CARDIOVASCULAR EFFECTS OF INTRATHECALLY INJECTED MU-OPIOID, DELTA-OPIOID AND KAPPA-OPIOID RECEPTOR AGONISTS IN RABBITS

1. Intrathecal saline, the mu opioid agonist [D-Ala(2), MePhe(4), Gly( 5)-ol] enkephalin (DAGO) and delta opioid agonist [D-Pen(2), D-Pen(5)] enkephalin (DPDPE) had no significant effects on systemic blood press ure and heart rate values. 2, The kappa opioid agonist bremazocine how ever, caused falls in blood pressure and reduction in heart rate. 3, I ntrathecal administration of saline, DPDPE and bremazocine had no effe ct on baroreflex sensitivity. 4, Intrathecal administration of DAGO ca used a reduction in baroreflex sensitivity; this effect was inhibited by naloxone and abolished after atenolol. 5, The role of spinal opioid systems as a possible site of action is discussed.