Comparison of [125I]iodolysergic acid diethylamide binding in human frontal cortex and platelet tissue

The human platelet contains a functional 5-hydroxytryptamine (5-HT) receptor that appears to resemble the 5-HT2 subtype. In this study, we have used the iodinated derivative [125I]iodolysergic acid diethylamide ([125I]iodoLSD) in an attempt to label 5-HT receptors in human platelet and frontal cortex membranes under identical assay conditions to compare the sites labelled in these two tissues. In human frontal cortex, [125I]iodoLSD labelled a single high-affinity site (KD = 0.35 +/- 0.02 nM). Displacement of specific [125I]iodoLSD binding indicated a typical 5-HT2 receptor inhibition profile, which demonstrated a significant linear correlation (r = 0.97, p less than 0.001, n = 17) with that observed using [3H]ketanserin. However, [125I]iodoLSD (Bmax = 136 +/- 7 fmol/mg of protein) labelled significantly fewer sites than [3H]ketanserin (Bmax = 258 +/- 19 fmol/mg of protein) (p less than 0.001, n = 6). In human platelet membranes, [125I]iodoLSD labelled a single site with affinity (KD = 0.37 +/- 0.03 nM) similar to that in frontal cortex. The inhibition profile in the platelet showed significant correlation with that in frontal cortex (r = 0.96, p less than 0.001, n = 16). We conclude that the site labelled by [125I]iodoLSD in human platelet membranes is biochemically similar to that in frontal cortex and most closely resembles the 5-HT2 receptor subtype, although the discrepancy in binding capacities of [125I]iodoLSD and [3H]ketanserin raises a question about the absolute nature of this receptor.

Sex-related differences in central adrenergic function and responsiveness to repeated administration of desipramine or electroconvulsive shock

1. Clonidine induces hypoactivity in rodents. Male rats were found to be markedly more susceptible to the sedative effects of this alpha 2-adrenoceptor agonist than females. Thus to obtain identical hypoactivity responses for subsequent experiments, clonidine was administered to male and female rats at doses of 0.2 and 0.5 mg kg-1, respectively. 2. The clonidine-induced hypoactivity response of female rats was not affected by the oestrous cycle. 3. Repeated injection of desipramine (DMI; 5 mg kg-1 b.d.) for up to 14 days progressively attenuated clonidine-induced hypoactivity in both male and female rats. However, in males the attenuation was more rapid in onset and a greater overall reduction was obtained. This alpha 2-adrenoceptor-mediated response was also progressively reversed by repeated daily administration of an electroconvulsive shock (ECS; 110 V, 1 s). In this case, although the maximum decrease was greater in males, the time of onset was identical in both sexes. 4. There were no sex-related differences in either the number or affinity of alpha 2- and beta-adrenoceptors in rat cortex. Cortical alpha 2-adrenoceptors were decreased by 14 days of DMI injection or 10 days of ECS treatment (ECS x 10) and these effects were identical in both sexes. These receptors were not altered by 2 days administration of DMI or ECS. Cortical beta-adrenoceptors were reduced in male and female rats by 2 and 14 days of DMI injection and by ECS x 10, but not ECS x 2. 5. Viewed overall, the data show differences in alpha 2-adrenoceptor function between the sexes, as determined by clonidine-induced hypoactivity and the responsiveness of this paradigm to repeated administration of DMI and ECS. In contrast, no differences were observed in complementary alpha 2- and beta-adrenoceptor binding experiments using rat cortical tissue.

The influence of injection of oestradiol to female rats on changes in alpha 2- and beta-adrenoceptor function induced by repeated administration of desipramine or electroconvulsive shock

Repeated daily administration to female rats of either an electroconvulsive shock (110 V, 1 sec) or desipramine (DMI; 5 mg/kg x 2) caused a progressive decrease in presynaptic alpha 2-adrenoceptor function assessed by the hypoactivity (sedation) response to clonidine (0.5 mg/kg). This reduction was maximal after approximately seven electroshocks or 8-12 days of injection of DMI. Daily administration of oestradiol (100 micrograms s.c.), starting one day prior to the commencement of administration of DMI or treatment with electroshock, markedly accelerated the onset of decreased hypoactivity responses to clonidine, but did not alter the maximum reduction induced by repeated injection of DMI or administration of electroshock. Injection of oestradiol alone had no effect on the responses to clonidine. Administration of DMI for 14 days decreased the number of both alpha 2- and beta-adrenoceptors in the cortex. Cortical beta-, but not alpha 2-adrenoceptors, were also decreased after 4 days of injection of DMI. Two and ten electroshocks moderately increased and decreased cortical alpha 2-adrenoceptors, respectively. beta-Adrenoceptors were also decreased by ten electroshocks, but two were without effect. Simultaneous administration of oestradiol had little influence on the changes in the binding of alpha 2- or beta-adrenoceptors induced by repeated administration of DMI or treatment with electroshock. Oestradiol increased the numbers of cortical alpha 2- and beta-adrenoceptors 3 and 15 days after injection, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Binding of tritiated yohimbine to platelets in women with maternity blues

