Anticholinergic and antiglutamatergic agents protect against soman-induced brain damage and cognitive dysfunction.
Soman, a powerful inhibitor of acetylcholinesterase, causes an array of toxic effects in the central nervous system including convulsions, learning and memory impairments, and, ultimately, death. We report on the protection afforded by postexposure antidotal treatments, combined with pyridostigmine (0.1 mg/kg) pretreatment, against these consequences associated with soman poisoning. Scopolamine (0.1 mg/kg) or caramiphen (10 mg/kg) were administered 5 min after soman (1.2 LD50), whereas TAB (i.e., TMB4, atropine, and benactyzine, 7.5, 3, and 1 mg/kg, respectively) was injected in rats concomitant with the development of toxic signs. Atropine (4 mg/kg) was given to the two former groups at the onset of toxic symptoms. Caramiphen and TAB completely abolished electrographic seizure activity while scopolamine treatment exhibited only partial protection. Additionally, no significant alteration in the density of peripheral benzodiazepine receptors was noted following caramiphen or TAB administration, while scopolamine application resulted in a complex outcome: a portion of the animals demonstrated no change in the number of these sites whereas the others exhibited markedly higher densities. Cognitive functions (i.e., learning and memory processes) evaluated using the Morris water maze improved considerably by the three treatments when compared to soman-injected animals; the following rank order was observed: caramiphen > TAB > scopolamine. Additionally, statistically significant correlations (r = 0.72, r = 0.73) were demonstrated between two learning parameters and [3H]Ro5-4864 binding to brain membrane. These results show that drugs with a pharmacological profile consisting of anticholinergic and antiglutamatergic properties such as caramiphen and TAB, have a substantial potential as postexposure therapies against intoxication by organophosphates.
Raveh
Lily
L
Department of Pharmacology, Israel Institute for Biological Research, P.O. Box 19, Ness Ziona 74100, Israel.
Brandeis
Rachel
R
Gilat
Eran
E
Cohen
Giora
G
Alkalay
David
D
Rabinovitz
Ishai
I
Sonego
Hagar
H
Weissman
Ben Avi
BA
D000818:Animals; D000931:Antidotes / Q000494:pharmacology*; D001570:Benzodiazepinones / Q000378:metabolism; D001921:Brain / Q000187:drug effects* / Q000378:metabolism; D018680:Cholinergic Antagonists / Q000494:pharmacology*; D002800:Cholinesterase Inhibitors / Q000506:poisoning*; D003072:Cognition Disorders / Q000139:chemically induced / Q000503:physiopathology / Q000517:prevention & control*; D004569:Electroencephalography; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology*; D066298:In Vitro Techniques; D008024:Ligands; D008297:Male; D018782:Maze Learning / Q000187:drug effects; D011869:Radioligand Assay; D051381:Rats; D017207:Rats, Sprague-Dawley; D012999:Soman / Q000506:poisoning*; D013997:Time Factors
D000931:Antidotes; D001570:Benzodiazepinones; D018680:Cholinergic Antagonists; D002800:Cholinesterase Inhibitors; D018691:Excitatory Amino Acid Antagonists; D008024:Ligands; C028513:4'-chlorodiazepam; D012999:Soman