Muscarinic depression of evoked surface-negative field potentials recorded from guinea-pig olfactory cortex in vitro

Abstract

The action of some cholinergic drugs has been studied on the field potentials evoked by orthodromic stimulation of the lateral olfactory tract (LOT) in guinea-pig olfactory cortex slices maintained in vitro. A reversible depression of the electrically evoked surface-negative field potential (N-wave) was seen following superfusion of muscarine (10-200 μM) or mixed-agonist choline esters but not nicotinic agonists. This depression was blocked by atropine and pirenzepine, but not d-tubocurarine or by antagonists active at γ-aminobutyric acid or adenosine receptors. Little effect of muscarinic agonists was observed on the compound action potential recorded from the LOT, or on pial surface DC potential. A possible presynaptic site of action of muscarinic agonists in the olfactory cortex is discussed.