Platelet alpha 2-adrenoceptor binding was measured in 108 women in the 36th week of pregnancy, at ten and twenty days and at three and six months post-partum. An age matched non-pregnant control group of women (N = 25) was also studied. The number (Bmax) of alpha 2-adrenoceptors was elevated antepartum but fell to control values on the tenth post-partum day. At three and six months post-partum, however, alpha 2-adrenoceptor Bmax was again increased. Women who developed maternity blues (N = 59) had significantly more platelet alpha 2-adrenoceptors than those who did not (N = 49) at both ten and twenty days post-partum. In addition their alpha 2-adrenoceptor Bmax was greater than controls at all time points measured except the tenth post-partum day. In contrast, the alpha 2-adrenoceptor Bmax of women without the blues did not differ from controls at any stage. It is suggested that women who develop maternity blues may have a relatively enduring abnormality in alpha 2-adrenoceptor sensitivity which is associated with psychological symptoms when concentrations of circulating sex-steroids suddenly change.

Human platelet 5-hydroxytryptamine receptors: binding of [3H]-lysergic acid diethylamide (LSD). Effects of chronic neuroleptic and antidepressant drug administration

Chronic treatment with phenothiazines and thioxanthenes has been found to enhance 5-HT-induced aggregation of human platelets. A method has been developed to study 5-HT2 receptor binding sites on platelets utilising [3H]-LSD and more recently 125I/LSD. Results are presented which suggest that the LSD binding site is indeed the 5-HT2 binding site and that the LSD binding characterises the specific receptor responsible for 5-HT-induced shape change and aggregation. In a group of patients receiving phenothiazines or thioxanthenes, the Bmax of LSD binding was increased. The mean binding affinity was decreased possibly due to a persistence of neuroleptic in the platelet membrane preparation. Analysis showed that this was not the reason why the mean binding capacity was increased. The results show that chronic phenothiazine and thioxanthene delta treatment 'up-regulates' platelet 5-HT2 binding sites and that this may be accompanied by increased sensitivity to platelet aggregation by 5-HT. In normal subjects desipramine treatment increased the Bmax of platelet LSD binding and this was accompanied by an increased prolactin response to tryptophan which is thought to be mediated by central 5-HT function.

Development of kinaesthetic sensitivity and motor performance in children

Kinaesthetic acuity of 100 children, aged from four to 13 years, was assessed and a developmental trend is described. The relationship between kinaesthetic acuity and motor performance on a range of motor tests commonly used for assessing children was also examined, and contrary to expectation no evidence of a relationship was discovered. There is little reported evidence for this relationship in the literature, and some possible reasons for this are discussed. A staircase procedure for threshold estimation was used and is described in detail.

Treatment of hypertension with enalapril and hydrochlorothiazide or enalapril and atenolol: contrasts in hypotensive interactions

To determine the nature of the resultant effect on blood pressure when angiotensin converting enzyme (ACE) inhibitors are combined with other hypotensive agents in the treatment of uncomplicated essential hypertension, two randomized, double-blind, crossover trials were conducted. In each trial there were four treatment phases, each 4 weeks in duration, comprising a 2 X 2 factorial experiment. Twenty-one patients completed the first study in which the effects of enalapril (10 mg twice daily) were compared with hydrochlorothiazide (25 mg twice daily), with the two drugs in combination and with placebo. All blood pressure parameters were reduced in the three active treatment phases compared with placebo (P less than 0.001). Enalapril and hydrochlorothiazide were equally effective and in combination their hypotensive effects were fully additive. Sixteen patients completed the second study which compared the effects of enalapril (20 mg daily), atenolol (50 mg daily), the two drugs in combination and placebo. All blood pressure parameters were again reduced in all phases compared with placebo (P less than 0.001). Enalapril and atenolol were also equally effective, but in combination their hypotensive effects were less than fully additive, with attenuation of the potential additive response by 30-50%. These results indicate that a diuretic-ACE inhibitor combination can be expected to have a greater hypotensive effect than a beta-blocker-ACE inhibitor combination. Both hydrochlorothiazide and atenolol increased plasma atrial natriuretic peptide (ANP) concentrations (P less than 0.01), suggesting that ANP could contribute to the hypotensive effects of these two drug classes.

The influence of L-triiodothyronine (T3) on the effects of repeated administration of desipramine or electroconvulsive shock on alpha 2- and beta-adrenoceptor function in the brain of the rat: implications for the potentiation of antidepressant therapy by T3

Repeated, daily administration of either an electroconvulsive shock (ECS; 110 V, 1 sec) or desipramine (DMI; 5 mg/kg X 2) to rats caused a progressive decrease in the function of presynaptic alpha 2-adrenoceptors, assessed by the hypoactivity (sedation) response to clonidine (0.2 mg/kg). This attenuation required approximately 7 days' administration of either treatment for maximum effect. A single injection of triiodothyronine (T3; 100 micrograms/kg) on day 1 of the treatment markedly accelerated the decreased responses to clonidine induced by DMI or electroconvulsive shock, but did not alter the maximum attenuation. By itself T3 did not affect the hypoactivity responses. alpha 2-Adrenoceptors, measured by the binding of [3H]idazoxan in the cortex, which are believed to be predominantly postsynaptic, were decreased by 14 days of DMI or electroconvulsive shock for 10 days, but not 2 days of either treatment. Triiodothyronine did not influence the decreased number of alpha 2-adrenoceptors induced by DMI or electroconvulsive shock but may have delayed the onset produced by DMI. Binding to beta-adrenoceptors in the cortex was measured using [3H]dihydroalprenolol. This was significantly decreased by 14 days administration of DMI, but not significantly by electroconvulsive shock for 10. Down-regulation of beta-adrenoceptors, induced by DMI was rapid, being observed after 1 day of treatment. Injection of T3 did not influence the final decreases produced by DMI or electroconvulsive shocks but moderately delayed their onset. Triiodothyronine alone caused a 25% reduction in cortical beta-adrenoceptors 24 hr after injection.(ABSTRACT TRUNCATED AT 250 WORDS)

