THE EFFECTS OF SOMATOSTATIN ON SERUM GROWTH-HORMONE LEVELS IN THE GOLDFISH, CARASSIUS-AURATUS

The effects of somatostatin on serum growth hormone (GH) levels in the goldfish, C. auratus, were investigated. A single i.p. injection of either 0.1 or 1.0 .mu.g somatostatin/g body wt caused a significant decrease in serum GH levels at 1 h postinjection compared to vehicle-injected controls. Two i.p. injections of somatostatin (1.0 .mu.g/g body wt), given 12 h apart, caused a significant decrease in serum GH levels, compared to both presample and vehicle-injected control groups at 1.5 and 6 h following the 2nd injection. In fish given 2 injections of somatostatin, a postinhibitory rebound in serum GH levels occurred by 24 h following the 2nd injection. TRH (1 .mu.g/g body wt), given as a control peptide, caused a significant increase in serum GH levels at 24 h, but no significant changes were found at 1.5 or 6 h following the 2nd of 2 i.p. injections given 12 h apart. The increases in serum GH at 24 h may be due to stress. Somatostatin causes a transient decrease in blood GH levels in goldfish.