Intensive glucose control and macrovascular outcomes in type 2 diabetes.

AIMS/HYPOTHESIS: Improved glucose control in type 2 diabetes is known to reduce the risk of microvascular events. There is, however, continuing uncertainty about its impact on macrovascular disease. The aim of these analyses was to generate more precise estimates of the effects of more-intensive, compared with less-intensive, glucose control on the risk of major cardiovascular events amongst patients with type 2 diabetes. METHODS: A prospectively planned group-level meta-analysis in which characteristics of trials to be included, outcomes of interest, analyses and subgroup definitions were all pre-specified. RESULTS: A total of 27,049 participants and 2,370 major vascular events contributed to the meta-analyses. Allocation to more-intensive, compared with less-intensive, glucose control reduced the risk of major cardiovascular events by 9% (HR 0.91, 95% CI 0.84-0.99), primarily because of a 15% reduced risk of myocardial infarction (HR 0.85, 95% CI 0.76-0.94). Mortality was not decreased, with non-significant HRs of 1.04 for all-cause mortality (95% CI 0.90-1.20) and 1.10 for cardiovascular death (95% CI 0.84-1.42). Intensively treated participants had significantly more major hypoglycaemic events (HR 2.48, 95% CI 1.91-3.21). Exploratory subgroup analyses suggested the possibility of a differential effect for major cardiovascular events in participants with and without macrovascular disease (HR 1.00, 95% CI 0.89-1.13, vs HR 0.84, 95% CI 0.74-0.94, respectively; interaction p = 0.04). CONCLUSIONS/INTERPRETATION: Targeting more-intensive glucose lowering modestly reduced major macrovascular events and increased major hypoglycaemia over 4.4 years in persons with type 2 diabetes. The analyses suggest that glucose-lowering regimens should be tailored to the individual.

Impact of a short home-based yoga programme on blood pressure in patients with hypertension: a randomized controlled trial in primary care.

The present study was designed to evaluate yoga's impact on blood pressure (BP) and quality of life (QOL) and on stress, depression and anxiety in patients with hypertension in a primary care setting. We conducted a multi-centre randomized controlled trial with follow-up after 12-week intervention completion. Adult primary care patients diagnosed with hypertension were randomly allocated to yoga or usual care. The intervention group performed a short home-based Kundalini yoga programme 15 min twice-daily during the 12-week intervention period. At baseline and follow-up, the participants underwent standardized BP measurements and completed questionnaires on QOL, stress, anxiety and depression. Data obtained from 191 patients (mean age 64.7 years, s.d. 8.4) allocated to yoga intervention (n=96) and control group (n=95), with a total proportion of 52% women, showed a significant reduction in systolic and diastolic BP for both groups (-3.8/-1.7 mm Hg for yoga and -4.5/-3.0 mm Hg for control groups, respectively). However, the BP reduction for the yoga group was not significantly different from control. There were small but significant improvements for the yoga group in some of the QOL and depression measures (P<0.05, Hospital Anxiety and Depression scale, HADS-D) compared with control. The findings of our study, which is the largest study from an OECD country (Organization for Economic Co-operation and Development) to date, do not support the suggestion from previous smaller studies that yoga lowers the BP. Further clinical trials are needed to confirm these findings. However, the yoga patients had other health benefits.

Bulbospinal serotonin pressor pathways and hypotensive action of methyldopa in the rat.

