The effects of a decrease of the K+ gradient on the extraneuronal inward transport and outward movement of catecholamines were studied in rat heart, rabbit aortic rings and guinea-pig trachealis smooth muscle. Elevation of the extracellular K+ concentration caused a) inhibition of the corticosteroid-sensitive extraneuronal uptake (uptake2) of 3H-isoprenaline in rat heart and of 3H-noradrenaline in rabbit aorta, and b) acceleration of efflux of 3H-isoprenaline from rat heart, 3H-noradrenaline from rabbit aorta and adrenaline (measured by microphotometry) from guinea-pig trachealis muscle. In rat heart and rabbit aorta, the acute omission of one or the other of the ions Na+, Cl-, K+ or Ca2+ from the perfusion of incubation medium had no effect on initial rates of uptake2 of catecholamines, except that the absence of K+ had a small inhibitory effect in the rat heart. The prolonged absence of Na+, Ca2+ or K+ from the perfusion or incubation medium caused a marked inhibition of uptake2 of catecholamines. These inhibitory effects developed more quickly in rat heart than in rabbit aorta. These results are compatible with the possibility that either the K+ gradient across the cell membrane or the resting membrane potential is the force driving uptake2.

Expression and in-vivo modulation of beta- and alpha-adrenoceptors on peripheral human natural killer (CD16+) cells was investigated. Ligand binding studies revealed that CD16+ lymphocytes express beta2, alpha1-, alpha2- but not beta1-adrenoceptors. Infusion of adrenaline, but not noradrenaline, significantly decreased beta2- and alpha1-adrenoceptor numbers on NK cells. Both catecholamines did not appreciably alter alpha2-adrenoceptor numbers. Additional analyses showed that adrenaline administration increases alpha2-adrenoceptor numbers on peripheral mononuclear blood cells (PBMC) and T-cell subsets (CD4+, CD8+) in contrast to decreased receptor numbers on CD16+ cells. These data demonstrate a specific effect of increasing levels of circulating catecholamines on beta2-adrenoceptors on NK cells.

BACKGROUND

Subarachnoid hemorrhage (SAH) often causes a prolongation of the corrected QT (QTc) interval during the acute phase. The aim of the present study was to examine independent risk factors for QTc prolongation in patients with SAH by means of multivariate analysis.

METHODS

We studied 100 patients who were admitted within 24 hours after onset of SAH. Standard 12-lead electrocardiography (ECG) was performed immediately after admission. QT intervals were measured from the ECG and were corrected for heart rate using the Bazett formula. We measured serum levels of sodium, potassium, calcium, adrenaline (epinephrine), noradrenaline (norepinephrine), dopamine, antidiuretic hormone, and glucose.

RESULTS

The average QTc interval was 466 +/- 46 ms. Patients were categorized into two groups based on the QTc interval, with a cutoff line of 470 ms. Univariate analyses showed significant relations between categories of QTc interval, and sex and serum concentrations of potassium, calcium, or glucose. Multivariate analyses showed that female sex and hypokalemia were independent risk factors for severe QTc prolongation. Hypokalemia (<3.5 mmol/l) was associated with a relative risk of 4.53 for severe QTc prolongation as compared with normokalemia, while the relative risk associated with female sex was 4.45 as compared with male sex. There was a significant inverse correlation between serum potassium levels and QTc intervals among female patients.

CONCLUSIONS

These findings suggest that female sex and hypokalemia are independent risk factors for severe QTc prolongation in patients with SAH.

