Mechanism involved in the response of granulated vesicles in the mouse pinealocyte to acute cold exposure.

Quantitative electron microscopic studies on the mouse pineal gland were done to elucidate the mechanism of the response of the granulated vesicles in pinealocytes to acute cold exposure. An increase in the number of the granulated vesicles in the mouse pinealocytes occurs following administration of isoproterenol and this increase is prevented by pretreatment with the beta-adrenergic blocking agent, propranolol. In addition, a numerical increase of the granulated vesicles in response to acute cold exposure is abolished in mice pretreated with propranolol or in adrenalectomized animals. The results suggest that catecholamines released from the adrenal medulla, but not from sympathetic nerve endings, may cause the response of the granulated vesicles to cold by way of beta-receptors.