone and could be involved in the abnormal brain 5-HT turnover suspected in migraineurs. The aim of this study was to investigate 5-HT(1A) receptors' availability during migraine attacks.

METHODS

Ten patients suffering from odor-triggered migraine attacks and 10 control subjects were investigated using positron emission tomography (PET) and [(18)F]MPPF PET tracer, a selective 5-HT(1A) antagonist. All subjects underwent calibrated olfactory stimulations prior to the PET study.

RESULTS

Four patients developed a migraine attack during the PET study. In these patients, statistical parametrical mapping and region of interest analyses showed an increased [(18)F]MPPF binding potential (BP(ND)) in the pontine raphe when compared to headache-free migraineurs and control subjects. This ictal change was confirmed at the individual level in each of the four affected patients. In comparison with the headache-free migraineurs, patients with a migraine attack also showed significantly increased [(18)F]MPPF BP(ND) in the left orbitofrontal cortex, precentral gyrus and temporal pole. No significant change in [(18)F]MPPF BP(ND) was observed between headache-free migraineurs and controls.

CONCLUSIONS

Our results emphasize the role of <em>5HT</em>(1A) receptors in the pontine raphe nuclei during the early stage of migraine attacks.

Mirtazapine is a novel antidepressant with a pharmacologic profile (alpha-2 antagonist, <em>5HT</em>-(1A) agonist, and <em>5HT</em>-(2) antagonist) that renders it potentially useful for l-dopa-induced dyskinesias. Drugs with <em>5HT</em>-(1A) agonistic activity, such as buspirone and tandospirone, have been reported to be effective in reducing l-dopa-induced dyskinesias. Furthermore, <em>5HT</em>-(2) antagonism may, by reducing substantia nigra pars reticulata hyperactivity, play a role in the improvement of Parkinsonian symptoms and l-dopa-induced dyskinesias, as has been observed with ritanserin, a <em>5HT</em>-(2) antagonist. Alpha-2 antagonists, such as idazoxan, have recently also been reported to improve l-dopa-induced dyskinesias. The authors investigated the antidyskinetic properties of mirtazapine by designing an open-label study of 20 Parkinsonian patients with l-dopa-induced dyskinesias. Mirtazapine proved to be moderately effective in reducing l-dopa-induced dyskinesias, either alone or in association with amantadine. Mirtazapine may be of use in patients who do not respond or are intolerant to amantadine.

Delirium exemplifies the interface between medicine and psychiatry. It is generally characterized by acute disturbances of consciousness, cognition, and perception that are precipitated by an underlying medical condition. The gold standard of psychiatric treatment is to treat the underlying medical cause and use high-potency antipsychotics to treat the clinical manifestations of delirium. In the early 1990s, a new generation of novel antipsychotics was developed. Their mechanism of action, preferential serotonergic (<em>5HT</em>(2a)) blockade, results in a markedly lower rate of extrapyramidal side effects, an advantage over the typical, older antipsychotic medications. These agents have been shown to be effective and well tolerated in common psychotic disorders (e.g., schizophrenia or bipolar disorder), but few studies have evaluated them in the treatment of delirium. This paper reviews the pertinent literature and summarizes tentative guidelines for novel antipsychotic use in delirium.

<em>5HT</em> has been implicated in mechanisms of anxiety and depression for many years but the evidence is contradictory. Perhaps one error has been to think of <em>5HT</em> as a unitary system when in reality it is highly differentiated. There has been an explosive increase in knowledge about different <em>5HT</em> receptor subtypes and it has long been known that there are different anatomical subsystems. Evidence will be summarised that the different systems subserve different psychological functions and that dysfunction in the different systems results in depression, anxiety, panic and OCD in an understandable way. Much evidence is compatible with the idea that <em>5HT</em> systems reduce the impact of impending or actual aversive events. Anticipation of an aversive event is associated with anxiety and this motivates avoidance behaviour--a normal adaptive response. There is evidence that this is mediated by projections of the dorsal raphe nucleus and associated <em>5HT</em>2 and <em>5HT</em>3 receptors. Projections of the median raphe nucleus and associated <em>5HT</em>1A receptors appear to mediate resilience to aversive events once they have occurred or if they persist. When this system breaks down depression results. It will be argued that all effective antidepressants act on <em>5HT</em>1A, natural mechanisms of resilience.

