Expression of the preproenkephalin gene in developing spinal cord-dorsal root ganglia (SC-DRG) cultures was determined by Northern analysis following treatments with different agonists and antagonists of the glutamate receptor. Cultures (10-12 days old) were treated with various concentrations (10(-7)-10(-3) M) of N-methyl-D-aspartate (NMDA), quisqualate, kainic acid (KA), 2-amino-5-phosphonovaleric acid (APV) and 5-methyl-10,11-dihydro-5H-dibenzo[a, d]cyclohepten-5,10-imine maleate (MK801) either with or without blocking spontaneous electrical activity with 1 microM tetrodotoxin (TTX). In electrically active cultures, treatments with NMDA and KA increased preproenkephalin transcripts (mRNAppENK), showing maximum effects at 1 microM (4-fold and 2-fold, respectively), while treatments with quisqualate and MK801 caused concentration-dependent down-regulation in mRNAppENK. The most effective concentrations of NMDA (1 microM) and quisqualate (10 microM) altered mRNAppENK levels within 4 h of treatment and peaked after 24 h for NMDA and 48 h for quisqualate treatment. Co-treatment with APV completely blocked the NMDA-induced rise of mRNAppENK. During electrical blockade, none of the concentrations of NMDA tested showed any effect on enkephalin expression, neither could NMDA pre-treatment prevent the TTX-induced down-regulation of mRNAppENK. Our results indicate that the activity-dependent establishment of the enkephalin phenotype is modulated through the selective activation of the NMDA-glutamate receptor.