The reactions of plexus‐free circular muscle of cat jejunum to drugs

Abstract

Studies on the behaviour of enteric plexus-free preparations of the small intestine were first carried out by Magnus (1904a-c). He found that when the longitudinal muscle of the cat's small intestine is stripped off the underlying circular coat, the ganglion cells of the myenteric plexus of Auerbach adhere to the longitudinal layer and the circular muscle can be freed from ganglia. Magnus found that these ganglion-free circular muscle preparations did not contract rhythmically when suspended in Locke's solution and concluded that spontaneous contractions normally observed in intestinal muscle are neurogenic in origin. All later workers, however, observed spontaneous activity in the completely ganglion-free circular muscle (Gunn & Underhill, 1914; Alvarez & Mahoney, 1922;Evans & Underhill, 1923;Gasser, 1926; Eura, 1927;Van Esveld, 1928).Magnus also used the ganglion-free preparations of circular muscle to study the site of action of certain drugs, including nicotine, eserine and barium. These pharmacological experiments have been repeated by Gasser (1926) and by Van Esveld (1928). Although these three workers used similar methods in preparing ganglion-free intestinal strips, their results disagree both with regard to spontaneous activity of the ganglion-free preparations and their reactions to nicotine. Magnus and Gasser found that nicotine does not cause contraction of the ganglion-free strips, and concluded that stimulation of the intestinal muscle by nicotine is due entirely to an action on the ganglion cells of the myenteric plexus. This view is now generally accepted, but is contradicted by the findings of Van Esveld who found that nicotine stimulates the ganglion-free preparations. Van Esveld's findings, which he checked by a careful histological search for ganglion cells, have received surprisingly little attention.

Nicotine‐like Actions in Auricles and Blood Vessels After Denervation

“…Ambache and Edwards (1951) believed that the inhibitory action of nicotine on the intestine was exerted on ganglion cells of the myenteric plexus which possessed adrenergic neurones. Evans and Schild (1953) found, however, that a transient inhibitory action of nicotine was obtained in ganglion-free specimens of cat jejunum, particularly in preparations stimulated by eserine and acetylcholine.…”

Spontaneous and evoked release of neurotransmitter substances in the longitudinal muscle of the anterior mesenteric artery of the domestic fowl

“…Thus nicotine contractions of low-tone preparations seem to result from the stimulation of the ganglia of cholinergic nerves (Bolton, 1968a), while nicotine contractions of barium-sensitized preparations must result from a direct stimulant action of nicotine on the muscle, as in other smooth muscle (Evans & Schild, 1953).…”

Pharmacological Responses of the Isolated Innervated Intestine and Rectal Caecum of the Chick

“…In the rectal caecum relaxations produced by nicotine were much more marked. Relaxations produced by ganglion stimulants in intestinal preparations are well known (Kuroda, 1917;Ambache & Edwards, 1951;Ambache, 1951;Evans & Schild, 1953;Jarrett, 1962;Greeff, Kasperat & Osswald, 1962;Weiss, 1962;Burn & Gibbons, 1964;Bucknell & Whitney, 1964;Fishlock & Parks, 1966;Burnstock, Campbell & Rand, 1966). Such relaxations produced by nicotine in preparations from other species are usually revealed or potentiated in the presence of atropine, but in the chick gut the contractile action of nicotine, TMA and DMPP were often resistant to the blocking action of atropine and hyoscine, and little or no potentiation of the relaxations occurred.…”