The proposed anxioselective drug, buspirone, interacts with <em>5HT</em>1 receptors. An analogue, MJ 13805, produces a <em>5HT</em> behavioural syndrome blocked by central <em>5HT</em> pathway lesion. Both compounds inhibit <em>5HT</em> neurone firing. An association of any such action with models of anxiety is not yet possible. Several compounds selective for <em>5HT</em> receptor sub-types have been tested in models of anxiety. Ritanserin, a selective <em>5HT</em>2 antagonist, shows activity in an emergence test but not conflict models. Preliminary clinical reports indicate qualitatively different anxiolytic activity from that of benzodiazepines. TVXQ 7821 is selective for <em>5HT</em>1 receptors and has shown activity in several models of anxiety. 8OHDPAT and RU 24969 are <em>5HT</em>1 agonists, selective for <em>5HT</em>1A and <em>5HT</em>1B sites respectively. 8OHDPAT released punished drinking but reversed a similar effect of PCPA. Its mode of action remains unclear. RU 24969 has shown no marked anxiolytic-like activity in food or water-motivated conflicts. Further studies are necessary before associating modulation of central <em>5HT</em> systems with anxiolytic activity, either in animal models or patients.

Ibogaine, one of several alkaloids found in the root bark of the African shrub Tabernanthe iboga, has been claimed to be effective in treating multiple forms of drug abuse. Problems associated with side effects of ibogaine have spawned a search for more effective and safer structural derivatives. 18-Methoxycoronaridine (18-MC), a novel iboga alkaloid congener, appears to have substantial potential for broad use as an anti-addictive therapy. Like ibogaine (40 mg/kg), 18-MC (40 mg/kg) decreases the intravenous self-administration of morphine and cocaine and the oral self-administration of ethanol and nicotine in rats; unlike ibogaine, 18-MC does not affect responding for a non-drug reinforcer (water). Ibogaine and 18-MC appear to reduce the reinforcing efficacies, rather than the potencies, of drugs of abuse. Both ibogaine and 18-MC decreases extracellular levels of dopamine in the nucleus accumbens while only ibogaine increases serotonin levels in this brain region. Both ibogaine and 18-MC block morphine-induced and nicotine-induced dopamine release in the accumbens; only ibogaine enhances cocaine-induced increases in dopamine levels. Ibogaine produces whole body tremors and, at high doses (at least 100 mg/kg), cerebellar damage; 18-MC does not produce these effects. Ibogaine, but not 18-MC, causes bradycardia at high doses. Ibogaine and its metabolite noribogaine have low microM affinities for kappa and mu opioid receptors, NMDA receptors, <em>5HT</em>-3 receptors, sigma-2 sites, sodium channels and the serotonin transporter. 18-MC has low microM affinities at all three opioid receptors and at <em>5HT</em>-3 receptors but much lower or no affinities for NMDA and sigma-2 receptors, sodium channels, and the <em>5HT</em> transporter. Both 18-MC and ibogaine are sequestered in fat and, like ibogaine, 18-MC probably has an active metabolite. 18-MC also has (+) and (-) enantiomers, both of which are active. Considered together, all of the data indicate that 18-MC should be safer than ibogaine and at least as efficacious as an anti-addictive medication.

The new <em>5HT</em>-uptake inhibitor, FG 4963, and some tricyclic thymoleptics antagonized p-chloroamphetamine (PCA)-induced hypermotility in rats. FG 4963 was active in about the same s.c. and p.o. doses as chlorimipramine. FG 4963, imipramine and chlorimipramine potentiated hypermotility induced in mice by the <em>5HT</em> precursor <em>5HT</em>P, FG 4963 being slighly more active than chlorimipramine. In contrast to the tricyclic thymoleptics FG 4963 did not potentiate the heart rate increasing effect of NA in pithed rats. The peripheral anticholinergic effect of FG 4963 and of desipramine was almost identical while the other imipramine derivatives were more active. All tricyclic thymoleptics were strong peripheral antihistaminics, but FG 4963 was almost devoid of this action. Acute tests for ECG changes in guinea pigs and toxicity in mice and rats showed that FG 4963 and chlorimipramine were less toxic than imipramine and amitriptyline. FG 4963 is presumably a selective <em>5HT</em>-uptake inhibitor producing much less potentiation of peripheral sympathetic mechanisms than do the tricyclic antidepressants.

