PINEAL METABOLIC REACTION TO RETINAL PHOTOSTIMULATION IN GANGLIONECTOMIZED RATS

The aim of the present work was to test the pineal gland metabolic rea ctivity to nocturnal retinal short term photic stimulation in superior cervical ganglionectomized rats. The experimental support for this wo rk is the appearance of a transitory post synaptic hyperactivity in th e pineal gland, during the anterograde degenerating process of the con arii sympathetic nerve fibers after surgical removal of the cell body. In this situation the pineal gland is deafferented from the periphera l sympathetic nervous system keeping intact, however, the direct centr al connections to the deep pineal/lamina intercalaris region (DP). The results show a blockade of the pineal noradrenergic stimulatory proce ss due to the retinal photostimulation. The inactivation of N-acetyltr ansferase led to a true metabolic shift to the oxidative pathway resul ting in a decrease of the amount of N-acetylserotonin and an increase of the amount of serotonin, 5-hydroxyindoleacetic acid and 5-hydroxytr yptophan. This inhibitory process brought into action by retinal illum ination is dependent on the direct central neural connections to the p ineal gland, since rats that were lesioned in the DP, previously to ga nglionectomy, did not show any alteration on the indolic content of th e pineal gland when subjected to nocturnal retinal photostimulation.