Afterpotentials and transduction properties in different types of central neurones.

In mammalian central neurones, the soma-dendritic spike is generally followed by afterpotentials, a brief depolarizing potential (delayed depolarization) and a more longlasting afterhyperpolarization (AHP). These afterpotentials, and in particular the AHP, have long been considered as important factors in the control of excitation-to-frequency transduction. Analysis of the afterpotential properties has been performed on various types of central neurones; spinal alpha-motoneurones, dorsal spinocerebellar tract cells, rubrospinal neurones and hippocampal CA1 pyramidal cells. These investigations have shown the afterpotentials to differ considerably in their characteristics among these types of neurones. Studies of the firing behaviour of the neurones have also shown great variations in their firing properties, the observed differences being well in accord with those expected on the basis of their different afterpotential characteristics. The results suggest that the afterpotentials play a major role in the control of excitation-to-frequency transduction in several types of central neurones.