Y. Takahashi et al., SYNAPTIC INPUT-INDUCED INCREASE IN INTRANEURONAL CA2-RATS( IN THE MEDIAL VESTIBULAR NUCLEUS OF YOUNG), Neuroscience research, 21(1), 1994, pp. 59-69
In the medial vestibular nucleus (MVN), an input-dependent influx of C
a2+ into neurons through N-methyl-D-aspartate (NMDA) receptor-linked c
hannels and/or voltage-dependent Ca2+ channels is suggested as underly
ing 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 [Ca(2+])i with
microfluorometry using a Ca2+ indicator, rhod-2, following electrical
stimulation of ipsilateral vestibular afferents and commissural fiber
s in slice preparations of the brainstem of young rats (4-7 days postn
atal). Single shock stimulation of ipsilateral afferents or commissura
l fibers induced an increase in fluorescence intensity lasting for sev
eral seconds. An application of 2-amino-5-phosphonovaleric acid (APV),
an antagonist of NMDA receptors, almost completely blocked this stimu
lus-induced rise in fluorescence intensity. Nifedipine, an L-type Ca2 channel blocker, also reduced the stimulus-induced rise in fluorescen
ce intensity to 44-51% of the control value. These results suggest tha
t synaptic inputs from the afferent and commissural pathways induce an
influx of Ca2+ into MVN neurons due, at least in part, to the activat
ion of NMDA receptors and the subsequent operation of L-type Ca2+ chan
nels in young rats.