Platelet 5-HT receptor binding during depressive illness and tricyclic antidepressant treatment

5-Hydroxytryptamine (5-HT) receptor binding was determined in intact human platelets using 125I-iodolysergic acid diethylamide (125I-iodoLSD). The assay revealed that platelets possess a single population of specific binding sites for 125I-iodoLSD which have a high affinity for the 5-HT2 receptor antagonists, ketanserin and spiperone. There was no difference in platelet 125I-iodoLSD receptor binding between depressed patients and controls. However, treatment with tricyclic antidepressants increased the number of 125I-iodoLSD receptor binding sites without significantly altering their affinity.

Dieting and weight loss in volunteers increases the number of alpha 2-adrenoceptors and 5-HT receptors on blood platelets without effect on [3H]imipramine binding

Platelet monoamine receptor binding was determined in normal male and female subjects before and at the end of a 2- to 3-week weight reducing diet (1200 kcal daily). Dieting was associated with an increase in platelet binding sites for both [3H]yohimbine and [125I]iodolysergic acid diethylamide (iodoLSD). The affinity at the platelet [125I]iodoLSD binding site was reduced. In contrast, [3H]imipramine binding was unchanged. These results have important implications for studies that employ platelet binding as a peripheral marker of neurotransmitter function in psychiatric illness.

Behavioural and biochemical evidence for the release of noradrenaline in mouse brain by TRH and some of its biologically stable analogues

Small doses of clonidine probably induce hypoactivity (a distinct form of sedation) by stimulating presynaptic alpha 2-adrenoceptors. This was attenuated by injection of 0.1-10 mg/kg of thyrotropin releasing hormone (TRH) or its biologically stable analogues, CG3509, CG3703 and RX77368, when these were given 10 min before clonidine. This effect was dose-dependent in all cases, but the analogues were more potent than TRH. The TRH metabolites, TRH acid and histidyl-proline diketopiperazine (10 mg/kg) were without effect. This response was still attenuated by the analogues, but not TRH, when these were given 1 hr before clonidine. The results, therefore, suggested that it was the basic tripeptide structure which was active and TRH was less potent than its analogues because of rapid metabolism. Attenuation of hypoactivity by TRH and analogues was not due to increased dopaminergic function because apomorphine (5 mg/kg) was ineffective. Thyrotropin releasing hormone (20 mg/kg), CG3509 (10 mg/kg) and CG3703 (1 mg/kg) also induced locomotor activity and produced various other behavioural changes. This was inhibited by prazosin (3 mg/kg) and haloperidol (0.5 mg/kg) but not by yohimbine (1 mg/kg). Apomorphine (5 mg/kg)-induced activity was inhibited by haloperidol and yohimbine but not by prazosin. This indicated that the activity produced by the TRH compounds, but not apomorphine, was partly mediated by alpha 1-adrenoceptors. Both CG3509 (10(-5) and 10(-4) M) and RX77368 (10(-4) M) evoked the release of endogenous noradrenaline from slices of hypothalamus in vitro. The TRH analogues, however, had no affinity for alpha 1- or alpha 2-adrenoceptors in ligand-receptor binding experiments. Viewed overall, the data showed that TRH and its analogues induced the release of noradrenaline in the brain. In addition, a comparison of the behavioural effects of TRH compounds with dopamine and alpha 1-adrenoceptor agonists suggested that in mice these behavioural responses resulted from stimulation of both noradrenergic and dopaminergic function.

Binding of yohimbine and imipramine to platelets in depressive illness

Radioligand binding to intact platelets was carried out in antidepressant-free patients and the 1 mg dexamethasone suppression test (DST) was performed. There were no differences in binding characteristics between patients and controls for either [3H]yohimbine or [3H]imipramine. There were no differences in binding between patients classified as endogenous using the Newcastle Scale, compared with non-endogenous patients, and no difference between DST suppressors and non-suppressors. The severity of depression did not affect binding values. After 4-6 weeks antidepressant treatment [3H]yohimbine binding was significantly reduced but [3H]imipramine binding was unaffected.

Increases in plasma neuropeptide Y concentrations during sympathetic activation in man

Neuropeptide Y (NPY) coexists with noradrenaline in postganglionic sympathetic neurons. In order to test the hypothesis that NPY may be released along with catecholamines by activation of the sympathoadrenal system we measured plasma NPY-like immunoreactivity (NPY-LI) concentrations during cold pressor test, head up tilt and bicycle exercise in healthy volunteers. All 3 manoeuvres resulted in elevation of blood pressure, heart rate and plasma noradrenaline and adrenaline concentrations. These were accompanied by increases in plasma NPY-LI concentrations on cold pressor test and exercise, but not with head up tilt. The increases in both NPY-LI and catecholamines were greatest with exercise. These findings suggest that NPY is released at the same time as noradrenaline when sympathetic noradrenergic nerves are activated.

