Cholinergic modulation of the picrotoxin-induced electrocorticographical events and behavioral "pain-like" symptoms at somatomotor cortical level in the rat.
In this study, we examined the modulation by acetylcholine of electrocorticographical (ECoG) ictal events and spontaneous pain-like behaviors following cortical application of the GABA(A) antagonist picrotoxin in the awake rat. Distilled water as vehicle, the cholinomimetic substance eserine, and the general muscarinic antagonist atropine were microinjected 10 min before the second microinjection of 2 microg picrotoxin into the hind paw region of the somatomotor cortex (SmI). Under these conditions, we observed that eserine (physostigmine, 1 microg, 10 microg, and 20 microg) did not consistently modify the number of the picrotoxin-induced ECoG spikes and bursts, but instead produced a massive enhancement of the number of hind paw licks compared with vehicle at 10 microg and, to a lesser extent, the number of the stereotyped "turn-in" and "neglected" paws following picrotoxin. In contrast, atropine (1 microg, 10 microg, and 20 microg) increased the number of the picrotoxin-induced spikes and bursts at 10 microg and, at all doses, decreased the number of the picrotoxin-induced pain-like symptoms. Statistically significant changes for the number of paw lifts, licks, and "turn-in" paws were observed only with 10 microg. These results tend to show that epilepsy and pain are not strictly related to each other and also emphasize the cortex as a target for interactions between GABA and acetylcholine relative to "central" pain.
Montagne-Clavel
J
J
Unité de Recherches de Physiopharmacologie du Système Nerveux de l'INSERM (U 161), Paris, France.
Oliveras
J L
JL
D000818:Animals; D001285:Atropine / Q000494:pharmacology; D001522:Behavior, Animal / Q000187:drug effects / Q000502:physiology; D002800:Cholinesterase Inhibitors / Q000494:pharmacology; D004569:Electroencephalography; D018756:GABA Antagonists / Q000633:toxicity*; D008297:Male; D008845:Microinjections; D009044:Motor Cortex / Q000187:drug effects / Q000503:physiopathology*; D018727:Muscarinic Antagonists / Q000494:pharmacology; D010146:Pain / Q000503:physiopathology*; D010830:Physostigmine / Q000494:pharmacology; D010852:Picrotoxin / Q000633:toxicity*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013003:Somatosensory Cortex / Q000187:drug effects / Q000503:physiopathology*
D001285:Atropine; D002800:Cholinesterase Inhibitors; D018756:GABA Antagonists; D018727:Muscarinic Antagonists; D010830:Physostigmine; D010852:Picrotoxin