IDENTIFICATION OF CARDIOVASCULAR PATHWAYS IN THE SYMPATHETIC NERVOUS SYSTEM

1. Sympathetic autonomic neurons show distinct patterns of expression of a range of neurochemicals that can be detected immunohistochemically. Often, functionally homologous neurons in the autonomic nervous system express identical combinations of substances that serve as a chemical code that allows them to be identified among other autonomic neurons. 2. In the rat stellate ganglion, where many neurons express either immunoreactivity (IR) to neuropeptide Y (NPY) or the calcium-binding protein calbindin, a population of large postganglionic neurons found along the medial border of the stellate ganglion, around the origin of the cardiac nerves, expressed intense IR to both substances at all ages examined, from early postnatal to adult. 3. In the heart, in the first few postnatal weeks, many nerve terminals were IR for both NPY and calbindin, but, with increasing age, calbindin-IR was progressively lost from NPY-IR terminals. Nerve terminals IR for both calbindin and NPY were not seen around pulmonary blood vessels or in the trachea or the thymus. 4. Nerve terminals IR for calretinin, another calcium-binding protein, were present in dense pericellular baskets around neurons in the stellate IR for both calbindin and NPY. The terminals also contained nitric oxide synthase (NOS)-IR. 5. It is suggested that the calbindin- and NPY-IR neurons in the stellate ganglion are the post-ganglionic neurons that innervate the heart and that the nerve terminal containing calretinin and NOS-IR that surround them are the cardiac preganglionic terminals. It thus appears possible, in the rat, to identify the sympathetic cardiac pathway arising in the spinal cord and controlling the heart purely on the basis of chemical coding.     

ACUTE HAEMODYNAMIC AND HORMONAL EFFECTS OF ORAL DOXAZOSIN IN NORMAL SUBJECTS

Haemodynamic and hormonal effects of doxazosin, a long-acting alpha 1-adrenoceptor antagonist (2 mg) were compared with placebo in six normal men. Doxazosin at 2 mg produced lower supine systolic blood pressure and plasma cortisol concentration than control at 4 h only, but these changes were not sustained. Both supine and standing pulse rate were increased by active drug after 6 h. In this acute study doxazosin did not affect plasma renin or aldosterone concentrations.     

AFFERENT CONTROL OF VASOPRESSIN AND RENIN RELEASE DURING HAEMORRHAGE IN NORMAL AND AUTONOMICALLY BLOCKED RABBITS

1. The role of the arterial and cardiac baroreceptors on the arginine vasopressin (AVP) and plasma renin activity (PRA) responses to haemorrhage was studied in conscious rabbits. They were bled at a rate of approximately 3% of their blood volume (BV)/min, both when the autonomic nervous system (ANS) was intact and during ANS blockade, which markedly enhances the AVP response due to the much greater haemodynamic disturbance. Under each condition of ANS function 2 x 2 factorial analysis was performed, each with four groups of rabbits, including animals with both sets of baroreceptors working, one or other set working and neither set working. 2. With intact ANS, haemorrhage had to be terminated at different times in the four groups. This presents problems for factorial analysis due to differences in the relationship between plasma AVP (or PRA) and release rate. A method for overcoming this was developed by extrapolating the BV-log AVP curves to a common time from the start of bleeding. 3. Under both conditions of ANS function the arterial and cardiac baroreceptors together accounted for 90-95% of the rise in AVP during haemorrhage. With normal ANS function, the rise in AVP was about 70% through cardiac (probably ventricular) baroreceptors (P = 0.01) and about 30% through arterial baroreceptors (P = 0.08). This compares with an earlier study at a rate of bleeding of 1.8% BV/min, where the entire drive came from the cardiac receptors. During ANS blockade, plasma AVP was enhanced approximately five-fold, which was mostly mediated through the arterial baroreceptors, but the cardiac baroreceptor component was also greater; arterial/cardiac baroreceptor drive was 2/1. 4. Baroreflexes played no role in renin release during haemorrhage, but the experiments with ANS blockade suggest that a hormonal factor, which was related to the cardiac innervation, may limit the rise in PRA in the latter part of haemorrhage.     