Aggressive melanoma cells can engage in a process termed vasculogenic mimicry (VM) that reflects the ability of tumor cells to express a multipotent, stem cell-like phenotype. Melanoma cell plasticity contributes to the lack of efficient therapeutic strategies targeting metastatic tumors. This study reveals cyclic AMP as a mediator of VM in vitro. In uveal and cutaneous metastatic aggressive human melanoma cells, an increase in cyclic AMP by forskolin, dibutyryl cyclic AMP, or G protein-coupled receptor (GPCR) ligands such as adrenaline and vasoactive intestinal peptide inhibited VM to different extents. Although chemical modulators of protein kinase A (PKA) had no effect, a specific pharmacologic activator of Exchange protein directly activated by cyclic AMP (Epac) impaired VM. Ras-associated protein-1 (Rap1) activation assays revealed that cyclic AMP-elevating agents induce a PKA-independent activation of Epac/Rap1. Pharmacologic inhibition of extracellular signal-regulated kinase 1/2 (ERK1/2) activity abolished VM. Phosphorylation of ERK1/2 was PKA-independently inhibited by forskolin but not inhibited by Epac/Rap1 signaling, PKA modulation, or GPCR ligands. Furthermore, the forskolin also inhibited phosphatidyl inositol-3-kinase (PI3K)-mediated activation of protein kinase Akt, as monitored by Ser473 phosphorylation. The pharmacologic activation of Epac and GPCR ligands slightly stimulated Akt, a likely concomitant process of VM modulation. Collectively, these data show that forskolin strongly inhibits VM through PKA-independent activation of Epac/Rap1, PKA-, and Epac-independent inactivation of ERK1/2 and inhibition of PI3K/Akt. The data also show that VM inhibition by GPCR ligands involves mainly the Epac/Rap1-activated signal. Thus cyclic AMP inhibits VM through multiple signaling pathways.

The aim of the present survey was to provide a literary review of current knowledge of the possible association between the psychosocial working environment and relevant physiological parameters measured in blood and urine. Literature databases (PubMed, Toxline, Biosis and Embase) were screened using the key words job, work-related and stress in combination with selected physiological parameters. In total, 51 work place studies investigated the associations between the psychosocial working environment and physiological changes, of which 20 were longitudinal studies and 12 population-based studies. The studied exposures in work place/population-based studies included: job demands (26/8 studies), job control (24/10 studies), social support and/or leadership behaviour (12/3 studies), effort-reward imbalance (three/one studies), occupational changes (four studies), shift work (eight studies), traumatic events (one study) and other (five studies). The physiological responses were catecholamines (adrenaline, noradrenaline) (14 studies), cortisol (28 studies), cholesterol (23 studies), glycated haemoglobinA(1c) (six studies), testosterone (nine studies), oestrogens (three studies), dehydroepiandrosterone (six studies), prolactin (14 studies), melatonin (one study), thyroxin (one study), immunoglobulin (Ig) A (five studies), IgG (four studies), IgM (one study) and fibrinogen (eight studies). In general, fibrinogen and catabolic indicators, defined as energy releasing, were increased, whereas the anabolic indicators defined as constructive building up energy resources were decreased when the psychosocial working environment was perceived as poor. In conclusion, in this review the association between an adverse psychosocial working environment and HbA(1c), testosterone and fibrinogen in serum was found to be a robust and potential candidate for a physiological effect of the psychosocial working environment. Further, urinary catecholamines appear to reflect the effects of shift work and monotonous work.

BACKGROUND

It has been suggested that profound acid inhibition along with endoscopic therapy might prevent rebleeding and reduce mortality in patients with peptic ulcer bleeding. The aim of the study was to test the possible equivalence of a high dose and the regular dose of omeprazole in peptic ulcer bleeding.

METHODS

We performed a prospective randomized double-blind study involving 142 patients with acute peptic ulcer bleeding (Forrest classification I-II: spurting or oozing bleeding, non-bleeding visible vessel, clot and black base). One-hundred-and-two (71.8%) patients received endoscopic treatment (adrenaline injection and/or heater probe) in pre-entry. Patients were randomly assigned to receive the regular dose of omeprazole intravenously (20 mg once a day for 3 days, i.e. 60 mg/72 h) or a high dose of omeprazole (80 mg bolus + 8 mg/h for 3 days, i.e. 652 mg/72 h). Rebleeding, surgery and death were the outcome measures.

RESULTS

Six (8.2%) of the 73 patients receiving the regular dose of omeprazole and 8 (11.6%) of the 69 patients receiving the high dose of omeprazole rebled (P = 0.002 for equivalence, equivalence limit 0.15). Three (4.1%) of the former patients and 5 (7.2%) of the latter group underwent surgery. Four (5.5%) patients in the regular-dose and 2 (2.9%) in the high-dose group died within 30 days.

