Stimulation of rat cerebellar guanosine 3',5'-cyclic monophosphate (cyclic GMP) levels: effects of amino acid antagonists.

1 The ability of glutamate, aspartate and related neuroexcitants to produce large calcium-dependent increases in the levels of guanosine 3',5'-cyclic monophosphate (cyclic GMP) in immature rat cerebellar slices has been demonstrated. 2 These effects were inhibited by selective antagonist compounds, indicating the presence of at least two types of excitatory amino acid receptor mediating the cyclic GMP response. 3 Protoveratrine also produced large increases in cyclic GMP, and this action was antagonized by L-glutamate diethylester suggesting that released endogenous glutamate, subsequently interacting with its postsynaptic receptors, is the predominant mechanism. 4 The kinetic characteristics of several of the inhibitor compounds were investigated.