Distribution of SNAP25, VAMP1 and VAMP2 in mature and developing deep cerebellar nuclei after estrogen administration.

Synaptosomal-associated protein of 25kDa (SNAP25), vesicle-associated membrane protein 1 (VAMP1) and 2 (VAMP2) are components of soluble N-ethylmaleimide-sensitive fusion attachment protein receptors (SNARE) complex which is involved in synaptic vesicle exocytosis, a fundamental step in neurotransmitter release. SNARE expression in cerebellum correlates with specific neurotransmitter pathways underlying synaptic diversification and defined synaptic properties. In this study we firstly characterized the distribution of SNAP25, VAMP1 and VAMP2 in the nerve terminals of a defined cerebellar region, the deep cerebellar nuclei (DCN), of adult and newborn rats. Then, given the pivotal role of estradiol (E2) in the synaptic organization of the cerebellar circuitry in early postnatal life, we examined whether administration of E2 in the newborn DCN affected synaptic density and changed the distribution of the presynaptic proteins SNAP25, VAMP1 and VAMP2, together with post synaptic density protein 95 (PSD95). Results showed that: (1) distribution of SNAP25, VAMP1 and VAMP2 in adult DCN differs significantly from that found in newborn DCN; (2) administration of E2 in the newborn DCN affected synaptic density and also changed the distribution of the pre- and postsynaptic proteins. The differential distribution of SNAP25, VAMP1 and VAMP2 in nerve terminals of adult and newborn rats may correlate with specific stages of neuronal phenotypic differentiation. The effects of E2 on SNAP25, VAMP1, VAMP2, PDS95 and synaptic density suggest that pre- and postsynaptic proteins are under estrogenic control during development and that synaptic maturation can also be related with the activity of this steroid.