Effect of repeated exercise on postnatal development of the noradrenaline content of the albino rat heart, spleen and skeletal muscle

The authors studied the effect of repeated elevation of sympathetic activity on the postnatal development of the noradrenaline content of tissues of the albino rat. Between the ages of 15 and 29 days, young rats were forced to swim in water heated to 25 degrees C, 3 X 30 min on weekdays and 1 X 30 min on Saturdays and Sundays. At 30, 45 and 65 days, the noradrenaline content of the tissues was determined spectrofluorometricaLly by the trihydroxyindole method. The noradrenaline content of the heart of trained rats was higher than in the controls in all the given age groups and the size of the absolute difference rose with advancing age. The noradrenaline content of the spleen developed similarly. Repeated exercise did not lead to an increase in the noradrenaline content of skeletal muscle. The results show that the repeated elevation of the activity of sympathetic adrenergic neurones which occurs in young rats during exercise is a long-term factor stimulating the development of sympathetic innervation of the heart and spleen. The development of the neurones innervating skeletal muscle was not stimulated, probably because the activity of these neurones is not increased by stress.     

Trypanosoma cruzi: acetylcholine content and cholinergic innervation of the heart in rats.

The acetylcholine content, as well as the density and distribution of cholinergic innervation were studied in the hearts of rats after inoculation with the Y strain of Trypanosoma cruzi. Cholinergic innervation was studied by histochemical techniques using acetylcholinesterase in the sinoatrial node, in fragments of the right atrium and auricular appendages. Acetylcholine was assayed on a strip of guinea pig ileum suspended in Tyrode's solution. Twenty days after inoculation, the cardiac content of acetylcholine dropped 40% and the cholinergic innervation was markedly reduced in 80 to 100% of the rats. However, at 70 and 97 days the cardiac content of acetylcholine was not different from that of the controls. The cholinergic innervation in the heart of the animals sacrificed 98 and 180 days after inoculation was normal in 60 to 66% of the rats. The results indicate that the cardiac parasympathetic innervation is damaged during the acute phase of experimental Chagas' disease, but returns to normal during the chronic phase in most animals.     

Postnatal development of chronotropic responses to chemical and electrical stimulation of adrenergic nerve endings in the sinoatrial node of the heart of the albino rat

The positive chronotropic response to stimulation of adrenergic nerve endings in the sinoatrial node was studied in isolated atria from the hearts of rats of different ages. Dimethylphenylpiperazinium (DMPP) was used for chemical stimulation and transmural stimulation of the sinoatrial node region as electrical stimulation; in both cases noradrenaline is released from the nerve endings. With both stimulation methods, postnatal development was recorded in two phases. In the first phase, positive chronotropic responses are markedly increased and attained the maximum at the age of 14 days on using DMPP and of 24 days on using electrical stimulation. In the second phase, positive chronotropic responses diminish and at the age of about 45 days, with both stimulation methods, they become reduced to adult level. The first developmental phase can be attributed to an increase in the noradrenaline content of the nerve endings and the release of a larger amount of the transmitter during stimulation, together with an increase in the noradrenaline sensitivity of the cells of the sinoatrial node. It is not clear why positive chronotropic responses decrease in the second phase, when the noradrenaline content of the myocardial tissue continues to rise and pacemaker sensitivity to noradrenaline is not reduced.     

Postnatal development of postganglionic parasympathetic neurones in the heart of the albino rat.

Electrical stimulation of the sinoatrial node region of isolated atria in medium containing physostigmine (0.1 micrograms/ml) produces a negative chronotropic effect whose intensity and duration depend mainly on the amount of acetylcholine released from postganglionic parasympathetic fibres endings. This technique was used to study functional maturation of the given neurones during postnatal development of albino rats. Preparations from animals of different ages were stimulated with 2-second bursts of rectangular pulses (frequency 50 Hz, pulse duration 0.02 ms, voltage 22.5--27.5 V) and frequency changes of the preparation were registered by recording extracellular action potentials. At 10 days the negative chronotropic effect is very weak and at 15 days it is only slightly stronger, but at 18 days it is almost the same as in adult animals. At 24 and 34 days the reaction is somewhat stronger than in adulthood. It can be concluded from these observations that functional maturation of the postganglionic parasympathetic neurones innervating the sinoatrial node in albino rats occurs between the 10th and 20th day of postnatal life.     