MEASUREMENTS OF VISUAL ACUITY, CARDIOVASCULAR AND ANTHROPOMETRIC PARAMETERS AMONG NKWU＇ CONSUMERS IN MID- WESTERN NIGERIA

'Nkwu' is the generic name for all kinds of alcoholic liquors locally brewed from palm sap. It is the beverage commonly consumed in the mid-western and eastern Nigeria. No information is yet available on the parameters, body mass index and visual acuity. Seven hundred and thirty-eight apparently healthy-looking, and most suitable men, who gave their consent were selected after interview. The results showed that long induced significant increase in mean blood pressure parameters (systolic blood pressure, diastolic blood pressure, mean arterial blood pressure and pulse rate) in older men (41-50 and 51-60 age brackets) when compared with their respective age-matched control (non-drinkers) mean value. Such drinking pattern also significantly (P＜0.05) reduced their body mass index when compared with similar control values. By extension, it can be cardiovascular dysfunction and nutritional complications. However, further epidemiological, biochemical and post-mortem investigations are required in order to generate data and information needed to alert the communities, and possibly advise the lay public.     

MEASUREMENTS OF VISUAL ACUITY,CARDIOVASCULAR AND ANTHROPOMETRIC PARAMETERS AMONG NKWU′ CONSUMERS IN MID-WESTERN NIGERIA

1INTRODUCTION‘Nkwu’is the name for the beverages locallyproduced frompalmjuice.These various products(‘Ozu’,‘Ogoro’,‘Nkwu-enu’,‘Mayan’,‘Tombo’,‘Obora’)of palm sap posses intoxicating and mood-altering property.It is commonly consumed for merry-making in order to live-up the social status.‘Nkwu’is used to entertain guests during social ceremonies likeburial,marriage,child naming,chieftaincy and othersocial engagements.Sometimes,individuals drink‘Nkwu’as a means of rela…     

吗啡依赖大鼠戒断后心血管活动的改变及机理

目的：观察吗啡依赖大鼠戒断反应后心血管活动的改变。方法：用递增法制备吗啡依赖大鼠模型，并用纳洛酮催促戒断，在清醒状态下用ＰＳ－１００型大鼠尾动脉血压记录仪记录平均动脉血压（ｍＡＢＰ）和心率（ＨＲ）。结果：吗啡依赖大鼠在纳洛酮催促戒断后ｍＡＢＰ明显升高，并持续３０ｍｉｎ以上。皮下注射可乐定可阻断吗啡依赖大鼠戒断后ｍＡＢＰ的升高，且呈明显的量效关系。结论：吗啡依赖大鼠戒断时ｍＡＢＰ有明显的上升，可乐定可使吗啡戒断时上升的ｍＡＢＰ下降     

DISSOCIATION OF BLOOD PRESSURE AND ALBUMINURIA IN NORMAL SUBJECTS INFUSED WITH ANGIOTENSIN II AND NORADRENALINE

1. Albuminuria is a predictor of diabetic renal disease and atherosclerosis. Changes in blood pressure (BP) may influence albuminuria. 2. The effect of acute BP elevation on albumin excretion rates (AER) using noradrenaline (NA) and angiotensin II (AII) infusions in six normal subjects was examined. 3. The average rise in BP during a 120 min infusion was 23 mmHg for AII and 16 mmHg for NA. 4. There was a marked dissociation between AER and BP levels in both AII and NA infusions. 5. Previously described correlations between BP and AER in ambulatory BP studies may be explained by other factors such as exercise and postural changes.     

ROLE OF THE DORSOMEDIAL HYPOTHALAMUS IN THE CARDIOVASCULAR RESPONSE TO STRESS

1. Disinhibition of the dorsomedial hypothalamus (DMH) in rats by local microinjection of GABA_A receptor antagonists evokes behavioural and physiological changes resembling those seen in acute experimental stress. 2. Conversely, similar microinjection of muscimol, a potent agonist at inhibitory GABA_A receptors, virtually abolishes stress-induced increases in heart rate and arterial pressure. 3. Blockade of excitatory amino acid (EAA) receptors in the DMH also attentuates stress-induced cardiovascular changes and microinjection of kainate, AMPA or NMDA at low doses elicits cardiovascular effects resembling those seen in stress. Paradoxically, injection of higher doses of NMDA or of glutamate into this region has no consistent effect. 4. The cardiovascular effects of bicuculline methiodide, a GABA_A receptor antagonist, as well as those of NMDA and/or kainate were assessed after identical injection into either the DMH, the paraventricular nucleus (PVN) or the area between the two nuclei in both anaesthetized and conscious rats. For each agent, a similar pattern was seen, with the largest increases in heart rate and arterial pressure occurring after injection into the DMH and the smallest changes resulting from injection into the PVN. 5. In a parallel study, bilateral microinjection of muscimol into the DMH dramatically reduced air stress-induced cardiovascular changes; similar injection into the area of the PVN had no effect, while injection into the area between the nuclei produced an intermediate effect. 6. Our findings suggest that activation of neurons in the region of the DMH mediates stress-induced cardiovascular changes and that the activity of these neurons may be determined by the balance of tone at inhibitory GABA_A receptors and EAA receptors.     

