A rapid liquid chromatography/tandem mass spectrometry (LC-MS/MS) method has been developed for the measurement of dopamine (DA), 5-hydroxytryptamine (<em>5HT</em>) and norepinephrine (NE) in brain microdialysates. The assay has also been utilised for the simultaneous measurement of these neurotransmitters and cocaine in brain dialysates. The neurotransmitters and cocaine were resolved in a single 4-min run using a binary gradient elution profile. The analytes were detected using tandem mass spectrometry in the positive ion electrospray mode. The limits of detection for DA, NE, <em>5HT</em> and cocaine were 200, 1000, 900 pM and 1 pg ml(-1), respectively.

The circadian timing system controls daily rhythms of physiology and behavior, and disruption of clock function can trigger stressful life events. Daily exposure to cigarette smoke (CS) can lead to alteration in diverse biological and physiological processes. Smoking is associated with mood disorders, including depression and anxiety. Patients with chronic obstructive pulmonary disease (COPD) have abnormal circadian rhythms, reflected by daily changes in respiratory symptoms and lung function. Corticosterone (CORT) is an adrenal steroid that plays a considerable role in stress and anti-inflammatory responses. Serotonin (5-hydroxytryptamine; <em>5HT</em>) is a neurohormone, which plays a role in sleep/wake regulation and affective disorders. Secretion of stress hormones (CORT and <em>5HT</em>) is under the control of the circadian clock in the suprachiasmatic nucleus. Since smoking is a contributing factor in the development of COPD, we hypothesize that CS can affect circadian rhythms of CORT and <em>5HT</em> secretion leading to sleep and mood disorders in smokers and patients with COPD. We measured the daily rhythms of plasma CORT and <em>5HT</em> in mice following acute (3 d), sub-chronic (10 d) or chronic (6 mo) CS exposure and in plasma from non-smokers, smokers and patients with COPD. Acute and chronic CS exposure affected both the timing (peak phase) and amplitude of the daily rhythm of plasma CORT and <em>5HT</em> in mice. Acute CS appeared to have subtle time-dependent effects on CORT levels but more pronounced effects on <em>5HT</em>. As compared with CORT, plasma <em>5HT</em> was slightly elevated in smokers but was reduced in patients with COPD. Thus, the effects of CS on plasma <em>5HT</em> were consistent between mice and patients with COPD. Together, these data reveal a significant impact of CS exposure on rhythms of stress hormone secretion and subsequent detrimental effects on cognitive function, depression-like behavior, mood/anxiety and sleep quality in smokers and patients with COPD.

U-46619 is a stable epoxymethano analogue of cyclic endoperoxide PGH2. We studied platelet aggregation, 14C-<em>5HT</em> release, LDH extrusion and prostaglandin and thromboxane production induced by this compound in platelet-rich plasma samples from 15 healthy volunteers. Each subject was tested both before and 90 min after aspirin (500 mg) ingestion. The threshold aggregating concentration (TAC) of U-44619 ranged between 0.18 and 0.90 micro M. Aggregation was maximal between 40 and 60 min after venipuncture and was concentration-dependent. At concentrations below the TAC, U-44619 induced primary reversible aggregation with minimal 14C-<em>5HT</em> release. At TAC or higher concentrations aggregation and release proceeded as parallel events. Neither prostaglandin or thromboxane production nor LDH loss could be detected in any of the situations tested. Aspirin ingestion did not modify the pattern of platelet responses. In unstirred, not aggregated platelet samples 14C-<em>5HT</em> release by U-46619 occurred to a similar extent as in stirred, aggregated platelet samples. Addition to citrated PRP of 0.3 mM Na2 EDTA blocked both aggregation and release induced by U-46619. This compound, however, aggregated washed platelets resuspended in Ca++-free-tyrode-albumin containing fibrinogen. The mechanism by which U-46619 activates platelets differs from that of all other common aggregating agents.

