A pharmacological analysis of the responses of the gastrointestinal smooth muscle of the bat to transmural and periarterial nerve stimulation

Abstract

I A comparative study of the responses of the gastrointestinal tract of the guinea-pig and of the fruiteating bat Eidolon helvum to transmural nerve stimulation (TNS) was made. 2 The stomach and rectum of the guinea-pig, the bat and the guinea-pig ileum contracted in response to TNS. These contractions were cholinergic in nature because atropine blocked and physostigmine potentiated them. 3 Tetrodotoxin reversibly abolished these contractions suggesting that they were nerve-mediated. 4 The bat isolated ileum usually responded to TNS with mixed motor and inhibitory components. In some cases, there were only motor or inhibitory components. 5 The motor component was abolished by atropine and potentiated by physostigmine. However, the inhibitory component was non-adrenergic and non-cholinergic (NANC). 6 Tetrodotoxin abolished the motor component without influencing the inhibitory component. 7 Periarterial nerve stimulation of the bat ileum produced a relaxation that was blocked by bretylium, propranolol, phentolamine, reserpine and tetrodotoxin. 8 It is concluded that the bat gastrointestinal smooth muscle, like the guinea-pig, has cholinergic excitatory innervation; however, the bat ileum has both a cholinergic excitatory innervation and a nonadrenergic and non-cholinergic inhibitory component.

The Pharmacology of Physostigmine

“…An early observation by Koster (144) showed that a non-lethal dose of physostigmine protected cats against the effects of several lethal doses of the organophosphate diisopropyl fluorophosphate. Many subsequent studies (59) have confirmed this observation and have demonstrated the efficacy of physostigmine prophylaxis against a variety of organophosphates, including Soman (106,117,151,175). This use would be in conjunction with post-exposure anticholinergic and oxime therapy.…”

Inhibition of field stimulation‐evoked relaxations in rat oesophageal smooth muscle by the calcium antagonist PN 200–110

“…By inference, the observed inhibition of TTX-sensitive relaxation would not be attributable to inhibition of putative inhibitory transmitter release, but an impairment of a postjunctional membrane response whose ionic mechanism may partially overlap with that underlying the TTX-insensitive relaxation. TTX-insensitive relaxations have been reported in other vascular and nonvascular smooth muscles (Daniel et al, 1979;Ebeigbe et al, 1983;Cole & Marquis, 1985), however, the cellular mechanisms mediating such relaxations have hitherto not been elucidated.…”