刺激家兔腹部迷走神经外周端引起的降压作用

本文对电刺激家兔腹部的迷走神经外周端所引起的降压反应进行了研究。在121只家兔中的实验结果表明:电刺激腹部迷走神经外周端可引起动脉压、小肠和后肢的灌流压同时降低,而心率则无明显变化。这一降压反应发生时,小肠静脉血中的组织胺含量较刺激前明显升高,然后恢复;将小剂量的组织胺 H_1受体阻断剂扑尔敏、非乃根和 H_2受体阻断剂甲氰咪胍(Cimetidine)分别注入肠系膜上动脉均能减弱刺激腹部迷走神经外周端引起的动脉压和小肠灌流压的降低。心得安能削弱此降压反应,而阿托品无效;切断两侧内脏大神经能显著削弱刺激腹部迷走神经外周端引起的降压反应。此残余的降压反应在注入抗组织胺剂后完全消失。由此推论,刺激家兔腹部迷走神经外周端引起的降压反应是通过中枢和外周两方面因素的作用,使血管舒张,外周阻力降低而实现的。     

Biocybernetic studies on reflectory heart modification in the rabbit]

In rabbits the depressor nerves and cardiac vagal branches were stimulated. Their actions on heart rate, atrio-ventricular conduction time, myocardial action potential and mean central blood pressure were recorded. The frequency-effect characteristics of the chronotropic, dromotropic and electrotropic actions on the heart, resulting from afferent and efferent nerve stimulation, are compared. The participation of each of the depressor nerves in their total effects on heart rate and blood pressure is studied. Time courses of heart rate and blood pressure decrease by afferent and efferent nerve stimulation with sinusoidally modulated pulse rates are presented. The results are discussed with respect to the different dynamics of blood pressure and heart rate control. It is concluded that at least two mechanisms are involved in blood pressure control by the depressor nerves: 1. Decrease of vascular resistance by lowering the sympathetic tone. 2. Decrease of heart rate by enhancing the cardiac vagal activity. It is suggested that the parasympathetic control unit compensates rapid disturbances, whereas the slow-acting sympathetic vascular mechanism exerts a long-time pressure control of high efficiency.     

Effect of cervical sympathetic trunk transection on renal sympathetic nerve activity in rats

Stellate ganglion blockade (SGB) with a local anesthetic increases muscle sympathetic nerve activity in the tibial nerve in humans. However, whether this sympathetic excitation in the tibial nerve is due to a sympathetic blockade in the neck itself, or due to infiltration of a local anesthetic to adjacent nerves including the vagus nerve remains unknown. To rule out one mechanism, we examined the effects of cervical sympathetic trunk transection on renal sympathetic nerve activity (RSNA) in anesthetized rats. Seven rats were anesthetized with intraperitoneal urethane. RSNA together with arterial blood pressure and heart rate were recorded for 15 min before and 30 min after left cervical sympathetic trunk transection. The baroreceptor unloading RSNA obtained by decreasing arterial blood pressure with administration of sodium nitroprusside was also measured. Left cervical sympathetic trunk transection did not have any significant effects on RSNA, baroreceptor unloading RSNA, arterial blood pressure, and heart rate. These data suggest that there was no compensatory increase in RSNA when cervical sympathetic trunk was transected and that the increase in sympathetic nerve activity in the tibial nerve during SGB in humans may result from infiltration of a local anesthetic to adjacent nerves rather than a sympathetic blockade in the neck itself.     

