Intracellular Ca(2+) signaling is required for neurotrophin-induced potentiation in the adult rat hippocampus.

Recent studies have demonstrated the importance of neurotrophin function in adult synaptic plasticity. In an effort to characterize the intracellular signaling pathways that couple Trk receptor activation to the final physiological effects of neurotrophins, we have examined the role of intracellular calcium rises in neurotrophin-induced synaptic enhancement in hippocampal slices. Using pharmacological blockers to two different calcium ion (Ca(2+)) sources, voltage-gated Ca(2+) channels and intracellular Ca(2+) stores, we show that the potentiating effects of neurotrophins in hippocampal slices are mediated by intracellular Ca(2+) signaling. Although basal synaptic transmission between hippocampal CA3 and CA1 neurons was not affected by nifedipine or thapsigargin, both drugs significantly attenuated brain-derived neurotrophic factor or neurotrophin-3-induced synaptic enhancement. The pharmacological blockade of Ca(2+) signaling is effective only during the initial period of neurotrophin-induced potentiation. These data suggest that the minimal requirements for inducing potentiation by neurotrophins involve a transient increase in intracellular Ca(2+) concentration, via voltage-gated Ca(2+) channels and/or intracellular Ca(2+) stores.