Effect of adrenergic drugs on the isolated colon of Rhesus cynomolgus.

The effects of adrenaline, noradrenaline, isoprenaline and dopamine were studied on the longitudinal muscle of the ascending and descending colon of the rhesus monkey. All these drugs induced a relaxation of the preparation, dopamine being the less active agonist. The responses seem to be the result of beta 2-adrenoceptor stimulation since their inhibition by practolol (beta 1) is weaker than their inhibition by propranolol (beta 1 and beta 2 dopaminergic). There is no evidence for the presence of dopaminergic receptors in this preparation.