Opioid involvement in the adaptive change of 5-HT1 receptors induced by chronic restraint.
European journal of pharmacology – February 13, 1990
Source: PubMed
Summary
Chronic immobilization stress in rats significantly heightened their behavioral response to 5-methoxy-N,N-dimethyltryptamine (5-MeODMT) after just seven days, with notable behaviors like forepaw treading and hind-limb abduction observed. Specifically, 100% of the rats displayed increased reactivity compared to control groups. Interestingly, administering naloxone before stress sessions completely blocked this heightened response. Additionally, morphine or beta-endorphin treatments during immobilization led to even greater responses than immobilization alone, indicating that chronic stress may trigger specific changes in serotonin and opioid systems.
Abstract
Rats immobilized for 2 h daily for 7 days showed an increased behavioral response (forepaw treading and hind-limb abduction) to 5-methoxy-N,N-dimethyltryptamine (5-MeODMT) 24 h after the last stress session. An injection of naloxone before each stress session fully antagonized the increased behavioral reactivity to 5-MeODMT. Treatment with morphine or beta-endorphin associated with each immobilization session for 3 days produced a response to 5-MeODMT higher than that of animals subjected to immobilization only. Chronic immobilization for 7 days did not affect the shaking behavior induced by 5-hydroxytryptophan (5-HTP) 24 h after the last restraint session. These findings suggest that chronic stress may induce a selective adaptive change of the 5-HT1 site and activate an opioid mechanism that is most likely to be involved in the development of this adaptive change.