title: Effects of organophosphates on rabbit pyramidal cells firing pattern and hippocampal theta rhythm.
abstract: The effects of the irreversible acetylcholinesterase (AChE) antagonist paraoxon (Px) on hippocampal neurophysiology were investigated and compared to those of physostigmine in urethane-anaesthetized rabbits. Hippocampal CA1 EEG signals were analyzed by power spectra. Following intracarotid administration, the two drugs induced a similar fundamental low-frequency theta power peak while the appearance of a second theta harmonic was commonly found under Px. Again, inhibition of CA1 pyramidal cells firing was significantly more pronounced after Px injection than after physostigmine. A potent inhibitory action was also described following local Px iontophoretic application. However, a discrepancy appeared between the effects of Px and the classical cholinergic drugs (acetylcholine, physostigmine). The results indicate that Px and physostigmine have a rather similar influence on the septo-hippocampal pathway and support suggestions that Px could act within local hippocampal circuitry through other systems than the cholinergic system exclusively.
authors.affiliation: Laboratoire de Neurophysiologie, Centre d'Etudes du Bouchet, Vert-le-Petit, France.
authors.forename: J
authors.initials: J
authors.lastname: Nio
authors.forename: P
authors.initials: P
authors.lastname: Breton
mesh_terms: D000818:Animals; D002339:Carotid Arteries; D004569:Electroencephalography; D005260:Female; D006624:Hippocampus / Q000187:drug effects* / Q000502:physiology; D007269:Injections, Intra-Arterial; D007478:Iontophoresis; D008297:Male; D009943:Organophosphorus Compounds / Q000494:pharmacology*; D010261:Paraoxon / Q000494:pharmacology; D010830:Physostigmine / Q000494:pharmacology; D017966:Pyramidal Cells / Q000187:drug effects* / Q000502:physiology; D011817:Rabbits; D013826:Theta Rhythm / Q000187:drug effects*
chemical_list: D009943:Organophosphorus Compounds; D010830:Physostigmine; D010261:Paraoxon