Effect of superior cervical ganglionectomy on 24-h variations in hormone secretion from the anterior hypophysis and in hypothalamic monoamine turnover during the preclinical phase of Freund's adjuvant arthritis in rats

The effect of superior cervical ganglionectomy (SCGx) on 24-h rhythms of ci rculating adrenocorticotropic hormone (ACTH), growth hormone (GH), prolacti n and luteinizing hormone (LH) and of hypothalamic noradrenaline content an d dopamine and serotonin turnover, was assessed in rats 3 days after admini stering Freund's complete adjuvant. In sham-operated rats, Freund's adjuvan t injection increased serum ACTH without affecting its diurnal rhythmicity. SCGx, performed 10 days earlier, suppressed 24-h rhythmicity and augmented mean values of circulating ACTH. A depressive effect of immunization on GH release was found in both sham-operated and SCGx rats. GH concentrations d id not exhibit diurnal rhythmicity and decreased after immunization. Time-o f-day-related changes in serum prolactin were significant for all examined groups, except for SCGx-immunized rats. Freund's adjuvant administration au gmented prolactin secretion. Daily changes in serum LH concentration and a decrease after immunization were found in both sham-operated and SCGx rats, SCGx: (i) counteracted inhibition of daily variations of noradrenaline con tent in medial hypothalamus of Freund's adjuvant-injected rats; (ii) decrea sed anterior hypothalamic dopamine turnover and augmented it in the medial hypothalamus; (iii) lowered amplitude of serotonin turnover rhythm in media l hypothalamus. The data indicate that several early changes in levels and 24-h rhythms of circulating ACTH and prolactin, and in hypothalamic noradre naline content and dopamine and serotonin turnover, were modified by a prev ious SCGx in Freund's adjuvant-injected rats.