The effects of intracisternal clonidine (0.04, 0.2, and 1.0 microgram/kg) and of alpha-methyldopa (alpha-MD; 400 micrograms/kg) on mean arterial pressure (MAP) and heart rate (HR) were studied in conscious rabbits before, and 7 and 14 days after, intracisternal injection of (a) vehicle, (b) 6-hydroxydopamine (6-OHDA; 600 micrograms/kg), or (c) 5,6-dihydroxytryptamine (5,6-DHT; 633 micrograms/kg) (n = 6 per group). In the initial control experiment clonidine and alpha-MD produced similar falls in MAP and HR in each group; there was also good reproducibility of responses in vehicle-treated rabbits on the 3 experimental days. But after 6-OHDA or 5,6-DHT administration the circulatory effects of clonidine and alpha-MD were markedly attenuated. On day 14 after injection of 6-OHDA, the clonidine-induced falls in MAP and HR averaged 38 and 18%, respectively, of the control responses (p less than 0.001). On day 14 after 5,6-DHT administration, the falls in MAP and HR after clonidine administration were reduced to 27 and 13% of control, respectively (p less than 0.01), while the corresponding responses after alpha-MD administration were 39 and 61% of control (p less than 0.05). Neurochemical findings suggest that 6-OHDA affected noradrenergic (NA), dopaminergic (DA), but not serotonergic (<em>5HT</em>) neurons, and that 5,6-DHT affected <em>5HT</em> but not NA and DA neurons. We conclude that the circulatory effects of clonidine and alpha-MD are mediated through both central NA and <em>5HT</em> neurons.

The effects on rat brain tissue monoamine and monoamine metabolite concentrations of chronic nicotine administration at two doses (3 and 12 mg/kg/day) using constant infusion were studied. After 21 days of treatment, tissue concentrations of dopamine (DA), norepinephrine (NE), 5-hydroxytryptamine (5-HT), and several metabolites in striatum, hypothalamus, and frontal cortex were determined by high performance liquid chromatography with electrochemical detection. Compared with a control group, nicotine treatment significantly decreased NE in frontal cortex but not in other regions. The concentration of <em>5HT</em> also was decreased in frontal cortex but increased in the hypothalamus at the higher dose of nicotine. The <em>5HT</em> metabolite 5-hydroxyindoleacetic acid (5-HIAA) was not significantly altered in any region. The <em>5HT</em> index (5-HIAA/5-HT) was significantly decreased in the hypothalamus and increased in frontal cortex at the higher dose. Concentrations of DA and the metabolite homovanillic acid (HVA) were not significantly altered by nicotine. Nevertheless, significant decreases in the DA metabolite dihydroxyphenyl-acetic acid (DOPAC) were observed in both striatum and hypothalamus. Moreover, the DA index [(DOPAC + HVA)/DA] was significantly decreased in all three brain regions. In contrast to other studies using acute dose and in vitro perfusion paradigms that have reported increased CNS catecholamine release stimulated by nicotine, chronic administration appears to be associated with decreased catecholamine turnover in some brain regions.

The aim of the present study was to characterize 5-hydroxytryptamine2 (5-HT2) receptors in the rat medial prefrontal cortex (mPFc) by single cell recording and microiontophoretic techniques. This was accomplished using 5-HT2 receptor agonists 1-[2,5-dimethoxy-4-iodophenyl]-2-aminopropane [(+/-)-DOI] and 1-[2,5-dimethoxy-4-bromophenyl]-2-aminopropane [(+/-)-DOB]. DOI ejected at a low current (0.5 nA) potentiates glutamate (GLU)-induced activation of mPFc neurons and this effect is blocked by spiperone. At higher currents. DOI invariably inhibits GLU-induced neuronal activity. The microiontophoretic ejection of both DOI and DOB predominantly inhibits spontaneously active mPFc cells. The inhibitory action of DOI on spontaneously active cells is dose-dependent and is blocked by putative 5-HT2 receptor antagonists, with a rank order of potency as follows: ritanserin greater than metergoline approximately LY-53857 greater than spiperone greater than mesulergine greater than mianserin approximately ketanserin. Interestingly, ketanserin and mianserin only weakly block the effect of DOI. The suppressant action of DOI is probably not related to its interaction with 5-HT10 sites as spiperone, which has low affinity for these sites, potently blocks the effect of DOI. The suppressant effect of DOI is not blocked by other receptor antagonists such as BRL-43694 (5-HT3), (+/-)-pindolol (<em>5HT</em> 1a,1b, beta adrenergic, beta), prazosin (adrenergic1, alpha-1), pyrilamine (histamine1, H1), l-sulpiride (dopamine2, D2) or SR 95103 (gamma-aminobutyric acid, GABAA). Overall our results indicate that DOI predominantly inhibits mPFc cells in a direct manner and this effect is mediated by 5-HT2 receptors.(ABSTRACT TRUNCATED AT 250 WORDS)

