NUCLEAR AND CYTOPLASMIC CA2-ROOT GANGLION NEURONS STUDIED IN EXCISED TISSUE( SIGNALS IN DEVELOPING RAT DORSAL)

Confocal microscopy and the Ca2+-sensitive fluorescent dye fluo-3 were used to study subcellular Ca2+ signals in embryonic, neonatal, and ad ult dorsal root ganglion (DRG) neurons in excised dorsal root ganglia. Optical images obtained from isolated whole embryonic and neonatal ga nglia revealed a marked variability in the resting Ca2+ signals of dif ferent neurons as compared to signals in adult neurons which were unif ormly faint. Many of the embryonic and neonatal neurons displayed nucl ear Ca2+ signals at rest which were larger than those in the cytoplasm . Embryonic DRG neurons showed a significant increase in nuclear and c ytoplasmic fluorescence in response to depolarization with elevated ex tracellular potassium or electrical stimulation. A single brief electr ical stimulus was sufficient to elicit nuclear Ca2+ signals in a subse t of the embryonic neurons. The depolarization-induced Ca2+ signals we re blocked by removal of extracellular Ca2+, but not by treatment with 2,5-di(telt-butyl)-1,4 benzohydroquinone (DTBHQ), a compound which de pletes intracellular Ca2+ stores. The intensity of the depolarization- induced Ca2+ signals declined significantly between the late embryonic (E18-E20) and early postnatal time periods (P0-P1). The nuclear and c ytoplasmic Ca2+ signals of the embryonic DRG neurons in the excised ti ssue preparation occur at a time of intense target innervation, sugges ting a role for Ca2+ signals in the development and maturation of rat DRG neurons.