REQUIREMENT OF BASOLATERAL AMYGDALA NEURON ACTIVITY FOR THE INDUCTIONOF LONG-TERM POTENTIATION IN THE DENTATE GYRUS IN-VIVO

We investigated the effect of injection of a local anesthetic, tetraca ine, into the ipsilateral basolateral amygdala (BLA) on long-term pote ntiation (LTP) in the medial perforant path-dentate gyrus granule cell synapses of anesthetized rats. The dentate gyrus synaptic potential e voked by low frequency test stimulation did not change following tetra caine injection into BLA. However, when tetanic stimulation (30 pulses at 60 Hz) was applied 10 min after tetracaine injection, the magnitud e of LTP was significantly attenuated in a dose-dependent manner. Inje ction of tetracaine after tetanic stimulation did not affect the estab lished LTP. The small LTP observed in the BLA-lesioned rats was regard ed as the BLA-independent component of LTP, which was not affected by tetracaine injection. These results suggest that neuron activities in the ipsilateral BLA are partly required for the induction of LTP in th e dentate gyrus in vivo.