The superior laryngeal nerve and the superior laryngeal artery

Length, diameter and anastomoses of the nervus vagus and its ganglion inferius were measured 44 halved heads. On the average, 8.65 fiber bundles of the vagus nerve leave the retro-olivary area. In the area of the jugular foramen is the near superior ganglion of the 10th cranial nerve. In this area were found 1.48 (mean value) anastomoses with the 9th cranial nerve. 11.34 mm below the margo terminalis sigmoidea branches off the ramus internus of the accessory nerve which has a length of 9.75 mm. Further anastomoses with the 10th cranial nerve were found. The inferior ganglion of the 10th nerve had a length of 25.47 mm and a diameter of 3.46 mm. Five mm below the ganglion the 10th nerve had a width of 2.9 and a thickness of 1.5 mm. The mean length of the superior sympathetic ganglion was 26.6 mm, its width 7.2 and its thickness 3.4 mm. In nearly all specimens anastomoses of the superior sympathetic ganglion with the ansa cervicalis profunda and the inferior ganglion of the 10th cranial nerve were found. The superior laryngeal nerve branches off about 36 mm below the margo terminalis sigmoidea. The width of this nerve was 1.9 mm, its thickness 0.8 mm on the right and 1.0 mm on the left side. The division in the internal and external rami was found about 21 mm below its origin. Between the n. vagus and thyreohyoid membrane the ramus internus had a length of 64 mm, the length of external ramus between the vagal nerve and the inferior pharyngeal constrictor muscle was 89 mm. Its mean length below the thyreopharyngeal part was 10.7 mm, 8.6 branchlets to the cricothyroid muscle were counted. The superior laryngeal artery had its origin in 80% of cases in the superior thyroideal artery, in 6.8% this vessel was a branch of the external carotid artery. Its average outer diameter was 1.23 mm on the right side and 1.39 mm on the left. The length of this vessel between its origin and the thyreohyoid membrane was 34 mm. In 7% on the right side and in 13% on the left, the superior laryngeal artery reached the larynx through a foramen thyreoideum. Ranges of diameters and lengths of vessels and nerves in the larynx are given.     

Neuropeptides as central integrators of autonomic nerve activity: effects of TRH, SRIF, VIP and bombesin on gastric and adrenal nerves

The nerve activity of the gastric ramus of the splanchnic (sympathetic) nerve, gastric ramus of the vagus, adrenal ramus of the splanchnic nerve and the superior laryngeal nerve (laryngeal ramus of vagus) were assessed before and after i.c.v. injection of neuropeptides in the rat. TRH stimulated the vagal branch but attenuated the sympathetic outflow to the stomach. In contrast, the sympathetic outflow to the adrenal was enhanced by TRH. SRIF suppressed the activity of all the nerves studied. VIP did not affect the sympathetic outflow to the stomach while suppressing the gastric branch of the vagus. The adrenal sympathetic branch as well as the superior laryngeal nerve was stimulated by VIP. Bombesin suppressed both vagal and sympathetic outflow to the stomach but markedly stimulated the laryngeal branch of the vagus. The adrenal sympathetic nerve was either stimulated or attenuated slightly by bombesin. These results indicate that centrally administered neuropeptides produce reactions specific for each nerve.     

Influence of substance P on carotid sinus nerve baro- and chemoreceptor activity in rabbits.

Substance P (SP) is abundant in the carotid sinus nerve (CSN) and has been implicated in baro- and chemoreceptor reflexes. We examined the effect of SP on blood pressure, heart rate, phrenic nerve activity, hindlimb perfusion pressure, and cardiac contractile strength in urethane-anesthetized rabbits with bilaterally cut cervical sympathetic, vagus, and aortic depressor nerves. Retrograde simultaneous injection of SP (0.5-2.7 micrograms/kg in 0.2-0.3 ml saline) into both carotid sinus areas via the internal carotid arteries decreased blood pressure (by 56%), heart rate (by 13%), cardiac contractility (by 25%) and phrenic nerve activity (by 77%). The effect on hindlimb perfusion pressure was variable. There was both a reflex effect and direct hindlimb vasodilation. In another group of rabbits, the carotid sinus areas were vascularly isolated and perfused with SP (0.19 micrograms/min dissolved in Locke's solution) or Locke's solution alone for 5 min. While carotid sinus perfusion pressure was maintained in the range of 80-120 mmHg, mean arterial blood pressure, heart rate, and unit activity from the CSN were recorded. SP increased the activity of 11 of 18 baroreceptor fibers and inhibited all of 20 chemoreceptor fibers. SP decreased mean arterial blood pressure and heart rate, but the changes were less than those obtained with injection of SP into nonisolated carotid sinus arteries because systemic effects of SP, which in some cases counteracted the reflex effects, were eliminated.     

