title: Action of general anaesthetics on unclamped Ca(2+)-mediated currents in unmyelinated axons of rat olfactory cortex.
abstract: Na+ and Ca2+ currents were monitored using a suction electrode in unclamped presynaptic axons of rat olfactory cortex pretreated with 0.1 mM 3,4-diaminopyridine and 5 mM tetraethylammonium. The effects of anaesthetics on these currents were compared with tetrodotoxin or cadmium. Ketamine (0.1-1 mM), ether (20-200 mM), diisopropylphenol (0.01-0.5 mM) and lignocaine (0.01-0.2 mmol/l) all depressed both the initial Na+ component and the Ca(2+)-mediated tail of the response. Urethane (5-100 mM), halothane (1-5 mM) and pentobarbitone (0.1-2 mM) showed slight selectivity for the axonal Ca2+ tail. Diisopropylphenol apparently enhanced the Ca2+ tail at low concentrations. The alphaxalone (1-50 microM) depression was very weak. In a few cases the depression may contribute to anaesthesia but with others, high concentrations may contribute to the toxicity of the substances in vivo.
authors.affiliation: School of Biomedical Science, Queens University, Belfast, U.K.
authors.forename: J
authors.initials: J
authors.lastname: McGivern
authors.forename: C N
authors.initials: CN
authors.lastname: Scholfield
mesh_terms: D000777:Anesthetics / Q000494:pharmacology*; D000818:Animals; D001369:Axons / Q000187:drug effects / Q000378:metabolism*; D015220:Calcium Channels / Q000187:drug effects / Q000378:metabolism*; D002540:Cerebral Cortex / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D004558:Electric Stimulation; D005260:Female; D066298:In Vitro Techniques; D008297:Male; D009830:Olfactory Bulb / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D015222:Sodium Channels / Q000187:drug effects / Q000378:metabolism*
chemical_list: D000777:Anesthetics; D015220:Calcium Channels; D015222:Sodium Channels