The present study analyzed the effects of chronic treatment with low doses of diazepam on body weight, defecations and urinations, vertical rears, the elevated platform test, and self-grooming in male rats exposed for 21 days to social isolation. The rats were treated for 21 days with diazepam (0.2 mg/kg, i.p) or its vehicle. Social isolation led to decreased body weight and vertical rears, more defecations and urinations, increased reluctance to step down from the test platform, shorter duration of grooming, and longer reluctance to start grooming. Chronic diazepam in individually housed rats produced increase in body weight and vertical rears, decrease in the number of defecations and urinations, and shortening of the time of reluctance to step down from the platform. The number of grooming bouts, their duration, and reluctance to start grooming were not altered by diazepam, but it decreased the percentage of incorrect transitions. The obtained data indicate that chronic diazepam treatment of socially isolated rats changes non-grooming behavior and some grooming behavior parameters.

The effects of diazepam (0.2 mg/kg/ during 21 days, i.p.) on behavior, pituitary-adrenocortical and sympatho-adrenomedullary system of socially isolated and group-housed adult male rats additionally exposed to immobilization, were studied. Social isolation led to a shorter duration of grooming and longer latency to start grooming. Diazepam in social isolated rats reduced incorrect transitions percentage, but the number of grooming bouts, duration and latency to start grooming remained unchanged. Long-term isolation significantly elevated plasma ACTH and corticosterone, while not affecting noradrenaline and adrenaline. Diazepam decreased only plasma ACTH. Social isolation and immobilization significantly elevated all examined hormones. Immobilization of diazepam-treated isolated rats enhanced plasma ACTH , the increase being significantly lower, comparing to isolated vehicle-treated rats. Immobilization significantly increased plasma adrenaline, noradrenaline and corticosterone of diazepam- or vehicle-treated socially isolated rats. No differences in adrenaline, noradrenaline and corticosterone level between these two groups were observed. This indicates that chronic diazepam treatment of socially isolated rats changes some grooming behavior parameters, but insignificantly affects stress-related adrenomedullary and adrenocortical alterations

Enhanced activation of sympathetic neurons during stress results in an increased cardiovascular function. Social isolation is a psychological stress which has deleterious effects on health and represents the most relevant cause of diseases in mammalian species. In this study we investigated the changes in catecholamine biosynthetic enzymes tyrosine hydroxylase (TH), dopamine β-hydroxylase (DBH) and phenylethanolamine N-methyltransferase (PNMT) gene expression and protein levels in the stellate ganglia of naive controls and chronically socially isolated (12 weeks) adult rats and the response of these animals to additional immobilization stress (2 h) by applying TaqMan RT-PCR assay and Western blot analysis. Psychosocial stress produced a significant increase of both TH mRNA (p<0.05) and DBH mRNA (p<0.05) levels in stellate ganglia. The exposure of control rats to acute immobilization significantly increased TH mRNA (p<0.001) and DBH mRNA (p<0.01) levels, while additional immobilization of chronic psychosocially stressed rats expressed no effect on gene expression of these enzymes. Protein levels of TH, and DBH remained unchanged in control and chronic social isolation rats and also after short-term immobilization. The results presented here suggest that psychosocial stress-induced an increase in gene expression of catecholamine biosynthetic enzymes in stellate ganglia and thus may be connected to the increased risk of cardiovascular disease

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