No abstract

Our data suggest that melatonin, by increasing reduced levels of α1- and β2-adrenoceptors mRNA and protein in the hippocampus of chronic stressed rats, may be beneficial in conditions such as chronic stress and provides an experimental opportunity to probe into further molecular mechanisms underlying the regulation of these receptor subtype (Fig. 2, Ref. 28).

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

In this study we tested changes in quantity of phenylethanolamine Nmethyltransferase (PNMT), a "rate limiting" enzyme in the synthesis of adrenaline (A), as an indicator of sympatho-adrenomedullary activity in the left and right adrenal medulla of control animals and animals exposed to intensive physical activity. We utilised the model of chronic forced running (CFR: 12 weeks of treadmill running), which according to intensity and duration falls under intensive physical activity. The tested parameters were quantified by using the Western blot. We discovered that CFR considerably increases the level of PNMT proteins in the right adrenal medulla, which suggests that, in the conditions of daily intensive exercise, the sympatho-medullary link greatly influences the right adrenal medulla. The considerable increase of PNMT proteins in the right adrenal medulla confirms that the left hemisphere of the brain is much more sensitive to intensive physical activity.

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