| Abstract: | The effects of noradrenaline and dopamine on heterosynaptic facilitation (HSF) were investigated during experiments on giant identified neurons from the cerebral ganglion of the freshwater molluskPlanorbis corneus. It was found that catecholamines, while inducing an increase in the amplitude of response obtained by iontophoretic application of acetylcholine, also sharply reduce the amplitude of EPSP occurring as a result of stimulating the cerebral nerve, although acetylcholine also acts as transmitter in this instance. Catecholamines were also found to exert a blocking action on synaptic transmission during the period of HSF. Noradrenaline washout immediately after blockade of HSF was shown to reinstate and promote continuing independent facilitation of synaptic transmission. Duration of this facilitatory after-effect frequently exceeded that of initial HSF. This would imply that if serotonin promotes development of HSF, then the secretion of noradrenaline and dopamine brought about by certain effects act as the mechanism controlling duration and intensity of HSF under naturally-occurring conditions of the mollusk and perhaps even human nervous system activity.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 21, No. 2, pp. 224–232, March–April, 1989. |