REPRODUCIBILITY OF PRESSOR RESPONSE TO HANDGRIP: INFLUENCE OF TIME INTERVALS, STRENGTH AND DURATION OF EXERCISE

1. The reproducibility of pressor response to handgrip performed at different time intervals and with different combinations of the product duration x strength of the exercise was evaluated in 14 normotensive subjects recording blood pressure with a noninvasive automatic device. 2. Subjects underwent five consecutive tests (30% of maximal voluntary contraction x 90 s) at 30 min, and 24 h intervals and repeated the test after 12 months. Furthermore, they underwent at 24 h intervals a randomized sequence of handgrip tests whose product strength x duration was combined in order to achieve either a constant or an increasing level of exercise. 3. Blood pressure response to exercise performed at 30 min intervals was much less reproducible than that induced by handgrip performed at time intervals greater than or equal to 24 h. 4. Increasing gradually the product strength x duration of the handgrip test there was a proportional blood pressure increase, whereas when the product was maintained constant diastolic blood pressure increase was also constant and reproducible within each subject. 5. This study shows that it is possible to obtain reproducible diastolic blood pressure responses to handgrip test measuring blood pressure with a non-invasive automatic device when the tests are performed at a time interval of at least 24 h. The choice of the strength and of the duration of the exercise is very important for the reproducibility of the test.     

多巴胺衍生物的合成及其对心功能的影响

合成了7个与三肽片段或活性分子联结的多巴胺衍生物。在麻醉犬心功能试验中,发现引入缓激肽片段 Phe-Ser-Pro 的多巴胺(SIPI-650)可非常显著地增加心肌收缩力、左心室压和平均动脉压;引入乙酰巯甲丙脯酸(SIPI-430)能显著增加心肌收缩力,对血压、心率则几无影响;在γ-谷氨酰多巴胺的α位再引入一个多巴胺(SIPI-689)能显著增加心肌收缩力、血压和左心室压。     

Effects of autonomic blockade on non-linear cardiovascular variability indices in rats

1. The present study assesses the effects of autonomic blockade (alpha- and beta-adrenoceptor and cholinergic) on cardiovascular function studied by heart rate variability (HRV), blood pressure variability (BPV) and baroreflex sensitivity in rats using non-linear dynamics. Little is known about the influence of pharmacological autonomic nervous system interventions on non-linear cardiovascular regulatory indices. 2. In 13 conscious rats, heart rate and aortic blood pressure were measured continuously before, during and after autonomic blockade with atropine, phentolamine and propranolol. Non-linear scaling properties were studied using 1/f slope, fractal dimension and long- and short-term correlation. Non-linear complexity was described with correlation dimension, Lyapunov exponent and approximate entropy. Non-linear indices were compared with linear time and frequency domain indices. 3. Beta-adrenoceptor blockade did not alter the non-linear characteristics of HRV and BPV, although low-frequency power of HRV was depressed. Alpha-adrenoceptor blockade decreased the scaling behaviour of HRV, whereas cholinergic blockade decreased the complexity of the non-linear system of HRV. For BPV, the scaling behaviour was increased during alpha-adrenoceptor blockade and the complexity was increased during cholinergic blockade. The linear indices of HRV and BPV were decreased. 4. The present results indicate that the beta-adrenoceptor system has little involvement in the generation of non-linear HRV and BPV in rats. 5. Alpha-adrenoceptor blockade mostly influenced the scaling properties of the time series, whereas cholinergic blockade induced changes in the complexity measures. 6. The absence of the baroreflex mechanism can trigger a compensatory feed-forward system increasing the complexity of BPV.     

EFFECTS OF RESPIRATION ON BLOOD PRESSURE AND HEART RATE VARIABILITY IN HUMANS

1. Non-invasive continuous finger blood pressure (BP) measurement and a spectral technique based on the Fourier transform (FT) were recently combined to quantify short-term fluctuations in haemodynamic variables. 2. Systolic BP (SBP) recording combined low frequency (LF, Mayer waves) plus high frequency (HF, respiratory) oscillations. The presence of HF oscillations of SBP probably reflects fluctuations in cardiac output. Heart rate (HR) also exhibited a combination of low and HF (respiratory) oscillations. The vagus nerve mediates the efferent control of the respiratory sinus arrhythmia (RSA). 3. During controlled breathing in a supine position, a change in SBP is associated with an opposite consequent change in HR. Respiratory sinus arrhythmia could therefore depend on the baroreceptor-HR response to underlying SBP oscillations. 4. The fast regulation of R-R interval by SBP through the baroreceptor-HR reflex may explain why the respiratory variations in the diastolic BP are small.     