CONCLUSIONS

Under the defined tolerance limits, the regular dose of omeprazole is as successful as a high dose in preventing peptic ulcer rebleeding.

Anaesthesia for Caesarean section was audited over a 5 year period: 5080 cases were performed using spinal 63%, epidural top-up 26%, combined spinal-epidural 5% and primary general anaesthesia 5%. The rate of general anaesthesia conversion of regional anaesthesia was 0.8% for elective and 4.9% for emergency Caesarean section compared to Royal College of Anaesthetists targets of 1% and 3%. The rate of conversion of regional to general anaesthesia in category 1 Caesarean section was 20%. A total of 8% of women had general anaesthesia when both primary general and conversion of regional anaesthesia were combined. The rate of failure to achieve a pain-free operation was 6% with spinals, 24% with epidural top-up and 18% with combined spinal-epidural. Besides the type of anaesthesia and operative urgency, other factors associated with pre-operative failure of regional anaesthesia included body mass index, no previous Caesareans, and indication for Caesarean of acute fetal distress or maternal medical condition. Inadequacy of pre-operative anaesthetic block and duration of surgery were important risk factors for intra-operative failure. For spinal anaesthesia, use of a spinal opioid was associated with less pre-operative failure. For epidural top-up anaesthesia, lower epidural top-up volume was associated with less pre-operative failure, and use of adrenaline was associated with both less pre-operative and intra-operative failure. The rate of serious adverse incidents was 1 : 126 with general anaesthesia and 1 : 501 with regional anaesthesia.

Local anesthetics are designed for application in or close to nerve tissue. In spite of their wide clinical use, surprisingly few investigations deal with the neural toxicity of modern local anesthetics. In this experimental study, the effects were investigated of intrafascicular or topical application of the long-acting local anesthetic bupivacaine on the rabbit sciatic nerve. Axonal degeneration was histologically evaluated and a fluorescence-microscopic technique used to detect lesions in the blood-nerve barrier. Topical application of bupivacaine in clinically recommended concentrations around the nerve caused no detectable nerve injury, while intrafascicular injections caused considerable axonal degeneration and damaged the blood nerve barrier. Axonal degeneration was the same after injection of physiologic saline solution and bupivacaine 0.5%, but it increased with increasing bupivacaine concentration and especially with the addition of adrenaline. On the other hand, the acute effects of intrafascicular injection, as visualized in the barrier experiments, changed little with the addition of adrenaline, indicating that it is the injection trauma itself which is deleterious. It is concluded that intraneural injections should be avoided and that plain bupivacaine solutions should be routinely used.

To study the possible benefits of N2O pneumoperitoneum, 40 patients scheduled for laparoscopic cholecystectomy for symptomatic cholelithiasis were randomized into either CO2-induced (n = 20) or N2O-induced (n = 20) pneumoperitoneum groups. The intensity of postoperative pain was assessed by the patients themselves using an visual analogue pain score scale. CO2 insufflation caused respiratory acidosis. The total amount of anesthetic enflurane needed was lower in the N2O than in the CO2 group (p < 0.041). The N2O group experienced less pain 1 hour (p < 0.040) and 6 hours (p < 0.017) postoperatively and the next morning. Serum cortisol and plasma adrenaline concentrations in the N2O group did not differ from those in the CO2 group. Patients with N2O pneumoperitoneum seem to have less pain without the side effects caused by CO2. The N2O pneumoperitoneum is a good alternative to the CO2 pneumoperitoneum, especially for prolonged laparoscopic operations in patients with chronic cardiopulmonary diseases.