A microbore column liquid chromatographic method for the simultaneous determination of norepinephrine (NE), serotonin (5-HT), and 5-hydroxyindole-3-acetic acid (5HIAA) in microdialysis samples from rat brain is described. The method is based on precolumn derivatization of NE, <em>5HT</em>, and 5HIAA with benzylamine in the presence of potassium hexacyanoferrate(III) resulting in the corresponding highly fluorescent and stable benzoxazole derivatives. A 15-microl sample was mixed with 15 microl derivatization reagent solution containing 0.3M 3-cyclohexylaminopropanesulfonic acid buffer (pH 12.0), 0.5M benzylamine, 10mM potassium hexacyanoferrate(III), and methanol (1/1/1/12, v/v/v/v). The derivatization was carried out at 50 degrees C for 20 min. The benzylamine derivatives of NE, <em>5HT</em>, and 5HIAA were separated on a reversed-phase column (100 x 1.0mm i.d., packed with C18 silica, 5 microm) within 30 min. The mobile phase consisted of 15 mM acetate buffer (pH 5.0) and acetonitrile (31%, v/v); the flow rate was 50 microl/min. The detection limits (signal-to-noise ratio of 3) for NE, <em>5HT</em>, and 5HIAA in the injection volume of 20 microl were 90, 210, and 260 amol, respectively. Microdialysis samples were collected in 7.5-min intervals from the probes implanted in the hippocampus and prefrontal cortex of awake rats. The basal levels of NE, <em>5HT</em>, and 5HIAA in the dialysates from the hippocampus were 4.2+/-0.5, 4.9+/-0.6, and 934.1 +/- 63.4 fmol/20 microl, and those from the prefrontal cortex were 6.0+/-1.2,5.51.3, and 669.1 +/- 96.0 fmol/20 microl (mean +/- SE, n=25), respectively. The NE and <em>5HT</em> levels were altered by perfusion of high-potassium or low-calcium solution and following antidepressant drugs imipramine and desipramine. It is concluded that the new fluorescence derivatization method in combination with microbore column liquid chromatography allows the simultaneous determination of NE, <em>5HT</em>, and 5HIAA in the microdialysis samples at higher sensitivity, providing easier maintenance in routine use than that achieved by high-performance liquid chromatographic methods with electrochemical detection.

BACKGROUND

Coptis chinensis rhizomes (Coptidis Rhizoma, CR), also known as "Huang Lian", is a common component of traditional Chinese herbal formulae used for the relief of abdominal pain and diarrhea. Yet, the action mechanism of CR extract in the treatment of irritable bowel syndrome is unknown. Thus, the aim of our present study is to investigate the effect of CR extract on neonatal maternal separation (NMS)-induced visceral hyperalgesia in rats and its underlying action mechanisms.

METHODS

Male Sprague-Dawley rats were subjected to 3-h daily maternal separation from postnatal day 2 to day 21 to form the NMS group. The control group consists of unseparated normal (N) rats. From day 60, rats were administrated CR (0.3, 0.8 and 1.3 g/kg) or vehicle (Veh; 0.5% carboxymethylcellulose solution) orally for 7 days for the test and control groups, respectively.

RESULTS

Electromyogram (EMG) signals in response to colonic distension were measured with the NMS rats showing lower pain threshold and increased EMG activity than those of the unseparated (N) rats. CR dose-dependently increased pain threshold response and attenuated EMG activity in the NMS rats. An enzymatic immunoassay study showed that CR treatment significantly reduced the serotonin (<em>5HT</em>) concentration from the distal colon of NMS rats compared to the Veh (control) group. Real-time quantitative PCR and Western-blotting studies showed that CR treatment substantially reduced NMS induced cholecystokinin (CCK) expression compared with the Veh group.

CONCLUSIONS

These results suggest that CR extract robustly reduces visceral pain that may be mediated via the mechanism of decreasing <em>5HT</em> release and CCK expression in the distal colon of rats.

