| Abstract: | The sucrose gap technique was used to study the long positive potential (P-potential) in a curarized cat superior cervical ganglion. The frequency of stimulating the preganglionic trunk optimal for P-potential production was 30–40 impulses/sec at a stimulus series duration of 1 sec. Proserine in low concentrations (1–5 µg/ml) increased amplitude and especially duration of the P-potential. Atropine (0.5–2 µg/ml) blocked it completely. Adrenaline and noradrenaline (10–50 µg/ml inhibited both the negative potential (corresponding to the fast EPSP of neurons) and the P-potential in equal measure. The nature of dependence of P-potential amplitude on value of the membrane potential was also studied. It was found that the P-potential is inhibited in solutions with low potassium ion content, and that amplitude of the P-potential rises with an increase of intracellular sodium concentration. The rate of its increase rises with an increase of temperature. Under the influence of strophathin, the P-potential is inhibited. The data obtained support the hypothesis that the P-potential is determined by synaptic activation of the electrogenic sodium pump.A. A. Bogomol'ets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 3, No. 1, pp. 76–83, January–February, 1971. |
