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At least 1,351 records · Page 75Linked to original sources
PubMed1997

[Efferent sympathetic preganglionic and afferent spinal transit pathways of the cat stellate ganglion].

Using a technique of retrograde axonal transport of horseradish peroxidase, labeled neurons were detected in the intermedialateral nucleus (pars principalis and pars funicularis), intercalatous spinal nucleus, and in the ventral horns of the spinal cord in cats. Afferent spinal transit pathways pass in all the above branches as well as the vertebral nerve. Bodies of the labeled neurons with branches passing in the vertebral nerve are located in the T2-T7 spinal ganglia, whereas those with branches passing in other nerves--are located in the C8-T8.

Afferent Pathways↗
PubMed2002

The influence of baclofen on reflex circulatory reactions evoked by stimulation of the vagus nerve in the rabbit.

The purpose of our investigations was to investigate the effect of baclofen upon the reflex fall of arterial blood pressure and heart rate evoked by stimulation of bilateral vagus nerves. The experiments were carried out on 30 rabbits of both sexes and mixed breed weighing 3000-4500 g under urethane anaesthesia (1.5 g/kg). Mean arterial pressure and heart rate were measured in the ear middle artery by the electromanometer and registered by PC computer. Parameters of stimulation were: frequency 5c/s., duration-20 s., width of single rectangular pulse-1 msec., intensity of stimulation--multiplicity of threshold excitation (T). The intervals between stimulations were not shorter than 5 min. Baclofen was administrated intravenously (1.0 mg/kg). In the control group the facilitation of circulatory reaction was observed only at the smallest intensity of stimulation (1.0T-1.5T). When greater intensity of stimulations was applied the sum of unilateral effects was greater than the effect of simultaneous bilateral vagus nerve stimulation. This occlusion effect increased up to the stimulus value of 4-5T. After baclofen administration the facilitation of circulatory responses disappeared and only occlusion was observed. Baclofen increased the size of the area of active overlapping of the afferent innervation of the vagus nerve. Administration of baclofen produced an increase in mean arterial blood pressure (15 +/- 6 mm Hg) and heart rate (16 +/- 5 beats per minute) and decrease in the vagal reflex fall of mean arterial pressure and heart rate. Stimulating of the GABAB receptors markedly attenuates the baroreceptor reflex resulting in increase in mean arterial blood pressure and heart rate. These results support the hypothesis that GABA acts tonically on GABAB receptors to attenuate the baroreceptor reflex, thereby contributing to the regulation of circulatory parameters.

Afferent Pathways↗
PubMed1985

[Reactions of hypothalamic neurons to stimulation of the pelvic and sciatic nerves].

Unit activity of posterior, tuberal and anterior parts of the hypothalamus was studied during stimulation of the pelvic nerve in anesthetized and immobilized cats. Comparative analysis showed that neurons of the posterior hypothalamus were more responsive (89.6%) and had a shorter mean latency (33.3 +/- 2.4 msec) than neurons of more rostral parts of the hypothalamus. The focus of maximal pelvic-induced unit activity seems to be located in the posterior hypothalamus. The unit responses of the posterior hypothalamus evoked by pelvic nerve stimulation had long recovery cycles and were suppressed at low frequencies of stimulation. These findings suggest a polysynaptic organization of pelvic afferent projection in the hypothalamus. A high degree of convergence of the visceral and somatic afferent signals onto single neurons was found during stimulation of pelvic and sciatic nerves. The functional role of neurons of integrative types is discussed.

Afferent Pathways↗
PubMed1973

Organization of efferent extraspinal sympathetic pathways in Rana esculenta.

