Figure 3.
Effects of costimulation of NMDA and muscarinic receptors on AA release. [3H]AA-prelabeled neuronal cultures (A), astrocyte cultures (B), and cocultures (C and D) were incubated for 15 min with NMDA (100 μM, 100 μM D-serine, 0 Mg2+), ACh (1 mM), or Carb (1 mM) applied alone or in combination. The effects of receptor antagonists, MK801 (1 μM), atropine (1 μM), or mepacrine (Mep) (50 μM, 20-min pretreatment), were tested on the response induced by NMDA + Carb in cocultures (D). Values of 3H radioactivity released after stimulation with NMDA + Carb varied from 19,000 to 30,000 dpm per well in neuronal cultures (A) and from 7,000 to 15,000 dpm per well in cocultures (C and D). The reduced capacity of neurons to release [3H]AA in cocultures may be attributed to the presence of serum because the application of 10% serum for 24 h on neuronal cultures reduced by 50% the response evoked by NMDA + Carb costimulation (data not shown). Data are expressed as the means ± SEM of results obtained from at least three independent experiments, each performed in quadruplicate. Statistical analysis was carried out on raw data by one-way ANOVA, followed by post hoc Bonferroni's multiple comparison.