Glutamate induces Cl− and K+ currents in the olfactory interneurons of a terrestrial slug

Abstract

Glutamate-induced responses in the procerebral neurons of the terrestrial slug Limax marginatus were examined using the nystatin-perforated patch recording technique applied in the voltage-clamp mode and local application of drugs. The procerebrum contains two types of interneurons with different spontaneous activities, bursting and nonbursting neurons. In the bursting neurons, a puff of glutamate evoked a rapidly desensitizing current followed by a smaller sustained current. The reversal potential of the early component showed that the current was mediated by Cl⁻ ions, while the late component was presumed to be mediated by K⁺ ions. In the nonbursting neurons, glutamate evoked a sustained current with a strong outward rectification, and the current was mediated by K⁺ ions. Ibotenate selectively evoked the rapidly desensitizing response in the bursting neurons, whereas quisqualate evoked a non-desensitizing K⁺ current both in the bursting and nonbursting neurons. The glutamate-induced K⁺ current had similar characteristics with the spontaneous synaptic activities in the procerebrum neurons, suggesting the possibility that glutamate receptors are involved in the spontaneous oscillatory activity.