Decrease of GABA During Long-Term Potentiation in the CA1 Region of Rat Hippocampal Slices: Immunohistochemical and Biochemical Analysis

To elucidate the participation of hippocampal interneurons on the occurrence of long-term potentiation (LTP), the functional change in GABA-ergic neurons during LTP was investigated in hippocampal slices immunocytochemically using anti-GABA serum, as well as neurochemically by HPLC procedures. Pyramidal GABA-like immunoreactive neurons had a decreased immunoreactivity in neuronal perikarya and terminal varicosities surrounding pyramidal cells of CA1 in LTP slices compared with those in controls. These changes were not observed in the other regions of CA1 or during short-term potentiation (STP). GABA concentration in CA1-CA3 regions displayed a significant reduction (28%) during LTP (P <0.05). These results suggested that the function of GABA-ergic interneurons in str. pyramidale may be altered during LTP.