title: The histamine H1-antagonist chlorpheniramine facilitates learning in aged rats.
abstract: The effect of the histamine H1-receptor antagonist chlorpheniramine on inhibitory avoidance conditioning was investigated in 31-month-old rats, using a one-trial step-through avoidance task. Immediately after the learning trial, old rats were injected intraperitoneally with 5 or 10 mg/kg d-chlorpheniramine. Control groups included vehicle-injected old and adult (4-month-old) rats and a group of aged animals given an injection of 10 mg/kg chlorpheniramine 5 h after the training trial. When tested 24 h after training, aged rats receiving 10 mg/kg chlorpheniramine exhibited longer step-through latencies than vehicle-treated old controls, indicative of superior learning of the task. The hypermnestic effects of 10 mg/kg chlorpheniramine were no longer evident when injection was performed 5 h, rather than immediately after the learning trial, ruling out enduring proactive effects of the treatment on test performance. Furthermore, vehicle-treated old rats showed poorer inhibitory avoidance performance than vehicle-treated adult controls. Thus, the improvement in performance after the 10 mg/kg dose of chlorpheniramine can be interpreted in terms of a compensation of performance deficits in the old rats.
authors.affiliation: Institute of Physiological Psychology and Center for Biological and Medical Research, Heinrich-Heine-University of Düsseldorf, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Frisch
authors.forename: R U
authors.initials: RU
authors.lastname: Hasenöhrl
authors.forename: J P
authors.initials: JP
authors.lastname: Huston
mesh_terms: D000375:Aging / Q000187:drug effects*; D000818:Animals; D002744:Chlorpheniramine / Q000494:pharmacology*; D006634:Histamine H1 Antagonists / Q000494:pharmacology*; D007858:Learning / Q000187:drug effects*; D008297:Male; D051381:Rats; D017208:Rats, Wistar
chemical_list: D006634:Histamine H1 Antagonists; D002744:Chlorpheniramine