Evidence that spinal endorphin mediates intraventricular beta-endorphin-induced tail flick inhibition and catalepsy.
Naloxone injected intrathecally had a different effect on the inhibition of the inhibition of the tail flick response produced by beta-endorphin and morphine injected intraventricularly. The intrathecal naloxone completely antagonized the effect of beta-endorphin but had only a very weak effect on morphine. In the same rats the cataleptic response to beta-endorphin was antagonized as well; however no definitive conclusion could be made regarding the antagonism of the morphine-induced catalepsy. The results indicate that spinal endorphin is involved in the production of intraventricular beta-endorphin-induced spinal tail flick inhibition and suggest that intraventricular beta-endorphin and morphine elicit their pharmacological action via the activation of different descending inhibitory systems.
D000818:Animals; D004723:Endorphins / Q000494:pharmacology* / Q000502:physiology*; D007276:Injections, Intraventricular; D008297:Male; D009020:Morphine / Q000494:pharmacology; D009043:Motor Activity / Q000187:drug effects* / Q000502:physiology; D009270:Naloxone / Q000494:pharmacology; D009433:Neural Inhibition / Q000187:drug effects*; D009619:Nociceptors / Q000187:drug effects* / Q000502:physiology; D051381:Rats; D011919:Rats, Inbred Strains; D013116:Spinal Cord / Q000187:drug effects* / Q000502:physiology; D001615:beta-Endorphin
D004723:Endorphins; D009270:Naloxone; D001615:beta-Endorphin; D009020:Morphine