Omega-3 polyunsaturated fatty acids (OPFA) have beneficial effects on inflammatory reactions and production of cytokines. They decrease the release of <em>5HT</em> by platelets and possess vasorelaxant activity. This led them to be tried in the prophylactic treatment of migraine. After 4 weeks of a single-blind placebo run-in period, patients were randomized and treated in double-blind condition by placebo or OPFA 6 g a day for 16 weeks, followed by a 4-week placebo run-out period. The intention to treat population included 196 patients. Those who received all four treatment periods included 96 patients taking OPFA and 87 taking placebo. The primary efficacy analysis was the number of migraine attacks during the last 4 weeks of treatment. During this period, the mean number of attacks was 1.20 +/- 1.40 in the OPFA group and 1.26 +/- 1.11 in the placebo group (NS). The total number of attacks during the 4-month period of the study was significantly different between groups: 7.05 in the placebo group, 5.95 in the OPFA group (P = 0.036). Mean intensity, mean duration of the attacks and rescue medication use, were not significantly different between the two groups. Except for a significant difference against OPFA for eructations, the tolerance was satisfying. Despite a run-in placebo period of 1 month, a very strong placebo effect was observed in this trial: 45% reduction of the attacks between run-in and 4-month treatment period (55% in the OPFA group, P = 0.058). Finally, this large study did not confirm two previous studies based on a small number of patients.

The efficacy of zolmitriptan (Zomig, 311C90), a 5-hydroxytryptamine (<em>5HT</em>)1B/1D receptor agonist, in the acute oral treatment of migraine was evaluated in an extensive clinical trial program. Four randomized, placebo-controlled studies (total 2480 patients) were performed; data from two of these trials established that a 2.5 mg dose was on the shoulder of the dose-response curve (2-h headache response rate 64%), showing similar efficacy to the 5 mg dose (67%). In this program, the efficacy of zolmitriptan was not influenced by the pretreatment headache duration; the presence of aura preceding the headache, migraine associated with menses or migraine upon awakening; or by concomitant use of oral contraceptives or antidepressants. In addition, zolmitriptan 5 mg proved consistently effective in the treatment of multiple migraine attacks for up to 1 year. Zolmitriptan reduced the incidence of nausea, photophobia and phonophobia, reduced impairment of normal activity and demonstrated positive effects on patients' quality of life. Thus, zolmitriptan is a highly effective acute oral antimigraine therapy, with 2.5 mg providing the optimal balance between efficacy and tolerability.

Normal human blood platelets in plasma were incubated at 2 degrees C with tritiated 5-hydroxytryptamine ([3H]<em>5HT</em>), and the specific receptor binding was displaced by the addition of unlabelled <em>5HT</em>. The kinetic parameters of this binding were established and a two-site model for the platelet <em>5HT</em> receptor demonstrated. Site A has a KD of 0.5-1 nM and capacity of 6-10 fmol/10(8) platelets, and site B a KD of 15-36 nM and a capacity of 100-150 fmol/10(8) platelets. Non-specific or non-receptor binding of [3H]<em>5HT</em> to platelets at 2 degrees C was resolved into a passive linear component and an active saturable component sensitive to metabolic inhibition. Binding to the lower affinity <em>5HT</em> receptor site was inhibited by drugs of the tricyclic antidepressant type with IC50 values similar to those against the active uptake component of non-specific binding as described. Isomers of the neuroleptic drug flupenthixol showed a differential and competitive antagonism of high affinity [3H]<em>5HT</em> binding. The <em>5HT</em> antagonist methysergide, and pizotifen and mianserin also were competitive inhibitors at this site. The rank order of potency of these drugs correlated with their action as inhibitors of <em>5HT</em> induced platelet aggregation. It is concluded that binding of [3H]<em>5HT</em> to intact human platelets satisfies all the criteria for specific binding and that the two sites demonstrated, of high and lower affinity, are concerned with the functions of <em>5HT</em> induced aggregation and <em>5HT</em> uptake respectively.

BACKGROUND

Disturbances in serotonin (<em>5HT</em>) transmission are the most frequently reported neurobiological substrates of suicidal behavior. Because <em>5HT</em> transporter plays a central role in the regulation of <em>5HT</em> synaptic function and its gene contains two functional polymorphisms (5-HTTLPR in the promoter region and VNTR in the second intron), it represents an interesting candidate for association studies in suicidal behavior.

METHODS

In this study, a possible association of 5-HTTLPR and intron 2-VNTR polymorphisms of the <em>5HT</em> transporter gene with suicidal behavior was investigated in a sample of 135 suicide victims and 299 healthy control subjects of Croatian/southern Slavic origin.

RESULTS

There were no significant differences in 5-HTTLPR and intron 2-VNTR genotype- and allele- frequency distributions between suicide victims and healthy control subjects; however, a tendency toward an increase of 5-HTTLPR allele L and VNTR-allele 10 were observed in suicide group. Analysis of distribution of estimated haplotype frequencies revealed differences between suicide victims and control subjects, with an excess of haplotype L10 among suicide victims (p =.0112).

