Opposite actions of muscarinic and nicotinic agents on hippocampal dendritic negative fields recorded in rats.

In rats under urethane anaesthesia, microiontophoretic application of muscarinic or nicotinic agents, in the pyramidal layer of the hippocampus, enhanced the population spike (s) evoked by fimbrial stimulation. In contrast, muscarinic and nicotinic agents had an opposite action on on the dendritic field potentials, they respectively reduced and enhanced the negative fields (field EPSP) recorded in the apical dendrites. These effects were antagonized by muscarinic and nicotinic antagonists, respectively.