Synaptic and antidromic potentials of visceral neurones in ganglia of the lumbar sympathetic chain of the cat

Experimental study on the location of neurons associated with the first sacral sympathetic trunk ganglion of the pig

The neurons associated with the left first sacral sympathetic trunk ganglion (STG S1), an autonomic ganglion particularly concerned in the innervation of the smooth and striated musculature associated with pelvic organs, were identified in the pig, using the non-trans-synaptic fluorescent retrograde neuronal tracer Fast Blue. The labelled neurons were located mostly ipsilaterally, in the intermediolateral nucleus of the spinal cord segments T10-L5, in the sympathetic trunk ganglia L3-Co1, in the caudal mesenteric ganglia, in the pelvic ganglia, and in the spinal ganglia T13-S4. Our results could indicate the existence of visceral neuronal circuits concerning the ganglia of the sympathetic trunk and the caudal mesenteric, pelvic and spinal ganglia with or without the intervention of the central nervous system, whose identification and preservation during surgical treatments could be helpful in reducing the risk of subsequent urinary and sexual disfunctions.

Comparison of central versus peripheral nerve pathways to the guinea pig inferior mesenteric ganglion determined electrophysiologically after chronic nerve section

The contributions of central versus peripheral nerve pathways to neurons of the inferior mesenteric ganglion of guinea pigs were studied. Nerve trunks innervating neurons in the ganglion were surgically sectioned and intracellular electrical responses to nerve stimulation were measured 6-8 days after surgery. Guinea pigs were divided into two experimental groups: (1) those that had the lumbar sympathetic chain ganglia (LSG) L2 through L4 removed and (2) those that had the intermesenteric, lumbar colonic and hypogastric nerves sectioned leaving central connections intact. After 6-8 days fast excitatory postsynaptic potentials (EPSPs) and slow EPSPs were recorded intracellularly in randomly selected principal ganglionic neurons. The threshold stimulus voltage to elicit a fast EPSP, the amplitude of the slow EPSP and the number of neurons in which each type of synaptic potential occurred in response to stimulation of each of the nerve trunks was compared between surgically-sectioned animals and sham-operated controls. Neither section of preganglionic nerve trunks nor of postganglionic nerve trunks eliminated all synaptic input to neurons in the ganglion, indicating that neurons with cell bodies located central to the ganglion as well as in visceral target organs made synaptic connections in the ganglion. Both fast and slow synaptic potentials could be evoked by stimulation of postganglionic nerve trunks even after they were sectioned provided that preganglionic nerves were intact, indicating that axons of central origin which synapse in the ganglion may continue out into postganglionic nerve trunks. In like manner, evidence was obtained indicating that fibers from peripheral nerve trunks which initiate either fast or slow synaptic potentials in ganglionic neurons may continue out into the lumbar splanchnic nerves. These studies demonstrate that the synaptic potentials recorded in the inferior mesenteric ganglion arise not only from neurons with cell bodies central to the ganglion but also from neurons with cell bodies located in the visceral organs which this ganglion subserves.

Morphological and electrophysiological properties of cat lumbar paravertebral neurones

The morphological and electrophysiological properties of neurones in the 3rd, 4th and 5th cat lumbar paravertebral ganglia were studied in vitro utilising intracellular injection of horseradish peroxidase (HRP) and intracellular electrophysiological recording techniques. Projections of neurones (T13-L5) were determined by in vivo HRP techniques. Two distinct soma morphologies were noted in all ganglia. Those whose long and short axes were approximately equal in length were designated as being 'spherical' and had a mean cross sectional area of 730 micron2. The remainder, whose long axis was at least 1.5 times the length of their short axis were called 'fusiform' and had a mean soma area of 540 micron2. The two cell types occurred in an approximate 2:1 ratio, respectively. The mean numbers of primary, secondary and tertiary dendrites for the population studied were 6.5, 6.3 and 3.4, respectively. Spherical cells had significantly more of each than fusiform cells as well as having a greater number of branch points and overall length of dendritic arbor. Neither cell type could be distinguished from the other based on the estimated number of fast excitatory postsynaptic potentials, the duration of the afterspike hyperpolarization or the duration of action potential discharge in response to 8-10-s depolarizing current pulses. The estimated number of synaptic potentials associated with both types of neurones (mean 10.6 +/- 1.6) correlated inversely only with the soma diameters (see Materials and Methods). It is concluded that while cat lumbar paravertebral neuronal soma may be classified into two morphologically distinct types, this is not reflected in their electrophysiological profiles. In addition, these data suggest that cat lumbar paravertebral neurones have a dendritic appearance and a degree of convergence of synaptic input previously shown to occur in this system.

Spinal origins of preganglionic B and C neurons that innervate paravertebral sympathetic ganglia nine and ten of the bullfrog

These experiments were designed to characterize the distribution, morphology, and number of spinal preganglionic neurons that selectively innervate the B- and C-type sympathetic neurons in paravertebral ganglia 9 and 10 of the bullfrog. For this purpose, horseradish peroxidase (HRP) was applied to the anterior end of the sectioned sympathetic chain between ganglia 8 and 9. Subsequent retrograde axonal transport of the HRP labeled ipsilateral spinal neurons whose cell bodies form a column having rostral and caudal boundaries that are, respectively, just caudal to the level of spinal nerve 4 and midway between the entry zones of spinal nerves 7 and 8. In all segments, the labeled preganglionic somata were found in the lateral half of the spinal gray and slightly dorsal to the central canal; a position analogous to that of the intermediolateral cell column in mammals. Most labeled preganglionic neurons were multipolar in shape, and the cell bodies lying between spinal nerves 4 and 5 were, on average, larger than those found between spinal nerves 7 and 8. In transverse sections that were cut near spinal nerve 5, the axons of preganglionic neurons could be seen to exit the cord through ventral roots. Counts of labeled preganglionic neurons indicate that an average +/- S.D. of 338 +/- 89 cells innervate ganglia 9 and 10. Selective labeling of preganglionic B neurons, by cutting spinal nerves 7 and 8 central to their rami communicantes at the time of HRP application, revealed an average +/- S.D. of 137 +/- 31 cells that lie exclusively between spinal nerves 4 and 6. By contrast, selective labeling of preganglionic C neurons, by cutting the sympathetic chain rostral to ganglion 7 at the time of HRP application, revealed an average +/- S.D. of 187 +/- 77 cells in an adjacent portion of the preganglionic column that is bounded by spinal nerve 6 and by a point midway between spinal nerves 7 and 8. These results thus demonstrate a clear segmental segregation between the preganglionic B and C neurons that innervate ganglia 9 and 10.

