Abstract
Effects of several opioid peptides administered in the lateral cerebroventricle on the changes in blood adrenaline (AD) levels were examined at 10, 20 and 30 min after the start of immobilization in conscious rats. β-Endorphin, (D-Ala2)-Met-enkephalinamide, morphiceptin and (D-Ala2, D-Leu5)-enkephalinamide produced significantly lower elevations of AD than the control, and the effect was enhanced by naloxone. The effect of dynorphin, however, was almost the same as that of the control.