Somatostatin and GABA correlate with cervical autonomic nerve activity

The mode of inhibitory action of centrally administered SRIF on the efferent activity of autonomic nerves was investigated in the rat by assessing the SRIF-induced change in the activity of the superior laryngeal nerve with or without pretreatment with various drugs. After picrotoxin or bicuculline treatment, the inhibition of nerve activity by SRIF was abolished while reserpine and atropine failed to abolish the SRIF effect. The centrally administered GABA inhibited the activity of the superior laryngeal nerve and the cervical sympathetic trunk. However, SRIF did not affect the sympathetic trunk. Arterial blood pressure was increased by SRIF while GABA produced hypotension.

These data provide evidence for a GABAergic system as the mediator of SRIF action in the brain and for the selectivity of SRIF action on the particular intermediary GABAergic neurones.     

Heart rate response to gentle handling of frog and lizard

Heart rate was counted telemetrically in lizards (Iguana iguana) and frogs (Rana catesbeiana and Rana pipiens) to estimate their response to gentle 1-min handling. The animals were kept at steady body temperatures of ca. 28 degrees C (lizards), and 24 degrees C (frogs). Handling increased the heart rate of lizards from ca. 70 to 110 beats per min immediately during and after handling and this tachycardia decreased in ca. 10 min. Similar handling did not modify significantly the frogs' heart rates. Although the absence of a response to mild stress is not synonymous with the absence of emotion, the absence of handling-tachycardia in frogs and its presence in lizards (as well as in mammals and birds), together with the emotional fever in mammals, birds, and reptiles, but not frogs or fish as reported in the literature, might suggest that 'emotional' response to stress emerged in phylogeny between amphibians and reptiles.     

Experimental studies on the afferent innervation of the cricothyroid muscle in dogs

The cricothyroid muscle in dogs received branches from two independent nerves, namely the external ramus of the cranial laryngeal nerve and the pharyngeal branch of the vagus. Classical spindles are infrequent in the muscle. Atypical forms of sensory endings were identified. Two end-plates were frequently met with on a single extrafusal fibre. Sectioning of the external ramus of the cranial laryngeal nerve was followed by degeneration of spindles. Intact axons detected up to 6 months after operation are probably derived from the pharyngeal branch of the vagus. Chromatolytic changes occurred in the ipsilateral dorsal vagal nucleus and the capsulated ganglion at the entry of the nerve into the muscle. Chromatolysis occurred in the intramuscular ganglion cell rows and in neurons of the ipsilateral nodose ganglion. Morphological alterations were more pronounced in the ipsilateral medial column of the nucleus ambiguus. No changes were observed in the somata of the mesencephalic nucleus.     

Comparative anatomical study of the autonomic cardiac nervous system in macaque monkeys

The main aim of this study was to clarify the general morphology of the autonomic cardiac nervous system in macaque monkeys. A submacroscopic comparative anatomical study of the autonomic cardiac nervous system was performed by examining 22 sides of 11 bodies of four species of macaque monkeys, including some previously unreported species (pig-tailed and stump-tailed monkeys), under a surgical stereomicroscope. The following results were obtained. 1) The basic arrangement of the autonomic cardiac nervous system is constant in all examined macaques. 2) A superior cardiac nerve originating from the superior cervical ganglion was not observed, whereas the thoracic cardiac nerve originating from the sympathetic trunk/ganglia under the cervicothoracic ganglion was rarely observed in all the examined macaques. 3) The main cardiac nerve is the middle cardiac nerve originating from the middle cervical ganglion, similar to the situation in humans. 4) Although the superior, inferior, and thoracic cardiac branches of the vagus nerve were consistently observed, the left thoracic cardiac branch is rarely absent because of its lower origin to the heart. 5) The cranial autonomic nerves tend to distribute into the heart medially (arterial porta), and the caudal autonomic nerves tend to distribute into the heart laterally (venous porta). To comprehend the comparative morphological and evolutionary changes more completely, these results were compared with our previous studies and some references. Consequently, differences in the sympathetic cardiac nerves of macaques and humans are recognized, in spite of the similar morphologies of the vagal cardiac branches. These differences include the composition of the cervicothoracic ganglion, the lower positions of the middle cervical and cervicothoracic ganglia, and the narrow range for the origin of the cardiac nerves in macaques compared to that in humans.     