The psychoneuroendocrine responses to sexual arousal have not been clearly established in humans. However, we have demonstrated previously that masturbation-induced orgasm stimulates cardiovascular activity and induces increases in catecholamines and prolactin in blood of both males and females. We presently investigated the role of orgasm in producing these effects. Therefore, in this study parallel analysis of prolactin, adrenaline, noradrenaline, and cortisol concentrations, together with cardiovascular variables of systolic/diastolic blood pressure and heart rate were undertaken during film-induced sexual arousal in nine healthy adult men and nine healthy adult women. Blood was drawn continuously via an indwelling cannula and connected tubing system passed through a mini-pump. In parallel, the cardiovascular parameters were recorded continuously via a computerised finger-cuff sensor. Subjective sexual arousal increased significantly in both men and women during the erotic film, with sexual arousal eliciting an increase in blood pressure in both males and females, and plasma noradrenaline in females only. In contrast, adrenaline, cortisol and prolactin levels were unaffected by sexual arousal. These data further consolidate the role of sympathetic activation in sexual arousal processes. Furthermore, they demonstrate that increases in plasma prolactin during sexual stimulation are orgasm-dependent, suggesting that prolactin may regulate a negative-feedback sexual-satiation mechanism.

Tension and action potentials have been measured simultaneously from isolated cat papillary muscles. Two groups of experiments are described. In the first group, the external conditions under which the muscle contracted were changed. Specifically, stimulation rate, extra-cellular [Ca++], extracellular [Na++] were altered, and adrenaline was added to the bathing fluid. A tendency for given levels of tension to be accompanied by action potentials of constant duration is demonstrated under some of these conditions. In the second group of experiments, tension and action potentials were recorded following some change in external conditions; specifically, after a long rest, after a change in muscle length, and after the muscle had been set up in the experimental apparatus (the 'running-in' period). In the period that followed each of these interventions, peak tension increased substantially over at least several minutes but all external conditions (for example, temperature, muscle length, stimulation rate, and composition of the bathing fluid) remained constant. In each of these three situations tension increased but in one case the action potential duration increased, in another it decreased, and in the third it was unchanged. It is concluded that change in action potential durations do not necessarily make an important contribution to the changes in tension of papillary muscles.

1. Changes of action potential duration in cat papillary muscle have been correlated with changes of peak tension. It has been assumed that peak tension is an approximate indicator of [Ca2+]i. 2. When stimulation is commenced after a rest of several minutes, or after a decrease or increase of the stimulus rate, or after rest periods of different duration the changes of action potential duration are closely related to changes of peak tension. These results suggest that [Ca2+]i is of primary importance in determining rate-dependent changes of action potential duration, including the shortening of the action potential at high rates of stimulation. 3. The results also indicate the presence of a factor which tends to prolong the action potential at high rates of stimulation. Thus the duration of the action potential at high stimulus rates is longer than at lower rates when measured at a given value of peak tension. Furthermore in low Ca2+ there can be a prolongation of the steady state action potential at high rates. Comparison with the work of Cohen et al. (1976) suggests that this factor is responsible for the polarity of the T-wave of the ECG. 4. The action of adrenaline on action potential duration has also been analysed. It is shown to have two effects--a prolonging effect probably related to the adrenaline induced increase of Isi, and a shortening effect probably related to an increase of [Ca2+]i (as judged by the increase of peak tension).

The insulin-antagonistic effect of adrenaline was studied in seven healthy subjects with the euglycaemic clamp technique using two insulin infusion rates (40 and 1200 mU X (m2)-1 min-1). The adrenergic receptor mediating the adrenaline effect was characterized by concomitant infusion of propranolol (beta 1 + beta 2-antagonist) or metoprolol (beta 1-antagonist). Each subject was studied four times (placebo, adrenaline, adrenaline + propranolol, adrenaline + metoprolol). Glucose turnover was measured with D(3-3H)-glucose. Similar plasma insulin levels were reached in all studies with the two insulin infusion rates (mean; placebo 51 +/- 3 and 7421 +/- 337 mU/l respectively). Glucose production was completely inhibited by the low insulin level during placebo infusion. Adrenaline antagonized this effect so that a significant glucose production was seen at the low but not at the high insulin level. Propranolol, but not metoprolol, reversed this insulin-antagonistic effect of adrenaline. Glucose utilization increased from 2.53 +/- 0.17 to 7.28 +/- 0.88 mg X kg-1 X min-1 during placebo when the insulin levels were increased from 4 +/- 0.3 to 51 +/- 3 mU/l. Increasing the insulin levels 150-fold to approximately 7500 mU/l only doubled the glucose utilization (14.68 +/- 1.14 mg X kg-1 X min-1). Adrenaline induced a pronounced inhibition of glucose utilization at both insulin levels (78% and 37% inhibition respectively). Propranolol, but not metoprolol, prevented this effect of adrenaline. Thus, physiological adrenaline levels exert a pronounced insulin-antagonistic effect which is mediated by beta 2-receptor stimulation. The inhibitory effect on glucose uptake is maintained even at high insulin levels when hepatic glucose production is completely abolished.

