Activation of quisqualate metabotropic receptors reduces glutamate and GABA-mediated synaptic potentials in the rat striatum.
The role of quisqualate (QUIS) metabotropic receptors in the synaptic transmission in the striatum was investigated using the cortico-striatal slice preparation. Low concentrations (1-30 microM) of trans-1-amino-cyclopentyl-1,3- dicarboxylic acid (t-ACPD), a selective agonist of QUIS metabotropic receptors, decreased glutamate-mediated synaptic potentials (EPSPs) evoked in the striatum by the stimulation of cortico-striatal fibers. This agonist decreased also GABA-mediated depolarizing synaptic potentials evoked by intrastriatal stimulation in the presence of 6-cyano-7-nitro-quinoxaline-2,3- dione (CNQX); this effect was less potent than the action of t-ACPD on glutamate-mediated potentials. Low concentrations of t-ACPD did not affect the intrinsic membrane properties of striatal neurons and their postsynaptic responses to exogenous glutamate and GABA. Higher concentrations (50-100 microM) to t-ACPD caused membrane depolarizations and inward currents in several neurons. Our data suggest that low concentrations of t-ACPD selectively reduce synaptic transmission while higher concentrations of this agonist may cause a direct excitatory action on striatal neurons.
Clinica Neurologica, Dip. Sanitá, II Universitá di Roma, Italy.
P
P
Calabresi
N B
NB
Mercuri
G
G
Bernardi
D018750:6-Cyano-7-nitroquinoxaline-2,3-dione; D000818:Animals; D003342:Corpus Striatum / Q000187:drug effects / Q000502:physiology*; D003515:Cycloleucine / Q000031:analogs & derivatives / Q000494:pharmacology; D005971:Glutamates / Q000502:physiology*; D018698:Glutamic Acid; D066298:In Vitro Techniques; D009498:Neurotoxins / Q000494:pharmacology; D011810:Quinoxalines / Q000494:pharmacology; D051381:Rats; D018091:Receptors, AMPA; D017981:Receptors, Neurotransmitter / Q000187:drug effects*; D013569:Synapses / Q000187:drug effects / Q000502:physiology*; D005680:gamma-Aminobutyric Acid / Q000502:physiology*
D005971:Glutamates; D009498:Neurotoxins; D011810:Quinoxalines; D018091:Receptors, AMPA; D017981:Receptors, Neurotransmitter; D003515:Cycloleucine; C036361:1-amino-1,3-dicarboxycyclopentane; D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione