Synaptic input-induced increase in intraneuronal Ca2+ in the medial vestibular nucleus of young rats.
In the medial vestibular nucleus (MVN), an input-dependent influx of Ca2+ into neurons through N-methyl-D-aspartate (NMDA) receptor-linked channels and/or voltage-dependent Ca2+ channels is suggested as underlying certain mechanisms of plasticity of the vestibular system. To see whether there is an increase in intracellular Ca2+ induced by afferent synaptic inputs to MVN neurons, we measured changes in [Ca2+]i with microfluorometry using a Ca2+ indicator, rhod-2, following electrical stimulation of ipsilateral vestibular afferents and commissural fibers in slice preparations of the brainstem of young rats (4-7 days postnatal). Single shock stimulation of ipsilateral afferents or commissural fibers induced an increase in fluorescence intensity lasting for several seconds. An application of 2-amino-5-phosphonovaleric acid (APV), an antagonist of NMDA receptors, almost completely blocked this stimulus-induced rise in fluorescence intensity. Nifedipine, an L-type Ca2+ channel blocker, also reduced the stimulus-induced rise in fluorescence intensity to 44-51% of the control value. These results suggest that synaptic inputs from the afferent and commissural pathways induce an influx of Ca2+ into MVN neurons due, at least in part, to the activation of NMDA receptors and the subsequent operation of L-type Ca2+ channels in young rats.
Takahashi
Y
Y
Department of Neurophysiology, Osaka University Medical School, Japan.
Takahashi
M P
MP
Tsumoto
T
T
Doi
K
K
Matsunaga
T
T
D000818:Animals; D001933:Brain Stem / Q000502:physiology*; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism / Q000502:physiology; D002531:Cerebellum / Q000502:physiology; D003592:Cytophotometry; D004558:Electric Stimulation; D005260:Female; D008297:Male; D008526:Medulla Oblongata / Q000502:physiology; D009474:Neurons / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D016194:Receptors, N-Methyl-D-Aspartate / Q000032:analysis / Q000378:metabolism; D014726:Vestibular Nuclei / Q000737:chemistry* / Q000378:metabolism / Q000502:physiology
D015220:Calcium Channels; D016194:Receptors, N-Methyl-D-Aspartate; D002118:Calcium