Abundant evidence indicates that ATP and adenosine act as neurotransmitters or co-transmitters, influencing nerve cell physiology in various ways. Therefore, regulation of ATP-metabolizing enzymes is essential for the normal development and function of neuronal tissue. In the present study we have examined the effect of gonadal (OVX) or adrenal (ADX) steroid hormone deprivation on the activity and expression of synaptic membrane ecto-ATPase in three extrahypothalamic brain areas of female rats, primarily not associated with reproductive function. It was shown that OVX significantly increased ecto-ATPase activity and the relative abundance of this enzyme in the hippocampal (Hip) and caudate nucleus (CN), but not in brain stem (BS) membrane preparations. ADX was followed by an upregulation of the enzyme activity and its relative abundance in all the brain areas investigated. The highest enzyme activity and the most profound effects of OVX and ADX were detected in the CN. The results obtained indicate that ADX and OVX upregulate the expression of ecto-ATPase, potentiating the production of adenosine in synaptic cleft thus modulating the activity of numerous neurotransmitter systems in distinct areas of the CNS., N. Nedeljkovic, V. Djordjevic, A. Horvat, G. Nikezic, D.T. Kanazir., and Obsahuje bibliografii
Glucocorticoids (GCS) are known to modulate cardiovascular response during stress conditions. The present study was aimed to test the hypothesis that permissive and/or stimulating effect of GCs is essential for the maintenance of peripheral vascular resistance and for the adequate response of cardiovascular system to stressor exposure. The effects of acute pharmacological adrenalectomy (PhADX) on humoral and cardiovascular parameters were studied in adult Wistar rats under the basal conditions and during the acute restraint stress. Acute PhADX was performed by the administration of metyrapone and aminoglutethimide (100 mg/kg s.c. of each drug) resulting in a suppression of endogenous glucocorticoid synthesis. Blood pressure (BP), heart rate (HR) and core body temperature were measured using radiotelemetry. BP responses to administration of vasoactive agents were determined in pentobarbital-anesthetized animals. PhADX considerably attenuated stress-induced increase of BP, HR and core body temperature. PhADX did not abolish BP and HR lowering effects of ganglionic blocker pentolinium indicating preserved sympathetic function in PhADX rats. BP response to exogenous norepinephrine administration was attenuated in PhADX rats, suggesting reduced sensitivity of cardiovascular system. Suppression of corticosterone synthesis by PhADX increased basal plasma levels of ACTH, aldosterone and plasma renin activity in unstressed animals but there was no further increase of these hormones following stressor exposure. In conclusion, PhADX attenuated stress-induced rise of blood pressure, heart rate and core body temperature indicating an important permissive and/or stimulating role of glucocorticoids in the maintenance of the adequate response of cardiovascular system and thermoregulation to several stimuli including acute exposure to stressor.