Effects of temperature on the exocytosis induced by action potential like stimuli.

MAURICIO MONTENEGRO; JOSÉ MOYA DÍAZ; FERNANDO D. MARENGO

Huerta Grande - Córdoba

Congreso; XXVII Congreso de la Sociedad Argentina de Neurociencias; 2012

Sociedad Argentina de Neurociencias

The immediately releasable pool (IRP) of chromaffin cells.is a group of ready releasable vesicles highly coupled to the voltage dependent P/Q-type Ca2+ channels, which is secreted by brief stimuli (Álvarez, et al.). In this work, we applied action potential like stimuli (APs) to analyze the temperature dependence of Ca currents (ICa2+), exocytosis and recovery of the vesicle pool released by this type of stimulation. The ICa2+ induced by APs were 106.1 ± 16.3 pA and 259.0 ± 25.7 pA for 20 ºC and 25ºC, respectively, while at 15ºC we did not observed significant ICa2+. The decrease of ICa2+ at low temperatures may be explained by changes in the activation time constant observed during 50 ms square depolarizations (2.75 ± 0.13 ms, 1.39 ± 0.21 ms and 0.86 ± 0.05 ms for 15 ºC, 20 ºC and 25ºC, respectively). The capacitance increases induced by APs at 20ºC and 25ºC, were 5.6 ± 0.3 fF and 7.4 ± 0.9 fF, respectively. Finally, we studied the recovery of exocytosis after the application of single action potentials. The time constants for this process were 2.37 ± 1.37 and 1.06 ± 0.48 sec. for 20ºC and 25ºC respectively. In conclusion, our results indicate that the Ca2+ currents, exocytosis and its recovery from IRP occur in a temperature dependent fashion.