Attenuating effect of serotonin receptor antagonists on impairment of mealtime-associated activity rhythm in old rats.
In the present study, we examined attenuating effect of serotonin (5-HT) receptor antagonists on the impairment of the time perception presented by daily scheduled feeding in old rats. When feeding was restricted to a single meal at a fixed time of day (1300-1700 h) for six consecutive days, young rats exhibited intense locomotor activity from 1-3 h before feeding time. Intense locomotor activity was observed between 1200 adn 1700 h in young animals even on the fasting day (day 7) (mealtime-associated activity). However, this mealtime-associated activity was impaired in 24-mo-old rats. Daily injections of 5-HT2 receptor antagonists, mianserin or ritanserin, or a 5-HT3 receptor antagonist, Y25130, at 1700 h for 6 consecutive days significantly and dose-dependently attenuated the impairment of mealtime-associated activity on the fasting day in old rats without affecting the food intake. Our results suggest that the blockade of 5-HT2 and/or 5-HT3 receptors attenuates impairment of the manifestation of mealtime-associated anticipatory activity related to temporal learning in old rats.
Shibata
S
S
Department of Pharmacology, Faculty of Pharmaceutical Science, Kyushu University, Fukuoka, Japan.
Ono
M
M
Minamoto
Y
Y
Watanabe
S
S
D000375:Aging / Q000523:psychology*; D000818:Animals; D000932:Antiemetics / Q000494:pharmacology; D001643:Bridged Bicyclo Compounds / Q000494:pharmacology; D019086:Bridged Bicyclo Compounds, Heterocyclic; D005215:Fasting / Q000523:psychology; D005247:Feeding Behavior / Q000187:drug effects*; D008297:Male; D008803:Mianserin / Q000494:pharmacology; D009043:Motor Activity / Q000187:drug effects*; D010078:Oxazines / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D016713:Ritanserin / Q000494:pharmacology; D012702:Serotonin Antagonists / Q000494:pharmacology*
D000932:Antiemetics; D001643:Bridged Bicyclo Compounds; D019086:Bridged Bicyclo Compounds, Heterocyclic; D010078:Oxazines; D012702:Serotonin Antagonists; D016713:Ritanserin; D008803:Mianserin; C070671:azasetron