Differential cardiovascular and respiratory responses to central administration of selective opioid agonists in conscious rabbits: correlation with receptor distribution.

Abstract

1. The effects of intracerebroventricular (i.c.v.) and intracisternal (i.c.) administration of a range of doses (0.01, 0.1 and 1.0 nmol kg-1) of specific mu- delta- and kappa-opioid agonists on cardiovascular and respiratory function and on plasma catecholamines have been studied in conscious rabbits. The distribution of mu- delta- and kappa-opioid receptors was localized in rabbit brain by in vitro autoradiography. 2. The mu-agonist [D-Ala2, MePhe4-Gly5-ol]enkephalin (DAGOL) given i.c.v. caused a large rise in plasma noradrenaline and adrenaline, hypertension accompanied by an initial bradycardia followed by tachycardia, respiratory depression and sedation. After i.c. administration there w..