title: Anaesthetics depress the sensitivity of cortical neurones to L-glutamate.
abstract: 1 The effects of general anaesthetics on the responses of neurones to iontophoretically applied L-glutamate have been examined in slices of the guinea-pig olfactory cortex in vitro. 2 Concentrations of pentobarbitone, ether, methoxyflurance, trichloroethylene and alphaxalone that are known to depress synaptic transmission in the prepiriform cortex also depressed the sensitivity of prepiriform neurones to L-glutamate. 3 Halothane, in concentrations that depress synaptic transmission (less than 1%) did not alter sensitivity of neurones to glutamate. Higher concentrations (greater than 1% produced a dose-related depression of the glutamate sensitivity of neurones. 4 All four volatile anaesthetics tested caused some cells to alter their glutamate-evoked firing pattern to one in which the spike discharges were more closely grouped. Pentobarbitone and alphaxalone had no such effect. 5 If the sensitivity of the neurones to the endogenous excitatory transmitter is affected by anaesthetics in the same way as the glutamate-sensitivity, these results suggest that halothane depresses synaptic transmission by decreasing the amount of transmitter released from the nerve terminals, whereas the other anaesthetics depress the sensitivity of the post-synaptic membrane to the released transmitter.
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology; D000777:Anesthetics; D000818:Animals; D002540:Cerebral Cortex / Q000166:cytology*; D003864:Depression, Chemical; D004986:Ether / Q000494:pharmacology; D005071:Evoked Potentials / Q000187:drug effects; D005971:Glutamates / Q000494:pharmacology*; D006168:Guinea Pigs; D006221:Halothane / Q000494:pharmacology; D006914:Hydroxysteroids / Q000494:pharmacology; D066298:In Vitro Techniques; D008274:Magnesium / Q000494:pharmacology; D008733:Methoxyflurane / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects*; D010424:Pentobarbital / Q000494:pharmacology; D011277:Pregnanediones / Q000494:pharmacology; D014241:Trichloroethylene
chemical_list: D000777:Anesthetics; D005971:Glutamates; D006914:Hydroxysteroids; D011277:Pregnanediones; D004986:Ether; D014241:Trichloroethylene; D008733:Methoxyflurane; C006477:alphaxalone; D008274:Magnesium; D010424:Pentobarbital; D000109:Acetylcholine; D006221:Halothane