MODULATION BY GALANIN OF GROWTH-HORMONE AND GONADOTROPIN-SECRETION FROM PERIFUSED PITUITARY AND MEDIAN-EMINENCE OF PREPUBERTAL MALE CALVES

Galanin is widely distributed in the peripheral and central nervous sy stem and has been indicated as a putative hypothalamic-hypophysiotropi c hormone. This study was performed to investigate the effects of gala nin on both growth (GH) and luteinizing hormones (LH) from pituitaries of young male calves. Pituitary slices (P, 500 mu m in thickness) wer e perfused alone or coincubated with median eminence terminals (ME) in DMEM-F12 plus BSA 0.1% and antibiotics. The perifusion chambers were kept in equilibrium for 150 min, and medium samples were collected eve ry 10 min for 240 min and stored at -20 degrees C until the measuremen t of LH and GH levels. Basal GH release increased up to 60% after gala nin infusion (p < 0.01 vs. baseline levels) for 60 min in P alone; in P + ME coincubation, galanin-stimulated GH secretion was further incre ased by up to 200%. Basal LH release in chambers with P was significan tly increased (up to 25%; p < 0.05) for 70 min after galanin infusion; P + ME coincubation showed a galanin-mediated increase in LH release of up to 50%. GH and LH responsiveness to exogenous GH-releasing hormo ne and gonadotropin-releasing hormone was not significantly modulated by galanin in our experimental model. In conclusion, galanin is demons trated to have a significant stimulatory role in the secretion of GH a nd LH, with a combined action at both the hypothalamic and pituitary l evels.