Effects of mild stress on adrenal and heart catecholamines in male and female rats.

The present study was undertaken with the aim of evaluating the sensitivity and convenience of a stress model reflecting sympatho-adrenal activation. Rats of both sexes were subjected to mild stress, consisting of four body temperature recordings, and investigated with regard to adrenal and heart catecholamine levels. Adrenal dopamine (DA) levels were considered to reflect medullary synthesis activity and heart adrenaline (A) concentrations were presumed to reflect A released from the adrenals. Expressed in relation to heart weight, adrenal catecholamine levels were about 50% higher in female rats. Following stress, adrenal DA levels were enhanced in both male and female rats; the magnitude of the stress response appeared similar in the two sexes. Concentrations of A in the hearts of unstressed animals were about 85% higher in females than in males but rose to a similar extent in male and female rats following stress. On the other hand, the stress-induced alterations in heart DA and NA concentrations, reflecting sympathetic activity, were gender-dependent. The advantages of the present model in relation to other techniques for measuring sympatho-adrenal activation in response to mild stress are discussed.