迷走神经对心室功能的调控机制研究进展

自主神经系统由交感神经系统和副交感神经系统（迷走神经）组成,二者相互拮抗,对哺乳动物心脏的功能调控具有重要的作用。副交感（迷走）神经对心房可产生变时、变传导和变力作用,但是对心室的支配及对心室的调控作用还不清楚。一直以来都存在一个误解,认为交感神经支配心脏的各个部位而副交感神经仅支配心脏的室上性组织,对心室没有支配。近年来的研究显示在一些哺乳动物的心脏上,胆碱能神经在心室也有分布,且对左心室的功能有重要的调控作用。本文从解剖及组织化学、分子生物学和功能学三个方面阐述迷走神经对心室的支配及调控证据,并对心章收缩功能的迷走神经（毒蕈碱）调控及其信号转导途径进行综述。     

Identification of development and autonomic nerve activity from heart rate variability in preterm infants

Heartbeat intervals, which are determined basically by regular excitations of the sinoatrial node, show significant fluctuation referred to as the heart rate variability (HRV). The HRV is mostly due to nerve activities through the sympathetic and parasympathetic branches of the autonomic nervous system (ANS). In recent years, it has been recognized that the HRV shows a greater complexity than ever expected, suggesting that it includes much information about ANS activities. In this study, we investigated relationship between HRV and development in preterm infants. To this end, heartbeat intervals were continuously recorded from 11 preterm infants in NICU. The recording periods were ranging from several days to weeks depending on the individuals. The HRV at various ages was then characterized by several indices. They include power spectrum as well as the mean and standard deviation of the series. For the power spectrum, the low-frequency band power (LF), high-frequency band power (HF), LF/HF (the ratio between LF and HF), beta (scaling exponent of the spectrum) were estimated. The detrended fluctuation analysis (DFA) was also employed to obtain short- and long-range scaling exponents. Each of these indices showed a correlation with the age. We showed that the long-range scaling exponent, derived from the DFA, was most significantly correlated with the age, suggesting that it could be a robust index to characterize the development of preterm infants.     

Relationship of the activity of cardiac cholinergic mechanisms to the state of the sympathetic innervation and its noradrenaline content in hypoxia]

Preliminary sympathectomia depletes acetylcholine (ACh) in the heart of rabbits under hypoxia. In these conditions the inhibitory action of ACh on the rat isolated heart is reduced under the noradrenaline content fall, while under increase it is potentiated. Under hypoxia noradrenaline increases concentration of potassium in the myocardium, thus stimulating ACh formation and activity. It is suggested that under deep hypoxia suppression of the sympathetic mechanisms causes functional isolation of the heart from nervous effects.     

Antiarrhythmic drugs and the modulation of autonomic control of heart rate in rabbits

A model of the components of autonomic control of heart rate was developed and used for the evaluation of quantitative contribution of sympathetic and vagal tone to cardiac function. In conscious rabbits, sequential inhibition of muscarinic and beta receptors was produced and the relative contributions of vagal and sympathetic tone were characterized. Based on the model, the magnitude of presynaptic interaction between the vagal and sympathetic nerve endings was evaluated. From data in the literature, similar analysis of the control of heart rate was performed for the rat, dog, and human subject and compared with that of the rabbit. The results show that the resting rabbit heart is under less vagal tone than sympathetic tone as compared with other species. The effects of acute administration of amiodarone on the sympathetic and parasympathetic control of heart rate as well as intrinsic heart rate were investigated. Amiodarone decreased the heart rate, which resulted from a direct effect on the sinoatrial (SA) node. In addition, it attenuated the vagal as well as the sympathetic effects on the SA node. The effect on vagal component was greater. Further, the effects of other antiarrhythmic drugs on the electrocardiographic PP and PR intervals were studied. The usefulness of this model for the analysis of the effects of antiarrhythmic drugs is presented.     

