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Functional organization of dendritic Ca2+ signals in midbrain dopamine neurons
Authors:Jang Miae  Jang Jin Young  Kim Shin Hye  Uhm Ki Bum  Kang Yun Kyung  Kim Hyun Jin  Chung Sungkwon  Park Myoung Kyu
Institution:aDepartment of Physiology, Sungkyunkwan University School of Medicine, 300 Chunchun-dong, Jangan-ku, Suwon 440-746, Republic of Korea;bCenter For Molecular Medicine, Samsung Biomedical Research Institute, 300 Chunchun-dong, Jangan-ku, Suwon 440-746, Republic of Korea;cDepartment of Pathology, Inje University Seoul Paik Hospital, 85, Jeo-dong 2-ga, Jung-gu, Seoul 100-032, Republic of Korea
Abstract:Dendritic Ca2+ plays an important role not only in synaptic integration and synaptic plasticity, but also in dendritic excitability in midbrain dopamine neurons. However, the functional organization of dendritic Ca2+ signals in the dopamine neurons remains largely unknown. We therefore investigated dendritic Ca2+ signals by measuring glutamate-induced Ca2+ increases along the dendrites of acutely isolated midbrain dopamine neurons.Maximal doses of glutamate induced a Ca2+]c rise with similar amplitudes in proximal and distal dendritic regions of a dopamine neuron. Glutamate receptors contributed incrementally to the Ca2+]c rise according to their distance from the soma, with a reciprocal decrement in the contribution of voltage-operated Ca2+ channels (VOCCs). The contribution of AMPA and NMDA receptors increased with dendritic length, but that of metabotropic glutamate receptors decreased. At low doses of glutamate at which spontaneous firing was sustained, the Ca2+]c rise was higher in the distal than the proximal regions of a dendrite, possibly due to the increased spontaneous firing rate.These results indicate that functional organization of Ca2+ signals in the dendrites of dopamine neurons requires different combination of VOCCs and glutamate receptors according to dendritic length, and that regional Ca2+ rises in dendrites respond differently to applied glutamate concentration.
Keywords:Midbrain dopaminergic neurons  Calcium signaling  Dendrites  Glutamate receptors  Voltage-operated Ca2+ channels
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