The administration of methyldopa (200 mg/kg i.p.) induced a green fluorescence typical of catecholamine fluorescence, in regions of the brain stem which coincided with all the major serotonin cell groups, including the B1, B2, and B3 cell groups in the medulla. Prior administration of 5,7-dihydroxytryptamine (5,7-DHT), a neurotoxin relatively specific for serotonin neurons, prevented the appearance of this methyldopa-induced fluorescence. Electrical stimulation of the ventrolateral medulla in areas that coincided with the lateral elements of the B1 and B3 serotonin cell groups evoked pressor responses recorded via cannulae in the abdominal aorta. The pressor responses were frequency-dependent and could be markedly attenuated by prior administration of 5,7-DHT either intracerebroventricularly (i.c.v.) or directly into the cervical cord to ablate descending serotonin nerve fibers. Microinjection of methyldopa (4-16 micrograms) directly into the region of the B1 and B3 cells in the ventrolateral medulla evoked a dose-dependent fall in arterial pressure observed for 4 hours. Here too, prior administration of 5,7-DHT either intracerebroventricularly or directly into the cervical cord largely prevented the hypotensive action of the microinjections of methyldopa. The administration of 5,7-DHT produced a highly selective depletion of serotonin stores without reducing the concentrations of norepinephrine. These experiments suggest that the activity of serotonin nerves descending into the spinal cord from the B1 and B3 cells in the ventrolateral medulla serves to elevate or maintain arterial pressure. They also suggest that these descending serotonin neurons may contribute to the hypotensive action of methyldopa.

Baroreflex control of myocardial contractility in conscious normotensive and renal hypertensive rabbits.

We have assessed resting myocardial contractility and its baroreflex control in normotensive and hypertensive conscious rabbits. Hypertension was induced by bilateral cellophane wrapping of the kidneys with experiments performed 6 weeks later during the established phase of hypertension. The peak rate of change of left ventricular pressure (peak LV dP/dt) was used as the index of myocardial contractility. Baroreflex control of contractility and heart period (HP) was assessed by constructing stimulus response curves relating change in mean arterial pressure (MAP), induced by balloon occluders around the abdominal aorta and inferior vena cava, to change in peak LV dP/dt and HP. These stimulus response curves were obtained in normotensive rabbits with and without cardiac pacing, and in both normotensive and hypertensive animals after cardiac beta sympathetic blockade with propranolol, vagal blockade with methylscopolamine, and combined cardiac autonomic blockade with propranolol and scopolamine, as well as in rabbits with intact autonomic effectors. Resting MAP was significantly higher in the hypertensive rabbits (119 +/- 2 mm Hg) compared to normotensive controls (76 +/- 1 mm Hg). Resting peak LV dP/dt was also greater by 51% in the hypertensive animals (7054 +/- 287 mm Hg sec-1) compared to controls (4690 +/- 223 mm Hg sec-1). There was no significant difference in the resting heart period or resting left ventricular end diastolic pressure. Transient changes in MAP induced by occlusion of the aortic or venous balloons produced significant alterations in peak LV dP/dt in normotensive animals with and without pacing and in hypertensive control animals. In animals with cardiac sympathetic block, the range and slope or sensitivity of the stimulus response curves were not significantly changed but in animals with vagal blockade the sensitivity was reduced by 90% and the range at 30 mm Hg by 88%. After propranolol and methylscopolamine were administered together, the stimulus no longer evoked a response. These experiments demonstrate that myocardial contractility is under baroreflex control and suggest that this is mediated principally via parasympathetic nerves to the heart. There was no significant difference between the sensitivity of baroreflex control of myocardial contractility in the normotensive (-84 +/- 14 mm Hg sec-1 per mm Hg) and the hypertensive (-110 +/- 14 mm Hg sec-1 per mm Hg) rabbits, unlike the baroreflex control of heart period where sensitivity was markedly impaired in the hypertensive (sensitivity 3.8 +/- 0.8 msec/mm Hg) compared to the normotensive (6.9 +/- 1.0 msec/mm Hg) animals.

Experimental hypertension produces diverse changes in the regional vascular responses to endothelin-1 in the rabbit and the rat.

