LONG-TERM POTENTIATION OF SYNAPTIC TRANSMISSION IN THE AVIAN HIPPOCAMPUS

The avian hippocampus plays a pivotal role in memory required for spat ial navigation and food storing. Here we have examined synaptic transm ission and plasticity within the hippocampal formation of the domestic chicken using an in vitro slice preparation. With the use of sharp mi croelectrodes we have shown that excitatory synaptic inputs in this st ructure are glutamatergic and activate both NMDA-and AMPA-type recepto rs on the postsynaptic membrane. In response to tetanic stimulation, t he EPSP displayed a robust long-term potentiation (LTP) lasting >1 hr. This LTP was unaffected by blockade of NMDA receptors or chelation of postsynaptic calcium. Application of forskolin increased the EPSP and reduced paired-pulse facilitation: (PPF), indicating an increase in r elease probability. In contrast, LTP was not associated with a change in the PPF ratio. Induction of LTP did not occlude the effects of fors kolin. Thus, in contrast to NMDA receptor-independent LTP in the mamma lian brain, LTP in the chicken hippocampus is not attributable to a ch ange in the probability of transmitter release and does not require ac tivation of adenylyl cyclase, These findings indicate that a novel for m of synaptic plasticity might underlie learning in the avian hippocam pus.