title: Input integration around the dendritic branches in hippocampal dentate granule cells.
abstract: Recent studies have shown that the dendrites of several neurons are not simple translators but are crucial facilitators of excitatory postsynaptic potential (EPSP) propagation and summation of synaptic inputs to compensate for inherent voltage attenuation. Granule cells (GCs)are located at the gateway for valuable information arriving at the hippocampus from the entorhinal cortex. However, the underlying mechanisms of information integration along the dendrites of GCs in the hippocampus are still unclear. In this study, we investigated the input integration around dendritic branches of GCs in the rat hippocampus. We applied differential spatiotemporal stimulations to the dendrites using a high-speed glutamate-uncaging laser. Our results showed that when two sites close to and equidistant from a branching point were simultaneously stimulated, a nonlinear summation of EPSPs was observed at the soma. In addition, nonlinear summation (facilitation) depended on the stimulus location and was significantly blocked by the application of a voltage-dependent Ca(2+) channel antagonist. These findings suggest that the nonlinear summation of EPSPs around the dendritic branches of hippocampal GCs is a result of voltage-dependent Ca(2+) channel activation and may play a crucial role in the integration of input information.
authors.affiliation: Graduate School of Brain Sciences, Tamagawa University, 6-1-1 Tamagawagakuen, Machida, Tokyo 194-8610 Japan.
authors.forename: Tadanobu Chuyo
authors.initials: TC
authors.lastname: Kamijo
authors.affiliation: Graduate School of Brain Sciences, Tamagawa University, 6-1-1 Tamagawagakuen, Machida, Tokyo 194-8610 Japan.
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Hayakawa
authors.affiliation: Faculty of Health and Welfare, Kawasaki University of Medical Welfare, Kurashiki, Japan.
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Fukushima
authors.affiliation: National Institute for Physiological Science, Okazaki, Japan.
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Kubota
authors.affiliation: Graduate School of Brain Sciences, Tamagawa University, 6-1-1 Tamagawagakuen, Machida, Tokyo 194-8610 Japan.
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Isomura
authors.affiliation: Graduate School of Brain Sciences, Tamagawa University, 6-1-1 Tamagawagakuen, Machida, Tokyo 194-8610 Japan.
authors.forename: Minoru
authors.initials: M
authors.lastname: Tsukada
authors.affiliation: Graduate School of Brain Sciences, Tamagawa University, 6-1-1 Tamagawagakuen, Machida, Tokyo 194-8610 Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Aihara
keywords: Dendrite; Excitatory postsynaptic potentials summation; Hippocampus; Supralinear amplification; Uncaging