THE G-PROTEIN GAMMA-SUBUNIT G-GAMMA-8 IS EXPRESSED IN THE DEVELOPING AXONS OF OLFACTORY AND VOMERONASAL NEURONS

The tissue localization of the G-protein gamma-subunit, G gamma 8, tha t is specifically expressed in the olfactory and vomeronasal neurons, was studied in rats at different ages: embryonic day 16, postnatal day s 1, 7, 14 and 35, and adult. G8 appears to be a specific marker of th e immature olfactory and vomeronasal neurons. Its distribution differs from that of Golf alpha, a G-protein alpha-subunit which is predomina ntly expressed in mature olfactory neurons. G8 immunoreactivity indica tes that an undifferentiated organization of the olfactory epithelium persists up to 3 weeks of age, though neonates possess a functional se nse of smell. G gamma 8 accumulates at the highest levels in the axons of the developing olfactory neurons 2 weeks after birth (postnatal da y 14). Moreover, up to postnatal day 14, G gamma 8-positive neurons ar e present in the region of the olfactory and vomeronasal epithelium, w here they are not observed in later life. In the olfactory epithelium and in the bulb, G gamma 8 expression becomes weaker and patchy with i ncreasing age, suggesting that the process of continuous regeneration of olfactory neurons occurs in discrete areas. G8-enhanced expression following axotomy indicates that this system is potentially active thr oughout life. Conversely, in the vomeronasal epithelium G gamma 8 expr ession persists virtually unmodified in the adult. This indicates that the degree of differentiation may differ between olfactory and vomero nasal neurons.