DOPAMINE AND GLUTAMATE AGONISTS STIMULATE NEURON-SPECIFIC EXPRESSION OF FOS-LIKE PROTEIN IN THE STRIATUM

1. The monoamine dopamine and the amino acid glutamate are major neurotransmitters in the basal ganglia implicated in the normal functions of the striatum and in extrapyramidal disease states. To study the effects of these neurotransmitters on gene transcription in striatal neurons, we treated rats with dopamine (monoamine) agonists and with glutamate agonists and monitored the induction of Fos-like protein in striatal neurons. We administered the indirect monoamine agonists cocaine and amphetamine intraperitoneally and gave the glutamate agonist quinolinic acid by direct intrastriatal injection. We identified the phenotypes of the responsive neurons by immunohistochemistry and by enzyme histochemistry in double staining protocols. 2. Both the indirect monoamine agonists and the glutamate receptor agonist stimulated rapid nuclear expression of Fos-like protein in specific classes of striatal neurons. The induction by cocaine and amphetamine was blocked by pretreatment with the dopamine D1-like receptor antagonist SCH23390, and the induction by quinolinic acid was blocked by pretreatment with MK-801, a noncompetitive antagonist of the N-methyl-D-aspartate (NMDA) glutamate receptor. 3. The monoamine and glutamate agonists both induced Fos-like protein exclusively in striatal neurons that constitutively expressed the protein phosphatase inhibitor DARPP-32 (dopamine and cAMP-regulated phosphoprotein). 4. The dopamine agonists failed to induce detectable Fos-like protein in striatal neurons expressing enkephalin, even though many such neurons expressed DARPP-32. By contrast, many enkephalinergic neurons did express Fos-like protein in response to glutamatergic stimulation. 5. Glutamate agonist stimulation, but not dopamine agonist stimulation, induced Fos-like protein in a subpopulation of striatal interneurons, namely, a group of neurons exhibiting NADPH-diaphorase activity. 6. These findings suggest that stimulation of dopamine D1-like receptors (or related monoamine receptors) and glutamate NMDA receptors activates neuron-specific programs of immediate-early gene expression in the striatum. Our findings further suggest that monoamine and glutamate may act cooperatively at the transcriptional level on a functionally defined subset of striatal neurons.