Na+-Ca2+ exchanger modulates AMPA-Induced Ca2+ Influx in Purkinje Neurons Acutely Dissociated from Rat Cerebellum

초록

Variations in intracellular calcium concentration ([Ca2+]i) play crucial roles in information processing, such as a synaptic plasticity, neurotransmission, cell death and neuronal development in Purkinje neurons. The physiological function of Na+-Ca2+ exchanger (NCX) in Purkinje neurons is not well understood, especially in cerebellar long-term depression (LTD) induction. Cerebellar LTD is expressed as a functional downregulation of AMPA receptors associated with ion channels. Thus, in the present study, we investigated the physiological roles of NCX in modulation of AMPA-induced Ca2+ responses of cerebellar Purkinje neurons. Immunoreactivity against NCX antibody was detected in Purkinje neurons and in situ hybridization revealed that NCX 1 is a dominant subtype. Pretreatments of AS-oligos reduced the AMPA-induced [Ca2+]i transient. And specific NCX blockers, bepridil (a forward mode inhibitor) and KB-R7943 (a reverse mode inhibitor), also depressed AMPA-induced Ca2+ responses to different degree. We also investigated NCX regulation of the expression of neuronal nitric oxide synthase (nNOS) and nitric oxide (NO) generation in cerebellar Purkinje neurons. Bepridil enhanced the expression of nNOS and fluorescence intensity of DAF-2DA, NO-sensitive fluorescence, but 7-nitroindazol, specific nNOS inhibitor, blocked these effects of bepridil. These data suggest that NCX, associated with NO, plays an important role in modulating intracellular Ca2+ activity and synaptic plasticity by interaction on AMPA receptors in Purkinje neurons.