The distribution of sympathetic nerve fibres in the AV node and AV bundle of the bovine heart

The sympathetic nervous system has important effects on the properties of the heart, including the conduction of the impulse. However, it is not known how this nervous system is distributed in the atrioventricular (AV) bundle, which together with the AV node constitutes the only conduction pathway between the atria and ventricles in normal hearts. Therefore, in the present study the adrenergic innervation in the bovine AV node/AV bundle was examined by use of the glyoxylic acid induced method for histofluorescence demonstration of catecholamines. Acetylcholinesterase (AChE) histochemistry was also used. It was found that the AChE-positive nerve fascicles in these regions partly contain sympathetic nerve fibres, that sympathetic nerve fibres occur in the proximity of some of the ganglionic cells that occur outside the AV node/AV bundle, that the arteries supplying AV bundle tissue as well as AV nodal tissue have perivascular plexuses of sympathetic nerve fibres, and that there is a substantial number of sympathetic nerve fibres outside Purkinje fibre bundle surfaces. The observations give new insight into the question of the distribution of the sympathetic nerves in the AV bundle in relation to the distribution of these nerves in the AV node. Possible functional implications of the observations are discussed.     

Histochemical and chemical studies on pre- and postnatal development of the different systems of “short” and “long” adrenergic neurons in peripheral organs of the rat

Summary The adrenergic innervation in the submaxillary gland, heart, kidney, small intestine, and accessory male genital organs and the development of the adrenal chromaffin cells and the sympathetic ganglia were studied in the rat from 15 days post coitum to 16 days post partum using the fluorescence histochemical method of Falck and Hillarp. The postnatal development of the noradrenaline concentrations in the heart and vas deferens was followed by fluorometric determinations.At about 15 days post coitum, the anlagen of the sympathetic chains were well visible in the form of two dorsal segmented columns of small branching sympathicoblasts exhibiting an intense catecholamine fluorescence. In the midline, ventrally to these two anlagen, another column of sympathicoblasts developed; this seemed to give rise to the prevertebral ganglia and to the short adrenergic neurons supplying the internal genital organs. At the level of the adrenal anlagen, small intensely fluorescent chromaffin cells were collected in two bilateral groups which became enclosed by adreno-cortical cells. This enclosure was, however, not complete even at two weeks post partum.Bundles of growing sympathetic nerves were visible in the periphery of the various organs studied at 19–21 days post coitum. A terminal innervation of the organs suggestive of a functional transmitter mechanism did not start to establish until at or immediately after birth. The final pattern of innervation was usually reached at about one week post partum, and the following development proceeded largely in the form of a quantitative increase in the number of nerves participating in the innervation apparatus. The adult level of noradrenaline in the heart and vas deferens was reached three to five weeks after birth. The small intestine was an exception in that the final pattern of innervation in the wall was attained immediately after birth.There was no overt difference in the rate of development of the terminal sympathetic innervation in organs supplied by short adrenergic neurons (accessory male genital organs) compared to the innervation of the submaxillary gland, heart and kidney, which receive classical long adrenergic neurons.The work was supported by a grant from the Association for the Aid of Crippled Children, New York, and was carried out within a research organization sponsored by the Swedish Medical Research Council (grants No. B71-14X-56-07A and B71-14X-712-06A).     

Age-related changes in the innervation of the prostate gland

The adult prostate gland grows and develops under hormonal control while its physiological functions are controlled by the autonomic nervous system. The prostate gland receives sympathetic input via the hypogastric nerve and parasympathetic input via the pelvic nerve. In addition, the hypogastric and pelvic nerves also provide sensory inputs to the gland. This review provides a summary of the innervation of the adult prostate gland and describes the changes which occur with age and disease. Growth and development of the prostate gland is age dependent as is the occurrence of both benign prostate disease and prostate cancer. In parallel, the activity and influence of both the sympathetic and parasympathetic nervous system changes with age. The influence of the sympathetic nervous system on benign prostatic hyperplasia is well documented and this review considers the possibility of a link between changes in autonomic innervation and prostate cancer progression.     