In binding experiments with the radioligands [3H]Ketanserin (HKet) and [125I]LSD (ILSD) 21 compounds were investigated using rat brain cortex membranes. The pKD-values of the compounds were virtually independent of the radioligand used and their rank order was consistent with classification of the binding sites as being of the 5-HT2-type. In contrast, in the longitudinal muscle of the guinea pig ileum in the presence of 0.3 microM cinanserin, ILSD labelled sites which were quite different to those in the cortex. In a functional test antagonism of the <em>5HT</em> induced contraction of the guinea-pig ileum was measured in the presence of 1 microM atropine. The pharmacological inhibition constants (IC50-values) of 8 compounds correlated well with the dissociation constants for HKet binding in the cortex and did not correlate with the data from ILSD binding in the guinea pig ileum. It is concluded that the ileum contains postjunctional <em>5HT</em>2-receptors which mediate contraction. The nature of the ILSD binding sites in the ileum remains to be elucidated.

The effects of the adenylate cyclase inhibitor GDP beta S on the response of Aplysia neuron R15 to serotonin (<em>5HT</em>) were investigated. Previous studies have demonstrated that <em>5HT</em> causes an increase in K+ conductance in R15 and that the response is mediated by cAMP. At concentrations in the micromolar range, GDP beta S inhibits the stimulation of adenylate cyclase by <em>5HT</em> in particulate fractions from Aplysia ganglia. When micromolar concentrations of GDP beta S are injected into neuron R15, there is no effect on the resting membrane conductance, but the increase in K+ conductance normally elicited by <em>5HT</em> is completely inhibited. Furthermore, the decrease in inward current normally elicited by dopamine (DA), which does not appear to involve cAMP, is not affected by micromolar concentrations of GDP beta S. In addition, application of 8-benzylthio cAMP to R15 can evoke an increase in K+ conductance even after the injection of GDP beta S, which indicates that events subsequent to the activation of adenylate cyclase are not inhibited by the GDP analogue. In contrast, when millimolar concentrations of GDP beta S are injected into R15, direct effects on membrane conductance are observed and the response of R15 to <em>5HT</em> is enhanced. Although these effects of high concentrations of GDP beta S are only poorly understood, the results with micromolar concentrations are consistent with the hypothesis that stimulation of adenylate cyclase is necessary for the <em>5HT</em>-induced increase in K+ conductance in neuron R15.

A single dose of mianserin (a <em>5HT</em>1C/<em>5HT</em>2 antagonist), administered 1 hr, 48 hr, or 7 days before testing, was evaluated for its efficacy in alleviating or preventing the occurrence of anxiogenic behaviors observed during ethanol withdrawal. Other behavioral experiments using selected drug interactions were conducted to examine whether the effect of mianserin was related to a long-term modification of 5-hydroxy-tryptamine (<em>5HT</em>) receptor function. Rats were fed a liquid diet containing 4.5% ethanol for 4 days. They were tested on the elevated plus-maze (EPM) 12 hr (acute withdrawal) and 5 days (protracted withdrawal) after the last ethanol dose. Ethanol withdrawal induced a pattern of "anxiogenic" behavior that consisted of reduced activity (total entries) and a reduced proportion of open arm activity. Mianserin, injected as a single dose given either 1 hr (0.16-5 mg/kg, ip) before testing or given (20 mg/kg, ip) on the morning of the 3rd day of ethanol administration, i.e., 48 hr and 7 days before testing, dose-dependently prevented or reversed the ethanol withdrawal induced reduction in open-arm activity. In contrast, the <em>5HT</em>1C/<em>5HT</em>2 receptor agonist (+/- )-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane HCl (DOl) did not affect behaviors in the EPM in ethanol-naive rats, nor in those undergoing ethanol withdrawal. However, although there was a marked tolerance to DOl-induced body shakes (a measure of <em>5HT</em>2 function) during withdrawal, DOl reversed the action of mianserin in the EPM. The <em>5HT</em>1 receptor agonist, <em>5HT</em>2 receptor antagonist 1-naphthyl-piperazine (1-NP) reduced open-arm activity in ethanol-naive rats and this action was enhanced during withdrawal.(ABSTRACT TRUNCATED AT 250 WORDS)

