title: [Effect of hyperbaric air on biorhythms of the pain sensitivity and analgesic effect of morphine].
abstract: The circadian and high-frequency (2-2.5 h) pain sensitivity rhythms were observed in male mongrel rats under natural illumination conditions (LD 24, January-February). A minimum pain sensitivity threshold with respect to subcutaneous electrode stimulation was observed in the dark phase of the LD 24 cycle. Morphine injections (5 mg/kg, i.p.) led to inversion of the circadian rhythm and expansion of the high-frequency spectrum. The rhythm synchronism was broken under the hyperbaria conditions, whereby the circadian acrophase shifted to exhibit a maximum within the day light phase. The concurrent morphine administration on the hyperbaria background induced the back inversion of the circadian pain sensitivity rhythm. The high-frequency rhythm was not significantly affected by increased pressure--neither alone nor in combination with morphine injections.
authors.affiliation: Department of Military and Extremal Medicine, Valdman Institute of Pharmacology, Pavlov State Medical University, St. Petersburg, Russia.
authors.forename: A N
authors.initials: AN
authors.lastname: Kubynin
authors.forename: A A
authors.initials: AA
authors.lastname: Miasnikov
authors.forename: Iu D
authors.initials: IuD
authors.lastname: Ignatov
mesh_terms: D000204:Activity Cycles; D000701:Analgesics, Opioid / Q000494:pharmacology*; D000818:Animals; D001273:Atmosphere Exposure Chambers; D002940:Circadian Rhythm; D008297:Male; D009020:Morphine / Q000494:pharmacology*; D017288:Pain Threshold; D011312:Pressure; D051381:Rats
chemical_list: D000701:Analgesics, Opioid; D009020:Morphine