title: Methadone effects on locomotor activity of young and aged mice.
abstract: The effect of age on the behavioral response to methadone hydrochloride was examined in male C57BL/6J mice. After 1 hr habituation to an oval runway, locomotor activity of young (6-8 months) and aged (30-32 months) mice was monitored for 3 hr following injections of saline or methadone hydrochloride (2.5, 7.5, 15.0 or 22.5 mg/kg). The three highest doses initially elevated activity which then declined over the next 1 1/2 to 2 1/2 hr. Compared to young mice, activity of aged mice was elevated less extensively, but remained elevated for a longer period of time. The attenuated elevation could be interpreted in terms of reduced physical capacity of aged mice; however, the more prolonged elevation was clearly an age-related difference in reaction to the drug. Although the mechanism accountable for this effect is unknown, it is not likely related to age differences in drug absorption or distribution to active sites.
mesh_terms: D000367:Age Factors; D000818:Animals; D004305:Dose-Response Relationship, Drug; D008124:Locomotion / Q000187:drug effects; D008297:Male; D008691:Methadone / Q000494:pharmacology*; D051379:Mice; D008810:Mice, Inbred C57BL; D009043:Motor Activity / Q000187:drug effects*; D013997:Time Factors
chemical_list: D008691:Methadone