Effects of fentanyl on acetylcholine release from hippocampus and righting reflex in rat: an in vivo brain microdialysis study
Sakai, M.; Fukuyama, H.; Sato, K.; Kudoh, I.
Masui. Japanese Journal of Anesthesiology 51(2): 118-123
2002
ISSN/ISBN: 0021-4892 PMID: 11889775 Document Number: 540852
Fentanyl, a synthetic mu-opioid agonist, is one of the most popular opioids in clinical anesthesia. It is well-known that memory is affected by opioids and opioid antagonists in animals. Cholinergic neurones releasing acethylcholine (ACh) particularly in the hippocampus have been shown to be related to memory. This study, therefore, was conducted to examine the effects of fentanyl on hippocampal ACh release in rats. The experiments were performed on male SD rats under freely moving condition by in vivo brain microdialysis technique. After taking initial three samples, test drugs were administered. The ACh release was determined by HPLC-ECD method. Effect on behavior was determined as loss of righting reflex (LRR). Fentanyl 50, 100 and 200 mug cntdot kg-1 i.p. significantly decreased the ACh release from the rat hippocampus. Naloxone, a mu-antagonist, 100 mug cntdot kg-1 i.p. antagonized the inhibitory effect of fentanyl 100 mug cntdot kg-1 i.p. on the ACh release in the hippocampus. Only fentanyl 200 mug cntdot kg-1 i.p. produced LRR. The effects of fentanyl, the dose of which is so little that it does not produce LRR, on the rat hippocampal ACh release may be controlled by the inhibitory actions of mu-opioid receptors.