The concentrations of dopamine (DA), serotonin (<em>5HT</em>) and their metabolites were quantified in 5 brain areas of rats exposed to saline, cocaine (15 mg/kg b.i.d.), amitriptyline (10 mg/kg), or amfonelic acid (AFA, 1.5 mg/kg) throughout gestation. Male pups from 3 similarly treated dams were fostered to 2 surrogate dams. The process of breeding and rearing was repeated 4 times with new dams to build the groups to 4-12, since only one pup per litter was used for any one measurement. AFA was used to mimic the dopamine (DA) uptake blockade and stimulant properties of cocaine and amitriptyline was used to mimic the other pharmacological effects of cocaine. At postnatal days (PND) 30, 60, and 180, one pup per litter was removed for HPLC analysis of monoamines. A second pup received 0.3 mg/kg haloperidol, catalepsy assessed after 1 hr, and the brain used for analysis. The cataleptic response to haloperidol was unaffected by any prenatal treatment. The striatum from PND 30 cocaine rats had decreased levels of DA without a decrease in DA metabolites. At PND 60 in cocaine exposed rats, DA and DOPAC concentrations were increased, and <em>5HT</em> levels were decreased in the striatum. The amitriptyline-exposed group exhibited decreased <em>5HT</em> and 5-HIAA levels in the striatum. The hypothalamus of the cocaine group had lower levels of 5-HIAA, and other brain areas had a trend for lower levels of <em>5HT</em> and 5-HIAA. At PND 180, DOPAC was increased in the striatum and prefrontal cortex of the cocaine group. Haloperidol-induced altered monoamine metabolism was unaffected by any prenatal treatment at any age. These data suggest that age-related changes in the DA and <em>5HT</em> neurotransmission systems occur in rats exposed prenatally to cocaine. However, the ability of the dopaminergic system to respond to a challenge by a DA receptor blocker is unaltered by these in utero treatments.

Serotonin (<em>5HT</em>) and dopamine (DA) induce, in neuroblastoma N1E-115 cells, a transient membrane depolarization associated with an inward current. The half-maximum response is obtained with 2 microM <em>5HT</em> or 200 microM DA. The maximum response to <em>5HT</em> is 2-3 times that to DA. The selective <em>5HT</em>3 receptor antagonists ICS 205-930 and MDL 72222 at nanomolar concentrations block both the <em>5HT</em>- and the DA-induced response. High concentrations (10 microM) of <em>5HT</em>2 receptor antagonists are without effect. It is concluded that, in N1E-115 cells, <em>5HT</em> and DA activate a single population of <em>5HT</em>3 receptors.

