NEUROANATOMICAL TRACT TRACING PROVIDES HISTOLOGICAL VERIFICATION OF NEURON LOSS FOLLOWING CYTOTOXIC LESIONS

In the present study we report a neuroanatomical procedure that provid es direct histological verification of the extent of neuron loss follo wing cytotoxic lesions of the lateral subdivision of the habenular com plex (Lhb). Following kainic acid-induced lesions of Lhb neurons, the fluorescent retrograde tracer Fluoro-Gold was injected into the ventra l midbrain where many medial habenula (Mhb) and Lhb neurons project. T he absence of retrogradely labeled neurons in the Lhb indicated the ex tent of neuron loss there, and the presence of Fluoro-Gold-labeled neu rons in the Mhb indicated that its neurons were intact. The extent of neuron loss in the Lhb was significantly correlated with behavioral da ta. Retrograde tract tracing can be used as an effective histological tool to verify the extent of neuron loss following a lesion procedure.