Origin and distribution of pre- and postsynaptic fibres in the sympathetic trunk of Rana esculenta (from ganglion 3 to ganglion 10) have been investigated by means of extracellular recordings. Two systems conducting efferent information appear to exist: 1) a system made of faster conducting fibres (B group pre- and postsynaptic fibres); presynaptic fibres originating from a very high monosegmental source (4th spinal root); postsynaptic fibres leave the sympathetic chain plurisegmentally (rami communicantes 5-10); 2) a system made of slower conducting fibres (C group pre- and postsynaptic fibres) originating plurisegmentally from spinal roots 5-8. Intracellular recordings have shown that: 1) integrative processes take place in the amphibian sympathetic trunk, as in the mammalian one, but are quantitatively lesser. Homonomous (B-B) and heteronomous (B-C) convergence has been observed in B neurons, and also the convergence of a collateral of a C postsynaptic axon on B neurons. 2) posthumous depolarizations are present: these are events modulating the activity of sympathetic neurons. In B neurons posthumous depolarization follows orthodromic responses, and a late posthumous depolarization can be seen in B and C neurons following either ortho- or antidromic stimulation.

Animals↗
PubMed1977

Changes of certain cardio-vascular parameters and the sympathetic nervous activity upon afferent vagal stimulation in cats.

Afferent stimulation of the cervical vagus in cats for 5 s upon bilateral vagotomy reduces systemic blood pressure by 15--50 percent. The maximum of this depressor reaction occurs 10--15 s after the beginning of the stimulation, its latency being 2--3 s. The decrease in the blood pressure is preceded by inhibition of the electrical activity of some preganglionic (n. splanchnicus) and postganglionic (n. cardiacus and n. renalis) sympathetic nerves with 100--200 ms latency. During the maximum pressure decrease activity appears in the above-mentioned nerves, afterwards the pressure begins to rise until its normalization. In addition to the decrease in systemic blood pressure changes are also observed in other cardio-vascular parameters, namely, decrease in the pressure in the left ventricle, decrease in the contractile force of the heart (dp/dt max) and of the heart rate.

Afferent Pathways↗
PubMed1982

Effects of stimulating the lumbar sympathetic trunk on cat hindlimb muscle spindles.

1. The effect of stimulating the lumbar sympathetic trunk has been observed on cat lumbrical and tenuissimus muscle spindles. 2. Spindle afferent discharges were recorded either from single Ia fibers in teased dorsal root filaments or from a large number of spindles by integrating their discharges led from muscles nerves. 3. Blood flow in small arteries supplying the muscle was observed through a microscope during and after the stimulation of the sympathetic trunk. 4. In some spindles repetitive stimulation of the sympathetic trunk elicited, after a few seconds delay, a small increase in firing rate. This can be ascribed to a direct action of sympathetic axons on the spindles because it precedes by about 20-30 sec the reduction of blood flow observed in the muscle arteries. This effect is not accompanied by a change in dynamic sensitivity of the primary ending. 5. This early effect is followed, after 20-30 sec, by a later rise in firing frequency which still progresses after the end of stimulation and eventually terminates in an abrupt fall in firing often leading to interruption of the ending activity. Recovery takes places at a variable time after the blood flow has bee reestablished. These long lasting effects can be ascribed to reduction of blood flow in muscle spindles since they are always associated with changes in blood flow in muscle arteries and since they are mimicked by occlusion of the muscle circulation. 6. In some spindles, the amplitudes of frequencygrams elicited by stimulation of static gamma axons were slightly increased suggesting a weak facilitatory effect on the contraction of some intrafusal muscle fibers.

Adrenergic Fibers↗
PubMed1981

Brain sites for the antihypertensive action of clonidine.

In conclusion, I reviewed recent literature that directly investigated the site and mechanism of action of clonidine in the central nervous system. One can interpret these data in the following manner. In the medulla, clonidine is acting as an alpha-adrenergic receptor antagonist that inhibits excitatory input to the sympathetic nervous system. In the anterior hypothalamus, clonidine is acting as an alpha-adrenergic receptor agonist that excites an inhibitory pathway which inhibits excitatory input to the sympathetic nervous system. Both actions produce the same final response; that is, diminished sympathetic outflow from the central nervous system.

Afferent Pathways↗
PubMed1983

[Functional characteristics of the conduction pathways of the caudal sympathetic mesenteric ganglion in the monkey (Macaca rhesus)].

