IMMUNOHISTOCHEMICAL LOCALIZATION OF LYN (P56) PROTEIN IN THE ADULT-RAT BRAIN

Expression of a sarcoma proto-oncogene, c-lyn, was mapped in the adult rat brain using immunohistochemistry. Lyn protein was prevalent in re stricted cell populations of the olfactory bulb and the basal forebrai n which included nuclei of accumbens, fundal striatum, bed stria, vent ral pallidum and central amygdala as well as deep entorhinal and pyrif orm cortices. Tightly packed Lyn-positive cells formed discrete multip le stripes crossing perpendicular to the rostral limb of the anterior commissure, and intense masses surrounding the caudal limb. In the tha lamus, the habenula, anterodorsal nucleus and medial geniculate body, together with the paraventricular hypothalamic nuclei, had prominent r eactive neuronal somata and dendrites in the neuropil. The lateral sep tal nucleus also had intense Lyn-positive neurons with overlapping den dritic fields. In addition, scattered neurons were evenly distributed throughout the striatum. The red, interpeduncular, auditory and trigem inal tract nuclei were intensely reactive. The cerebellar molecular la yer was uniformly labeled except for a few isolated fiber bundles in t he lowest part of this layer. The granule cells adjacent to the Purkin je cell layer appeared in reactive patches. In the spinal cord, the po steromarginal nucleus had intense labeling. The significance of this h ighly localized distribution pattern of Lyn protein may be related to connections forming functional compartments serving signal transductio n within specific central nervous system circuitry.