Modulation of gamma-aminobutyric acid responses in the rat optic nerve.
Depolarising GABA(A) receptor-mediated responses recorded from the optic nerve using a grease gap technique were modulated by classical potentiators of GABA(A) receptors. The benzodiazepine, chlordiazepoxide, the barbiturate, pentobarbitone and the widely used anaesthetic, propofol, all potentiated gamma-aminobutyric acid (GABA) responses. They did so with different maximal efficacies, propofol>pentobarbitone>chlordiazepoxide, and potencies on the basis of EC(50) estimates, chlordiazepoxide>propofol>pentobarbitone. The greater than expected GABA potentiating properties of propofol were explained by a direct hyperpolarising action that occurred in the same concentration range as its action at the GABA(A) receptor but that was unlikely to be mediated by GABA(A) receptors.
Empson
R M
RM
Cerebrus Ltd, Oakdene Court, 613 Reading Road, Winnersh, Berkshire, RG41 5UA, Wokingham, UK. r.empson@rhbnc.ac.uk
Sheardown
M J
MJ
Newberry
N R
NR
D000818:Animals; D002707:Chlordiazepoxide / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D004594:Electrophysiology; D066298:In Vitro Techniques; D008297:Male; D009900:Optic Nerve / Q000187:drug effects* / Q000502:physiology; D010424:Pentobarbital / Q000494:pharmacology; D015742:Propofol / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D011963:Receptors, GABA-A / Q000187:drug effects / Q000502:physiology; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology*
D011963:Receptors, GABA-A; D005680:gamma-Aminobutyric Acid; D002707:Chlordiazepoxide; D010424:Pentobarbital; D015742:Propofol