Complexes of alpha(2A)-ARs (alpha(2A)-adrenergic receptors) and MORs (mu-opioid receptors), probably hetero-oligomers, were detected by co-immunoisolation after extraction from HEK-293 cells (human embryonic kidney 293 cells). Functional communication between these receptors is revealed by alpha(2A)-AR activation of a pertussis toxin-insensitive G(i)alpha subunit (termed as G(i)1) when fused with the MOR and evaluated in membranes from pertussis toxin-treated cells. However, the alpha(2A)-AR does not require transactivation through MOR, since quantitatively indistinguishable results were observed in cells co-expressing alpha(2A)-AR and a fusion protein of G(i)1 with the first transmembrane span of MOR (myc-MOR-TM1). Functional cross-talk among these alpha(2A)-AR-MOR complexes does not occur for internalization profiles; incubation with adrenaline (epinephrine) leads to endocytosis of alpha(2A)-AR but not MOR, while incubation with DAMGO ([D-Ala,NMe-Phe,Gly-ol]enkephalin) leads to endocytosis of MOR but not alpha(2A)-AR in cells co-expressing both the receptors. Hence, alpha(2A)-AR and MOR hetero-oligomers, although they occur, do not have an obligatory functional influence on one another in the paradigms studied.

1. The uptake of (+/-)-(3)H-noradrenaline was studied in isolated perfused hearts of rat, mouse, guinea-pig, pigeon and toad (Bufo marinus), and the IC50 (concentration causing 50% inhibition) values for inhibition of uptake of (+/-)-(3)H-noradrenaline by (-)-noradrenaline were calculated. IC50 values ranging from 0.28 muM (rat heart) to 2.34 muM (toad heart) were found.2. In all species except the toad, (-)-noradrenaline showed a higher affinity than (-)-adrenaline for the uptake process, but the reverse was found for the toad heart.3. Mouse and pigeon hearts contained increasing amounts of metabolites of noradrenaline with increasing perfusion concentrations of noradrenaline, but the guinea-pig and toad hearts did not. The in vitro activities of noradrenaline catabolizing enzymes in heart homogenates were measured but did not explain the differences in the pattern of catabolism of noradrenaline found in the intact hearts of the different species.4. In all hearts except the toad, cocaine was an effective blocking agent for the uptake of (+/-)-(3)H-noradrenaline and led to an increase in (3)H-normetanephrine in these hearts. In the pigeon heart, cocaine plus phenoxybenzamine in the perfusate resulted in an inhibition of both (3)H-noradrenaline uptake and (3)H-normetanephrine formation.5. In guinea-pig and pigeon perfused hearts, the uptake of (3)H-noradrenaline into atria and ventricles reflected the relative concentrations of endogenous catecholamines in these regions, but this was not found for rat, mouse and toad hearts.6. It was concluded that species differences exist for both the accumulation and metabolism of catecholamines in isolated perfused hearts.

This paper reviews the literature, describes and discusses methods by which whole body hydration status can be determined in humans. A method of determining whether or not an individual is hypohydrated is of particular significance in an exercise situation as even moderate levels of hypohydration have a negative impact on exercise performance. Inspection of the published literature indicates that a number of methods have been used to determine hydration status. Body mass changes, urinary indices (volume, colour, protein content, specific gravity and osmolality), blood borne indices (haemoglobin concentration, haematocrit, plasma osmolality and sodium concentration, plasma testosterone, adrenaline, noradrenaline, cortisol and atrial natiuretic peptide), bioelectrical impedance analysis, and pulse rate and systolic blood pressure response to postural change are discussed. The urinary measures of colour, specific gravity and osmolality are more sensitive at indicating moderate levels of hypohydration than are blood measurements of hematocrit and serum osmolality and sodium concentration. Currently no "gold standard" hydration status marker exists, particularly for the relatively moderate levels of hypohydration that frequently occur in an exercise situation. The choice of marker for any particular situation will be influenced by the sensitivity and accuracy with which hydration status needs to be established together with the technical and time requirements and expense involved.

