Stimulatory and inhibitory effects of 5-HT(1A) receptors on adrenocorticotropic hormone and cortisol secretion in a teleost fish, the Arctic charr (Salvelinus alpinus).

The serotonin(1A) (5-HT(1A)) receptor agonist 8-hydroxy-2-(di-N-propylamino)tetralin (8-OH-DPAT) was administrated to juvenile Arctic charr either by intraperitoneal (i.p.) injections or through a permanent i.p. implanted catheter. 8-OH-DPAT induced an elevation of plasma cortisol in non-stressed fish (receiving the drug through a permanent i.p. catheter), whereas 8-OH-DPAT had the opposite effect when administrated through a standard i.p. injection, dampening the rise in cortisol induced by handling and injection, an effect which was most pronounced at low doses of 8-OH-DPAT. In both cases, plasma levels of adrenocorticotropic hormone followed the same general pattern as plasma cortisol. The results suggests that 5-HT(1A) receptors are involved in the regulation of hypothalamic-pituitary-interrenal axis activity in Arctic charr, but the effect of 5-HT(1A) stimulation seems to vary depending on the state of the fish.