OBJECTIVE: To examine the effects of hypertension on systemic and regional haemodynamic responses to endothelin-1. DESIGN: Comparison of responses between age-matched control and hypertensive rabbits (two-kidney, two wrapped), and between spontaneously hypertensive rats (SHR) and control Wistar-Kyoto rats. METHODS: Arterial pressure, heart rate and blood flow responses to 0.2 nmol/kg intravenous endothelin-1 were measured in conscious animals. Blood flow was measured by pulsed ultrasound Doppler in the ascending aorta, distal abdominal aorta, left renal artery and superior mesenteric artery. RESULTS: Endothelin-1 produced qualitatively similar effects in the hypertensive and control animals. In the systemic circulation, brief initial vasodilation preceded sustained vasoconstriction. In the hindlimb, marked vasodilation preceded relatively minor vasoconstriction, and profound vasoconstriction occurred in the renal and mesenteric vascular beds. In the rats but not the rabbits, fleeting vasodilation preceded the renal and mesenteric vasoconstriction. Significant differences between hypertensive and control animals were: accentuation of the pressor effect and heart rate responses in hypertensive animals of both species, and accentuation of hindlimb vasodilation in hypertensive rabbits but not SHR; and attenuation of the depressor effect in SHR but not hypertensive rabbits, attenuation of the mesenteric vasoconstriction in both hypertensive rabbits and rats, and attenuation of renal vasoconstriction in SHR. CONCLUSIONS: The increased responses to endothelin-1 of some variables in the hypertensive animals may involve structural changes in the resistance vessels. However, the reduced responses in the mesenteric vasculature of both species and the renal vasculature of the SHR are due to some mechanism other than structural change.

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.

Optimal size of cuff bladder for indirect measurement of arterial pressure in adults.

This study tested the hypothesis that a sphygmomanometer cuff bladder long enough to encircle the arm in most adults ('obese cuff') would provide a more accurate and precise estimate of intra-arterial pressure than the usual 'standard' cuff bladder. In 53 patients undergoing diagnostic coronary angiography (35 males, 18 females, aged 36-79 years), indirect blood pressure, measured in the left arm with a random-zero sphygmomanometer, was compared with simultaneously measured femoral intra-arterial pressure. Duplicate indirect measurements were made with each of two cuffs containing bladders measuring 39 x 15 cm ('obese') and 23 x 12 cm ('standard'). The obese cuff bladder encircled 80% or more of the arm circumference in all subjects, whereas the standard cuff bladder met this requirement in only 19% of the subjects. For both systolic and diastolic pressure there was marked interindividual variability in the differences between indirect and direct measurements with both cuffs. With the obese cuff there was no systematic error in the diastolic blood pressure measurement. The standard cuff consistently overestimated diastolic pressure by 7.7 +/- 8.3 mmHg (mean +/- s.d.). For both cuffs, the difference between indirect and direct diastolic pressure increased with arm size (P less than 0.05). Both cuffs underestimated systolic blood pressure, the obese cuff by 15.5 +/- 11.7 mmHg and the standard cuff by 7.6 +/- 12.1 mmHg. These systolic blood pressure underestimates were greater at higher blood pressures (P less than 0.01) and with smaller arms (P less than 0.05). Age was not related to measurement error with either cuff.(ABSTRACT TRUNCATED AT 250 WORDS)

Bulbospinal sympatho-excitatory neurons in the rat caudal raphe.