Effects of enalapril and hydrochlorothiazide on blood pressure, renin-angiotensin system, and atrial natriuretic factor in essential hypertension: a double blind factorial cross-over study

The hypotensive and hormonal effects of the angiotensin converting enzyme (ACE) inhibitor enalapril (10 mg twice daily) were compared with those of hydrochlorothiazide (25 mg twice daily), with the two drugs in combination and with placebo in 21 patients with essential hypertension. For each patient there were four randomised double-blind treatment phases, each of four weeks' duration, which comprised a 2 X 2 factorial experiment. All blood pressure parameters were reduced in the three active treatment phases compared to placebo (p less than 0.001). Supine mean blood pressures were 119 mmHg (placebo), 113 mmHg (hydrochlorothiazide), 108 mmHg (enalapril), and 98 mmHg (hydrochlorothiazide plus enalapril) (SEM 3 mmHg, ANOVA). Enalapril and hydrochlorothiazide were equally effective and well tolerated and their hypotensive effects were additive. Enalapril increased plasma renin activity (PRA), reduced plasma angiotensin II (AII) and aldosterone concentrations, and reduced ACE activity, whereas hydrochlorothiazide increased PRA, plasma AII, and aldosterone concentrations without altering ACE activity. With combination treatment the effects of enalapril on PRA and plasma AII concentrations were potentiated whereas those on plasma aldosterone concentration and ACE activity were additive. Atrial natriuretic factor plasma concentration in the placebo phase was 92 pg/ml and increased to 145 pg/ml in the hydrochlorothiazide phase (p less than 0.001, SEM 13 pg/ml), but there was no significant change in either the enalapril or combination phases.

Plasma neuropeptide y levels rise in patients undergoing exercise tests for the investigation of chest pain

Neuropeptide Y (NPY) is colocalised with noradrenaline in post-ganglionic sympathetic neurons. In order to examine the possibility that activation of the sympathetic nervous system might cause release of NPY into the plasma NPY levels were measured in 16 patients undergoing exercise tests for investigation of chest pain. Plasma NPY concentrations rose in 14 out of the 16 patients, and the mean level of plasma NPY increased from 335 (s.e.m. = 37) to 455 (s.e.m. = 41) pg/ml. Plasma noradrenaline and adrenaline levels increased four- and two-fold respectively. The increase in NPY correlated with the increase in noradrenaline, suggesting that NPY may be released with noradrenaline when sympathetic noradrenergic nerves are activated.

Measurement of kinaesthetic sensitivity

Two recent papers (Laszlo and Bairstow 1980, Bairstow and Laszlo 1981) have used the method of constant stimuli to measure kinaesthetic difference thresholds. If this method is used, however, certain constraints must be observed: these concern the values of the stimuli relative to the threshold, and the numbers of observations made at each value. Laszlo and Bairstow appear to have neglected these constraints, which must cast doubt on their results. In any case, the method of constant stimuli has largely been superseded by staircase techniques for threshold estimation, on grounds of economy of trials for a given level of accuracy in estimation. It is concluded, therefore, that the details of the method as described by Laszlo and Bairstow are unsuitable for testing kinaesthetic sensitivity, and that other methods are preferable.

Desipramine treatment in normal subjects. Effects on neuroendocrine responses to tryptophan and on platelet serotonin (5-HT)-related receptors

Normal subjects took the tricyclic antidepressant, desipramine hydrochloride, for 16 days. Following treatment there was an increase in the number of specific binding sites on the platelet for both tritiated imipramine and tritiated LSD, the latter site probably representing a platelet serotonin (5-HT) receptor. During desipramine treatment the prolactin response to tryptophan (L-tryptophan) was enhanced, and this enhancement correlated with the increase in platelet LSD binding. The results confirm previous observations that desipramine administration increases certain 5-HT-mediated neuroendocrine responses. Our findings further indicate that desipramine may alter both 5-HT uptake and 5-HT receptor sensitivity, and suggest that the platelet LSD receptor may in certain conditions provide a useful model of 5-HT receptors in the brain.

Increased platelet membrane [3H]-LSD binding in patients on chronic neuroleptic treatment

Using a [3H]-lysergic acid diethylamide [( 3H]-LSD) binding technique, platelet 5-hydroxytryptamine (5-HT) receptor number and affinity were compared in schizophrenics treated with depot thioxanthenes and phenothiazines and controls. There was an approximately 30% increase in platelet receptor number (Bmax) in the patient group. There was a decrease in affinity (increase in Kd) of about 30% in the patient group. This was probably due to the persistence of the neuroleptic in the platelet membrane preparation. There was a weak positive correlation between receptor number and total neuroleptic dosage. The increased number of 5-HT receptors is consistent with the previously reported enhancement of 5-HT-induced platelet aggregation in patients treated with long-term phenothiazines and thioxanthenes. Our findings are compatible with 5-HT up-regulation in human platelets produced by depot neuroleptic therapy. It is not known whether parallel changes may be occurring in brain 5-HT receptors.

