Portacaval anastomosis attenuates the impairing effect of cyproheptadine on avoidance learning in rats--an involvement of the serotonergic system.
Portacaval-anastomized (PCA) rats were used to demonstrate the involvement of the serotonergic system in long-term memory formation. Significant increases in the concentration of 5-hydroxyindoleacetic acid, a metabolite of 5-hydroxytryptamine (5-HT), in all regions examined and the turnover rate of this indoleamine transmitter in the hippocampus, hypothalamus, midbrain and medulla oblongata were observed in PCA rats in comparison with sham-operated controls. Cyproheptadine, a 5-HT receptor blocking agent, impaired the retention of two-way avoidance learning reinforced by light stimuli when the drug was intraperitoneally injected immediately after the completion of training. PCA treatment attenuated the impairing effect of cyproheptadine. When cyproheptadine was injected 2 h after the completion of training, the correct response in the retention test period was not decreased. The present results suggest that memory formation is a time-requiring process and is mediated by the central serotonergic mechanism.
Kubo
T
T
Department of Pharmacology, Nihon University School of Medicine, Tokyo, Japan.
Shibanoki
S
S
Matsumoto
A
A
Tsuda
K
K
Ishikawa
K
K
D000818:Animals; D001362:Avoidance Learning / Q000187:drug effects*; D001921:Brain / Q000187:drug effects* / Q000378:metabolism; D003533:Cyproheptadine / Q000494:pharmacology*; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D008297:Male; D011939:Mental Recall / Q000187:drug effects; D011167:Portacaval Shunt, Surgical; D051381:Rats; D011919:Rats, Inbred Strains; D011985:Receptors, Serotonin / Q000187:drug effects*; D012153:Retention, Psychology / Q000187:drug effects; D012701:Serotonin / Q000378:metabolism
D011985:Receptors, Serotonin; D003533:Cyproheptadine; D012701:Serotonin