EFFECT OF ROUTE AND FREQUENCY OF ADMINISTRATION OF APOMORPHINE ON GROWTH-HORMONE RELEASE IN AFRICAN CATFISH (CLARIAS-GARIEPINUS)

Apomorphine is known to stimulate growth hormone release in African ca tfish following an intraperitoneal (IF) injection. In the present stud y the effect of apomorphine (5 or 20 mg/kg body weight) on plasma GH l evels was evaluated after gastro-intestinal or parenteral delivery. Ap omorphine increased the plasma GH concentration regardless of the rout e of administration, indicating that apomorphine can be absorbed from the intestinal tract. The effect of repeated administration of apomorp hine differed clearly between the tested doses. Although a single IP i njection with 20 mg apomorphine/kg body weight resulted in a clear inc rease in plasma GH levels, a second injection given 12 hours later was ineffective. In contrast the last of 4 consecutive injections with 5 mg apomorphine/kg body weight given at intervals of 12 hours stimulate d the plasma GH levels in a similar way to a single IP injection with the same dose.