OBJECTIVES: To explore the rat caudal raphe nuclei for neurons that respond to activation of baroreceptor nerves and that have a spinal axon, and to compare the behavioural properties of barosensitive bulbospinal neurons in the rat caudal raphe with the properties of barosensitive bulbospinal neurons in the rostral ventrolateral medulla. DESIGN: Extracellular unit recordings were obtained from an area extending up to 1.0 mm caudally from the caudal edge of the facial nucleus. Two sites were explored: the rostral ventrolateral medulla and the midline. MATERIALS AND METHODS: Single-unit recordings were made in anaesthetized (75 mg/kg chloral hydrate and 30 mg/kg sodium pentobarbitone then 3-6 mg intravenously as required), immobilized (2 mg pancuronium as required) Sprague-Dawley rats. Central respiratory drive was recorded from phrenic nerve discharge. The barosensitivity of single units was assessed by R-wave triggered histograms and by histograms of their responses to aortic nerve stimulation or to intravenous injection of phenylephrine. Nociceptors were activated by a brief pinch of the tail. RESULTS: Eleven spontaneously active units in the midline that were inhibited by baroreceptor stimulation and had a spinal axon were studied. Respiratory modulation was present and was predominantly inspiratory. Barosensitive neurons in the rostral ventrolateral medulla were activated by nociceptive inputs; midline barosensitive neurons were not. CONCLUSIONS: The behavioural characteristics of midline neurons differ from those of the bulbospinal barosensitive neurons in the rostral ventrolateral medulla, indicating that raphe spinal neurons have different sets of afferent inputs and may subserve to a distinct physiological role. The present paper is the first report of bulbospinal neurons in the rat caudal raphe that are inhibited by activation of arterial baroreceptors.

Lack of effect of fish oil supplementation on blood pressure in treated hypertensives.

Fish and fish oils have been reported to reduce blood pressure in normotensives and untreated hypertensives. The present study examined the effect of dietary supplementation with fish oil on blood pressure in 20 treated hypertensives with controlled blood pressures who continued their usual antihypertensive drug treatment throughout. A double-blind, randomized crossover design was used, with two phases, each of 8 weeks' duration. In one phase, subjects took fifteen 1 g fish oil capsules (Lipitac; Reckitt and Colman Pharmaceuticals, Sydney, Australia) daily, and in the other, 15 capsules of identical appearance containing 1 g olive oil daily. There was no difference between the treatment phases for any blood pressure parameter, heart rate or body weight, but blood pressure was lower in both phases compared with pretreatment values. The fasting plasma triglyceride concentration was 30% lower in the fish oil phase (P less than 0.001), but there was no difference between the phases for plasma concentrations of total or high-density lipoprotein (HDL) cholesterol. We conclude that, in treated hypertensives with controlled blood pressures, any additional fall in blood pressure produced by dietary supplementation with fish oil is so small that the requirement for antihypertensive drug therapy is unlikely to be reduced.

Lacidipine, hydrochlorothiazide and their combination in systolic hypertension in the elderly.

OBJECTIVE: To compare with placebo the efficacies of once-daily administrations of lacidipine and hydrochlorothiazide separately and in combination to elderly patients with systolic hypertension. DESIGN AND METHODS: Nineteen elderly subjects (five men and 14 women, median age 71 years, range 62-79 years) participated in the study, which had a randomized double-blind crossover design. For each subject there were four treatment phases, each of duration 4 weeks. The initial treatments in each phase were 2 mg lacidipine once a day and 25 mg hydrochlorothiazide once a day, separately and in combination, and placebo. Doses of each agent could be doubled after 2 weeks in each phase if the patient's goal systolic blood pressure had not been achieved. The numbers of subjects administered the higher dose of each treatment were 13 for placebo, 14 for lacidipine, 11 for hydrochlorothiazide and eight for lacidipine plus hydrochlorothiazide. RESULTS: End-of-phase mean clinic blood pressures were 164/85 mmHg with placebo, 159/82 mmHg with lacidipine, 157/84 mmHg with hydrochlorothiazide and 152/82 mmHg with lacidipine plus hydrochlorothiazide. Systolic blood pressure was significantly reduced during all active treatment phases compared with placebo and that for the lacidipine plus hydrochlorothiazide phase was also significantly less than those for both of the other active treatment phases. There was no difference between sitting and standing blood pressure for any phase. Factorial analysis of the main effects of treatment indicated that the effects of lacidipine and hydrochlorothiazide on clinic blood pressure were additive and also that heart rate was higher when hydrochlorothiazide had been administered. Ambulatory blood pressure monitoring confirmed the pattern of the responses of blood pressure and showed that administration of hydrochlorothiazide had a significantly greater effect on systolic blood pressure and a longer duration of action than did administration of lacidipine. There was no difference in the frequency of adverse effects among any of the phases. CONCLUSIONS: In treating elderly systolic hypertensives the diuretic hydrochlorothiazide is a more effective antihypertensive agent with a longer duration of action than is the calcium channel antagonist lacidipine. In combination the effects of these two drugs on blood pressure are additive.

