Chronic administration of imipramine antagonizes deranged circadian rhythm phases in individually housed rats.
The circadian rhythms of hypothalamic serotonin (5HT), tryptophan (TP) and 5-hydroxy-indoleacetic acid (5HIAA), and serum corticosterone were determined in male Wistar rats. The animals underwent a five-week 12:12-hr light/dark cycle conditioning period and were divided into three groups: rats housed four to a cage (group C, control), rats housed individually (group I), and rats housed individually and treated for two weeks with 10 mg/kg/day of imipramine continuously administered by osmotic pumps implanted under the skin (group T). Significant differences were found in the acrophases of 5HT, TP and 5HIAA between group I and group C, and corticosterone mesor was higher in group I than in group C. On the contrary, no differences were observed between group T (individually housed, but given imipramine) and group C. Therefore, chronically administered imipramine antagonizes the circadian changes induced by individual housing.
Istituto di Scienze Fisilogiche Umane, II Facoltà di Medicina e Chirurgia Università degli Studi di Napoli Federico II, Italy.
A M
AM
Greco
P
P
Gambardella
R
R
Sticchi
D
D
D'Aponte
P
P
De Franciscis
D000818:Animals; D002940:Circadian Rhythm / Q000187:drug effects*; D003345:Corticosterone / Q000097:blood; D006897:Hydroxyindoleacetic Acid / Q000378:metabolism; D007031:Hypothalamus / Q000187:drug effects; D007099:Imipramine / Q000493:pharmacokinetics / Q000494:pharmacology*; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D012701:Serotonin / Q000378:metabolism; D012931:Social Environment; D012934:Social Isolation; D014364:Tryptophan / Q000378:metabolism
D012701:Serotonin; D006897:Hydroxyindoleacetic Acid; D014364:Tryptophan; D007099:Imipramine; D003345:Corticosterone