Effects of fimbria-fornix transection and ganglioside treatments on histochemical staining for glucose-6-phosphate dehydrogenase in the lateral septum.

Abstract

The present study examined whether ganglioside treatments would affect an enzyme marker (glucose-6-phosphate dehydrogenase; G6PDH) of neural metabolism in an established model system (the hippocamposeptal projection) of deafferentation and sprouting. Rats were subjected to unilateral transections of the fimbria-fornix (FF) in order to (1) interrupt the hippocamposeptal projection, (2) deafferent the lateral septal nucleus (LSN) ipsilaterally, and (3) induce sprouting by the contralateral FF. In untreated rats which were killed at 2-4 days postlesion, histochemical staining for G6PDH was reduced by 35-40% in the deafferented LSN relative to the contralateral side. However, at 6-8 days (i.e., when sprouting begins), staining intensity returned toward contralateral values (i.e., recovered). This pattern of changes in G6PDH staining was not observed in the caudate nucleus adjacent to the LSN. In ganglioside-treated rats which were killed at 4 days, there was a significantly smaller reduction of G6PDH staining in the deafferented LSN (23%; P = .05). This effect was not observed in the LSN of treated rats killed at 2 days, nor in the caudate nucleus at either time point. The present data indicate that (1) FF transection results in a reduction and subsequent recovery of G6PDH staining in the deafferented LSN; and (2) ganglioside treatments may accelerate the onset of the recovery of G6PDH activity. We suggest that gangliosides' effect on G6PDH reflects an acute enhancement of biosynthetic events in deafferented neurons.