Preferential release of neuroactive amino acids from the ventrolateral medulla of the rat in vivo as measured by microdialysis.

The basal overflow of extracellular endogenous amino acids was measured from the ventrolateral medulla of urethane anaesthetized rats in vivo by microdialysis. Inclusion of a mercury salt, p-chloromercuriphenylsulphonic acid, in the dialysate (Krebs' solution), results in a preferential increase in the overflow of aspartate, glutamate, glycine and GABA. A smaller increase in the overflow of the glutamate precursor and metabolite, glutamine, was also found. There was no significant change in the basal extracellular levels of taurine, asparagine, alanine, serine, ornithine or lysine. Inclusion of a specific GABA uptake inhibitor, nipecotic acid, in the dialysate results in an immediate, dose dependent increase in the overflow of GABA, and to a lesser extent, taurine. Since it is likely that mercury salts increase neurotransmitter release by increasing free intracellular calcium ion concentrations, it is suggested that these results provide further evidence for a physiologically relevant neurotransmitter role for aspartate, glutamate, glycine and GABA in the ventrolateral medulla.

Neurokinin-1 receptor-immunoreactive sympathetic preganglionic neurons: target specificity and ultrastructure.

Substance P is involved in cardiovascular control at the spinal cord level, where it acts through neurokinin-1 receptors. In this study we used immunocytochemistry and retrograde tracing to investigate the presence of the neurokinin-1 receptor and its ultrastructural localization in rat sympathetic preganglionic neurons that project to the superior cervical ganglion or the adrenal medulla. Immunofluorescence for the neurokinin-1 receptor outlined the somatic and dendritic surfaces of neurons in autonomic subnuclei of spinal cord segments T1-T12, whereas immunofluorescence for the tracer, cholera toxin B subunit, filled retrogradely labelled cells. There was a significant difference in the proportion of neurokinin-1 receptor-immunoreactive sympathetic preganglionic neurons supplying the superior cervical ganglion and the adrenal medulla. Thirty-eight percent of the neurons that projected to the superior cervical ganglion were immunoreactive for the neurokinin-1 receptor compared to 70% of neurons innervating the adrenal medulla. Of neurons projecting to the superior cervical ganglion, significantly different proportions showed neurokinin-1 receptor immunoreactivity in spinal cord segment T1 (15%) versus segments T2 T6 (45%). At the ultrastructural level, neurokinin-1 receptor staining occurred predominantly on the inner leaflets of the plasma membranes of retrogradely labelled sympathetic preganglionic neurons. Deposits of intracellular label were often observed in dendrites and in the rough endoplasmic reticulum and Golgi apparatus of cell bodies. Neurokinin-1 receptor immunoreactivity was present at many, but not all, synapses as well as at non-synaptic sites, and occurred at synapses with substance P-positive as well as substance P-negative nerve fibres. Only 37% of the substance P synapses occurred on neurokinin-1-immunoreactive neurons in the intermediolateral cell column. These results show that presence of the neurokinin-1 receptor in sympathetic preganglionic neurons is related to their target. The ultrastructural localization of the receptor suggests that sympathetic preganglionic neurons may be affected (i) by substance P released at neurokinin-1 receptor-immunoreactive synapses, (ii) by other tachykinins (e.g., neurokinin A), which co-localize in substance P fibres in the intermediolateral cell column, acting through other neurokinin receptors, and (iii) by substance P that diffuses to neurokinin-1 receptors from distant sites.

Ongoing trials of angiotensin-converting enzyme inhibition: what they can tell us.

