The action potential in ureter of guinea pig is consisted of two components, i. e. slow potential and oscillating spike potentials, which superimposes on the initial part of the former.
High temperature causes to decrease the number of spike potentials and their amplitude, and finally they disappeared in long invasion of high temperature.
The spike component is also rapidly abolished in Ca _??_ free environment. Adding of excess of Ca _??_ to the normal environment increases the number of spike potentials at first and then decreases it gradually untill it attain its initial number.
After vanishing of spike oscillation induced by high temperature, if excess of Ca _??_ is added to the environment, spike potentials reappear. Such an effect of Ca _??_ does not last for long time.
If the temperature is raised above 39°-40°C, Ca _??_ loses such an effect to gain spike potential.
As many investigator reported, there are two stable states of calcium in the excitable membrane i. e. free and bounded. Between them, following relationship might exist.
free Ca _??_→← bounded Ca
Decrease or increase of free calcium would cause to shift the equilibrium point of the calcium either to bounded Ca side or to free Ca side. Change of the temperature may cause also shift of equilibrium point. From such speculation, reciprocal change of calcium between two situations is supposed to be a underlying mechanism to explain the appearance of oscillatory spike potentials and the effect of Ca and temperature on them.
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