Blood flow to long bones indicates activity metabolism in mammals, reptiles and dinosaurs

The cross-sectional area of a nutrient foramen of a long bone is related to blood flow requirements of the internal bone cells that are essential for dynamic bone remodelling. Foramen area increases with body size in parallel among living mammals and non-varanid reptiles, but is significantly larger in mammals. An index of blood flow rate through the foramina is about 10 times higher in mammals than in reptiles, and even higher if differences in blood pressure are considered. The scaling of foramen size correlates well with maximum whole-body metabolic rate during exercise in mammals and reptiles, but less well with resting metabolic rate. This relates to the role of blood flow associated with bone remodelling during and following activity. Mammals and varanid lizards have much higher aerobic metabolic rates and exercise-induced bone remodelling than non-varanid reptiles. Foramen areas of 10 species of dinosaur from five taxonomic groups are generally larger than from mammals, indicating a routinely highly active and aerobic lifestyle. The simple measurement holds possibilities offers the possibility of assessing other groups of extinct and living vertebrates in relation to body size, behaviour and habitat.     

The area postrema: a cardiovascular control centre at the blood-brain interface?

The area postrema (AP) is one of the circumventricular organs of the brain and as such it is highly vascular and lacks the normal blood-brain barrier. Anatomical tracing studies have demonstrated afferent projections to AP originating from the paraventricular nucleus, lateral parabrachial nucleus (l-PBN), nucleus tractus solitarius (NTS), as well as the vagus nerve. AP neurons have been shown to project primarily to l-PBN, and NTS. Receptor localization studies have reported dense aggregations of many specific peptide receptors in AP including those for angiotensin II (ANG), atrial natriuretic peptide (ANP), and endothelin (ET). Electrical stimulation studies have shown that activation of AP neurons at low frequencies (less than 15 Hz) results in decreases in blood pressure and heart rate, while higher frequency (greater than 20 Hz) stimulation causes increases in blood pressure. These low frequency effects on blood pressure and heart rate appear to result from activation of separate components of the autonomic nervous system. Extracellular single unit recordings have identified two functionally separate populations of AP neurons: one responsive to circulating ANG and a second apparently responsive to changes in blood pressure. In addition, AP neurons are activated by increases in circulating ET. Afferent inputs to AP neurons from 1-PBN have separate excitatory (12% of AP neurons) or inhibitory (12% of AP neurons) effects on a relatively small proportion of AP neurons. In contrast, preliminary evidence suggests a much more broadly distributed excitatory input to approximately 70% of tested AP neurons originating from the aortic depressor nerve. These studies provide considerable evidence implicating the AP as a significant neural structure regulating the cardiovascular system.     

Effect of lithium preparations on cardiac arrhythmias resulting from ligation of the common carotid arteries

In experiments on cats with dissected vagus and aortal nerves under chloralose-urethane anesthesia, ventricular disorders of the cardiac rhythm were induced by ligation of the common carotid arteries. Appearance of arrhythmias was preceded by an increase in the sympathetic activity (recorded from the inferior cardiac or renal nerve) accompanied by a rise of the arterial blood pressure and of the heart rate. Intravenous injection of lithium chloride or hydroxybutyrate resulted in lowering of the sympathetic activity, arterial blood pressure, and heart rate, and led to the recovery of the sinus rhythm.     