1 The content of adrenaline (Ad), noradrenaline (NA) and dopamine was measured in human, guinea-pig, cat, rabbit and rat blood platelets by a highly sensitive and specific radioenzymatic method.2 In all platelet specimens analyzed, the content of the three catecholamines (CA) was several thousand times lower than that of 5-hydroxytryptamine (5-HT).3 In basal conditions, the NA concentration in platelets and plasma always exceeded that of Ad and dopamine.4 In rat and rabbit platelets, Ad, NA and dopamine were present only in the free (unconjugated) form.5 Platelets of rats with storage pool deficiency (Fawn-hooded) contained much less 5-HT and CA than normal rat platelets.6 Following restraint stress, platelets of Fawn-hooded rats, in contrast to normal rat platelets, did not accumulate CA in spite of a dramatic rise in plasma CA.7 Reserpine, a monoamine depletor, released CA as well as 5-HT from rabbit platelets in vivo.8 Subcellular fractionation experiments with rabbit platelets indicate that both CA and 5-HT are most concentrated in the fraction consisting of pure 5-HT organelles.9 Both in humans and rabbits the concentration gradient between platelets and plasma was much lower for CA than for 5-HT, indicating that a high affinity transport mechanism operates in vivo for 5-HT but not for CA.10 In conclusion, the present data show that both human and animal platelets contain Ad, NA and dopamine. The bulk of the CA seems to be stored as unconjugated amines together with 5-HT, histamine and p-octopamine in a multitransmitter storage site, namely the 5-HT organelle.

1. The relaxant effects to the beta-adrenoceptor agonists isoprenaline, adrenaline, noradrenaline, RO363, procaterol and fenoterol were investigated in carbachol-contracted mouse isolated tracheal preparations. 2. The order of potencies for those beta-adrenoceptor agonists that induced full relaxation of carbachol-contracted mouse tracheal preparations was isoprenaline greater than RO363 greater than noradrenaline = adrenaline greater than fenoterol. The EC50 value of isoprenaline for relaxation was 46 nM. The beta 1-adrenoceptor-selective agonist, RO363 was ten times more potent than the beta 2-adrenoceptor-selective agonist, fenoterol. The highly beta 2-adrenoceptor-selective agonist procaterol was a partial relaxant and induced only 28 +/- 4% relaxation. 3. Relaxations induced by noradrenaline and isoprenaline were not significantly affected by the neuronal uptake inhibitor, cocaine (10 microM) or by the extraneuronal uptake inhibitor, deoxycorticosterone acetate (25 microM) respectively. The alpha-adrenoceptor agonist methoxamine induced no observable elevation of mouse tracheal smooth muscle tone. 4. Schild plots for the beta-adrenoceptor antagonists, atenolol and betaxolol (beta 1-adrenoceptor-selective) and ICI 118,551 (beta 2-adrenoceptor-selective) were linear, with slope values approaching unity. Mean pA2 values derived for atenolol, betaxolol and ICI 118,551 for antagonism of beta-adrenoceptor-mediated relaxation were 7.1, 8.4 and 7.2, respectively. These data were independent of the use of isoprenaline or noradrenaline as the agonist. 5. These findings indicate that beta-adrenoceptor-mediated relaxations of mouse isolated trachea occur predominantly through activation of beta 1-adrenoceptors.