Cardiovascular effects of intracisternal 6-hydroxydopamine and of subsequent lesions of the ventrolateral medulla coinciding with the Al group of noradrenaline cells in the rabbit

The acute cardiovascular effects of intracisternal injections of 6-hydroxydopamine (6-OHDA), 5,6-dihydroxytryptamine and 5,7-dihydroxytryptamine and the degree of neurotransmitter depletion achieved by such injections were studied. The two different vehicles used--0.2% ascorbic acid in 0.9% NaCl, or 0.9% NaCl--had little effect on the cardiovascular response to 6-OHDA injections but had a striking effect on levels of noradrenaline (NA) subsequently measured in the thoracic spinal cord. 6-OHDA (600 micrograms kg-1 free base) dissolved in normal saline depleted spinal cord NA to less than 1% of control levels whereas the same dose of 6-OHDA dissolved in ascorbate saline only depleted spinal cord NA to 24% of control levels. The degree of depletion of NA in medulla, pons and hypothalamus was similar in the two groups. Ascorbic acid also appeared to contribute to the non-specific toxicity of intracisternal injections of 6-OHDA. The hypertension and bradycardia that followed lesions of the ventrolateral medulla coinciding with the A1 group of noradrenergic cells (Al lesions) were attenuated in animals in which spinal cord NA had been depleted to 2% of control using 6-OHDA in normal saline. However, pretreatment with 6-OHDA in ascorbate saline, which only reduced spinal cord NA to 23% of control, had no effect on the cardiovascular response to Al lesions. It seems likely that the effects of Al lesions are mediated, at least in part, by NA projections descending within the spinal cord.

The mechanism of hypertension and bradycardia following lesions of the caudal ventrolateral medulla in the rabbit: the role of sympathetic nerves, circulating adrenaline, vasopressin and renin

Lesions of the ventrolateral medulla of the rabbit, coinciding with the A1 noradrenaline cell bodies (A1 lesions) produced fortyfold increases in the plasma levels of vasopressin and adrenaline, a twofold increase in plasma noradrenaline and a substantial increase in plasma renin activity. These increases accompanied the hypertension and bradycardia that follow A1 lesions. The vasoconstriction and hypertension were completely abolished by phentolamine, an alpha-adrenoceptor antagonist, when it was administered before lesions and were markedly reduced when it was given after lesions. On the other hand, administration of an antagonist to the vasoconstrictor action of vasopressin (d(CH2)5Tyr(Me)AVP) or an angiotensin converting enzyme inhibitor had little effect. Prior removal of the adrenal glands prevented any rise in plasma adrenaline levels but had no effect on the pressure response to subsequent A1 lesions. These results indicate that the vasoconstriction and hypertension were predominantly mediated by alpha-adrenoceptor stimulation, acting mainly through sympathetic vasoconstrictor nerves. The fall in heart rate following A1 lesions was approximately halved by pretreatment either with d(CH2)5Tyr(Me)AVP alone, or by blockade of the vagus and sympathetic with scopolamine and propranolol; it was completely abolished by combined pretreatment with all three agents. The experiments show that vasopressin release makes a major contribution to the bradycardia acting at least in part through mechanisms that are independent of cardiac vagal or sympathetic nerves.

Effects of vasopressin on heart rate in conscious rabbits

The effects of vasopressin on heart rate and on the baroreceptor-heart period reflex were assessed during graded intravenous infusions of arginine vasopressin. Infusions which elevated plasma arginine vasopressin to 200 pg/ml had no effect on blood pressure, but induced a fall in heart rate and cardiac output and an increase in peripheral resistance. These effects were unaltered by vagal blockade with methylscopolamine and cardiac sympathetic blockade with propranolol but were prevented by pretreatment with a specific vascular antagonist to vasopressin, d(CH2)5Tyr(Me)AVP. Baroreflex control of heart rate was studied during vasopressin infusion by monitoring the heart period responses to graded changes in mean arterial blood pressure produced by inflation of balloon occluders around the abdominal aorta and thoracic vena cava. Elevation of plasma arginine vasopressin to 50 pg/ml and 200 pg/ml had no significant effect on the slope or sensitivity of the baroreceptor-heart period reflex but increased the maximum bradycardia elicited in response to large increases in blood pressure. We conclude that at physiological levels, arginine vasopressin has a direct cardiodepressant action that is not dependent on cardiac vagal or sympathetic activity. Our results indicate that arginine vasopressin increases the maximum bradycardia that can be elicited through baroreceptor reflexes but does not alter the slope relating change in heart rate to change in blood pressure.

Criteria for detection of Clostridium difficile toxin production by counterimmunoelectrophoresis

Counterimmunoelectrophoresis (CIE) was compared with a cytotoxicity assay and isolation of toxin-producing Clostridium difficile for the diagnosis of antibiotic-associated diarrhea. Standardized criteria for CIE positivity were established as two major precipitin lines with specific C. difficile antitoxin. Using these criteria on 425 fecal specimens, we determined the sensitivity of CIE (80%) to be comparable to that of the cytotoxicity assay (82%). Both methods were highly specific. With carefully controlled techniques, CIE can be used in routine diagnostic laboratories to screen for toxigenic C. difficile.

