Roles of presynaptic TrkB receptors in synaptic plasticity in the hippocampal CA1 region

Abstract

TrkB receptors, whose ligands are brain-derived neurotrophic factor (BDNF) and neurotrophin (NT)-4/5, are known to be essential for neuronal proliferation and differentiation during development, but growing evidence suggests that they are crucial modulators for synaptic plasticity in adults as well. Although TrkB receptors are expressed at both pre- and postsynaptic sites in the hippocampal CA1 region, their precise roles are not well understood. Thus, we have generated conditionally gene-targeted mice in which the knockout of the trkB gene is restricted to the CA3 region from which presynaptic afferents in the CA1 region originate. Adult mutant mice show impairment of short-term presynaptic plasticity and long-term potentiation induced by high-frequency conditioning stimulation. Our results suggest that the presynaptic TrkB receptor plays significant roles in the modulation of hippocampal synaptic plasticity. We will discuss possible mechanisms by which presynaptic TrkB receptors regulate hippocampal synaptic plasticity. [Jpn J Physiol 55 Suppl:S124 (2005)]