Spike-generation in Dendrites and Synaptic Inhibition in Immature Cerebral Cortex

Abstract

THE extent to which dendrites of neurones in the central nervous system are capable of supporting conductile activity has been a matter of considerable controversy¹. Impulse initiation in the vast majority of neurones occurs in the initial axonal segment or cell body and this is followed by a variable degree of dendritic invasion by the spike potential^2–5. Partial spikes in dendrites, which electrotonically influence low-threshold trigger zones in the initial axonal segment, have been observed in a small proportion of hippocampal neurones⁶ but only rarely in neocortical neurones^7,8. Spike-generation in dendrites with conduction into the soma has not been demonstrated with intracellular recording in the mammalian brain although such a mode of impulse initiation has recently been shown for crustacean pit receptor neurones⁹. In contrast to the stereotyped pattern of impulse initiation in neurones of adult animals, we have observed a remarkable lability in respect to spike-generation in neurones of immature cerebral cortex.