Cardiac performance in the conscious rabbit with acute hypertension following brainstem lesions coinciding with the A1 group of catecholamine neurons

Electrolytic lesions of the ventrolateral medulla, coinciding with the A1 catecholamine cells of the conscious rabbit (A1 lesions) cause acute hypertension and bradycardia and in some animals, pulmonary oedema. We have assessed the change in cardiac performance after an A1 lesion, the role of cardiac autonomic effectors in this change; and the mechanism of the pulmonary oedema. Following A1 lesions there was a profound (over 100%) rise in total peripheral resistance and a fall in cardiac output which was mainly due to a fall in stroke volume since it occurred even in animals in which the heart rate was held constant by atrial pacing. This reduced stroke volume occurred despite a 40% increase in myocardial contractility (peak LV dP/dt) and elevation of left ventricular end diastolic pressure. beta-Adrenoceptor blockade with propranolol abolished the rise in peak LV dP/dt, while vagal blockade with methylscopolamine abolished the bradycardia and combined blockade with propranolol and methylscopolamine abolished the rise in peak LV dP/dt and reduced the bradycardia. In rabbits which developed pulmonary oedema, left ventricular end diastolic pressure rose to 35 +/- 3.5 compared to 16 +/- 2.7 mmHg in those which did not, suggesting that the pulmonary oedema was due to raised left ventricular filling pressure.

Decreased platelet 3H-imipramine binding sites in classical migraine

Patients with classical migraine investigated between attacks had significantly fewer platelet 3H-imipramine binding sites than control subjects and this finding was more marked in males than in females. There was no abnormality of binding characteristics of platelet 5-hydroxytryptamine receptors or of platelet alpha 2-adrenoceptors. Because the reduced 3H-imipramine binding capacity was found in classical migraineurs who were investigated between attacks, it may reflect a predisposition to migraine rather than being a consequence of attacks.

A classification of manipulative hand movements

The nature of manual manipulation of objects is discussed. It is argued that a functional distinction should be made between palmar grips which immobilise an object in the hand, and digital patterns which permit manipulation. Such a distinction is separate from any anatomically defined power and precision configurations. Manipulative hand movements may be grouped into three classes, based on differences between sequenced patterns of movement and synergies, the latter being further subdivided into simple and reciprocal patterns. Within each of the three classes, a number of individual movement patterns are described. These differ mainly in the number of digits involved and the way in which the thumb is employed. The classification is concerned with movements of the digits directed at manipulating an object within the hand. It is not concerned with movements of the hand as a whole, using the wrist or more proximal joints, while holding an immobilised object.

The Schematic Representation of Effector Function Underlying Perceptual-Motor Skill

Conceptual and methodological problems related to Schmidt' (1975) motor schema theory are discussed. In particular, the motor schema is interpreted as representing the dynamics of the system being controlled, which may or may not be associated with a referent movement pattern. Furthermore, it is suggested that prior familiarity with a control system's dynamics is a critical but uncontrolled factor in tests of the theory, and largely accounts for their equivocal findings. These ideas are examined by two experiments in which subjects had to bimanually control the movement of a computer-displayed cursor along a track on a CRT screen. Different track orientations required different patterns of movement not entailing a single generalized motor program. Experiment 1 shows that variable track performance with a given control system, results in better transfer to novel tracks than does fixed practice. Experiment 2 demonstrates that altering the control system disrupts performance whether or not the required movements remain the same. These results indicate the need for a fundamental modification of schema theory, such that a schematic representation of effector-environment relations (effector function) is available independently of particular movement patterns used in its acquisition.

A comparison of alpha 2-adrenoreceptor binding characteristics of intact human platelets identified by [3H]-yohimbine and [3H]-dihydroergocryptine

The binding characteristics of [3H]-yohimbine on intact human platelets were investigated and compared to those of [3H]-dihydroergocryptine. A significant correlation (r = 0.92, P less than 0.01, n = 7) was observed between the inhibition of [3H]-yohimbine binding and of noradrenaline-induced platelet aggregation, indicating that [3H]-yohimbine binds to the alpha 2-adrenoreceptor responsible for noradrenaline-induced platelet aggregation. The binding capacity of [3H]-yohimbine in 20 young male volunteers was 39 +/- 2.2 fmol/10(8) platelets (mean +/- s.e.m.). This is considerably lower than the binding capacity of [3H]-dihydroergocryptine previously reported. Simultaneous analysis of [3H]-yohimbine and [3H]-dihydroergocryptine binding in 10 subjects showed a significantly lower binding capacity for [3H]-yohimbine (P less than 0.001, paired t-test). This difference was not present in every subject, and was consistent within individuals on repeated testing. Possible causes of this difference in radioligand binding are discussed.

Changes in platelet alpha 2-adrenoceptor binding post partum: possible relation to maternity blues

Platelet alpha 2-adrenoceptor binding characteristics were investigated in 28 healthy women during the peripartum period. The number of platelet alpha 2-adrenoceptors fell after childbirth, corresponding to a fall in the circulating levels of oestrogen and progesterone. Two-thirds of the women had an episode of maternity blues. At 7-10 days post partum the platelet alpha 2-adrenoceptor capacity in these subjects was significantly higher than in those women who did not show signs of maternity blues and significantly higher than a control group of normally menstruating women. We conclude that platelet alpha 2-adrenoceptors may be affected by the circulating levels of endogenous oestrogen and progesterone and that a delayed or diminished fall in platelet alpha 2-adrenoceptor capacity after childbirth may be associated with the development of maternity blues.

