THE INFLUENCE OF CERVICAL SYMPATHETIC NEURONS ON PARATHYROID-HORMONE AND CALCITONIN RELEASE IN THE RAT - INDEPENDENCE OF PINEAL MEDIATION

The objective of this study was to evaluate the involvement of the pin eal gland in modulation of parathyroid hormone (PTH) and calcitonin re lease found in rats after changes in activity of cervical sympathetic nerves. The response of serum PTH to a hypocalcemia produced by EDTA i njection, and of serum calcitonin to a hypercalcemia produced by admin istering calcium chloride, were studied in rats at the time of the wal lerian degeneration of regional sympathetic nerves (i.e., 16 hr after superior cervical ganglionectomy, SCGx). Rats received a pinealectomy or its sham-operation 4 days before SCGx. During wallerian degeneratio n of nerves after SCGx, a higher hypocalcemia and a lower PTH response were found as compared to sham-SCGx rats, regardless of whether the p ineal gland was present or not. When the response of calcitonin to a b olus injection of calcium chloride was assessed, rats subjected to SCG x 16 hr earlier showed a depressed calcitonin release, which was also unaffected after pinealectomy. To a similar extent in pinealectomized and sham-pinealectomized rats, a mild stress given by the subcutaneous injection of turpentine oil brought about a greater hypocalcemia afte r EDTA, concomitantly with a higher PTH secretory response. In turpent ine oil-injected rats, the rise of serum calcitonin was significantly greater than that of vehicle-treated rats, regardless of pineal presen ce. The results further indicate that cervical autonomic nerves consti tute a pathway through which the brain modulates calcium homeostasis a nd do not support the participation of the pineal gland in short term changes of PTH or calcitonin release.