Effects of pituitary adenylate cyclase-activating polypeptide on cardiovascular and respiratory responses in anaesthetised dogs

This study examines some of the cardiovascular and respiratory effects of pituitary adenylate cyclase-activating polypeptide (PACAP) in anaesthetised dogs. Intravenous injection of PACAP 27 caused an increase in arterial blood pressure and an increase in heart rate. The blood pressure response was significantly reduced by adrenoceptor blockade suggesting a mechanism of action mediated in part via catecholamines. The heart rate increase was unaltered by adrenoceptor blockade suggesting a direct effect of PACAP 27. PACAP 27 also caused potentiation of cardiac slowing caused by stimulation of the vagus nerve. In addition, PACAP 27 powerfully stimulated breathing. This was probably evoked by stimulation of arterial chemoreceptors, because bilateral section of the carotid sinus nerves abolished this effect. PACAP 27 had no effect on the ability of the cardiac sympathetic nerve to increase heart rate, nor on the interaction between the sympathetic and parasympathetic systems in the heart.     

迷走神经兴奋性对HRV的影响及其机制的初步分析

实验在氯醛糖加氨基甲酸乙酯麻醉的新西兰兔上进行。记录血压,心率,心电图和心率变异性频谱分析。电刺激减压神经,疑核和右侧迷走神经外周端,均引起心率和血压下降,总变异性,低频成分,高频成分,ＬＦ／ＨＦ比值和极代频成分增大。静脉注射阿托品可使上述反应显著减小,而静脉注射心得安仅可阻断ＤＮ和ＮＡ所致ＬＦ的增大。     

Vagal innervation of guinea pig bronchial smooth muscle

We isolated the guinea pig right bronchus with the vagus nerves intact and evaluated the changes in isometric tension of the smooth muscle in response to nerve stimulation. Brief (10-s) trains of electrical field stimulation or vagus nerve stimulation caused a biphasic contraction: the "first phase" sensitive to atropine and the "second phase" sensitive to capsaicin. The two phases could be dissociated by adjusting the stimulus intensity; greater stimulus intensities (pulse durations or voltage) were required to evoke the capsaicin-sensitive phase. When stimulated at 30-min intervals, the magnitude of both phases of the contractions declined over a 2-h period of repeated stimulation; however, this was prevented by indomethacin. Stimulation of the left vagus nerve resulted in a monophasic contraction of the right bronchus, with little evidence of a capsaicin-sensitive phase. Blocking neurotransmission through the bronchial ganglion, as monitored by intracellular recording techniques, abolished the first-phase contraction but had no effect on the capsaicin-sensitive phase. Selective blockade of muscarinic M1 receptors had no effect on vagus nerve-mediated contractions. The results demonstrate that the left and right vagus nerves carry preganglionic fibers to the right bronchial ganglion. The right but not the left vagus nerve also carries capsaicin-sensitive afferent fibers that, when stimulated, result in a persistent contraction of the right bronchus. Finally, we provide functional and electrophysiological evidence supporting the hypothesis that capsaicin-sensitive afferent neurons communicate with postganglionic motoneurons within the bronchus.     

A description of the upper thoracic autonomic nervous system in the rhesus monkey (Macaca mulatta)

The purpose of this study was to describe the autonomic innervation of the carotid sinus and heart in the rhesus monkey. Nine male rhesus monkeys (Macaca mulatta) and one male crab-eating macaque (M. fascicularis) were carefully dissected from the origin of the vagus nerves and superior cervical ganglia to the level of the fourth thoracic ganglion. The specimens were either freshly killed or obtained no later than 24 hours post mortem. The macaque monkeys were found to possess an innervation pattern that displayed features common to dog (connections between the vagus nerves and middle cervical ganglia), baboon (distinct cervical sympathetic and cervical vagal nerve trunks), and man (nerves projecting from the middle cervical and stellate ganglia to the heart). Distinct inferior cervical and first thoracic ganglia were never seen, but rather, large and well defined stellate ganglia were found. The macaque innervation pattern, when considered as a whole, most closely resembled the baboon.     

