Journal of the autonomic nervous system
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The role of autonomic and somatic neural pathways involved in the control of penile erectile tissue was investigated in an in vivo rat model. Intracavernous pressure (ICP) changes were recorded during single or combined electrical stimulation of peripheral nerves in anesthetized rats. Stimulation of the pelvic and cavernous nerves elicited similar ICP increases. ⋯ In this model, penile erection appeared to be dependent on the recruitment of sacral parasympathetic outflow. Additional recruitment of efferent somatic fibers present in the motor branch of the pudendal nerve could participate in more rigid erection. This study provides new information about the organization of the pathways through which the rat penis is innervated, and would be of interest to investigators in the field of male sexual function.
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J. Auton. Nerv. Syst. · May 1995
Internal connections in the rostral ventromedial medulla of the rat.
Physiological and pharmacological data suggest that the rostral ventromedial medulla (RVM) is an important site where integration between somatic and visceral functions might occur. The aim of the present study was to describe the interconnections between various nuclei of the rostral ventromedial medulla and thus reveal the possible anatomical basis for such functional interactions. The topography of anterogradely labelled internal projections was examined following iontophoretic microinjections of Phaseolus vulgaris leucoagglutinin (PHA-L). ⋯ Connections from the raphe magnus were altogether restricted to the RVM and the medial aspects of the lateral paragigantocellular nucleus. The diffuse and dense intramedullary connections of the raphe obscurus suggest that it might have an important role in coordinating the activity of rostral ventral medullary cells. The raphe pallidus and the ventral gigantocellular nuclei, areas that were innervated from widespread regions of the rostral ventral medulla but gave only limited projections there, are more likely to be involved in the direct descending control of spinal activities.
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J. Auton. Nerv. Syst. · Apr 1995
Clinical TrialClassification of human peripheral nerve fibre groups by conduction velocity and nerve fibre diameter is preserved following spinal cord lesion.
(1) Single nerve fibre action potentials (APs) of lower sacral nerve roots were recorded extracellularly with two pairs of wire electrodes during an operation in which an anterior root stimulator for bladder control was implanted in 9 humans with a spinal cord lesion and dyssynergia of the urinary bladder. Roots that were not saved and that were used to record from were later used for morphometry. (2) Nerve fibre groups were identified by conduction velocity distribution histograms of single afferent and efferent fibres and partly by nerve fibre diameter distribution histograms, and correlation analysis was performed. Group conduction velocity values were obtained additionally from compound action potentials (CAPs) evoked by electrical stimulation of nerve roots and the urinary bladder. (3) The group conduction velocities and group nerve fibre diameters had the following pair-values at 35.5 degrees C: Spindle afferents: SP1 (65 m/s/13.1 microns), SP2 (51/12.1); touch afferents: T1 (47/11.1), T2 (39/10.1), T3 (27/9.1), T4 (19/8.1); urinary bladder afferents: S1 (41 m/s/-), ST (35/-); alpha-motoneurons: alpha 13 (-/14.4), alpha 12 (65m/s/13.1 microns), alpha 11 (60?/12.1)(FF), alpha 2 (51/10.3)(FR), alpha 3 (41/8.2)(S); gamma-motoneurons: gamma beta (27/7.1), gamma 1 (21/6.6), gamma 21 (16/5.8), gamma 22 (14/5.1); preganglionic parasympathetic motoneurons: (10 m/s/3.7 microns). (4) The values of group conduction velocity and group nerve fibre diameter measured in the paraplegics were very similar to those obtained earlier from brain-dead humans and patients with no spinal cord lesions. ⋯ Thus, the classification and identification of nerve fibre groups remained preserved following spinal cord lesion. A direct comparison can thus be made of natural impulse patterns of afferent and efferent nerve fibres between paraplegics (pathologic) and brain-dead humans (supraspinal destroyed CNS, in many respects physiologic). (5) When changing the root temperature from 32 degrees C to 35.5 degrees C, the group conduction velocities changed in the following way in one case: SP2: 40 m/s (32 degrees C) to 50 m/s (35.5 degrees C), S1: 31.3 to 40, ST: 25 to 33.8, M: 12.5 to 13.8; alpha 2: 40 to 50, alpha 3: 33 to 40. The group conduction velocities showed different temperature dependence apart from SP2 fibres and alpha 2-motoneurons. (6) Upon retrograde bladder filling the urinary bladder stretch (S1) and tension receptor afferent (ST) activity levels were undulating and increased.(ABSTRACT TRUNCATED AT 400 WORDS)
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J. Auton. Nerv. Syst. · Dec 1994
Neuronal expression of Fos protein in the rat brain after baroreceptor stimulation.
The purpose of this study was to identify the CNS neurons that express Fos protein after repeated activation of the baroreceptor reflex. This was done in Wistar rats anesthetized with urethane and alpha-chloralose with careful physiological controls. The intact control rat showed few Fos-immunoreactive (ir) neurons, whereas the anesthetized control rat showed many Fos-ir neurons in the CNS from the medulla oblongata to the forebrain. ⋯ No significant correlation was found in the humoral control nuclei in the preoptico-hypothalamic structure. Fos expression was never detected in the sensory neurons in the ganglia petrosum and nodosum, and in the sympathetic preganglionic neurons in the intermediolateral nucleus of the thoracic spinal cord. This study shows that Fos expression in the CNS neurons is induced not only by baroreceptor stimulation but also by anesthesia and/or sham-operation, and that Fos expression in the NTSm and PAG neurons faithfully responds to baroreceptor stimulation.
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J. Auton. Nerv. Syst. · Mar 1994
Role of vagal afferents in the haemodynamic response to acute central hypovolaemia in unanaesthetized rabbits.
In unanaesthetized mammals, including rabbits, the response to acute central hypovolaemia is biphasic. An initial phase of baroreflex-mediated systemic vasoconstriction is succeeded by an abrupt failure of sympathetic vasoconstrictor drive and haemodynamic decompensation. We have tested whether a signal travelling in the cervical vagus nerves is responsible for the second phase. ⋯ Vagotomy had no effect on Phase I, but the onset of Phase II was delayed until CI had fallen by approximately 53% in 6 rabbits. In 1 rabbit, Phase II did not occur, even though CI had fallen by 67%. We conclude that an afferent vagal signal does not contribute to the compensatory Phase I, and is not essential for the occurrence of the decompensatory Phase II, of acute central hypovolaemia in unanaesthetized rabbits.