Physioloogical activities of Na+-Ca2+ exchanger in rat cerebellar pirkinje neurons

초록

Cerebellar long-term depression (LTD) is produced when climbing fiber and parallel fiber inputs to a Purkinje neuron are stimulated conjunctively at low frequencies and is expressed as an attenuation of synaptic strength of Purkinje neuron. Variations in intracellular calcium activity ([Ca2+]i) play crucial roles in information processing in Purkinje neurons. Purkinje neurons have powerful systems to modulate [Ca2+]i, such as Ca2+-binding proteins, intracellular stores, Ca2+-ATPase and Na+-Ca2+ exchanger. Na+-Ca2+ exchanger has been shown to participate in the regulation of Ca2+ homeostasis and secretion in neuronal cells. Although the presence of Na+-Ca2+ exchanger in Purkinje neurons has been identified with antibodies against mRNA encoding the cardiac type of exchanger, the physiological activities of Na+-Ca2+ exchanger in Purkinje neurons are not well understood. Thus, in this study, Purkinje cells were visualized by immunocytochemical staining for calbindin D-28k and, changes in [Ca2+]i were measured with cellular Ca2+ imaging technique. Acutely dissociated cells were prepared at postnatal 10 days and cultured Purkinje cells (p1) were stained at days in vitro (DIV) 1, 8, 14 and 16. The expression of Na+-Ca2+ exchanger in the soma of Purkinje cells was identified with the immunostaining technique in the parasagittal sections of rat cerebellum. [Ca2+]i of Purkinje neurons increased with the reverse mode of Na+-Ca2+ exchanger and decreased with the forward mode. We also observed an age-dependence of intracellular Ca2+ changes by Na+-Ca2+ exchanger, and the involvement of Na+-Ca2+ exchanger in developing Purkinje neurons are under further investigation.