Baroreceptor reflexes in conscious guinea-pigs are unaffected by depletion of cardiovascular substance P nerves

Adult guinea-pigs were injected with doses of capsaicin increasing from 10 mg/kg to 400 mg/kg over 6-days. The guinea-pigs were supplied with indwelling arterial cannulae 14 days later and the next day cardiovascular function was assessed in the conscious animals. Resting blood pressures and heart rates were recorded and then baroreceptor reflex function was evaluated by recording the changes in heart period which were evoked by blood pressure responses to injections of phenylephrine and glyceryl trinitrate. Substance P was measured by radioimmunoassay and its localization examined by immunohistochemistry. The capsaicin treatment caused a substantial reduction in substance P levels in vascular and cardiac nerves. However, there were no changes in resting heart rate, blood pressure or baroreceptor sensitivity. It is concluded that the widespread substance P nerves associated with the heart and blood vessels are not necessary for baroreceptor reflex function. Their role or roles remain unknown.

The effects of monovalent and divalent cations on the alpha-adrenoceptor of intact human platelets

1 We have examined the effects of monovalent and divalent cations and purine nucleotides on the binding of agonists and antagonists to the alpha-adrenoceptor of intact human platelets. 2 Replacement of Na+ (150mM) by NH4+ (150mM) in the incubation medium significantly reduced the binding affinity of [3H]-dihydroergocryptine (P less than 0.05) but did not alter the binding capacity. The competitive binding affinity of adrenaline and noradrenaline was unaltered. 3 The addition of Ca2+ (1mM) or Mg2+ (1mM) to the platelet suspension significantly reduced the platelet alpha-adrenoceptor capacity as indicated by either [3H]-dihydroergocryptine (P less than 0.05) or [3H]-yohimbine (P less than 0.01; Ca2+ only). 4 The addition of Ca2+ (1mM) or Mg2+ (1mM) had no effect on the binding affinity of [3H]-dihydroergocryptine but significantly reduced that of [3H]-yohimbine (P less than 0.05). The competitive affinity of adrenaline and noradrenaline determined by inhibition of [3H]-dihydroergocryptine binding, was unchanged in the presence of either cation. 5 Addition of the purine nucleotides ADP, ATP, GDP or GTP (final concentration 10 microM), either alone or in the presence of 1 mM Ca2+ or 1 mM Mg2+, had no effect on the binding of [3H]-dihydroergocryptine or on the competitive affinity of adrenaline or noradrenaline. 6 We conclude that the alpha-adrenoceptor of intact human platelet displays the binding characteristics of the alpha 2L form of the receptor previously identified in the platelet lysate preparation.

The binding characteristics of [3H]-dihydroergocryptine on intact human platelets

1 We have characterized the binding of [3H]-dihydroergocryptine to intact human platelets. 2 The values of the association and dissociation rate constants, affinity and capacity of specific [3H]-dihydroergocryptine binding on intact cells closely resemble those previously reported on the human platelet lysate preparation. 3 The affinity of alpha-adrenoceptor antagonists, determined from inhibition of [3H]-dihydroergocryptine binding, is similar in intact and lysed platelet preparations, but the affinity of agonists is considerably lower in intact cells. 4 The potency of alpha-adrenoceptor antagonists as inhibitors of noradrenaline-induced platelet aggregation and as inhibitors of [3H]-dihydroergocryptine binding on intact platelets demonstrate a significant correlation (r = 0.92, p less than 0.01). 5 The affinity and capacity of [3H]-dihydroergocryptine binding to platelets from a group of healthy, young, male subjects show a high degree of consistency both between subjects (Kd = 2.81 +/- 0.27 nM; Bmax = 63 +/- 3 fmol/10(8) platelet: mean +/- s.e. mean, n = 10) and between sampling occasions in a single subject (Kd = 3.28 nM +/- 13%; Bmax = 70 fmol/10(8) platelet +/- 16%: mean +/- coefficient of variation, n = 5). 6 There is no significant difference in the binding capacity of platelets from a group of elderly male subjects (mean age 73) compared to those from young males (mean age 27) or elderly females (mean age 77). The affinity of binding is slightly but significantly (P less than 0.05) higher in the elderly male group compared to the two other groups. 7 We conclude that [3H]-dihydroergocryptine binds to the alpha 2-adrenoceptor of intact human platelets which is responsible for noradrenaline-induced platelet aggregation. The high consistency of the binding characteristics of [3H]-dihydroergocryptine indicate that this assay may be useful as a monitor of platelet alpha-adrenoceptor sensitivity in clinical investigation.