Cholinergic excitatory synaptic potentials of neurones in mammalian lumbar paravertebral ganglia

Synaptic potentials and the electrophysiological properties of 201 cells in the 4th lumbar paravertebral ganglia of the rabbit were studied in vitro using intracellular electrophysiological recording techniques. Cells had a mean transmembrane potential of 55.1 +/- 0.8 mV, a mean input resistance of 37.0 +/- 6.6 M omega (range 29.9-61.1) and a mean membrane time constant of 6.0 +/- 0.6 ms. Synaptic potentials in ganglionic neurones were evoked by electrical stimulation of the rami communicantes, inferior lumbar splanchnic nerves and the paravertebral chain from segments both above and below the L4 ganglion. Synaptic responses consisted of a fast, hexamethonium-sensitive component and, following short periods of higher frequency stimulation, a slow, long lasting, pirenzepine and atropine-sensitive depolarization (slow-EPSP). No phenomenon corresponding to a late slow-EPSP was observed and, under our recording conditions no cells exhibited non-cholinergic slow excitatory or slow inhibitory postsynaptic potentials. It is concluded that fast excitatory synaptic events were mediated by nicotinic receptors whereas slow excitatory synaptic events were mediated by muscarinic m1 receptors. McNeil-A-343, a muscarinic agonist, produced membrane depolarization, a decrease in membrane input conductance and in some cells a repetitive discharge of action potentials. In 60% of cells tested substance P produced a depolarization of the membrane potential with an associated decrease in membrane input conductance.

The sympathetic and sensory components of the caudal lumbar sympathetic trunk in the cat

The cell bodies of the lumbar sensory and sympathetic pre- and postganglionic neurons that project in the caudal lumbar sympathetic trunk of the cat have been labeled retrogradely with horseradish peroxidase applied to the central end of their cut axons. The application was made just proximal to the segmental ganglion that sends its gray rami to the L7 spinal nerve, and so identified the sympathetic outflow concerned primarily with the vasculature of the hindlimb and tail. The numbers, segmental distribution, location, and size of the labeled somata have been determined quantitatively. Labeled cell bodies were found ipsilaterally, but the segmental distributions of the different cell types were not matched. Afferent cell bodies lay in dorsal root ganglia L1-L5 (maximum L4), preganglionic cell bodies in spinal segments T10-L5 (maximum L2/3), and postganglionic cell bodies in ganglia L2-L5 (maximum L5). Both numbers and dimensions of labeled dorsal root ganglion cells were variable between experiments (maximum about 1,000); the majority were small relative to the entire population of sensory neurons. Labeled preganglionic cell bodies were located right across the intermediate region of the spinal cord, extending from the lateral part of the dorsolateral funiculus to the central canal. The highest density of labeled neurons lay at the border between the white and gray matter (corresponding to the intermediolateral cell column) with smaller proportions medially in L1-L2, and laterally in caudal L4-L5. Medial preganglionic neurons were generally larger than those lying in lateral positions. From the data, it is estimated that about 650 afferent, about 4,500 preganglionic, and some 2,500 postganglionic neurons project in each lumbar sympathetic trunk distal to the ganglion L5 in the cat.

The afferent and sympathetic components of the lumbar spinal outflow to the colon and pelvic organs in the cat. III. The colonic nerves, incorporating an analysis of all components of the lumbar prevertebral outflow

The cell bodies of the lumbar sensory and sympathetic pre- and postganglionic neurons that project to the colon along the inferior mesenteric artery of the cat have been labeled retrogradely with horseradish peroxidase applied to the central end of their cut axons. The numbers, segmental distribution, location, and size of these labeled somata have been determined quantitatively. Afferent cell bodies were symmetrically distributed bilaterally in dorsal root ganglia T13-L5, with the maximum number (about 80%) in L3 and L4 and most of the rest in L2. Labeled afferent somata were small relative to the entire population of DRG cells. Occasionally a few preganglionic somata were labeled in the intermediate zone of L3 and L4 spinal cord segments. Postganglionic cell bodies were labeled bilaterally in the proximal lobes of the inferior mesenteric ganglion (70-95%), in accessory ganglia of the intermesenteric nerve and of the lumbar splanchnic nerves, and in lumbar paravertebral ganglia. The segmental distribution in the lumbar sympathetic trunk was symmetrical on both sides and was the same as that of the afferent cells. Labeled postganglionic cell bodies in both the IMG and the accessory ganglia were larger than labeled and unlabeled ganglion cells in the paravertebral ganglia. From these data, it is estimated that about 2,100 afferent neurons and about 29,000 postganglionic neurons project in the lumbar colonic nerves. In conjunction with equivalent data for the hypogastric and lumbar splanchnic nerves, the results provide a quantitative and spatial description of the afferent and efferent components of the lumbar innervation of the colon and pelvic viscera.