Field test of a paradigm: hysteresis of heart rate in thermoregulation by a free-ranging lizard (Pogona barbata).

The discovery that changes in heart rate and blood flow allow some reptiles to heat faster than they cool has become a central paradigm in our understanding of reptilian thermoregulation. However, this hysteresis in heart rate has been demonstrated only in simplistic laboratory heating and cooling trials, leaving its functional significance in free-ranging animals unproven. To test the validity of this paradigm, we measured heart rate and body temperature (Tb) in undisturbed, free-ranging bearded dragons (Pogona barbata), the species in which this phenomenon was first described. Our field data confirmed the paradigm and we found that heart rate during heating usually exceeded heart rate during cooling at any Tb. Importantly, however, we discovered that heart rate was proportionally faster in cool lizards whose Tb was still well below the 'preferred Tb range' compared to lizards whose Tb was already close to it. Similarly, heart rate during cooling was proportionally slower the warmer the lizard and the greater its cooling potential compared to lizards whose Tb was already near minimum operative temperature. Further, we predicted that, if heart rate hysteresis has functional significance, a 'reverse hysteresis' pattern should be observable when lizards risked overheating. This was indeed the case and, during heating on those occasions when Tb reached very high levels (> 40 degrees C), heart rate was significantly lower than heart rate during the immediately following cooling phase. These results demonstrate that physiological control of thermoregulation in reptiles is more complex than has been previously recognized.     

Vasoactive intestinal polypeptide-like immunoreactivity in nerves of the pancreatic islet of the teleost fish,Gillichthys mirabilis

Summary In the teleost fish, Gillichthys mirabilis, vasoactive intestinal polypeptide (VIP)-like immunoreactivity is present in some nerve fibres of the principal pancreatic islet and surrounding tissues, the vagus and splanchnic nerves, the coeliac ganglion and the wall of the intestine. The nerves of the pancreatic islet that contain VIP-like immunoreactivity probably correspond to one of the two types of non-cholinergic, non-adrenergic (peptidergic) nerve previously described in this fish. Similarities in the localisation of hormonal peptides in fish and mammals suggest that the regulation of gastroenteropancreatic physiology in fish may resemble that of mammals.This work was supported by grants from the Medical Research Council of Great Britain and the National Institutes of Health, USA (Grant No. AM 17161)     

Distribution, origin and sensitivity to capsaicin of primary afferent substance P-immunoreactive nerves in the heart

This report is intended as an overview of the distribution, origin and sensitivity to capsaicin of substance P-immunoreactive (SP-I) primary afferent cardiac nerves. Immunohistochemical and physiological methods were employed to compare the presence and density of these nerve fibers in the guinea pig and rat hearts. SP-I fibers are numerous in the guinea pig heart including the parietal pericardium, atria, ventricles, valves, coronary arteries and around intrinsic cardiac ganglion cells. The rat heart contains few SP-I fibers. Vagotomy does not influence the number of intensity of immunoreactive fibers in the guinea pig heart. By stimulating the atrium or ventricle and recording from the second or third thoracic dorsal roots Ad1, Ad2 and C fibers were demonstrated in the atria, but only Ad fibers in the guinea pig ventricle; in addition, only Ad fibers were recorded from the vagus nerves. Only Ad1 fibers were demonstrated in the rat heart. Treatment with capsaicin depletes the SP-I and decreases the conduction velocity of C-fibers and some Ad2 fibers in the guinea pig heart. We suggest that SP-I primary afferent nerve fibers are unmyelinated (C-type) or small myelinated (Ad2-type) nerves in the guinea pig heart and that their cell bodies of origin are predominantly in dorsal root ganglia.