AXONAL ACCUMULATION OF P75(NTR) AND TRKA IN THE SEPTUM FOLLOWING LESION OF SEPTOHIPPOCAMPAL PATHWAYS

Septal cholinergic neurones depend on trophic support by nerve growth factor (NGF) which can rescue them from injury-induced degeneration. S ince NGF exerts its effects via p75(NTR) and TrkA receptors coexpresse d in vast majority of these neurones and down-regulated without NGF tr eatment after injury, in this study we aimed to examine how does the l esion to the cholinergic tracts affect distribution of both types of r eceptor proteins in damaged fibres. Early changes (two and seven days) were examined immunocytochemically within the septum and supracallosa l stria after unilateral lesion to the supracallosal area and cingulum transecting some septal cholinergic efferents. We found accumulation of p75(NTR) and TrkA immunoreactive material (so-called ''pile-up'') w ithin axonal segments of distended appearance proximal to the transect ion at two days postlesion and its translocation towards cell bodies s even days NTR pile-up to be more intense than postsurgery. We observed p75(NTR) pile-up to be more intense than TrkA, which may indicate dif ferent cellular concentrations of both receptors. Receptor pile-up res embled acetylcholinesterase pile-up reported previously, suggesting a common response mechanism involving axonal transport disturbances.