Further evidence for excitatory amino acid transmission in the lateral habenular projection to the rostral raphe nuclei: lesion-induced decrease of high affinity glutamate uptake.

In previous autoradiographic studies we reported selective retrograde D-[3H]aspartate labelling of lateral habenular afferents to the nuclei raphe dorsalis (NRD) and centralis superior (RCS). This study reports biochemical support, lesion-induced decrease of high affinity glutamate uptake, for excitatory amino acid transmission in the habenulo-raphe connection. Rats received bilateral electrolytic lesions in the lateral habenular nuclei and survived 9-10 days. Brainstems were sectioned on a Vibratome, and NRD and RCS tissue microdissected. Glutamate uptake in sham-operated rats was in the NRD 23.6 +/- 2.3 nmol/g prot. (mean +/- S.E.M.) ([3H]glutamate 10(-7) M, 3 min, 25 degrees C) and in the RCS 14.6 +/- 1.0 nmol/g. Habenular lesions reduced glutamate uptake in the NRD by 20.7 +/- 2.0% (P less than 0.001) and in the RCS by 10.7 +/- 4.3% (P less than 0.05).