Increase of mammalian intestinal motility by the iminopurine caissarone isolated from the sea anemone Bunodosoma caissarum

Abstract

The effects of caissarone (C 8H 11N 5O) on guinea-pig ileum and rat duodenum preparations are reported. Caissarone evoked, at first, a small response, as compared with that of applied acetylcholine. This effect was blocked by atropine, hexamethonium and slightly reduced by tetrodotoxin. The main caissarone effect seems to be on the myenteric plexus as it increased spontaneous activity, tone and peristalsis; these effects being counteracted by tetrodotoxin, hexamethonium and atropine. Extracellular electrophysiological recording of the action potentials of myenteric plexus neurons showed an increase in frequency in the presence of caissarone. Caissarone potentiated the longitudinal muscle tension responses elicited by transmural electric stimulation in both control conditions, and when tension was reduced by pretreatment with tetrodotoxin or adenosine triphosphate. Caissarone also potentiated the longitudinal muscle tension responses to applied acetylcholine and this effect was reduced, but not abolished, by tetrodotoxin. Caissarone may have an indirect excitatory action on nicotinic receptors at the ganglia or may act as a reversible antagonist of purine transmitters released by neurons of the myenteric plexus involved in the physiological inhibition of intestinal motility.