Long T methamphetamine schedules produce circadian ensuing drug activity in rats.
Eight female Sprague-Dawley rats were housed in isolated continuous 24-h/day environments under conditions of constant dim light and a rate-limited feeding schedule. Following 2 months of free-running activity, all animals were administered methamphetamine (MA) i.p. (2 mg/kg) once every 31 h for 24 injection cycles. Average wave forms of wheel-running activity showed that animals did not anticipate the 31-h schedule of MA injections, but rather displayed circadian ensuing drug activity (CEDA) between 24 and 28 h following the injections. Post-injection meals failed to meet reliably the threshold necessary to achieve food-engendered anticipatory or ensuing activity. Cosinor analysis showed that the intensity of CEDA was strongly influenced by the relative phase of the free-running rhythm. CEDA was moderately influenced by the size of the post-injection bout of activity. Because injection times rotated daily throughout local time without repeating a time of day, CEDA resulting from a long T schedule of MA administration appeared to be based on one-trial resetting of a circadian-related mechanism by a major drug of abuse.
Pecoraro
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N
Department of Psychology, Indiana University, Bloomington, IN 47405-7007, USA. npecorar@indiana.edu
Kosobud
A E
AE
Rebec
G V
GV
Timberlake
W
W
D000818:Animals; D001835:Body Weight / Q000187:drug effects; D000697:Central Nervous System Stimulants / Q000008:administration & dosage / Q000494:pharmacology*; D002940:Circadian Rhythm / Q000187:drug effects*; D005247:Feeding Behavior / Q000187:drug effects; D005260:Female; D008694:Methamphetamine / Q000008:administration & dosage / Q000494:pharmacology*; D009043:Motor Activity / Q000187:drug effects*; D051381:Rats; D017207:Rats, Sprague-Dawley
D000697:Central Nervous System Stimulants; D008694:Methamphetamine