EFFECT OF THE COMBINED ADMINISTRATION OF GALANIN AND CLONIDINE ON SERUM GROWTH-HORMONE LEVELS IN NORMAL SUBJECTS AND IN PATIENTS UNDER CHRONIC GLUCOCORTICOID TREATMENT

Aim of our study was to investigate the effect of clonidine and galani n (alone or in combination) on growth hormone (GH) secretion in normal subjects and in adult patients with increased somatostatin tone due t o chronic daily immunosuppressive glucocorticoid treatment. We studied 7 adult patients undergoing long-term (no less than 6 months) immunos uppressive glucocorticoid treatment for non endocrine diseases (4F, 3M ; age 49.7+/-6.3 years). Six normal adult nonobese subjects (3F, 3M; a ge 34+/-2.7 years) served as controls. All subjects underwent the foll owing three tests in random order: 1) iv infusion of clonidine, 150 mu g in 10 mL of saline, from time 0 to 10 min; 2) iv infusion of synthe tic porcine galanin, 500 mu g in 100 mL of saline from -15 to 30 min; 3) iv infusion of clonidine from 0 to 10 min combined with synthetic p orcine galanin iv infusion from -15 to 30 min. Blood samples for GH as say were taken at -15, 0, 15, 30, 45, 60, 90, 120 min. No significant differences in GH absolute values were observed at any time between th e three different tests within each group of subjects. Normal subjects showed significantly (p<0.05) higher GH peaks and GH absolute values from 15 to 90 min after galanin alone, clonidine alone and clonidine+g alanin with respect to the glucocorticoid-treated patients. The absenc e of any either synergistic or at least additive effect on GH secretio n of galanin and clonidine in conditions of both normal and increased somatostatin tone Suggests that also in man, as well as in the rat, th e action of galanin on the Oh axis may be mediated through alpha-adren ergic pathways.