[A chronobiological study of behavioral changes in rats].

A chronobiological study of behavioral changes in Wistar Kyoto rats (WKY), spontaneously hypertensive rats (SHR) and stroke prone spontaneously hypertensive rats (SHRSP) was undertaken. Attention was focused on changes in ambulatory activity and drinking behavior using an Ambulo-Drinkometer, the effects of centrally acting antihypertensive drugs, and the relationship between behavioral changes and humoral factors. (1) The experiment was performed during a light-dark alternation cycle. Approximately 10 days were required for rats to acclimate to new cages. (2) Using power spectral analysis, a 24 hr periodicity was dominant in both sexes of WKY and SHRSP. A 120 hr periodicity was demonstrated in female SHRSP. This long periodicity may have been due to a female sexual rhythm. (3) Ambulatory activity of WKY and SHRSP tended to decrease with age. (4) After abrupt cessation of clonidine administration, an ambulatory ultradian rhythm was demonstrated. Guanfacine treated SHR showed less change in ambulatory ultradian rhythm than clonidine treated SHR. (5) Using a Drinkometer with attached metabolic cages, drinking counts, urinary volumes, urinary aldosterone and catecholamine excretion rates were higher during the dark phase than during the light phase. It was demonstrated that analysis of rhythmicities and measurement of behavioral amplitude are both needed in the study of behavioral pharmacology.