Pineal and Vasopressin Synthesis by Ewa Bojanowska, Marlena Juszczak, Jan W. Guzek, Ryszard
effect of pineal removal on vasopressin (AVP) synthesis in the
rat hypothalamus two or eight weeks after pinealectomy was investigated
using the colchicine method. Pinealectomized or sham-operated
rats were injected intracerebroventricularly with colchicine
solution (5 µg/5 µl) or saline and decapitated 20 h later. The
hypothalamic AVP content was increased whereas the neurohypophysial
secretory activity was not affected by colchicine injection.
The AVP synthesis rate as well as the plasma AVP concentration
were significantly higher two weeks after pinealectomy. On the
contrary, both the AVP synthesis rate and its plasma level were
markedly reduced eight weeks after pineal removal. We suggest
that the pineal suppresses the synthesis of AVP. With passage
of time, however, the functional exhaustion of the vasopressinergic
system develops and the hormone synthesis is reduced.