Thematic review series: adipocyte biology. Sympathetic and sensory innervation of white adipose tissue

During our study of the reversal of seasonal obesity in Siberian hamsters, we found an interaction between receptors for the pineal hormone melatonin and the sympathetic nervous system (SNS) outflow from brain to white adipose tissue (WAT). This ultimately led us and others to conclude that the SNS innervation of WAT is the primary initiator of lipid mobilization in these as well as other animals, including humans. There is strong neurochemical (norepinephrine turnover), neuroanatomical (viral tract tracing), and functional (sympathetic denervation-induced blockade of lipolysis) evidence for the role of the SNS in lipid mobilization. Recent findings suggest the presence of WAT sensory innervation based on strong neuroanatomical (viral tract tracing, immunohistochemical markers of sensory nerves) and suggestive functional (capsaicin sensory denervation-induced WAT growth) evidence, the latter implying a role in conveying adiposity information to the brain. By contrast, parasympathetic nervous system innervation of WAT is characterized by largely negative neuroanatomical evidence (viral tract tracing, immunohistochemical and biochemical markers of parasympathetic nerves). Functional evidence (intraneural stimulation and in situ microdialysis) for the role of the SNS innervation in lipid mobilization in human WAT is convincing, with some controversy regarding the level of sympathetic nerve activity in human obesity.     

White adipose tissue lacks significant vagal innervation and immunohistochemical evidence of parasympathetic innervation

Converging evidence indicates that white adipose tissue (WAT) is innervated by the sympathetic nervous system (SNS) based on immunohistochemical labeling of a SNS marker (tyrosine hydroxylase [TH]), tract tracing of WAT sympathetic postganglionic innervation, pseudorabies virus (PRV) transneuronal labeling of WAT SNS outflow neurons, and functional evidence from denervation studies. Recently, WAT para-SNS (PSNS) innervation was suggested because local surgical WAT sympathectomy (sparing hypothesized parasympathetic innervation) followed by PRV injection yielded infected cells in the vagal dorsomotor nucleus (DMV), a traditionally-recognized PSNS brain stem site. In addition, local surgical PSNS WAT denervation triggered WAT catabolic responses. We tested histologically whether WAT was parasympathetically innervated by searching for PSNS markers in rat, and normal (C57BL) and obese (ob/ob) mouse WAT. Vesicular acetylcholine transporter, vasoactive intestinal peptide and neuronal nitric oxide synthase immunoreactivities were absent in WAT pads (retroperitoneal, epididymal, inguinal subcutaneous) from all animals. Nearly all nerves innervating WAT vasculature and parenchyma that were labeled with protein gene product 9.5 (PGP9.5; pan-nerve marker) also contained TH, attesting to pervasive SNS innervation. When Siberian hamster inguinal WAT was sympathetically denervated via local injections of catecholaminergic toxin 6-hydroxydopamine (sparing putative parasympathetic nerves), subsequent PRV injection resulted in no central nervous system (CNS) or sympathetic chain infections suggesting no PSNS innervation. By contrast, vehicle-injected WAT subsequently inoculated with PRV had typical CNS/sympathetic chain viral infection patterns. Collectively, these data indicate no parasympathetic nerve markers in WAT of several species, with sparse DMV innervation and question the claim of PSNS WAT innervation as well as its functional significance.     

Autoimmune sympathectomy in fetal rabbits

An autoimmune model for in utero immunosympathectomy of fetal rabbits was developed. Non-pregnant, female rabbits were injected with purified nerve growth factor and then bred after confirmation of high titers of anti-nerve growth factor antiserum. Fetuses were delivered and sacrificed at 27 and 31 days gestation and tissue norepinephrine concentration was used as an index of sympathetic innervation. There were significant reductions in tissue norepinephrine at both gestational ages. At 31 days there was a 32% reduction in lung norepinephrine concentration, 46% in the heart and 60% in brown adipose tissue. Corresponding reductions at 27 days were 68% for lung, 44% for heart and 49% for brown adipose tissue. Adrenal catecholamine content was unaffected but para-aortic gland catecholamines were slightly increased. Pulmonary beta adrenergic receptors showed a 30% up regulation in response to dennervation. Carcass weight was reduced 15% to 11% in the dennervated animals. These results demonstrate that dependence of organ sympathetic innervation on nerve growth factor can be demonstrated as early as 27 days gestation. This is a useful model to study the timing and dependence of organ sympathetic innervation on nerve growth factor and the factors which regulate this dependence.     

