Evidence for a serotonin‐mediated slow excitatory potential in the guinea‐pig coeliac ganglia.

Abstract

SUMMARY1. The nature of the putative transmitters) mediating the non-cholinergic excitatory post-synaptic potential (e.p.s.p.) described in the preceding paper was investigated by means of electrophysiological, pharmacological and immunohistochemical methods.2. Serotonin (1-10 ,SM) when applied by superfusion caused a slow depolarization that closely mimicked the synaptic response in about 60 % of the coeliac neurones that exhibited a non-cholinergic e.p.s.p. The serotonin depolarization evoked in low-Ca2+, highMg2+ solution or in a Krebs solution containing cholinergic antagonists was quantitatively similar to that elicited in normal Krebs solution.3. When compared in the same neurones the membrane resistance change during the course of the serotonin depolarization and of the non-cholinergic e.p.s.p., as well as their respective responses to conditioning polarization, were similar.4. The non-cholinergic e.p.s.p. was reversibly abolished during serotonin-induced depolarization; the blockade persisted when the membrane potential was restored to the resting level by hyperpolarizing current.5.

Two calcium‐activated potassium conductances in a subpopulation of coeliac neurones of guinea‐pig and rabbit.

“…We were unable to evoke a slow depolarization in l.a.h. neurones using the stimulus parameters reported by Dun et al (1984). Further, we have been unable to demonstrate nerve terminals with 5-HT immunoreactivity in guinea-pig coeliac ganglia, even after colchicine or L-tryptophan pre-treatment (C. R. Anderson & E. M. McLachlan, personal observations), although it was readily observed if the ganglia had been exposed for an hour to 1 /uM-5-HT.…”

The effects of 5‐HT on articular sensory receptors in normal and arthritic rats

“…Alternative mechanisms could include the involvement of a second messenger system in the afferent nerve terminal or the release of other algogenic substances from surrounding tissues by 5-HT. Evidence for a direct effect is suggested from studies on isolated neuronal preparations where a slow response produced by 5-HT has also been described (Kiraly et al, 1983;Dun et al, 1984).…”

Serotonin and Blood Pressure Regulation

“…The enzymes for dedicated 5-HT synthesis-tryptophan hydroxylase and an aromatic acid amino decarboxylase-exist in sympathetic ganglia. 5-HT has been immunohistochemically localized in sympathetic ganglia (Verhofstad and Jonsson, 1983;Dun et al, 1984;Häppölä, 1988;Päivärinta et al, 1989;Karhula et al, 1995). mRNA for SERT (Nishimura et al, 1999) and multiple 5-HT receptors Pierce et al, 1996;Watkins and Newberry, 1996) are present in ganglia.…”