CHANGES IN THE HYPOTHALAMO-NEUROHYPOPHYSICAL NEURO-SECRETORY MATERIALS OF RATS DURING DIFFERENT PHASES OF MORPHINE ADMINISTRATION

Abstract—

• 1 Acute morphine treatment of rats increased the concentration of neuro-secretory material in the posterior pituitary. These changes were accompanied by the presence of more neurosecretory materials in the axons of the hypothalamic supraoptic and paraventricular neurons and in the hypothalamic capillaries and sinuses. In the perikarya of the hypothalamic supraoptic and paraventricular neurons, the neurosecretory material is in a dispersed state.
• 2 Following chronic morphine treatment, neurosecretory material was almost absent from the posterior pituitary, whereas in the perikarya of the supraoptic and paraventricular neurons, congestion of neurosecretory material is observed which is accompanied by the absence of the neurosecretory material from the axons arising from the supraoptic and paraventricular nuclei and from the hypothalamic capillaries and sinuses.
• 3 During nalorphine-induced abstinence, there was sudden reappearance of the neurosecretory material in the posterior pituitary along with the appearance of neurosecretory material in the hypothalamic neurosecretory neuronal tracts, blood capillaries and sinuses together with the dispersion of the neurosecretory materials from the hypothalamic neurosecretory neurons.