CONCLUSIONS

Our results provide modest evidence for a possible association of the <em>5HT</em> transporter gene with a completed suicide. Further studies are needed to determine whether alterations in <em>5HT</em>t gene expression are involved in suicidal behavior.

BACKGROUND

Despite considerable progress in the pharmacological treatment of schizophrenia, about 30% of patients are minimally responsive to antipsychotics and there is still an excessively high rate of mortality in schizophrenia patients. Clozapine , a D(2)-<em>5HT</em>(2) antagonist, was the first antipsychotic to demonstrate efficacy in treatment-resistant patients, and to be associated with the lowest risk of death.

METHODS

The pharmacodynamics, pharmacokinetics, clinical efficacy, safety and cost-effectiveness of clozapine are covered in this article, based on a literature review (PubMed) from 1975 to 2012. Pivotal, as well as supporting, randomized controlled trials are reviewed, along with observational and/or naturalistic safety studies. This review of clozapine will allow the reader to determine the place for clozapine in the schizophrenia treatment landscape.

CONCLUSIONS

Studies conducted so far suggest that clozapine is the treatment of choice for schizophrenic patients who are refractory to treatment, display violent behaviors, or who are at high risk of suicide. However, it is also the antipsychotic with the worst side effect profile, the highest risk of complications, and the most difficult to prescribe. Experience with clozapine should therefore be included in the education of future physicians.

It is known that the activation of 5-hydroxytryptamine receptor type 1A (<em>5HT</em>(1A) receptor) may protect against brain damage induced by transient global ischemia. The biochemical mechanisms that underlie this neuroprotective effect remain however to be fully elucidated. Given that serotonergic drugs may regulate N-methyl-d-aspartate (NMDA) receptor function, which is implicated in events leading to ischemia-induced neuronal cell death, and also stimulate the expression of brain-derived neurotrophic factor (BDNF), which is down-regulated in cerebral ischemia, we sought to determine the effects of the selective 5-HT1A receptor agonist, 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT), on the levels of NMDA receptor NR1 subunit and BDNF in gerbil hippocampus after transient global cerebral ischemia. Pretreatment with 8-OH-DPAT (1 mg/kg) prevented the neuronal loss in CA1 subfield 72 h after ischemia and also the dramatic decrease in BDNF immunoreactivity observed in this area at an earlier time. NMDA receptor NR1 levels in whole hippocampus were not affected 24 h after ischemia, but the levels of the subunit phosphorylated at the protein kinase A (PKA) site, pNR1(Ser897), were significantly increased, and this increase was prevented by the same 8-OH-DPAT dose, a probable consequence of the increased phosphatase 1 (PP1) enzyme activity found in ischemic gerbils pretreated with the 5-HT(1A) receptor agonist. The results indicate that both NR1 subunit phosphorylation and the neurotrophin BDNF account, at least in part, for the neuroprotective effect of 8-OH-DPAT on cell damage induced by global ischemia in the gerbil hippocampus and support the potential interest of 5-HT1A receptor activation in the search for neuroprotective strategies.

Monoamine transporters terminate synaptic neurotransmission and are molecular targets for antidepressants and psychostimulants. Fluorescent reporters can monitor real-time transport and are amenable for high-throughput screening. However, until now, their use has mostly been successful to study the catecholamine transporters but not the serotonin (<em>5HT</em>) transporter. Here, we use fluorescence microscopy, electrophysiology, pharmacology, and molecular modeling to compare fluorescent analogs of 1-methyl-4-phenylpyridinium (MPP(+)) as reporters for the human serotonin transporter (hSERT) in single cells. The fluorescent substrate 4-(4-(dimethylamino)phenyl)-1-methylpyridinium (APP(+)) exhibits superior fluorescence uptake in hSERT-expressing HEK293 cells than other MPP(+) analogs tested. APP(+) uptake is Na(+)- and Cl(-)-dependent, displaced by <em>5HT</em>, and inhibited by fluoxetine, suggesting APP(+) specifically monitors hSERT activity. ASP(+), which was previously used to study catecholamine transporters, is 10 times less potent than APP(+) at inhibiting <em>5HT</em> uptake and has minimal hSERT-mediated uptake. Furthermore, in hSERT-expressing oocytes voltage-clamped to -60 mV, APP(+) induced fluoxetine-sensitive hSERT-mediated inward currents, indicating APP(+) is a substrate, whereas ASP(+) induced hSERT-mediated outward currents and counteracted <em>5HT</em>-induced hSERT currents, indicating ASP(+) possesses activity as an inhibitor. Extra-precise ligand receptor docking of APP(+) and ASP(+) in an hSERT homology model showed both ASP(+) and APP(+) docked favorably within the active region; accordingly, comparable concentrations are required to elicit their opposite electrophysiological responses. We conclude APP(+) is better suited than ASP(+) to study hSERT transport fluorometrically.