Substance P (determined as immunoreactive substance P [i-SP]), noradrenaline, and adrenaline were measured in plasma of 18 patients with hepatic coma (stage I-IV), 16 healthy controls, and 10 critically ill patients without evidence of hepatocellular disease. Plasma i-SP (119 +/- 13 fmol/ml) was significantly higher in patients with hepatic coma than in healthy controls (13 +/- 2 fmol/ml) or control patients (23 +/- 4 fmol/ml). Plasma i-SP rose in parallel with plasma noradrenaline and adrenaline. There was a significant direct correlation between plasma i-SP and noradrenaline. Increase in plasma i-SP and noradrenaline was associated with a decrease in systemic vascular resistance and an increase in cardiac index and was most pronounced in those patients who finally died in coma. Deterioration in the dying patients was accompanied by a further significant increase in plasma i-SP. Immunoreactivity was identified as authentic SP by high performance liquid chromatography in 3 representative patients. Accumulation of the vasodilating peptide SP in plasma of patients with hepatic coma may be important in the pathogenesis of the cardiovascular disturbances associated with this disease.

1. Sudden death is a recognized hazard of volatile substance abuse and may occur during exposure or in the subsequent hours. Intoxication may also lead to indirect deaths due to trauma. 2. Specific post-mortem features have not as yet been identified either macroscopically or microscopically in VSA-related deaths. Toxicological examination for volatile substances of all unnatural teenage deaths is strongly recommended. 3. Four mechanisms for acute, direct VSA-related deaths are discussed, viz anoxia, vagal inhibition, respiratory depression and cardiac arrhythmia. Of these, cardiac arrhythmia due to 'sensitization' of the heart to adrenaline is probably the most common and is well documented in experimental conditions. 4. Deaths from cardiac arrhythmia during or soon after VSA are unpredictable, unpreventable and resuscitation is rarely successful. Previous uneventful sessions of abuse provide no protection from this mode of death.

1. Neurones dissociated from Rana pipiens paravertebral sympathetic ganglia were studied by means of the whole-cell patch-clamp technique. Responses to agonists were best recorded when cyclic AMP was included in the patch pipette. 2. Two populations of cells were identified on the basis of size (input capacitance, Cin) and the presence or absence of a fast, transient outward current (A-current, IA). This current was usually present in the 'large' cells (Cin = 40.5 +/- 1.5 pF, n = 66) but absent from 'small' cells (Cin = 21.0 +/- 0.8 pF, n = 70). 3. Both cell types exhibited a slowly activating, non-inactivating K+ current (M-current, IM) which was suppressed by luteinizing hormone-releasing hormone (LHRH, 10-100 microM). Threshold for activation of IM was about -75 mV, half-maximal activation was at -50 mV and the M-conductance GM increased e-fold for at 7 mV change in membrane potential. The maximum value for IM studied in large cells by patch-clamp procedures was less than 0.2 nA. More M-channels were available per unit membrane area in the small cells (GM = 1495 microS cm-2) than in the large cells (GM = 1034 microS cm-2). Time constants for IM deactivation at -70 mV were faster in the large cells (37.2 +/- 4.6 ms, n = 16) than in the small cells (66.1 +/- 5.9 ms, n = 9). 4. Muscarine (10 microM) produced inward current in the large cells as a result of IM suppression. In 40% of the large cells, some of the M-channels were also sensitive to adrenaline (10-100 microM). In a few large cells (less than 10%) adrenaline produced outward current by increasing IM. 5. Muscarine failed to effect IM in the small cells and instead produced an inwardly rectifying K+ current which activated within 5 ms at -110 mV. The outward current produced in twenty out of thirty-seven small cells by adrenaline was occluded by that produced by muscarine, suggesting that both agonists affect the same K+ channels. 6. Inclusion of the protein kinase inhibitors, 1-(5-isoquinolinyl-sulphonyl)-2-methyl piperazine (H-7, 50 microM) or gold sodium thiomalate (GST, 50 microM) in the pipette solution failed to antagonize either muscarine-induced current. Both currents were prolonged when the 'internal solution' contained GTP-gamma-S (50 microM). 7. Phorbol-12-myristate-13-acetate (PMA, 2-5 microM) produced an inward current as a result of IM suppression in both small and large cells.(ABSTRACT TRUNCATED AT 400 WORDS)