ROLE OF THE HYPOTHALAMIC PARAVENTRICULAR NUCLEUS IN CARDIOVASCULAR REGULATION

1. The paraventricular hypothalamic nucleus (PVH) is a complex structure with both neuroendocrine and autonomic functions. It is a major source of vasopressin and the primary source of corticotropin-releasing factor. In addition, parvicellular PVH neurons have reciprocal connections with brain-stem autonomic centres and directly innervate sympathetic preganglionic neurons. Evidence is reviewed which indicates that in conscious rats PVH activation increases blood pressure, heart rate, renal nerve activity and plasma renin activity. 2. In conscious rats, a non-hypotensive haemorrhage (13 mL/kg blood loss over 24 min) results in increased numbers of Fos-immunoreactive cell nuclei within both magnocellular and parvicellular PVH neurons, including the ventral medial parvicellular regions known to contain neuronal projections to brainstem autonomic centres and spinal cord sympathetic preganglionic neurons. 3. Cell-selective ibotenate lesions of the parvicellular PVH significantly blunt the corticosterone response but do not alter blood pressure, heart rate or plasma renin concentration response to non-hypotensive or hypotensive haemorrhage. This and earlier studies indicate that, while the PVH is necessary for the corticosterone response and contributes to increased vasopressin release during blood loss, it does not play an important role in the sympathetic nervous system and renin-angiotensin responses to hypovolaemia and hypotension. 4. There is evidence to indicate that the parvicellular PVH serves as a necessary relay for cardiovascular and renin responses to certain behavioural stressors. We propose that cardiovascular information relayed to parvicellular PVH autonomic regions may be used to modulate behavioural, rather than homeostatic, effects on haemodynamics and renin release.     

EFFECTS OF NEUROPEPTIDE Y ON BAROREFLEX CONTROL OF HEART RATE AND MYOCARDIAL CONTRACTILITY IN CONSCIOUS RABBITS

1. The effects of intravenous (i.v.) neuropeptide Y (NPY, 10 micrograms/kg bolus) on the stimulus-response curves relating changes in heart period (HP) and in peak left ventricular (LV) dP/dt to acute changes in mean arterial pressure (MAP) were determined in conscious, normotensive rabbits. 2. The relationship between increases and decreases in MAP and the subsequent changes in HP were represented by a sigmoid-shaped curve described by a logistic function. Following NPY administration there was a baroreflex-dependent increase in the maximum slope (sensitivity) at the midpoint of this MAP-HP curve from 7.0 +/- 0.5 to 10.6 +/- 1.3 ms/mmHg (P less than 0.05). NPY caused an upward shift in the whole curve which reflected the NPY-induced bradycardia and was independent of baroreflexes. 3. The relationship between increases in MAP and decreases in peak LV dP/dt was determined during fixed-rate atrial pacing to prevent the effects of the accompanying bradycardia. Increases in MAP and the corresponding reductions in peak LV dP/dt were represented by an exponential function. The slope of the curve, measured at its origin 5-15 min after NPY administration, was reduced from -0.9 +/- 0.2 to -0.4 +/- 0.1 units (P less than 0.05). 4. The effects of NPY are consistent with an action on efferent connections of the arterial baroreceptor reflex, mediated through a reduction in cardiac beta-adrenergic tone. They would also be explained through actions on the afferent or central neural connections of the baroreflex.     

EFFECTS OF CLONIDINE ON BLOOD PRESSURE AND HEART RATE RESPONSES TO AN EMOTIONAL STRESS IN THE RAT: A SPECTRAL STUDY

1. The fluctuations that underlie the spontaneous variability of blood pressure (BP) and heart rate (HR) were investigated in conscious normotensive rats using power spectral analysis. 2. Air jet stimulation determined a significant BP rise associated with a tachycardia. This environmental mild stressor amplified the 195-605 mHz oscillations of HR which are under autonomic control. No habituation to this stressor was observed since a second stimulation determined similar responses. 3. Clonidine (10 micrograms/kg, i.v.) prevented the BP rise normally associated with air jet stimulation. In addition, clonidine dramatically reduced the amplitude of BP and HR oscillations in the frequency region of 195-605 mHz. 4. It is concluded that a mild emotional stressor elicits in normotensive rats a rise in BP and HR associated with modified spectral profiles reflecting sympathetic hyperactivity. Clonidine minored the effects of stress on BP and HR variability and also prevented BP elevation.