Previous studies reported that drugs acting as monoamine oxidase (MAO)-B inhibitors prevented biochemical effects induced by the neurotoxins N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine (DSP-4) and 3,4-methylenedioxymethamphetamine (MDMA, "ecstasy"). In this study, we administered DSP-4 (50 mg/kg) or MDMA (50 mg/kg x 2, 2 h apart) to MAO-B deficient mice. Monoamine content in various brain regions (cerebellum, frontal cortex, hippocampus, hypothalamus, striatum, substantia nigra) was assayed 1 week after neurotoxin administration. Injection of DSP-4 to wild-type mice caused a marked norepinephrine (NE) loss in specific brain regions. Unexpectedly, DSP-4 caused similar effects in MAO-B-deficient and in wild-type mice in all brain regions investigated. These results suggest that MAO-B is not involved in DSP-4 toxicity. In wild-types, the neurotoxin MDMA induced both serotonin (<em>5HT</em>) and dopamine (DA) depletion in specific brain areas. In MAO-B-deficient mice, <em>5HT</em> depletion observed in wild-types did not occur. In contrast, MDMA produced a more pronounced DA loss in knockout mice compared with wild-types. The present findings, together with previous data obtained using selective enzyme inhibitors, suggest that MAO-B is not involved in the mechanism of action of DSP-4, whereas it plays opposite roles in MDMA-induced DA and <em>5HT</em> depletions.

The established microanatomical association of rat intestinal mucosal mast cells (IMMC) and mucosal nerves raises the possibility that there is crosstalk between mast cells and extrinsic nerves that connect to the CNS. The idea of mast cell-CNS interactions is supported by the demonstration that rat mast cell protease II (RMCPII), found predominantly in IMMC, can be conditionally released by pairing an audio-visual cue with antigen challenge. That the vagus nerve is involved in the IMMC-nerve axis was further demonstrated in a series of our studies showing that: (a) vagal afferents penetrate the small intestinal mucosa and contact IMMC; (b) vagotomy causes a reduction in IMMC density, suggesting a trophic relationship (typical of nerve-target interactions); and (c) stimulation of the cervical vagus causes an increase in histamine and serotonin in IMMC. To further investigate the IMMC-nerve axis in a model of post-inflammatory bowel disorders, infection with Nippostrongylus brasiliensis (Nb) was used to demonstrate an increase in mast cell numbers in the intestinal mucosa and mucosal nerve remodelling with hyperinnervation. Administration of Nb antigen resulted in dramatic increases in mesenteric afferent nerve firing in Nb infected rats, that was absent in sham animals. Moreover, challenge of post-Nb rats with 2-methyl-<em>5HT</em> caused increased mesenteric afferent firing, indicating that vagal afferent innervation remains intact in the post-infection state. These data suggest a functional connection between mast cells and extrinsic afferent nerves. Nb infection provides a useful model of altered communication between IMMCs, peripheral nerves and the CNS, as may occur in post-inflammatory disease states. Since a close anatomical relationship has also previously been demonstrated between nerves and IMMC in humans, further understanding the mast cell-nerve axis may be of critical importance in the development of treatments for various human disease states, including functional bowel disorders.

Activity-dependent changes in neuronal efficacy underlie the formation and storage of new memories. Several studies indicate that modification of the phosphorylation/activation state of different protein kinases localized in the synapses or the nucleus plays a critical role in the induction and maintenance of plastic mechanisms and in the consolidation of long-lasting memories. Here we review some of the more recent findings concerning the regulation of two of the main protein kinase groups involved in memory processes and in neuronal plasticity: Ca2+/calmodulin-dependent protein kinase II (CaMKII), and the mitogen-activated protein kinase (MAPK) family. Since this issue of the journal is dedicated to serotonin (<em>5HT</em>) regulation of behavior, we will comment on the so far scanty, but significant, evidence for a role of <em>5HT</em> in the regulation of CaMKII and MAPK.

