The effects of the metabotropic glutamate receptor agonist 1S,3R-ACPD on neurones in the rat primary somatosensory cortex in vivo.

The selective glutamate metabotropic receptor agonist (1S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid (1S,3R-ACPD) was applied iontophoretically to cells in the rat primary somatosensory cortex (SI) in vivo. In contrast to other in vivo studies, distinct excitatory and depressant effects were observed. The excitatory responses could not be blocked by ionotropic antagonists, as evidence that they were mediated by a metabotropic receptor. The depressant effects were most pronounced on natural synaptic transmission, suggesting that a presynaptic receptor may be involved, although responses to iontophoretically applied agonists were also affected. Comparison with the presumed presynaptic glutamate receptor agonist L-2-amino-4-phosphonobutyrate (L-AP4) suggest that the depressant effects of 1S,3R-ACPD could be partially mediated by a presynaptic autoreceptor.