Regional and postnatal heterogeneity of activity-dependent long-term changes in synaptic efficacy in the dorsal striatum

High-frequency activation of excitatory striatal synapses produces lasting changes in synaptic efficacy that may contribute to motor and cognitive fun ctions. While some of the mechanisms responsible for the induction of long- term potentiation (LTP) and long-term depression (LTD) of excitatory synapt ic responses at striatal synapses have been characterized, much less is kno wn about the factors that govern the direction of synaptic plasticity in th is brain region. Here we report heterogeneous activity-dependent changes in the direction of synaptic strength in subregions of the developing rat str iatum. Neurons in the dorsolateral region of the anterior striatum tended t o express LTD after high-frequency afferent stimulation (HFS) in slices fro m animals aged P15-P34. However, HFS in dorsolateral striatum from P12-P14 elicited an N-methyl-D-aspartate (NMDA) receptor-dependent form of LTP. Syn apses in the dorsomedial anterior striatum exhibited a propensity to expres s an NMDA-receptor dependent form of LTP across the entire developmental ti me period examined. The NMDA receptor antagonist (+/-)-2-amino-5-phosphopen tanoic acid (APV) inhibited evoked excitatory postsynaptic potentials recor ded in striatum obtained from P12-P15 rats but had little effect in striatu m from older animals. The expression of multiple forms of synaptic plastici ty in the striatum suggests mechanisms by which this brain region plays piv otal roles in the acquisition or encoding of some forms of motor sequencing and stereotypical behaviors.