Morphodynamic response of the pineal gland to initial stress attack.

The influence of an initial stress attack (a subcutaneous saline injection plus rough handling) on the morphofunctional behaviour of the pineal gland was studied. Both light and electron microscopy pointed to an enhanced endocrine activity on the gland parenchyma. The occurrence of the clusters of highly activated light pinealocytes, as well as the appearance of two functionally different types of these cells, revealed that the introduction of the pineal gland to a new stress-induced steady state was based on the gradual promotion of a number of pinealocytes to the level of a high activity. Dark pinealocytes were less numerous and rather engaged in the synthesis than in the secretion. The ultrastructural characteristics of both pinealocyte populations show that the pineal gland meets the secretory demands upon an initial stress attack by a striking discharge of its active compounds and a successive activation of a new elaborative cycle. The morphodynamic conclusion about an enhanced pineal gland secretory activity is fully evaluated in the change of the rate of prolactin surge. A possible impact of the morphodynamic reactivity of the endocrine parenchyma of the pineal gland upon the functional interpretation of the morphological properties of pinealocytes in case of some manipulative procedures with animals was discussed.