Intestinal ischemia impairs gastrointestinal motility. The aims of this study were to investigate the effect of intestinal ischemia on gastrointestinal transit and on the expression of enteric transmitters in the rat, and whether the glutamate N-methyl-d-aspartate receptors influence these effects. Ischemia (1 h), induced by occluding the superior mesenteric artery, was followed by 0 or 24 h of reperfusion. Normal and sham-operated rats served as controls. Serosal blood flow was measured with laser Doppler flow meter. Gastrointestinal transit was measured as time of appearance of a marker in fecal pellets. Immunohistochemistry was used to evaluate the number of neurons immunoreactive for neuronal nitric oxide synthase (NOS) or vasoactive intestinal polypeptide and the density of substance P immunoreactive fibers in the myenteric plexus. The N-methyl-d-aspartate receptors antagonist, (+)-5-methyl-10,11-dihydro-<em>5HT</em>-[a,b] cyclohepten-5,10-imine (MK-801) (1 mg/kg i.v.) or the NOS inhibitor, N-nitro-l-arginine (10 mg/kg i.v.) was administered prior to ischemia. Serosal blood flow was decreased by 70% during ischemia, but it was not altered in sham-operated rats. Gastrointestinal transit was significantly prolonged in ischemic/reperfused rats compared with controls. There was a significant increase in the number of vasoactive intestinal polypeptide and neuronal nitric oxide synthase immunoreactive neurons, and a marked decrease of substance P immunoreactive fibers in ischemia followed by 24 h of reperfusion animals compared with controls. These alterations were not observed in ischemia without reperfusion. A significant delay of gastrointestinal transit and increase of vasoactive intestinal polypeptide neurons were also observed in sham-operated rats. The changes in transmitter expression and gastrointestinal transit in ischemic/reperfused rats were prevented by pre-treatment with the NOS inhibitor, N-nitro-l-arginine or the N-methyl-d-aspartate receptors antagonist, MK-801. This study suggests an involvement of the glutamatergic system and its interaction with nitric oxide in intestinal ischemia/reperfusion. Ischemia/reperfusion might induce local release of glutamate that activates N-methyl-d-aspartate receptors leading to increased production of nitric oxide and adaptive changes in enteric transmitters that might contribute to gastrointestinal dysmotility.

Drugs such as alosetron that modulate serotonin effects by stimulating or blocking its receptors may play an important role in the treatment of some patients with irritable bowel system. In the case of alosetron, a <em>5HT</em>-3 antagonist, an analysis of data from randomized clinical trials and postmarketing experiences have demonstrated a causal relationship between this drug and ischemic colitis and serious complications of constipation. Because the mechanism(s) of drug-induced ischemic colitis and possibly other forms of intestinal ischemia associated with alosetron have not been elucidated, there is need to further assess risk with regard to patient susceptibility and other factors.

Developing in vitro blood-brain barrier (BBB) models that closely mimic the natural state is important for theoretical and practical applications, including drug development. We previously developed an in vitro BBB model based on co-culturing endothelial cells with glia in the presence of flow on hollow fiber tube culture substrates. We now report that this dynamic in vitro BBB (DIV-BBB) can be successfully used to co-culture differentiated serotonergic neurons in the presence of a BBB. These neurons demonstrated fluoxetine-sensitive serotonin (<em>5HT</em>) uptake and depolarization-induced release of [3H]<em>5HT</em>. Our results demonstrate that the DIV-BBB is a suitable model for culturing of neurons in a quasi-physiological microenvironment and in the presence of a high-resistance, stereoselective BBB.

m-Chlorophenylpiperazine (MCPP), a direct <em>5HT</em> receptor agonist, was administered orally to 20 normal subjects in two doses (0.25 and 0.5 mg/kg) in a placebo-controlled design. Behavioral responses; ACTH, cortisol, prolactin and MCPP blood level; temperature and pulse rate were measured over a 210-min period after administration of tablets. Non-linear dose-response relationships between MCPP and ACTH, cortisol and prolactin response were found. On the higher dose, a significant increase in the number of physical symptoms was also noted and three subjects (15%) had a panic attack, while one subject (5%) had a panic attack on the lower dose. No effects on other behavioral variables, pulse rate and temperature were found using either dose. These findings attest to the usefulness of MCPP as a challenge agent to assess <em>5HT</em> receptor hypersensitivity when given at a low oral dose (i.e. around 0.25 mg/kg), and to assess <em>5HT</em> receptor hyposensitivity when given at higher oral doses (i.e. around 0.5 mg/kg).