Heart rate variability in conscious neonatal swine: spectral features and responses to short-term intermittent hypoxia

Background  

Spectral analysis of the cardiac time series has been used as a tool for assessing levels of parasympathetic and sympathetic modulation of the sinoatrial node. In the present investigation we evaluated daily changes in heart rate variability spectra in conscious neonatal piglets that were either neurally intact (n = 5) or had undergone right stellate ganglionectomy (n = 5). The partial stellectomized animals and their intact litter mates were exposed to four days of intermittent hypoxia, each day comprising nine episodes of hypoxia alternating with nine episodes of normoxia. A time control group (n = 7) comprised animals from different litters that were not exposed to intermittent hypoxia. We hypothesized that exposure to intermittent hypoxia would increase sympathetic efferent neuronal modulation of heart rate variability spectra in neurally intact animals and in those with right stellate ganglionectomy, and that his effect would be observed in heart rate variability spectra computed from baseline recordings.     

Interactions within the intrinsic cardiac nervous system contribute to chronotropic regulation

The objective of this study was to determine how neurons within the right atrial ganglionated plexus (RAGP) and posterior atrial ganglionated plexus (PAGP) interact to modulate right atrial chronotropic, dromotropic, and inotropic function, particularly with respect to their extracardiac vagal and sympathetic efferent neuronal inputs. Surgical ablation of the PAGP (PAGPx) attenuated vagally mediated bradycardia by 26%; it reduced heart rate slowing evoked by vagal stimulation superimposed on sympathetically mediated tachycardia by 36%. RAGP ablation (RAGPx) eliminated vagally mediated bradycardia, while retaining the vagally induced suppression of sympathetic-mediated tachycardia (-83%). After combined RAGPx and PAGPx, vagal stimulation still reduced sympathetic-mediated tachycardia (-47%). After RAGPx alone and after PAGPx alone, stimulation of the vagi still produced negative dromotropic effects, although these changes were attenuated compared with the intact state. Negative dromotropic responses to vagal stimulation were further attenuated after combined ablation, but parasympathetic inhibition of atrioventricular nodal conduction was still demonstrable in most animals. Finally, neither RAGPx nor PAGPx altered autonomic regulation of right atrial inotropic function. These data indicate that multiple aggregates of neurons within the intrinsic cardiac nervous system are involved in sinoatrial nodal regulation. Whereas parasympathetic efferent neurons regulating the right atrium, including the sinoatrial node, are primarily located within the RAGP, prejunctional parasympathetic-sympathetic interactions regulating right atrial function also involve neurons within the PAGP.     

Causal interactions between the cerebral cortex and the autonomic nervous system

Mental states such as stress and anxiety can cause heart disease.On the other hand,meditation can improve cardiac performance.In this study,the heart rate variability,directed transfer function and corrected conditional entropy were used to investigate the effects of mental tasks on cardiac performance,and the functional coupling between the cerebral cortex and the heart.When subjects tried to decrease their heart rate by volition,the sympathetic nervous system was inhibited and the heart rate decreased.When subjects tried to increase their heart rate by volition,the parasympathetic nervous system was inhibited and the sympathetic nervous system was stimulated,and the heart rate increased.When autonomic nervous system activity was regulated by mental tasks,the information flow from the post-central areas to the pre-central areas of the cerebral cortex increased,and there was greater coupling between the brain and the heart.Use of directed transfer function and corrected conditional entropy techniques enabled analysis of electroencephalographic recordings,and of the information flow causing functional coupling between the brain and the heart.     

