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.