Fluorimetric determination of electrically evoked increase in intracellular calcium in cultured cerebellar granule cells.
A technique is described to measure the electrically evoked increase in intracellular calcium in cerebellar granule cells cultured on glass coverslips and preloaded with FURA-2. To minimize light scattering, the coverslip containing the granules was placed in the fluorimeter cuvette at a 30 degrees angle to the exciting light beam. The cuvette was provided with 2 platinum electrodes so as to stimulate the neurons with a tangential field. The [Ca2+]i transients were maximized by omitting Mg2+. The fluorescence peaks were directly related to the pulse (1 ms, 100 mA) frequency and to the train length. The responses were completely tetrodotoxin- and [Ca2+]o-dependent and could be replicated 5-6 times at 5-min intervals. At the stimulation rate of 20 Hz for 5 s, a condition ensuring submaximal peaks, the [Ca2+]i rose from the basal levels of 41 +/- 2.7 nmol/l to 89.6 +/- 5.8 nmol/l. The participation of various membrane channels in the electrically induced [Ca2+]i increase was demonstrated. 4-Aminopyridine (1 mM) increased the height of the peaks to 240%. Both nifedipine (10 microM) and omega-conotoxin (1 microM) reduced the transients by about 25%. The residual response (in the absence of Mg2+) depended mostly on the release of endogenous glutamate as it proved sensitive to NMDA, AMPA and t-ACPD receptor antagonists. Since a technique to measure the electrically evoked release of D-[3H]aspartate is presently available, the parallel determination of release and of [Ca2+]i in twin populations of cultured granule cells is possible.
Beani
L
L
Department of Pharmacology, University of Ferrara, Italy.
Tomasini
C
C
Govoni
B M
BM
Bianchi
C
C
D000818:Animals; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D002478:Cells, Cultured; D002531:Cerebellum / Q000166:cytology / Q000378:metabolism*; D004558:Electric Stimulation; D004594:Electrophysiology; D005470:Fluorometry; D007425:Intracellular Membranes / Q000378:metabolism*; D007473:Ion Channels / Q000502:physiology; D008274:Magnesium / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D012146:Rest; D012964:Sodium / Q000494:pharmacology
D007473:Ion Channels; D012964:Sodium; D008274:Magnesium; D002118:Calcium