THE ROLE OF THE SEPTOHIPPOCAMPAL PATHWAY IN THE MEDIATION OF COLCHICINE-INDUCED COMPENSATORY CHANGES IN THE RAT HIPPOCAMPUS

To study the involvement of the septohippocampal pathway in colchicine -induced changes in the hippocampus, colchicine was used to lesion the septum and/or hippocampus of male, Fischer-344 rats. Rats were killed 12 weeks post-lesion and histochemical and biochemical measurements w ere performed. [H-3]-QNB binding, choline acetyltransferase (ChAT) act ivity and agonist-stimulated release of inositol phosphates (IPs) were measured in hippocampal slices. AChE histochemistry was also performe d to visualize AChE positive fibers in the hippocampus. Increases in C hAT activity, AChE staining and carbachol-stimulated IP release observ ed in hippocampal-lesioned animals were attenuated in animals receivin g both septal and hippocampal lesions. However, the decrease observed in [H-3]-QNB binding sites after intradentate colchicine was not affec ted by septal lesions. Subsequent studies also found enhanced sensitiv ity to excitatory amino acid (EAA)-stimulated IP release in hippocampa l-lesioned animals. Similar to the changes observed in carbachol-stimu lated PI hydrolysis, this increase was also long-lasting. However, the hyperstimulation of EAA-induced IP release was not attenuated by the septal lesion. Thus, it appears that the neurochemical and morphologic al changes observed in the hippocampus following intradentate colchici ne are dependent upon more than one afferent projection to the hippoca mpus. (C) 1993 Intox Press, Inc.