DEVELOPMENTAL EXPRESSION OF GAP-43 AND SNAP-25 IN HETEROTOPIC RAT CORTICAL GRAFTS

In situ hybridization techniques were used to assess (i) whether the t emporal developmental profiles of the nervous system specific growth a ssociated phosphoprotein (GAP-43) and the 25-kDa synaptosomal-associat ed protein (SNAP-25) are maintained in heterotopic cortical transplant s, and (ii) whether the hybridization intensity in morphologically dif ferentiated heterotopic transplants is comparable to that in the corte x of host animals. Cortical primordia at embryonic day 14 were stereot actically grafted into the striatum of adult recipient rats. Grafts at days 4, 7, 14, 35 and 56 after transplantation demonstrated developme ntal changes with a progressive decline of GAP-43 and a continuous up- regulation of SNAP-25 expression. Our data provide evidence of distinc t molecular alterations during the differentiation process of cortical grafts, which are strikingly similar to previous studies investigatin g the temporal profile and intensity of GAP-43 and SNAP-25 gene expres sion in normal developing cortex of the rat.