Postsynaptic and presynaptic GABAB receptor-mediated inhibition in rat superficial superior colliculus neurons

It has been reported that GABAB receptors are abundantly expressed in the superficial superior colliculus (sSC). To elucidate the action of GABAB receptors in the sSC, we tested the effect of a specific GABAB receptor agonist baclofen on sSC neurons in slices obtained from rats (16–22 days postnatal) using the whole-cell patch clamp technique. Bath application of baclofen (10–30 μM) elicited hyperpolarization associated with an increase in potassium conductance in morphologically different types of neurons including putative excitatory and inhibitory neurons. In addition, baclofen presynaptically suppressed electrically induced excitatory postsynaptic currents and inhibitory postsynaptic currents. These effects of baclofen were antagonized by a specific GABAB receptor antagonist CGP55845A (1 μM). The results suggest that the GABAB receptors have an inhibitory action at both post- and pre-synaptic sites in the sSC. [Copyright &y& Elsevier]