Postsynaptic and presynaptic GABA(B) receptor-mediated inhibition in rat superficial superior colliculus neurons.
It has been reported that GABA(B) receptors are abundantly expressed in the superficial superior colliculus (sSC). To elucidate the action of GABA(B) receptors in the sSC, we tested the effect of a specific GABA(B) 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 microM) 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 GABA(B) receptor antagonist CGP55845A (1 microM). The results suggest that the GABA(B) receptors have an inhibitory action at both post- and pre-synaptic sites in the sSC.
Endo
Toshiaki
T
Department of Integrative Physiology, National Institute for Physiological Sciences, Myodaiji, Okazaki, Japan. tendo@nips.ac.jp
Isa
Tadashi
T
D000818:Animals; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology*; D018755:GABA Agonists / Q000494:pharmacology; D018756:GABA Antagonists / Q000494:pharmacology; D058786:GABA-B Receptor Agonists; D058788:GABA-B Receptor Antagonists; D009433:Neural Inhibition / Q000502:physiology* / Q000528:radiation effects*; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D018080:Receptors, GABA-B / Q000502:physiology*; D017661:Receptors, Presynaptic / Q000819:agonists / Q000037:antagonists & inhibitors / Q000502:physiology; D013477:Superior Colliculi / Q000166:cytology / Q000187:drug effects / Q000502:physiology*
D018755:GABA Agonists; D018756:GABA Antagonists; D058786:GABA-B Receptor Agonists; D058788:GABA-B Receptor Antagonists; D018080:Receptors, GABA-B; D017661:Receptors, Presynaptic