Chronic experiments in anesthetized monkeys showed that pathways from the preganglionic branches of the ganglion (the lumbar splanchnic nerves) to the postganglionic branches were represented by fibers with different conduction velocity which ran through the ganglion without interruption. These pathways are, probably, the afferents or fibers of postganglionic sympathetic neurons. In addition, synaptically contacting pathways are present. All peripheral nerves of the ganglion are connected with each other through synaptically contacting pathways. The preganglionic branches (the lumbar splanchnic nerves, intermesenteric tract) are the independent channels without tracts connecting them. The proper reflexes related to the function of the pelvic organs are assumed to be actualized by the fibers of the reflex are closed in the ganglion. The scheme of conducting pathways of the ganglion in monkeys is presented.

Action Potentials↗
PubMed1983

[Neural control of saliva secretion. Review of questions on special neurosecretory functions of the facial nerve].

Fifty years ago, anatomists and physiologists still held the opinion that the N. facialis had a purely motor fuction without any sensory or secretory components. With respect to the previously only occasionally mentioned possibility of an additional neurosecretory function of the N. facialis, clinical and experimental, especially neurophysiological research and experiences of the last five decades have however led to results which are being discussed under particular consideration of the neural control of salivary secretion. In this connection, side-functions are discussed that are just appearing in outlines and have not yet been fully cleared up, for example questions regarding an internal secretion of certain parts of the facial nerve, especially related to the patotid gland. In connection with this question, the author considered it necessary to refer to some medical-historical findings of earlier times.

Afferent Pathways↗
PubMed1994

[Bronchial hyperreactivity: neurogenic factors].

Over the last fifty years, the role of neurogenic factors in asthma and bronchial hyperreactivity has been intensively investigated. The roles of the cholinergic and adrenergic nervous systems have been clarified and several sub-types of muscarinic receptors identified. The localisation and functions of both muscarinic and adrenergic receptors have been further specified. It has also been shown that afferent nerve fibers as well as sympathetic and parasympathetic nerve fibers secrete various neuropeptides. The physiological role of these peptides is not yet known but it appears that they have a powerful effect on bronchial smooth muscle tone, microvascular permeability, mucus secretion and secretion of mediators by inflammatory cells. The results of numerous studies suggest that there are several abnormalities in the adrenergic and cholinergic nervous systems of asthmatic patients, but that these abnormalities are not themselves the cause of bronchial hyperreactivity. They may however contribute to enhance it. The role of the various newly identified neuropeptides in the genesis and maintenance of bronchial hyperreactivity remains to be determined.

Adrenergic Fibers↗
PubMed1995

[A pharmacological analysis of the central control of the preganglionic sympathetic neurons during stimulation of the afferent nerve fibers of the digestive tract].

In acute experiments on cats, effect of adrenergic brain neurons on impulse activity of preganglionic fibers of the left splanchnic nerve was studied. Afferent fibers of nerves innervating the stomach, duodenum, ileum and ileocecal angle were electrically stimulated. Phenoxybenzamine, obsidan, amizyl, iprazid, nuredal, dalargine, and morphine were used for pharmacological analysis. Nerves, stimulation at 20 Hz of different segments of the digestive tract was accompanied by different inhibition of preganglionic neurons. Sympathetic-stimulating effects were observed more frequently at 5 Hz stimulation. After vagotomy, alpha- and beta-adrenoreceptor block, central cholinoreceptor and monoamine oxidase (MAO) block, and after dalargine (0.1 and 0.01 mg/kg) nerves stimulation at 20 Hz was followed by sympathetic-stimulating effect. A weak regulatory effect of morphine (1 and 10 mg/kg) on ileal nerve stimulation effects was shown. It is suggested that excitation from afferent neurons of the vagus is transmitted to central cholinergic neurons which, in their turn, excite adrenergic neurons of the brain, and the latter inhibit impulsation of preganglionic fibers. MAO block increased the balance of excitatory effect of serotonin on spinal reflexes. Morphine and dalargine intracentrally may block adrenergic and cholinergic transmissions, as well as decrease the release of substance P from afferent neurons. Their regulatory action is revealed when different frequencies of stimulation are used.

Afferent Pathways↗