title: Antagonism of the actions of glutamate by pentobarbitone or midazolam in the frog optic tectum in vitro.
abstract: Excitatory synaptic transmission, induced by electrical stimulation of optic nerve fibres on relay neurones, was recorded from in vitro preparations of the optic tectum of the frog. Bath-applied glutamate (the putative excitatory transmitter of the optic nerve) produced transient enhancement of tectal field potentials, followed by a depression, presumably caused by sustained neuronal depolarization. Pentobarbitone potently antagonized the depressant effect of glutamate, producing an approximate 50% reduction in the response of the tectum to glutamate at 25 microM. Midazolam also decreased the effect of glutamate with an IC50 value of 5 nM. Since, in the optic tectum of the frog, neither pentobarbitone nor midazolam enhance responses to bath-applied GABA, it is suggested that this area of the brain is a useful preparation in which to investigate the interaction of barbiturates and benzodiazepines with glutamate receptor mechanisms, without concurrent interactions with GABAergic processes.
authors: Department of Pharmacology, St Bartholomew's Hospital Medical College, University of London, U.K.
authors: L
authors: L
authors: Sivilotti
authors: A
authors: A
authors: Nistri
mesh_terms: D000818:Animals; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation; D004594:Electrophysiology; D005071:Evoked Potentials / Q000187:drug effects; D018691:Excitatory Amino Acid Antagonists; D066298:In Vitro Techniques; D008874:Midazolam / Q000494:pharmacology*; D010424:Pentobarbital / Q000494:pharmacology*; D011896:Rana temporaria; D013477:Superior Colliculi / Q000187:drug effects*
chemical_list: D018691:Excitatory Amino Acid Antagonists; D010424:Pentobarbital; D008874:Midazolam