Figure 2. Role of spontaneous neuronal activity on basal cGMP production in cultured neurons. Cyclic GMP production was determined in cultures of neurons after a 10-min exposure to 1 micro Meter TTX or vehicle (control) in the absence of exogenous stimulating agents (basal). Data represent the mean plus/minus SEM for n = 3 experiments, each performed in triplicate. *P < 0.05 control versus the presence of TTX (Student's t test).