Dual action of excitatory amino acids on the metabolism of inositol phosphates in striatal neurons.

Glutamate is able to stimulate inositol phosphate (IP) formation in striatal neurons in primary culture, mainly via an excitatory amino acid receptor of the quisqualate subtype. In the present study we show that carbachol (Carb)-(a cholinergic agonist), but not neurotensin or norepinephrine-induced IP production could be reduced by 40% when measured in the presence of Glu. The inhibition of the Carb response by Glu was dose dependent and reproduced by N-methyl-D-aspartate (NMDA). Quisqualate elicited an additive response with Carb. 2-Amino-5-phosphonovalerate (APV) completely reversed the NMDA-induced inhibition. APV had no significant effect on Glu- or kainate-induced inhibition. Therefore, striatal neurons contain at least three different excitatory amino acid receptors: a quisqualate receptor triggering the stimulation of IP metabolism, and an NMDA and a kainate receptor, both able to decrease the Carb-induced IP formation.