Naloxone blocks the release of opioid peptides in periaqueductal gray and N. accumbens induced by intra-amygdaloid injection of morphine.
The working hypothesis that the periaqueductal gray (PAG), N. accumbens and amygdala were connected serially in a unidirectional loop for antinociception, in which Metenkephalin and beta-endorphin were considered to be two important analgesic neurotransmitters, was examined by simultaneously perfusing the PAG and N. accumbens after microinjection of morphine into the amygdala. Intra-amygdaloid injection of morphine increased the release of enkephalins and beta-endorphin in the PAG and N. accumbens. When the perfusion fluid contained 3 microM of naloxone, the release of enkephalins and beta-endorphin was reduced in both the PAG and the N. accumbens. These results do not support the hypothesis of a unidirectional loop and its putative sequence.
Ma
Q P
QP
Department of Physiology, Beijing Medical University, China.
Han
J S
JS
D000679:Amygdala / Q000187:drug effects; D000818:Animals; D004723:Endorphins / Q000378:metabolism*; D004745:Enkephalins / Q000378:metabolism; D008297:Male; D009020:Morphine / Q000008:administration & dosage; D009270:Naloxone / Q000494:pharmacology*; D009619:Nociceptors / Q000187:drug effects; D009714:Nucleus Accumbens / Q000187:drug effects* / Q000378:metabolism; D010487:Periaqueductal Gray / Q000187:drug effects* / Q000378:metabolism; D011817:Rabbits; D001615:beta-Endorphin / Q000378:metabolism
D004723:Endorphins; D004745:Enkephalins; D009270:Naloxone; D001615:beta-Endorphin; D009020:Morphine