[Effects of fentanyl on acetylcholine release from hippocampus and righting reflex in rat: an in vivo brain microdialysis study].
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 acetylcholine (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 micrograms.kg-1 i.p. significantly decreased the ACh release from the rat hippocampus. Naloxone, a mu-antagonist, 100 micrograms.kg-1 i.p. antagonized the inhibitory effect of fentanyl 100 micrograms.kg-1 i.p. on the ACh release in the hippocampus. Only fentanyl 200 micrograms.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.
Sakai
Makoto
M
Department of Anesthesia, Yokohama City Kowan Hospital, Yokohama 231-0801.
Fukuyama
Hiroshi
H
Sato
Kazuo
K
Kudoh
Ichidai
I
D000109:Acetylcholine / Q000378:metabolism*; D000701:Analgesics, Opioid / Q000494:pharmacology*; D000818:Animals; D005283:Fentanyl / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D006624:Hippocampus / Q000378:metabolism*; D008297:Male; D017551:Microdialysis; D009270:Naloxone / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D017450:Receptors, Opioid, mu / Q000819:agonists / Q000037:antagonists & inhibitors / Q000502:physiology; D012018:Reflex / Q000187:drug effects*
D000701:Analgesics, Opioid; D009292:Narcotic Antagonists; D017450:Receptors, Opioid, mu; D009270:Naloxone; D000109:Acetylcholine; D005283:Fentanyl