A substantial proportion of migraine patients have gastric stasis and suffer severe nausea and/or vomiting during their migraine attack. This may lead to erratic absorption from the gastrointestinal tract and make oral treatment unsatisfactory. For such patients, an intranasal formulation may be advantageous. Sumatriptan is a potent serotonin <em>5HT</em>(1B/1D) agonist widely used in the treatment of migraine; the effectiveness of the intranasal formulation (20mg) has been well established in several clinical studies. This article reviews the pharmacokinetics of intranasal sumatriptan and includes comparisons with oral and subcutaneous administration. After intranasal administration, sumatriptan is directly and rapidly absorbed, with 60% of the maximum plasma concentration (C(max)) occurring at 30 minutes after administration of a single 20mg dose. Following intranasal administration, approximately 10% more sumatriptan is absorbed probably via the nasal mucosa when compared with oral administration. Mean C(max) after a 20mg intranasal dose is approximately 13.1 to 14.4 ng/mL, with median time to C(max) approximately 1 to 1.75 hours. When given as a single dose, intranasal sumatriptan displays dose proportionality in its extent of absorption and C(max) over the dose range 5 to 10mg, but not between 5 and 20mg for C(max). The elimination phase half-life is approximately 2 hours, consistent with administration by other routes. Sumatriptan is metabolised by monoamine oxidase (MAO; predominantly the A isozyme, MAO-A) to an inactive metabolite. Coadministration with a MAO-A inhibitor, moclobemide, leads to a significant increase in sumatriptan plasma concentrations and is contraindicated. Single-dose pharmacokinetics in paediatric and adolescent patients following intranasal sumatriptan were studied to determine the effect of changes in nasal morphology during growth, and of body size, on pharmacokinetic parameters. The pharmacokinetic profile observed in adults was maintained in the adolescent population; generally, factors such as age, bodyweight or height did not significantly affect the pharmacokinetics. In children below 12 years, C(max) is comparable to that seen in adolescents and adults, but total exposure (area under the concentration-time curve from zero to infinity) was lower in children compared with older patients, especially in younger children treated with 5mg. Clinical experience suggests that intranasal sumatriptan has some advantages over the tablet (more rapid onset of effect and use in patients with gastrointestinal complaints) or subcutaneous (noninvasive and fewer adverse events) formulations.

Platelets contain a large amount of 5-hydroxytryptamine (<em>5HT</em>, serotonin). Intravenous injection into BALB/c mice of a Boivin's preparation of lipopolysaccharide (LPS) from Escherichia coli induced rapid <em>5HT</em> accumulation in the lung (within 5 min) and slow <em>5HT</em> accumulation in the liver (2 to 5 h later). The rapid response required high doses of LPS (more than 0.1 mg/kg). On the basis of <em>5HT</em> measurements, 70% or more of the platelets which disappeared from the blood appeared to have accumulated rapidly in the lung, and a large number of platelets were found there by electron microscopy. A shock, which was manifested by crawling, convulsion, or prostration, followed shortly after the rapid accumulation of <em>5HT</em> in the lung. On the other hand, the slow accumulation of <em>5HT</em> in the liver could be induced by much lower doses of LPS (1 microg/kg or less), even when given by intraperitoneal injection. This <em>5HT</em> accumulation appears to be a reflection of platelet accumulation in the liver (Y. Endo and M. Nakamura, Br. J. Pharmacol. 105:613-619, 1992). The combination of a low dose of LPS with D-galactosamine amplified the hepatic accumulation of <em>5HT</em>, and the mice developed a severe hepatic congestion resulting in death. The rapid response was not induced at all in C3H/HeN mice. These results and comparison with other LPS preparations indicate that some component(s) of LPS from E. coli induces a biphasic, organ-specific and strain-specific accumulation of platelets, and it is proposed that this effect is involved in the development of shock.

