Electrical properties and synaptic connections of the sympathetic neurons in the rat and guinea-pig superior cervical ganglion

SUMMARY1. Na and K contents of isolated rat superior cervical ganglia were measured by flame photometry, and intracellular Na and K concentrations ([Na] 4. Restitution of ganglionic Na and K after carbachol was inhibited by washing with K-free solution, and slowed by ouabain (0-14 mM), cyanide (2 mM) or cooling (Q10 2-7 between 17 and 270 C).5. Equilibrium potentials for Na and K (EN., ER) at rest were calculated to be + 49 and -88 mV. At a membrane potential (Em) of -70 mV, the permeability ratio PNa: PK was calculated at 0-04:1 (assuming PC1: PR < 0.1).

Section: Discussionmentioning

confidence: 99%

Changes of intracellular sodium and potassium ion concentrations in isolated rat superior cervical ganglia induced by depolarizing agents

Brown¹,

Scholfield²

1974

“…In the sacral parasympathetic pathway to the large intestine and urinary bladder, preganglionic C fibres provide the major synaptic input to extramural colonic ganglia and to the large intestine, whereas preganglionic B fibres provide the major synaptic input to vesicular ganglia and to the urinary bladder (de Groat & Krier, 1976). In 135 J. KRIER, P. F. SCHMALZ AND J. H. SZURSZEWSKI the rabbit and guinea-pig superior cervical ganglion, some neurones receive convergent input from both B and C fibres (Erulkar & Woodward, 1968;Mirgorodsky & Skok, 1970;Perri, Sacchi & Casella, 1970). Thus, neurones in this ganglion, as in the inferior mesenteric ganglion of the cat, receive convergent presynaptic input from both B and C fibres.…”

Section: Discussionmentioning

confidence: 99%

Central innervation of neurones in the inferior mesenteric ganglion and of the large intestine of the cat

Krier

Schmalz

Szurszewski

1982

SUMMARY1. Segmental, lumbar sympathetic outflow to neurones in the cat inferior mesenteric ganglion and to the large intestine were studied. Synaptic responses of neurones in the inferior mesenteric ganglion were recorded intracellularly, in vitro, during electrical stimulation of preganglionic fibres in the lumbar white rami. Synaptic responses consisted of excitatory post-synaptic potentials and/or action potentials.2. None of the neurones tested received synaptic input from spinal cord segment L,. There was synaptic input from segments L2-L5 of the spinal cord. The strongest synaptic input arose from spinal cord segments L3 and L4.3. 42 % of the neurones tested received synaptic input from only one spinal cord segment. 54 % of the neurones tested received convergent synaptic input from two, three or four adjacent lumbar segments.4. Electrophysiological measurements indicated that the number of preganglionic fibres in any lumbar white ramus communicans which provided synaptic input ranged from one to thirteen. Each lumbar white ramus contained, on average, five preganglionic fibres which provided synaptic input to neurones in the inferior mesenteric ganglion.5. Changes in intraluminal colonic pressure were measured in vivo during electrical stimulation of preganglionic fibres in the different lumbar white rami and lumbar ventral roots. Electrical stimulation of white rami L3 and L4 abolished phasic changes in intraluminal colonic pressure and reduced basal pressure to near zero. Electrical stimulation of preganglionic fibres in lumbar ventral roots L3 and L4 abolished phasic changes in intraluminal colonic pressure and reduced basal pressure to near zero.Stimulation of ventral roots L,, L2 and L5 had little to no effect on intraluminal pressure.6. Based on the data obtained in this study, two hypotheses are proposed. First, spinal cord segments L3, L4 and L5 are the primary sources of central synaptic input to neurones in the inferior mesenteric ganglion. Secondly, spinal cord segments L3 and L4 control colonic motility.

“…The peak rate of 24Na extrusion (10-4 m-mole (kg cell fluid-' min-, Table 1), when adjusted for the attenuation by extracellular clearance and the specific activity of the intracellular 24Na, corresponds to about 24 m-mole, (kg cell fluid)-' min-' total Na extrusion. Assuming (i) a total intracellular volume of 05 #1. per ganglion (Brown & Scholfield, 1974 and Table 1), (ii) between 10,000 and 30,000 neurones per ganglion (per-24Na MOVEMENTS IN GANGLIA sonal observation), (iii) a coupling ratio of 3 Na: 2 K (Thomas, 1969), and (iv) a cell membrane resistance of 60-80 MQ (Perri, Sacchi & Casella, 1970;Adams & Brown, 1973 and unpublished observations), the Na current would produce an electrogenic hyperpolarization of somewhere between 15 and 60 mV. This appears an appropriate order of magnitude to account for the post-carbachol hyperpolarization (up to 5 mV observed with extracellular electrodes; Brown et al 1972).…”

Section: Discussionmentioning

confidence: 99%

Movements of labelled sodium ions in isolated rat superior cervical ganglia

Brown¹,

Scholfield²

1974

SUMMARY1. Isolated rat superior cervical ganglia were incubated in Krebs solution containing 24Na and carbachol for 4 min at 250 C. They were then washed at 30 C for 15 min to remove extracellular 24Na and the efflux of residual intracellular 24Na stimulated by warming to 250 C.2. During the 15 min wash at 30 C desaturation curves became exponential with a rate constant of 0-012 + 0 001 min-' (n = 24). This was assumed to represent loss of intracellular 2MNa, and initial uptake of 24Na was calculated therefrom by back-extrapolation to zero wash-time. After 4 min in 24Na + 180,u/M carbachol intracellular [24Na] so calculated was 61-6 + 341 mM (n = 18), representing 83 % labelling of intracellular Na.In the absence of carbachol intracellular [24Na] was 10-0 + 0-5 mM, representing 49 % labelling. Extracellular Na was labelled by > 90 % after 4 min in "Na. The apparent rate constant for washout of extracellular 2ANa was 0-6 min-' at 30 C and 0-95 min-' at 250 C.3. The loss of the residual intracellular 2MNa during temperature stimulation was interpreted quantitatively in terms of an exponential decline of the bulk of intracellular 24Na with an extrusion rate constant of 0-39 + 0-1 min-' (n = 18), efflux being delayed by passage through the extracellular space with an effective rate constant of 0-8-1-2 min-. 8. The properties of the ganglionic Na pump deduced from rates of temperature-stimulated 2MNa extrusion accord with the view that the ganglion hyperpolarization observed after Na loading by exposure to nicotinic depolarizing agents results from electrogenic Na extrusion. A comparable hyperpolarization is observed after temperature stimulation following Na loading.