SUPERIOR CERVICAL GANGLIONECTOMY SUPPRESSES CIRCADIAN CORTICOTROPIC RHYTHMS IN MALE-RATS IN THE SHORT-TERM (5 DAYS) AND LONG-TERM (10 DAYS)

Superior cervical ganglionectomy (SCGx) has drastic effects on numerou s hormonal circadian rhythms and particularly on pineal melatonin secr etion. We investigated the hormonal consequences of ablation of the su perior cervical ganglion on the corticotropic circadian rhythms in the male rat. Plasma were obtained by sampling blood every 4 h, using a c hronic carotid cannula. Adreno-corticotropin hormone (ACTH) was assaye d by radioimmunoassay (RIA) and corticosterone (B) by radiocompetition . Urinary 6-sulphatoxymelatonin (aMT6s), considered as an index of the pineal gland activity, was assayed by specific RIA: a decrease in the aMT6s concentration after ganglionectomy was taken as proof of adequa te surgical operation. Control animals showed classical circadian rhyt hms for ACTH and B with basal values during the light phase and circad ian peaks around the light/dark interface. Five and ten days after gan glionectomy, the circadian rhythms of ACTH and B were suppressed. In a ddition, the mean ACTH concentrations increased significantly 10 days after ganglionectomy compared to those in sham-operated rats and 5 day s post-operation group. The mean plasma corticosterone levels were sim ilar in those three groups of animals. This is the first study demonst rating the suppressive effect of superior cervical ganglionectomy on t he circadian corticotropic hormonal cycle.