OBJECTIVE

Discuss the theory of modulation of receptor activity or the blockade of the reuptake of multiple neurotransmitter systems for the future treatment of MDD. Major depressive disorder (MDD) is a serious and often crippling psychiatric illness with a high risk of relapse and treatment resistance. In this article, we discuss the role of the serotonergic system in MDD including our current understanding of how various serotonin (<em>5HT</em>) receptors modulate monoamine neurotransmission and behavior. We also discuss how pharmacologic interventions, including novel and existing antidepressants and atypical antipsychotics, may be utilized to adjust serotonergic neurotransmission and provide more effective treatments for patients with MDD.

BACKGROUND

There is increasing recognition that obsessive-compulsive disorder (OCD) is not a homogeneous entity. It has been suggested that gender may contribute to the clinical and biological heterogeneity of OCD.

METHODS

Two hundred and twenty patients (n=220; 107 male, 113 female) with DSM-IV OCD (age: 36.40+/-13.46) underwent structured interviews. A subset of Caucasian subjects (n=178), including subjects from the genetically homogeneous Afrikaner population (n=81), and of matched control subjects (n=161), was genotyped for polymorphisms in genes involved in monoamine function. Clinical and genetic data were statistically analyzed across gender.

RESULTS

Compared with females, males with OCD (1) had an earlier age of onset, and a trend toward having more tics and worse outcome, (2) had somewhat differing patterns of OCD symptomatology and axis I comorbidity, and (3) in the Caucasian group, were more likely to have the high activity T allele of the EcoRV variant of the monoamine oxidase A (MAO-A) gene compared to controls, and (4) in the Afrikaner subgroup, were more frequently homozygous for the C allele at the G861C variant of the <em>5HT</em>(1D beta) gene than controls. Females with OCD (1) reported more sexual abuse during childhood than males, (2) often noted changes in obsessive-compulsive symptoms in the premenstrual/menstrual period as well as during/shortly after pregnancy, and with menopause, and (3) in the Caucasian subgroup, were more frequently homozygous for the low activity C allele of the EcoRV variant of the MAO-A gene compared to controls, with this allele also more frequent in female patients than controls.

CONCLUSIONS

This study supports the hypothesis that gender contributes to the clinical and biological heterogeneity of OCD. A sexually dimorphic pattern of genetic susceptibility to OCD may be present. Further work is, however, needed to delineate the mechanisms that are responsible for mediating the effects of gender.

Metabolomics provides valuable tools for the study of drug effects, unraveling the mechanism of action and variation in response due to treatment. In this study we used electrochemistry-based targeted metabolomics to gain insights into the mechanisms of action of escitalopram/citalopram focusing on a set of 31 metabolites from neurotransmitter-related pathways. Overall, 290 unipolar patients with major depressive disorder were profiled at baseline, after 4 and 8 weeks of drug treatment. The 17-item Hamilton Depression Rating Scale (HRSD₁₇) scores gauged depressive symptom severity. More significant metabolic changes were found after 8 weeks than 4 weeks post baseline. Within the tryptophan pathway, we noted significant reductions in serotonin (<em>5HT</em>) and increases in indoles that are known to be influenced by human gut microbial cometabolism. <em>5HT</em>, 5-hydroxyindoleacetate (5HIAA), and the ratio of 5HIAA/<em>5HT</em> showed significant correlations to temporal changes in HRSD₁₇ scores. In the tyrosine pathway, changes were observed in the end products of the catecholamines, 3-methoxy-4-hydroxyphenylethyleneglycol and vinylmandelic acid. Furthermore, two phenolic acids, 4-hydroxyphenylacetic acid and 4-hydroxybenzoic acid, produced through noncanconical pathways, were increased with drug exposure. In the purine pathway, significant reductions in hypoxanthine and xanthine levels were observed. Examination of metabolite interactions through differential partial correlation networks revealed changes in guanosine-homogentisic acid and methionine-tyrosine interactions associated with HRSD₁₇. Genetic association studies using the ratios of these interacting pairs of metabolites highlighted two genetic loci harboring genes previously linked to depression, neurotransmission, or neurodegeneration. Overall, exposure to escitalopram/citalopram results in shifts in metabolism through noncanonical pathways, which suggest possible roles for the gut microbiome, oxidative stress, and inflammation-related mechanisms.