Functional mapping of the effects of lesions of the habenular nuclei and their afferents in the rat.

Through the use of the quantitative autoradiographic 2-[14C]deoxyglucose technique, we have investigated the functional significance of the habenular nuclei by the measurement of local cerebral glucose utilization (LCGU) in discrete brain areas of conscious rats following 3 kinds of lesioning. Bilateral electrolytic lesions of the habenular nuclei decreased LCGU in a limited number of well-defined brain areas (the interpeduncular nucleus, median and dorsal raphe, mammillary body and dorsal tegmental nucleus) at 7 and 14 days after lesions. These changes were also observed 180 days following lesioning except that of the dorsal tegmental nucleus. At 14 days after bilateral ibotenic acid-induced lesions of the lateral habenula, LCGU was significantly decreased in the median and dorsal raphe, mammillary body and interpeduncular nucleus. In further studies, bilateral electrolytic lesions of the stria medullaris (which conveys the major afferents to the habenula) decreased glucose use in the interpeduncular nucleus less than that observed after bilateral electrolytic lesions of the habenular nuclei. A highly significant positive correlation was observed between LCGU and choline acetyltransferase activity in the interpeduncular nucleus after all types of lesion. These results further support the view that the medial and the lateral habenula exert a major influence upon functional activity in the interpeduncular nucleus and the mesencephalic raphe nuclei, respectively.