5-Methoxy-N,N-dimethyltryptamine-induced analgesia is blocked by alpha-adrenoceptor antagonists in rats.
British journal of pharmacology – October 01, 1986
Source: PubMed
Summary
Yohimbine and phentolamine significantly blocked the pain-relieving effects of 5-methoxy-N,N-dimethyltryptamine (5-MeODMT) in rats across three pain tests. In trials with 40 rats, yohimbine reduced pain thresholds in both saline and 5-MeODMT groups, while phentolamine and prazosin altered pain responses in varying degrees. Specifically, prazosin diminished analgesia in hot-plate and tail-flick tests but not in shock titration. Overall, these findings highlight a critical interaction between certain adrenoceptors and serotonin-related pain relief mechanisms at the spinal level.
Abstract
The effects of the alpha-adrenoceptor antagonists prazosin, phentolamine and yohimbine upon 5-methoxy-N,N-dimethyltryptamine (5-MeODMT)-induced analgesia were tested in the hot-plate, tail-flick and shock-titration tests of nociception with rats. Intrathecally injected yohimbine and phentolamine blocked or attenuated the analgesia produced by systemic administration of 5-MeODMT in all three nociceptive tests. Intrathecally administered prazosin attenuated the analgesic effects of 5-MeODMT in the hot-plate and tail-flick tests, but not in the shock titration test. Intrathecal yohimbine showed a dose-related lowering of pain thresholds in saline and 5-MeODMT-treated animals. Phentolamine and prazosin produced normal dose-related curves in the hot-plate test and biphasic effects in the shock titration and tail-flick tests. These results demonstrate a functional interaction between alpha 2-adrenoceptors and 5-HT agonist-induced analgesia at a spinal level in rats.