THE GABA-B RECEPTOR ANTAGONIST, CGP-35348, INHIBITS PAIRED-PULSE DISINHIBITION IN THE RAT DENTATE GYRUS INVIVO

Extracellular field potentials were recorded from the dentate gyrus of adult rats during electrical stimulation of the angular bundle in vivo. Paired pulses produced inhibition of the second population spike (PS2) at 25 ms, and potentiation at inter-stimulus intervals from 50 to 200 ms. The GABA(B) receptor antagonist, CGP 35348, reduced the amplitude of PS2 at each of these inter-stimulus intervals while producing no effect on the first population spike of the pair (PS1). Under control conditions, the duration of the second population EPSP (pEPSP2) was increased relative to the first at inter-stimulus intervals from 100 to 400 ms, and CGP 35348 reduced these durations to baseline levels. These results demonstrate that GABA(B) receptors modulate synaptic inhibition in vivo.