The Pharmacological Properties of an Evoked Potential in the Midbrain Reticular Formation

This study was made to determine whether brain stem evoked potentials could be altered by a variety of pharmacological agents. Evoked potentials in the midbrain reticular formation and in the posterior lateral ventral nucleus of the thalamus (VPL) were studied in 31 cats. The results show that there was no consistent alteration in the evoked potentials following the administration of any drug except pentobarbital. The following conclusions were reached: Pentobarbital depressed the evoked potential in the midbrain reticular formation of the cat, and the locus of action of lysergic acid diethylamide (LSD) chlorpromazine, physostigmine, atropine, adrenaline, gamma aminobutyric acid (GABA), succinylcholine, mecholyl, and reserpine either is not at the recording sites investigated in this study (midbrain reticular formation and posterior lateral ventral nucleus of the thalamus), or the alterations in electrical activity produced by the drugs are too subtle to be detected by the methods used.