ROLE OF EXTRINSIC AND INTRINSIC NERVES IN THE COORDINATION OF GUT MOTILITY IN THE STOMACHLESS FLATFISH RHOMBOSOLEA-TAPIRINA AND AMMOTRETIS-ROSTRATA GUENTHER

1. The vagal motor supply of the gut of the stomachless flatfish Ammotretis and Rhombosolea is restricted to oesophageal striated muscles and blocked by d-tubocurare (3 × 10-6 g/ml). 2. the intestine is inhibited by sympathomimetic amines (effective doses: isoprenaline 10-8, adrenaline 3 × 1010-7, noradrenaline 10-5, phenylephrine 10-4 M) which act on β-adrenoceptors since propranolol is a competitive antagonist (pA2 = 7.9). 3. Acetylcholine (pD2 = 6.1) is excitatory on intestinal muscarinic receptors since atropine (pA2 = 8.7) is a competitive antagonist; 5-hydroxytruptamine (pD2 = 6.8 is apparently an indirect stimulant since atropine (pD'2 = 6.2) is a non-competitive antagonist. 4. Paravascular sympathetic nerve stimulation activates adrenergic neurons, which are demonstrated histochemically and are blocked by propranolol, as well as cholinergic neurons which are blocked by atropine. 5. Transmural stimulation of the intestine shows that, in addition to extrinsic nerves, the enteric plexus contains a population of excitatory cholinergic neurons and non-adrenergic/non-cholinergic inhibitory neurons which inhibit the circular muscle coat. © 1979.