Differences in home cage behavior and endocrine parametres in rats of four strains.
OBJECTIVE
The majority of studies that involve behavioral testing in different rat strains is based on measuring behavioral responses to stressful situations in a novel environment. Very little is known on the spontaneous behavior in rat strains. The aim of the present study was to compare home cage behavior and basal hormone levels in two outbred rat strains, Sprague-Dawley (SD) and Wistar as well as two inbred strains, Lewis and Spontaneously Hypertensive Rats (SHR).


METHODS
Twenty-eight male rats from four strains of rats (n=7/strain) were used in this study. Behavior of each rat in his home cage was recorded by a video camera for 45 minutes during the dark phase of the day. The parameters considered included rearing, jumps, ambulation, grooming, feeding/drinking and no movements. Blood plasma was analyzed for aldosterone, plasma renin activity (PRA), adrenocorticotropin hormone (ACTH) and corticosterone by specific radioimmunoassays.


RESULTS
One-way ANOVA revealed significant inter-strain differences in counts of jumps and rearing. In comparison with Sprague-Dawley and Wistar rats, Lewis rats displayed significantly more jumps and rearing. Statistical analysis showed significant inter-strain differences in the levels of aldosterone and of plasma renin activity. The highest levels of aldosterone were found in Lewis rats. Plasma renin activity was significantly lower in SHR than in Sprague-Dawley rats. Correlation analysis failed to reveal any relationships between behavioral and endocrine parameters. Significant strain differences were observed also in relative weights of the spleen, adrenals and thymus.


CONCLUSIONS
Plasma renin activity and basal mineralocorticoid secretion did not show parallel pattern if compared among different rat strains. Locomotor activity in the home cage, which could represent general activity to be considered in evaluating emotional responses, was highest in the Lewis rats.
Hlavacova
Natasa
N
Institute of Experimental Endocrinology, Laboratory of Pharmacological Neuroendocrinology, Slovak Academy of Sciences, 833 06 Bratislava, Slovakia. natasa.hlavacova@savba.sk
Bakos
Jan
J
Jezova
Daniela
D
D000324:Adrenocorticotropic Hormone / Q000097:blood; D000450:Aldosterone / Q000097:blood; D000818:Animals; D001522:Behavior, Animal; D001835:Body Weight; D006728:Hormones / Q000097:blood*; D008297:Male; D009929:Organ Size; D017440:Photoperiod; D051381:Rats; D011917:Rats, Inbred Lew / Q000097:blood / Q000523:psychology; D011918:Rats, Inbred SHR / Q000097:blood / Q000523:psychology; D017207:Rats, Sprague-Dawley / Q000097:blood / Q000523:psychology; D017208:Rats, Wistar / Q000097:blood / Q000523:psychology; D012083:Renin / Q000097:blood
D006728:Hormones; D000450:Aldosterone; D000324:Adrenocorticotropic Hormone; D012083:Renin