Physiology of the Autonomic Nervous System

103

104

Section: Discussionmentioning

confidence: 56%

Slow excitatory synaptic potentials recorded from neurones of guinea‐pig submucous plexus.

Surprenant¹

1984

103

104

“…Similar results have been reported by Katayama & Nishi (1982) and Jan & Jan (1982) for the late slow e.p.s.p. and by Kobayashi & Libet (1968, Kuba & Koketsu (1974, 1976), and McCort, Nash & Weight (1982 for the muscarinic e.p.s.p.…”

Section: Discussionmentioning

confidence: 99%

“…Attention has recently been focussed on the paravertebral sympathetic ganglia of the frog in which four distinct synaptic signals are produced by nerve stimulation (Skok, 1973;Nishi, 1974;Volle, 1975;Ginsborg, 1976;Kuba & Koketsu, 1978;Libet, 1979;Kuffler, 1980;Weight, 1982). Following stimulation of preganglionic fibres, release of acetylcholine (ACh) from nerve terminals evokes in a ganglion cell a fast excitatory post-synaptic potential (e.p.s.p.)…”

Section: Introductionmentioning

confidence: 99%

Peptidergic and muscarinic excitation at amphibian sympathetic synapses.

Kuffler¹,

Sejnowski²

1983

123

SUMMARY1. A single-electrode voltage clamp was used to study the slow muscarinic and late slow peptidergic excitatory post-synaptic currents (e.p.s.c.s) in B cells of the paravertebral sympathetic ganglia of the bull-frog.2. Conductance decreases were measured during peptidergic e.p.s.c.s in nearly all cells at clamped potentials near the resting level. In about half of the cells the size of the peptidergic e.p.s.c.s increased with hyperpolarization and in some of these cells conductance increases were found at hyperpolarized levels. In the remaining cells conductance decreases occurred at all levels of membrane potential tested, and in a few of these the polarity of the e.p.s.c.s reversed at hyperpolarized potentials. A similar diversity was observed among muscarinic e.p.s.c.s.3. At least two simple ionic mechanisms are required to explain the heterogeneous voltage dependencies observed: a conductance decrease primarily to K+ that dominates at depolarized potentials and a conductance increase to other ions that is more prominent at hyperpolarized potentials. The proportion of these two mechanisms appears to differ among B cells.4. The two slow e.p.s.c.s recorded in the same neurone had the same voltage dependence and were accompanied by the same conductance changes in each of eight cells despite differences between cells. The muscarinic e.p.s.c. was reduced during the peptidergic e.p.s.c. in each of twenty-five neurones tested over a range of membrane potentials.5. Externally-applied luteinizing hormone releasing hormone (LHRH) produced currents with the same voltage dependence and conductance changes as the nerveevoked peptidergic e.p.s.c. in each of fifteen cells tested.6. Bethanechol, a muscarinic agonist, and LHRH produced currents with the same voltage dependence and conductance changes in each of the twelve cells studied. In several cells a saturating response to a prolonged application of LHRH completely occluded the response to bethanechol, and vice versa.7. Slow currents were recorded from dissociated cell bodies in response to bethanechol and LHRH; these responses exhibited the same diversity of voltage dependence and conductance changes as was observed in intact ganglia.8. Activation of muscarinic and peptidergic receptors may control shared ionic mechanisms in single ganglion cells.

“…One of the most widespread objections to the possible role of slow synaptic potentials in the physiological modulation of ganglionic transmission is that the intense stimulation used to evoke the slow IPSP, slow EPSP and late-slow EPSP in vitro is far higher than the level of activity that has been assumed to occur in vivo (Ginsborg, 1976). Although no obvious, discrete, spontaneous slow IPSP were observed during in vivo recording from C-cells, this observation does not preclude a role for inhibitory muscarinic effects.…”

Section: Characteristics Of B-sympathetic Pathwaysmentioning

confidence: 99%

“…Peptide released following stimulation of C-fibres in VIIth or VIIIth spinal nerve is thought to diffuse within the ganglion so as to produce a late-slow EPSP in B-cells (Jan et al 1979(Jan et al , 1980. Although the cellular organization and biophysical properties of B-and C-neurones in the paravertebral sympathetic ganglia of various amphibians have been extensively investigated in vitro (Nishi et al 1965;Skok, 1973;Ginsborg, 1976;Kuba & Koketsu, 1978; Adams, Jones, Pennefather, Brown, Koch & Lancaster, 1986;Smith, 1994), it is not known whether different types of peripheral target tissue receive specific patterns of activity from distinct subsets of ganglionic neurones, whether any integration of spinal sympathetic outflow occurs in A ganglionic neurones or whether ganglionic peptides and non-nicotinic slow synaptic events have any role in ganglionic transmission in vivo. These questions have been addressed in the present study by exploiting the simplicity of organization of the discrete B-and C-fibre systems in the bullfrog and by making extracellular and intracellular recordings of their in vivo activity.…”

mentioning

confidence: 99%

In vivo activity of B‐ and C‐neurones in the paravertebral sympathetic ganglia of the bullfrog.

Ivanoff

Smith

1995

1. Spontaneous, in vivo synaptic activity was recorded from 146 B‐cells and 60 C‐cells in the IXth and Xth paravertebral sympathetic ganglia of the urethane‐anaesthetized bullfrog. Sympathetic outflow to the blood vessels, which are innervated by C‐cells, is different from that received by targets in the skin, which are innervated by B‐cells. 2. B‐cells were divided into three groups: the first (61 cells) exhibited only action potentials (APs) at 0.01‐0.3 s‐1; the second (59 cells) exhibited APs and EPSPs and the third (26 cells) were silent. In addition to their usual suprathreshold input from the ipsilateral sympathetic chain, 53% of B‐cells received subthreshold input which probably arose from fibres in the contralateral chain. ‘Slow’ B‐cells exhibited less subthreshold activity and a slightly higher AP frequency than ‘fast’ B‐cells. All B‐cells are involved in a sympathetic reflex which is activated by tactile stimulation of the skin of the hindlimb. Activation of this reflex increased AP frequency without promoting long‐lasting depolarization. 3. Sixty‐seven per cent of C‐cells exhibited rhythmic bursting activity with or without small intraburst EPSPs. Bursts tended to correlate with electrocardiographic (ECG) activity. The remainder exhibited an irregular pattern of activity which was not correlated with ECG activity and which included one to three APs and EPSPs interspersed between the bursts. Activity of both types of C‐cell was inhibited following stimulation of the skin. 4. An average of twenty‐three B‐cells and twenty‐one C‐cells discharge simultaneously in vivo. This reflects branching of preganglionic fibres and results in synchrony of discharge in both postganglionic B‐ and C‐fibres.(ABSTRACT TRUNCATED AT 250 WORDS)