Innervation of the proximal urethra of ovariectomized and estrogen-treated female rats

The proximal urethra plays a central role in maintaining urinary continence, and sympathetic excitatory innervation to urethral smooth muscle is a major factor in promoting tonic contraction of this organ. Elevated estrogen levels are often associated with incontinence in humans. Because elevated estrogen levels result in degeneration of sympathetic nerves from the closely related uterine smooth muscle, we examined the effects of chronic estrogen administration on proximal urethral innervation. Ovariectomized virgin female rats received either vehicle or 17 beta-estradiol for 1 week, and smooth muscle size and parasympathetic, sensory and sympathetic nerve densities were assessed quantitatively throughout the first 3 mm of the proximal urethral smooth muscle. In vehicle-infused ovariectomized rats, parasympathetic nerves immunoreactive for vesicular acetylcholine transporter were most abundant, while calcitonin gene-related peptide-immunoreactive sensory nerves and tyrosine hydroxylase-immunoreactive sympathetic nerves were less numerous. The densities of parasympathetic and sensory nerves remained constant along the proximal urethra, while sympathetic nerves showed a significant increase along a proximal-distal gradient. Administration of 17beta-estradiol for 7 days via subcutaneous osmotic pump did not change smooth muscle area in sections, and neither densities nor total innervation of any nerve population was altered. These findings reveal a rich cholinergic innervation of the proximal urethra, and a pronounced gradient in sympathetic innervation. Unlike the embryologically similar uterine smooth muscle, estrogen does not influence muscle size or composition of innervation, indicating that estrogen's actions on innervation are highly target-specific. Thus, estrogen's effects on urinary continence apparently occur independently of any significant remodeling of smooth muscle or resident innervation.     

Autonomic nervous nonlinear interactions lead to frequency modulation between low- and high-frequency bands of the heart rate variability spectrum

Cardiac sympathetic and parasympathetic neural activities have been found to interact with each other to efficiently regulate the heart rate and maintain homeostasis. Quantitative and noninvasive methods used to detect the presence of interactions have been lacking, however. This may be because interactions among autonomic nervous systems are nonlinear and nonstationary. The goal of this work was to identify nonlinear interactions between the sympathetic and parasympathetic nervous systems in the form of frequency and amplitude modulations in human heart rate data. To this end, wavelet analysis was performed, followed by frequency analysis of the resultant wavelet decomposed signals in several frequency brackets defined as very low frequency (f < 0.04 Hz), low frequency (LF; 0.04-0.15 Hz), and high frequency (HF; 0.15-0.4 Hz). Our analysis suggests that the HF band is significantly modulated by the LF band in the heart rate data obtained in both supine and upright body positions. The strength of modulations is stronger in the upright than supine position, which is consistent with elevated sympathetic nervous activities in the upright position. Furthermore, significantly stronger frequency modulation than in the control condition was also observed with the cold pressor test. The results with the cold pressor test, as well as the body position experiments, further demonstrate that the frequency modulation between LF and HF is most likely due to sympathetic and parasympathetic nervous interactions during sympathetic activations. The modulation phenomenon suggests that the parasympathetic nervous system is frequency modulated by the sympathetic nervous system. In this study, there was no evidence of amplitude modulation among these frequencies.     

Dependence of the cytotoxic effect of guanethidine on the degree of sympathetic activity

Young rats aged 15-29 days received a subcutaneous injection of guanethidine sulphate (5 mg/kg body weight) every day. Owing to damage to the postganglionic sympathetic neurones, on about the 60th day of life we observed a significant decrease in the noradrenaline concentration in these animals' hearts compared with the controls. If every guanethidine injection was followed immediately by intensive physical exercise, there was no drop in the heart noradrenaline concentration. Physical exercise of the same intensity performed a few hours before injecting guanethidine did not prevent the drop in the noradrenaline concentration in the heart. The results show that an exercise-induced increase in sympathetic activity, at a time when guanethidine is circulating in the blood and accumulating in the adrenergic neurones, inhibits the cytotoxic effect of guanethidine. Isolated physical exercise performed between the 15th and 29th day of life leads to an increase in the noradrenaline content of the heart of rats aged 60 days.