Abundant evidence has accumulated showing that angiotensin converting enzyme (ACE) inhibitors reduce long-term cardiovascular morbidity and mortality rates in patients with heart failure and myocardial infarction. Fewer completed trials have assessed their potential benefits in this regard in hypertensive subjects, but evidence of benefit is beginning to accrue from studies examining patients with hypertension, particularly in the presence of diabetes and after infarction. Ongoing trials of blood pressure (BP) lowering using ACE inhibition fall into three main categories: 1) those comparing ACE inhibitors with older drugs such as diuretics and beta blockers; 2) those examining more aggressive versus less aggressive lowering of BP; and 3) those investigating BP lowering in patients at high risk for a cardiac event. Among those in the last group is the Perindopril Protection Against Recurrent Stroke Study (PROGRESS), which examines the effects of perindopril-based ACE inhibitor therapy in both normotensive and hypertensive patients who have survived a stroke. This trial is particularly important because it serves as a model for studies of BP lowering across a wide range of BP and BP-related conditions.

Central serotonergic mechanisms in hypertension.

Serotonin-containing neurons in the central nervous system are grouped into a number of discrete and distinctive collections with cell bodies in the brainstem and projections passing to many regions of the brain and spinal cord. Evidence is presented that activation of one projection of serotonin-containing neurons from the midbrain to the hypothalamus elevates arterial pressure. Evidence is also presented that activation of a projection descending from the lateral B3 serotonin cell group to the spinal cord elicits a pressor response that is accompanied by increased release of serotonin in the spinal cord and is independent of the C1 adrenaline-containing neurons that lie close by. In contradistinction, experiments are described demonstrating that activation of the midline group of B3 serotonin cells in the raphe nucleus causes a fall in arterial pressure, consistent with the view that different groups of serotonin neurons in the brain and spinal cord participate in the control of blood pressure in diverse ways and can have different effects on blood pressure. Finally, experiments are described showing that the hypotensive action of methyldopa is mediated in part through central serotonin nerves.

Altered responsiveness of medullary depressor neurones to L-glutamate and D-serine in SHR rats.

We have investigated the effects of microinjection of L-glutamate, D-serine and glycine into the caudal ventrolateral medulla (CVLM) of spontaneously hypertensive (SHR) and Wistar Kyoto (WKY) rats. In SHR the depressor responses to L-glutamate were significantly enhanced compared to WKY rats, while those to the NMDA-glycine site agonists, D-serine and glycine (in the presence of strychnine) were significantly diminished. Depressor responses to NMDA and D-serine could be blocked with 5-fluro-indole-2-carboxylic acid (FICA, an NMDA-glycine site antagonist). In support of our previous findings, the larger responses of NMDA-glutamate site agonists and smaller responses of NMDA-glycine site agonists in SHR, may suggest that SHR have reduced levels of the endogenous glutamate antagonist, kynurenic acid.

c-fos identifies GABA-synthesizing barosensitive neurons in caudal ventrolateral medulla.

Hypertension in the conscious rat, elicited by i.v. infusion of phenylephrine, evoked expression of the immediate early gene c-fos in discrete groups of brain stem neurons. Fos-immunoreactive neurons were located in the caudal ventrolateral medulla (CVLM); others were located in the nucleus of the tractus solitarius (NTS). Because of their sensitivity to alterations in arterial pressure, these neurons are likely to subserve the arterial baroreceptor reflex. The aim of this study was to identify the brain stem projections and the neurotransmitter content of the barosensitive CVLM neurons using neuronal tracing and immunohistochemistry. Some of the barosensitive CVLM neurons projected directly to the rostral ventrolateral medulla (RVLM), and many contained the GABA synthesizing enzyme, glutamic acid decarboxylase (GAD). Other CVLM neurons, containing markers of glutamate or catecholamine synthesis, were insensitive to baroreceptor stimulation. This study delineates neuronal pathways acting in the arterial baroreceptor reflex and identifies precisely GABA-synthesizing CVLM neurons as the source of inhibitory input to the RVLM.

