Ontogeny of the somatostatin variant [Pro2,Met13]somatostatin-14 in the brain, pituitary, and sensory organs of the frog Rana esculenta.
Two forms of somatostatin are expressed in the frog brain, i.e., somatostatin-14 (SS1) and the [Pro(2), Met(13)]somatostatin-14 variant (SS2). We have previously described the ontogeny of SS1-immunoreactive cells in the brain of Rana esculenta. In the present study, we have investigated the distribution of prepro-SS2 (PSS2)-expressing neurons in the brain of the same species during development by using antibodies directed against the N-flanking region of SS2 (PSS2(54-66)). Immunoreactive perikarya first appeared in the ventral hypothalamus at stages IV-VII. Subsequently, positive neurons were seen in the nucleus of the diagonal band of Broca, the anterior preoptic area, the posterior tuberculum (stages VIII-XII), as well as the dorsal (stages XIII-XV) and medial (stages XIX-XX) periventricular preoptic nucleus. At metamorphic climax and in newly metamorphosed frogs, positive perikarya were found in the striatum and in the interpeduncular nucleus. PSS2(54-66)-immunoreactive fibers were already widely distributed during the first stages of development, indicating that SS2 may act as a neuromodulator and/or neurotransmitter during ontogeny. The presence of PSS2(54-66)-positive nerve fibers in olfactory structures suggests that, in tadpoles, SS2 may be involved in the processing of olfactory information. The occurrence of PSS2(54-66)-like immunoreactivity in taste buds, and in the olfactory and vomeronasal organs indicates that SS2 may mediate the unconditioned and reinforcing properties of natural chemicals. Finally, the intenseexpression of PSS2(54-66)-like immunoreactivity in melanotrope cells of the pituitary suggests that SS2 may diffuse toward the pars distalis to regulate the activity of adenohypophysial cells during tadpole development.
Vallarino
Mauro
M
Department of Experimental Biology, DIBISAA, University of Genova, 16132 Genova, Italy. mvallari@unige.it
Bruzzone
Federica
F
Mathieu
Maura
M
Chartrel
Nicolas
N
Vieau
Didier
D
Ciarlo
Monica
M
Fournier
Alain
A
Vaudry
Hubert
H
D000818:Animals; D001921:Brain / Q000254:growth & development / Q000378:metabolism*; D007150:Immunohistochemistry; D007814:Larva / Q000254:growth & development / Q000378:metabolism; D008675:Metamorphosis, Biological / Q000502:physiology; D010902:Pituitary Gland / Q000254:growth & development / Q000378:metabolism*; D011893:Rana esculenta / Q000033:anatomy & histology / Q000254:growth & development / Q000378:metabolism*; D012679:Sense Organs / Q000254:growth & development / Q000378:metabolism*; D013004:Somatostatin / Q000031:analogs & derivatives / Q000378:metabolism*
D013004:Somatostatin