Oestrogen and progesterone change the binding characteristics of alpha-adrenergic and serotonin receptors on rabbit platelets

The binding characteristics of the alpha-adrenergic and serotonin receptors on intact rabbit platelets were identified using [3H]-dihydroergocryptine and [3H]-5-hydroxytryptamine respectively. In untreated female rabbits a single slpha-adrenoceptor and two serotonin receptors were identified with ligand affinities similar to those in human platelets. The effects of oestrogen and/or progesterone on the alpha-adrenergic and serotonin receptors of rabbit platelets were studied. Oestrogen alone increased the capacity of serotonin receptors but reduced that of the alpha-adrenoceptor. Oestrogen plus progesterone reduced the capacity of both receptors and reduced the affinity of the alpha-adrenoceptor. The possible mechanisms of the steroid-induced changes and the implications of these with regard to the effects of the oral contraceptive pill are discussed.

Cigarettes and accelerated hypertension

The smoking and drinking habits of 58 patients with accelerated hypertension were compared with those of a control group of 58 patients with benign hypertension, each individually matched for age, sex and date of presentation. Thirty-eight (66 percent) of the patients with accelerated hypertension were regular smokers compared to 26 (45 percent) of the control group. This excess of smokers was significant, but the average number of cigarettes smoked by smokers in the two groups was similar. The number of patients known to consume alcohol was the same in the two groups; and there were no significant differences in amount of alcohol drunk. Smoking and alcohol habits were not related. Thirty-six patients (62 percent) with accelerated hypertension had serum creatinine levels greater than 0.12 mmol/l compared with nine (16 percent) of the control group. Seventeen (29 percent) patients with accelerated hypertension were known to have died compared with five (9 percent) of the control group. This survey confirms that, as shown by recent studies in Britain, smoking is more common in patients presenting with accelerated than with benign hypertension. It appears that hypertensive patients who smoke regularly are more likely to develop the accelerated phase than those who do not.

Effect of oral contraceptives on platelet noradrenaline and5-hydroxytryptamine receptors and aggregation

Characteristics of receptor sites on platelets for noradrenaline (NA) and serotonin (5-HT) changed significantly between day 21 and day 28 of treatment in healthy women taking oral contraceptives. NA-induced and 5-HT-induced platelet aggregation and 5-HT uptake vaired accordingly. In untreated women with normal cycles no changes in either receptor site or in platelet function occurred between the luteal and postmenstrual phases. It is concluded that the observed changes are due to a pharmacological effect of the oral contraceptive rather than a normal physiological variation.

The effect of visual frame of reference on a judgement of plane stimulus orientation by children

Three studies are reported with children aged 4 1/2 to 9 1/2 years and also with educationally subnormal children, in which it was found that up to about 7 years children's selection of one of a pair of line stimuli as 'falling over' is affected by the nature of the visual surround contours provided. Both the form of the stimulus surround and the presence or absence of a baseline tilted 45 degrees relative to the horizontal were found to affect the children's judgements. The plane (horizontal or vertical) in which the stimuli were presented had no effect on the results. It is argued that while the results show the influence of the visual surround on children's comprehension of 'falling over', this may not be wholly explicable in terms of surround contour matching, as conventionally correct judgements were obtained in the absence of all straight line contours in the immediate surround.

Changes in muscarinic ligand binding to intestinal muscle strips produced by pre-exposure to hypotonic conditions

The extent of the binding of [3H]propylbenzilylcholine mustard (3H-PrBCM) to muscarinic receptors in longitudinal muscle strips from guinea-pig small intestine is increased by nearly 50% when the strips are preexposed to distilled water before measurement of 3H-PrBCM binding in Krebs-Henseleit solution. The apparent rate constant for 3H-PrBCM-receptor complex formation is more than double that of intact strips. The curves for the inhibition of 3H-PrBCM binding by methylatropinium bromide in normal and treated strips are superimposable, but, in contrast, distilled water pretreatment shifts the inhibition curve for carbachol to lower concentrations by a factor of 5-6. The inhibition curve for methylfurmethide is also shifted, by a factor of approximately 4, but the effect on the curve for hexyltrimethylammonium (C6TMA) is slight. The relative inhibition produced by benzhexol in the two preparations was variable. Comparison of the rate of equilibration of benzhexol with muscarinic receptors in intact and in distilled water pretreated muscle indicates that this inconsistency is unlikely to be due to incomplete equilibration.

Changes in rat hind limb vascular resistance following intracerebroventricular drug administration

The right hind limbs of rats (which had previously implanted intraventricular guide cannulae) were isolated from the systemic circulation, but with the nerves to the limb remaining intact, and perfused using a constant output blood pump. Using this preparation, changes in vascular resistance, blood pressure and heart rate were monitored following injection of noradrenaline, phentolamine and propranolol into the lateral cerebral ventricles (i.c.v.) of rats anaesthetised with alpha-chloralose. All three drugs lowered blood pressure. Noradrenaline administered i.c.v. induced a nervously mediated vasocilatation and an insignificant fall in heart rate whereas i.c.v. phentolamine administration was followed by a nervously mediated vasoconstriction in the isolated hind limb and a gradual rise in heart rate. After i.c.v. administration of propranolol there was no evidence of an immediate nervously mediated vasodilatation but heart rate fell significantly. Following i.c.v. phentolamine or propranolol vasodilatation did not occur in the hind limb until after the time taken for circulating blood ro reach the isolated vascular bed. The vasodilatatory and hypotensive responses to i.c.v. noradrenaline were not evident following prior i.c.v. injection of phentolamine. These results indicate the suitability of this preparation for investigations of central actions of other drugs.