SUPPRESSION OF CASTOR OIL-INDUCED DIARRHEA BY ALPHA-2-ADRENOCEPTOR AGONISTS

The effects of systemic administration of alpha-2-adrenoceptor agonists on migrating myoelectric complexes and castor oil-induced diarrhoea of the small intestine were studied in conscious rats. Castor oil (1 mg/kg, intraduodenally) disrupted the migrating myoelectric complexes and induced irregular spiking activity with sporadic bursts of myoelectric activity. This change of motility pattern was present concomitant with diarrhoea 1-2 h after instillation of castor oil and during the whole period of diarrhoea. Pre-treatment with clonidine (5-10-mu-g/kg i.v.) or oxymetazoline (5.6-11.2-mu-g/kg i.v.), a peripherally active alpha-2-agonist, inhibited the irregular spiking induced by castor oil and no diarrhoea occurred during the experimental period of 6 h. Thus, the antidiarrhoeal action of peripherally acting alpha-2-adrenoceptor agonists such as oxymetazoline, may be of clinical value in the treatment of diarrhoea.