PINEAL-GLAND AND SYMPATHETIC CERVICAL-GANGLIA AS SITES FOR STEROID REGULATION OF PHOTOSENSITIVE NEURO-ENDOCRINE PATHWAYS

Secretions from the pineal gland participate in endocrine responses to changes in daily photoperiod, e.g., gonadal growth. In turn feedback regulation by gonadal steroid hormones takes place at the level of pinealocytes and their sympathetic innervating neurons located in the superior cervical ganglia (SCG). In the present work various experiments were conducted to assess the effects of oestradiol (E) treatment on relevant enzyme activities and metabolic components of the SCG of spayed rats. E administration decreased tyrosine hydroxylase activity and enhanced dopamine-beta-hydroxylase activity and norepinephrine uptake significantly regardless of whether intact preganglionic connections were present. E injection increased monoamine oxidase (MAO) activity type A in controls but not in animals bearing decentralized ganglia. Both MAO type A and B activities, tubulin levels and norepinephrine uptake by SCG were depressed by decentralization whereas catechol-O-methyl transferase increased following surgery. E treatment counteracted the depression in tubulin levels of decentralized SCG. In another series of experiments 3H-E uptake by rat SCG in vivo and in vitro was assessed. A single population of binding sites with a KD = 5.5 nM was detected in cytosol fractions of SCG. Translocation of hormone-receptor complexes from cytoplasm to the nucleus occurred following a single injection of 2 μg of E. These results suggest that SCG is a target tissue for oestrogens. © 1979.