[Effects of nicotine on circadian rhythm of ambulatory activity and drinking in rats].
Effects of the intake of nicotine solution and/or forced administration of nicotine at a fixed time-of-day on circadian rhythm of ambulatory activity and drinking in rats were observed under various conditions. Rats showed nocturnal pattern under the light-dark cycle (L: D = 12:12, light period 6:00-18:00), and the patterns scarcely altered while the rats were given 150 micrograms/ml of nicotine solution. When a restricted feeding only for 1 h per day (10:00-11:00) was loaded to the rats, the ambulatory activity and drinking appeared in the light period, especially around the feeding time. While rats were given 15-150 micrograms/ml of nicotine solution under the restricted feeding condition, they demonstrated a marked phase-shift in the circadian rhythm in the concentration-dependent manner. Rats showed free-running rhythms with tau value of longer than 24 h under the constant red dim light condition (CRDL), and such rhythm was scarcely modified by the intake of nicotine solution of 50-150 micrograms/ml. However, when nicotine (1.5 mg/kg po), but not tap water, was administered at 10:00 every day under the CRDL condition, it also produced phase-shift which was similar to that induced by the nicotine ingestion under the redose of nicotine is administered or taken at a fixed time-of-day.
Umezu
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T
Division for Behavior Analysis, Behavior Research Institute, Gunma University School of Medicine, Maebashi, Japan.
Kuribara
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H
Tadokoro
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D000284:Administration, Oral; D000818:Animals; D002940:Circadian Rhythm / Q000187:drug effects*; D004326:Drinking / Q000187:drug effects*; D008124:Locomotion / Q000187:drug effects*; D008297:Male; D009538:Nicotine / Q000008:administration & dosage / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar
D009538:Nicotine