The respiratory control system is sexually dimorphic. In many brain regions, including respiratory motor nuclei, serotonin (<em>5HT</em>) levels are higher in females than in males. We hypothesized that there could be sex differences in <em>5HT</em> input to the hypoglossal nucleus, a region of the brainstem involved in upper airway control. Adult Fischer 344 rats were anesthetized and a retrograde transsynaptic neuroanatomical tracer, Bartha pseudorabies virus (PRV), was injected into the tongue. Sections through the medulla were reacted immunocytochemically for the presence of (i) PRV, (ii) tryptophan hydroxylase (TPH; marker of <em>5HT</em> neurons), (iii) PRV combined with TPH, and (iv) <em>5HT</em>. Sex hormone levels were measured in female rats and correlated with TPH immunoreactivity, as hypoglossal <em>5HT</em> levels vary with the estrous cycle. The number of PRV neurons was comparable in male and female rats. The number and distribution of TPH immunoreactive neurons in the caudal raphe nuclei were similar in male and female rats. The subset of <em>5HT</em> neurons that innervate hypoglossal motoneurons was also similar in male and female rats. With the exception of the ventrolateral region of the hypoglossal nucleus, <em>5HT</em> immunoreactivity was similar in male and female rats. These data suggest that sex differences in <em>5HT</em> modulation of hypoglossal motoneurons in male and female rats are not the result of sex differences in TPH or <em>5HT</em>, but may result from differences in neurotransmitter release and reuptake, location of <em>5HT</em> synaptic terminals on hypoglossal motoneurons, pre- and postsynaptic <em>5HT</em> receptor expression, or the distribution of sex hormone receptors on hypoglossal or caudal raphe neurons.

In view of the reported immunomodulatory properties of the monoaminergic neurotransmitter, serotonin (<em>5HT</em>), this study aimed to assess whether <em>5HT</em> specifically associates with immunocompetent cells. Although murine splenocytes appear to lack high-affinity membrane binding sites for <em>5HT</em>, they do possess a specific, active, <em>5HT</em> uptake system similar in affinity (Km = 40 nM) to that described in platelets. This uptake system appears to be confined to macrophages. Further, macrophages rapidly metabolize <em>5HT</em> to its 5-hydroxyindole acetic acid metabolite. Specific uptake of serotonin by macrophages may thus constitute an important mechanism whereby this amine is able to regulate immune function.

The zebrafish is becoming increasingly popular in behavior genetics because it may allow one to conduct large scale mutation and drug screens facilitating the discovery of mechanisms of complex traits. Strain differences in adult zebrafish behavior have already been reported, which may have important implications in neurobehavioral genetics. For example, we have found the AB and SF strains to differ in their behavioral responses to both acute and chronic alcohol exposure. In the current study, we further characterize these strains using semi-quantitative RT-PCR to measure the expression of ten selected genes and HPLC to measure the levels of nine neurochemicals. We chose the target genes and neurochemicals based upon their potential involvement in alcohol and other drugs of abuse related mechanisms. We quantified the expression of the genes encoding D1-R, D2a-R, D4a-R dopamine receptors, GABA(A)-R, GABA(B)-R1, GAD1, MAO, NMDA-R (NR2D subunit), <em>5HT</em>-R1bd and SLC6 a4a. We found the gene encoding D1 dopamine receptor over-expressed and the genes encoding GABA(B1) receptor and solute family carrier protein 6 (SLC6) 4a under-expressed in SF compared to AB. We also found the level of all (dopamine, DOPAC, Serotonin, GABA, Glutamate, Glycine, Aspartate, Taurine) but one (5HIAA) neurochemicals tested decreased in SF as compared to AB. These results, combined with previously identified behavioral differences between the AB and SF strains, demonstrate the importance of strain characterization in zebrafish. They now also allow formulation of working hypotheses about possible mechanisms underlying the differential effects of acute and chronic alcohol treatment on these two zebrafish strains.

Inflammation and neuronal degeneration of the substantia nigra (SN) occur in Parkinson's disease (PD). We studied the effects of intranigral lipopolysaccharide (LPS) injection on adult Sprague-Dawley rats. Locomotor activity measurement, neurotransmitter determination and perfusion fixation for immunohistochemistry were done on the 7th day. Bilateral LPS injection increased locomotor activity 2- to 3-fold. In the SN, dopamine (DA) and serotonin (5-HT) decreased but the ratios dihydroxyphenylacetic acid (DOPAC)/DA, homovanillic acid (HVA)/DA and 5-hydroxyindole-acetic acid (5-HIAA)/5-HT increased. In the striatum, DA, DOPAC, HVA, 3-methoxytyramine and epinephrine decreased but HVA/DA and 5-HIAA/<em>5HT</em> ratios increased. Unilateral LPS decreased dopamineric neurons ipsilaterally but increased contralaterally. This study provides the first evidence of behavioral hyperactivity, epinephrine suppression and neuronal plasticity in the LPS model of PD.

