Specificity of the effect of repeated handling on sympathetic-adrenomedullary and pituitary-adrenocortical activity in rats.

The response of the pituitary-adrenocortical and sympathetic-adrenomedullary system to single and repeated handling was studied in rats. After repeated handling (14 days, 3 x 1 min daily or 1 day, 6 x 1 min at 30 min intervals) a reduction of plasma epinephrine and ACTH level was observed, while norepinephrine levels increased to the same extent as after the first handling. When repeatedly handled rats were handled by a different person, hormonal responses were altered: The reduction in the ACTH and epinephrine response was no longer apparent, whereas the norepinephrine response was potentiated.

Adrenocorticotropin release induced by N-methyl-d-aspartate or stress: mediation by the area postrema.

N-methyl-D-aspartic acid (NMDA) is known to stimulate adrenocorticotropin (ACTH) release after peripheral administration in spite of its inability to readily cross the blood-brain barrier (BBB). The importance of the area postrema, the hindbrain circumventricular organ which lacks a BBB, for NMDA action and ACTH release during stress was evaluated in this study. ACTH response to NMDA injection (4 mg/kg ip) was significantly reduced in rats with ablation of the area postrema compared to sham-operated animals.

Do the circulating neurohypophysial hormones affect basal or stress induced prolactin (PRL) release in male rats?

The action of acute administration of oxytocin (OXY), vasopressin (AVP) or its analog 1-deamino-8-D-arginine-vasopressin (dDAVP) on basal and stress induced PRL release in normal male rats and the effect of chronic injection of AVP on PRL stress response in AVP deficient rats were studied. The hormones (OXY, 600 ng min-1 per rat; AVP 6, 12 or 24 ng min-1 per rat and dDAVP 24 ng min-1 per rat) were infused to conscious rats via the jugular vein for 10 min and then the rats were immobilized under continuing the infusion for further 20 min. In parallel experiments arterial blood pressure (BP) was measured.

[The effect of chronic stress on the activity of the sympathetic-adrenomedullary system].

Plasma levels of adrenaline (ADR) and noradrenaline (NA) belong to the best parameters of activity of the sympatho-adrenomedullary system (SAS). Introduction of a sensitive radioenzymatic method for the determination of catecholamines in small volumes of plasma (0.05 ml) and observing conditions of stressless blood collection by means of an indwelling catheter made in possible to determine basal plasma catecholamine levels and their dynamics during stress.