NEURONAL COEXISTENCE OF TRKB AND GLUTAMIC-ACID DECARBOXYLASE(67) MESSENGER-RNAS IN RAT HIPPOCAMPUS

We have in earlier studies shown that brain derived neurotrophic facto r (BDNF) mRNA expression is increased in the hippocampus following sti mulation of excitatory cortical afferents and spatial learning. Furthe rmore, we have observed that excitatory influence in the hippocampus s eems to increase in vivo release of gamma-aminobutyric acid (GABA), in dicated by microdialysis perfusion of the CA1 region. In this study we have investigated whether the receptor for BDNF, TrkB, may be express ed in GABA containing neurons in the CA1, thereby suggesting a possibl e role for BDNF in the trophic regulation of these neurons. We provide evidence of a neuronal coexistence of the mRNAs encoding TrkB and glu tamic acid decarboxylase, the key enzyme in the synthesis of GABA. Thi s finding indicates that TrkB can be synthesized in GABA producing neu rons in the hippocampus.