Effects of methamphetamine on development of circadian rhythms in rats.
To determine the effect of continuous methamphetamine treatment on development of the circadian system, the daily courses of spontaneous locomotor activity and plasma corticosterone level were determined in infant rats. Methamphetamine was dissolved in drinking water at a concentration of 0.005%, and administered to rats from postnatal day 14. The circadian locomotor rhythm in methamphetamine treated rats was not significantly different from that in non-treated rats for the first 4 weeks of drug treatment. Then the rhythm began to show signs of relative coordination and finally split into two activity components. One component entrained to the light-dark cycle, whereas the other free-ran in spite of the light cycle. The rhythm of plasma corticosterone in the methamphetamine treated group was not different from that in the control group at 4 weeks after birth, but was significantly phase-delayed at 8 weeks. Splitting was not observed for the corticosterone rhythm. It is concluded that continuous administration of methamphetamine to infant rats affects the circadian rhythms for spontaneous locomotor activity and plasma corticosterone level. Possible mechanisms of methamphetamine effects were discussed in terms of the circadian system underlying these rhythms.
D000284:Administration, Oral; D000818:Animals; D002940:Circadian Rhythm / Q000187:drug effects*; D003345:Corticosterone / Q000097:blood; D004327:Drinking Behavior / Q000187:drug effects; D008297:Male; D008694:Methamphetamine / Q000008:administration & dosage / Q000494:pharmacology*; D009043:Motor Activity / Q000187:drug effects; D051381:Rats; D011919:Rats, Inbred Strains
D008694:Methamphetamine; D003345:Corticosterone