INVOLVEMENT OF THE CERVICAL SYMPATHETIC NERVOUS-SYSTEM IN THE CHANGESOF CALCIUM HOMEOSTASIS DURING TURPENTINE OIL-INDUCED STRESS IN RATS

Hypocalcemia is a common finding during stress. The objective of this study was to examine: (a) the changes in circulating calcium, parathyr oid hormone (PTH) and calcitonin (CT) concentration in rats stressed b y being given a subcutaneous injection of turpentine oil, and (b) the involvement of the sympathetic cervical pathway in stress-induced chan ges of calcium homeostasis. Four hours after receiving turpentine oil or vehicle, rats were subjected either to hypocalcemia, by being given EDTA intraperitoneally, or to hypercalcemia, by being injected CaCl2 intraperitoneally. Significant changes in serum calcium (10% decrease) , serum PTH (28% increase) and CT levels (40% decrease) were observed in stressed rats. EDTA administration brought about a significantly gr eater hypocalcemia, and a higher PTH secretory response in turpentine oil-stressed rats. During stress, the increase of serum calcium after CaCl2 was significantly smaller, and the rise of CT was greater than i n controls. In the case of CT the changes were still observed in rats subjected to superior cervical ganglionectomy (SCGx) 14 days earlier. In the case of PTH, the increase found in stressed rats, but not the a ugmented response after EDTA, was blunted by SCGx. The potentiation of hypocalcemia brought about by turpentine oil was no longer observed i n SCGx rats. In vehicle-treated controls, SCGx delayed PTH response to hypocalcemia, but did not affect the increased response of CT to CaCl 2 challenge. The results indicate that a number of changes in calcium homeostasis arise during turpentine oil stress in rats. SCGx was effec tive to modify the set point for PTH release, but played a minor role in affecting the augmentation of CT release during stress.