Melanin concentrating hormone (MCH) gonadotrophin releasing hormone (GnRH) as regulators of somatolactin in the teleost fish Cichlasoma dimerus

CANEPA M; POZZI AG; MAGGESE MC; VISSIO PG

IBYME

Jornada; VII Jornadas Multidisciplinarias de la Sociedad Argentina de Biología; 2006

Sociedad Argentina de Biología

In most vertebrates, the pars intermedia (PI) presents only MSH cells but in teleost and lung fishes, somatolactin (SL) expressing cells can be observed to. The structure of SL is similar to vertebrate Growth Hormone and Prolactin. Moreover, a multitud of biological functions were described for this hormone. In C. dimerus, we found clear evidence about a possible involvement of SL together with MSH and MCH in background adaptation (Canepa et al., 2006). However there scarce information on the regulation of SL secretion. This work analyzes the effect of GnRH and MCH on SL secretion and the morphological association between MCH and GnRH fibers with SL cells. We observed  that MCH (10µM, 24 hs) and GnRH (10µM, 24 hs) stimulate the SL secretion from organ-cultured pituitary. By double immunohistochemistry and confocal microscopy we demonstrate a close association between MCH fibers proceeding from nucleus lateralis tuberis (NLT) and SL cells. Futhermore, we found GnRH fibers from the ventral forebrain (in lower proportion than MCH) in association with SL cells. On the other hand, we observed that in the NLT, fibers of GnRH were associated to the soma and fibers of the magnocellular MCH neurons. These results suggest that, in C. dimerus, SL is under hypothalamic control of the MCH and GnRH. Moreover the close association between GnRH fibers and MCH cells in the hypothalamus imply that GnRH also acts like MCH neuromodulator.