Individual Housing Modulates Daily Rhythms of Hypothalamic Catecholaminergic System and Circulating Hormones in Adult Male Rats

Abstract

Circadian rhythms of hypothalamic catecholamines and their metabolites and of prolactin and corticosterone circulating hormones were determined over 24 h in group-housed (six per cage; control) and individually housed, 90-day-old male albino rats adapted to a 12:12 light/dark cycle. After 5 weeks of adaptation, in individually housed rats, norepinephrine (NE) turnover increased, since lower NE (p < 0.01) and higher MOPEG metabolite (p < 0.01) levels were measured. As concerns the dopaminergic system, individually housed rats increased both dopamine (DA) synthesis and turnover as revealed by higher DOPAC (p < 0.01) and HVA (p < 0.05) metabolites without modification of DA levels. Moreover, in individually housed rats, corticosterone (p < 0.01) and prolactin (p < 0.05) mean levels were higher than in the control group.

24-hour changes in circulating prolactin, follicle-stimulating hormone, luteinizing hormone and testosterone in male rats subjected to social isolation

“…The present results on decreased prolactin levels in isolated male rats disagree with the previously reported increase in prolactin levels in a similar psychosocial stress paradigm [16]. Some conditions of the experiments, like the age of rats, i.e., growing rats in this study vs. adult rats in the study by Gambardella and colleagues, could explain this discrepancy.…”

“…Indeed, stressors have been shown to modify gonadotropin and testosterone secretion, acute stressors activating and chronic stressors suppressing the activity of the hypophysial gonadal axis [14]. It must be noted that, except for some exceptions [15,16], studies on the subject were performed at single time-points, generally in the morning, a serious drawback in view of the circadian nature of hormone release for most of the hormones considered [17,18]. In this study we measured the daily pattern of plasma prolactin, luteinizing hormone (LH), follicle-stimulating hormone (FSH) and testosterone levels at 6 different time points within a 24-h cycle in growing male rats kept in isolation or group-caged for 30 days.…”

Circadian Rhythms in Adenohypophysial Hormone Levels and Hypothalamic Monoamine Turnover in Mycobacterial-Adjuvant-Injected Rats

“…at 04.00 h). This increase in hypothalamic DA and 5HT turnover at night in control animals resembled those reported in the literature [22,23].…”

The effects of Spirulina (Arthrospira) platensis on morphological and hematological parameters evoked by social stress in male rats

“…All these instances are correlated with growth and physiology (Miller, 1998;Dantzer et al, 1999;Kiecolt-Glaser and Glaser, 2002). Some researchers reported that hosting alone stress is more stressful than other stress factors, whereas some of them observed no differences (Giralt and Armario, 1989;Gambardella et al, 1994;Sharp et al, 2002). However, in the present study, no differences were occurred on morphological parameters and weights for the stress conditions.…”