title: Involvement of coerulospinal noradrenergic pathway in fentanyl-induced muscular rigidity in rats.
abstract: Unilateral, site-specific microinjection of fentanyl (2.5 micrograms/50 nl) into the locus coeruleus (LC) in Sprague-Dawley rats anesthetized with ketamine evoked a significant increase in the electromyographic activity recorded from both caudal lateral extensor and gastrocnemius muscles. This correlate of opiate-induced muscular rigidity was appreciably antagonized by a pretreatment with the specific alpha 1-adrenoceptor blocker, prazosin (250 micrograms/kg, i.v.). On the other hand, an equimolar dose (0.65 mumol/kg) of the specific alpha 2-adrenoceptor blocker, yohimbine (0.23 mg/kg, i.v.) failed to prevent the occurrence of fentanyl-induced EMG activation. We suggest that the coerulospinal noradrenergic pathway may be directly involved in the elicitation of muscular rigidity by fentanyl, possibly via alpha 1-adrenoceptors in the spinal cord.
authors.affiliation: Department of Anesthesiology, Veterans General Hospital, Taipei, Taiwan, Republic of China.
authors.forename: P W
authors.initials: PW
authors.lastname: Lui
authors.forename: T Y
authors.initials: TY
authors.lastname: Lee
authors.forename: S H
authors.initials: SH
authors.lastname: Chan
mesh_terms: D000320:Adrenergic Fibers / Q000187:drug effects / Q000502:physiology*; D000818:Animals; D004305:Dose-Response Relationship, Drug; D005283:Fentanyl; D008125:Locus Coeruleus / Q000187:drug effects / Q000503:physiopathology*; D008297:Male; D008845:Microinjections; D009127:Muscle Rigidity / Q000139:chemically induced* / Q000503:physiopathology; D011224:Prazosin / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D013116:Spinal Cord / Q000187:drug effects / Q000503:physiopathology*; D015016:Yohimbine / Q000494:pharmacology
chemical_list: D015016:Yohimbine; D005283:Fentanyl; D011224:Prazosin