BACKGROUND

In a previous report, we showed that the clustering of serotonin (<em>5HT</em>) transporter (SERT) protein on cell membranes of peripheral lymphocytes predicts responsivity to antidepressant medication in two subpopulations of naïve depression patients (Rivera-Baltanas et al., J Affect Disord, 2012, 137, 46-55). In this study, we extended this idea to 5-HT2A receptor clusters in a similar patient population.

METHODS

We collected blood samples from a subset of patients from our previous study on SERT clustering (20 untreated and newly diagnosed depression patients, and 20 matched control subjects). Blood samples were collected at the time of diagnosis and after 8 weeks of pharmacological treatment and at analogous times in control subjects. We used the Hamilton scale to quantify the level of depression in patients both before and after treatment. We then used immunocytochemistry to assess 5-HT2A receptor clusters in lymphocytes at the same time points.

RESULTS

We found that both the size and number of 5-HT2A receptor clusters were increased in naïve depression patients compared to control subjects. Interestingly, there were individual differences in the distribution of 5-HT2A receptor cluster size that allowed us to differentiate the depression patients into two subgroups: a D-I group and a D-II group. After 8 weeks of pharmacological treatment, patients in both groups showed an improvement of symptoms, but patients in the D-II group had a much better outcome with many of them showing remission of symptoms. Furthermore, although treatment decreased cluster number and size in both D-I and D-II groups, only the D-II patients showed an increase in the number of clusters within the modal peak. Importantly, the same patients that belonged in the D-I or D-II groups in the present report were also assigned to the same groups in our previous study on SERT clustering.

CONCLUSIONS

The data should be replicated within a proper clinical trial.

CONCLUSIONS

5-HT2A receptor clusters in peripheral lymphocytes are altered in major depression, partially reversed by antidepressant treatment, and may be considered a putative biomarker of therapeutic efficacy in major depression.

The levels and turnovers of NE, DA and <em>5HT</em> were determined in whole brain, brain stem, cervical and thoracic spinal cord and carotid bodies (CB) of rats exposed to from 1 h to 7 days of hypobaric hypoxia (PB = 450 torr). Monoamine levels decreased only transiently upon acute exposure to hypoxia. Monoamine turnover in the CNS was estimated from the average of (a) monoamine buildup following inhibition of catabolism, and (b) monoamine breakdown following inhibition of synthesis. Hypoxic effects on CNS monoamine turnover showed that: (a) NE was not affected; (b) DA was not affected in acute hypoxia, but was reduced to about 40% of normoxia control after 1-7 days hypoxia; (c) <em>5HT</em> fell 50-60% during acute hypoxia but returned to and was maintained at control over 1-7 days of hypoxia; (d) acute restoration of normoxia following acute hypoxia restored <em>5HT</em> and DA to control or above and in the acclimatized animal acute normoxia increased DA and <em>5HT</em> turnover to about 1.4 and 1.8 X control. In the CB, DA levels gradually increased to 4 X control after 7 days of hypoxia and further increased to 6 X control upon acute restoration of normoxia. Changes in the metabolism of both central <em>5HT</em> and CB DA may be related to the mechanisms mediating ventilatory acclimatization to chronic hypoxia.

Serotonergic dysfunction is believed to be involved in the susceptibility to suicide due to functional alternations in the serotonin-related genes. Serotonin 1B (<em>5HT</em>-1B) receptor mediates aggressive behavior in mice models and was proposed to be involved in the control of aggression and impulsivity in humans. In this study we have investigated the association of G861C polymorphism of the <em>5HT</em>-1B receptor gene with suicide commitment. Study was based on two independent samples, one of German (245 suicide victims vs. 248 controls) and the other of Slavic/Croatian (118 suicide victims vs. 192 controls) ethnicity. No significant differences in allele or genotype frequencies between victims and controls were demonstrated either in German or Croatian sample. There were no differences in allele frequencies between German and Croatian population, and the combined sample, having high statistical power, also did not demonstrate significant differences between victims and controls. Results provide evidence that the investigated <em>5HT</em>-1B receptor gene variants are not implicated in the susceptibility to suicide.