A simple, sensitive method for the determination of extracellular catecholamines in the rat hypothalamus using in vivo dialysis.

The design, construction and characterisation of a dialysis probe suitable for perfusing any deep brain structures is described. Using high-performance liquid chromatography with electrochemical detection (HPLC-ECD) the effects of flow rate, concentration, dialysate composition and temperature on the recovery within the dialysate of authentic catecholamines are detailed. The dialysis probe was used to collect endogenous catecholamines from the anterior hypothalamus of urethane-anaesthetised rats. Following organic phase extraction of the in vivo samples, a small basal release of noradrenaline (NA) of 37 +/- 4 pg/30 min sample was found. Potassium stimulation markedly elevated the release of NA and dopamine from the anterior hypothalamus in a calcium ion and dose dependent manner. It appears therefore that the dialysis probe described here, in conjunction with HPLC-ECD, can be used to follow changes in neuronally released catecholamines within the anterior hypothalamus, providing a valuable tool to study the role of these neurotransmitters in physiological and pharmacological function.

Increased number of PNMT-immunofluorescent nerve cell bodies in the medulla oblongata of stroke-prone hypertensive rats.

An antiserum to bovine adrenal PNMT was used to identify PNMT-containing nerve cell bodies in the medulla oblongata of 4-week-old normotensive Wistar-Kyoto rats and stroke-prone spontaneously hypertensive rats. The regional distribution of PNMT cells and the total number of PNMT cell profiles in tranverse sections of the medulla were examined in each of the two strains. While there was no significant difference in the pattern of distribution of the cells, both the number of PNMT cell profiles per section and the total number seen in all sections of the medulla were significantly higher in the hypertensive rats. The increase in counts of PNMT cell profiles in the medulla suggests that there is a genetic difference in the number of central adrenaline neurons in these hypertensive rats. This is supported by the finding of similar increases of PNMT enzyme activity in the medulla of both stroke-prone spontaneously hypertensive rats and spontaneously hypertensive rats compared with Wistar-Kyoto rats.

Spinal cord serotonin release and raised blood pressure after brainstem kainic acid injection.

The recently developed technique of in vivo dialysis has permitted us to make direct measurements of serotonin release in a specific region of the spinal cord and to relate this to changes in blood pressure elicited by chemical stimulation of the brainstem. In the present experiments we have shown that chemical stimulation of bulbospinal neurons in the region of the B3 cell group in the ventromedial medulla, causes an increase in the release of serotonin in the thoracic spinal cord and that this release is associated with an increase in blood pressure.

Glutamate-immunoreactive synapses on retrogradely-labelled sympathetic preganglionic neurons in rat thoracic spinal cord.

Retrograde tracing with cholera toxin B subunit (CTB) combined with post-embedding immunogold labelling was used to demonstrate the presence of glutamate-immunoreactive synapses on sympathetic preganglionic neurons that project to the adrenal medulla or to the superior cervical ganglion in rat thoracic spinal cord. At the electron microscope level, glutamate-immunoreactive synapses were found on retrogradely labelled nerve cell bodies and on dendrites of all sizes. Two-thirds of the vesicle-containing axon profiles that were directly apposed to, or synapsed on, CTB-immunoreactive sympathoadrenal neurons were glutamate positive. The proportion of glutamate-immunoreactive contacts and synapses on sympathoadrenal neurons decreased to zero when the anti-glutamate antiserum was absorbed with increasing concentrations of glutamate from 0.1 mM to 10 mM. Double immunogold labelling for glutamate and gamma-aminobutyric acid (GABA) showed that glutamate-immunoreactive profiles did not contain GABA and that GABA-immunoreactive profiles did not contain glutamate. These results suggest that glutamate is the major excitatory neurotransmitter to sympathoadrenal neurons and possibly to other sympathetic preganglionic neurons in the intermediolateral cell column of the spinal cord.