title: Neuroprotective efficacy of caramiphen against soman and mechanisms of its action.
abstract: OBJECTIVE
  Caramiphen is a muscarinic antagonist with potent anticonvulsant properties. Here, we investigated the efficacy of caramiphen against behavioural seizures and neuropathology induced by the nerve agent soman, and revealed two mechanisms that may underlie the anticonvulsant efficacy of caramiphen.
  
  
  METHODS
  Rats were given caramiphen at 30 or 60 min after treatment with soman. Neuronal loss in the basolateral amygdala (BLA) and neuronal degeneration in the amygdala, hippocampus, piriform cortex, entorhinal cortex and neocortex, were investigated 24 h after soman, using design-based stereology and FluoroJade-C staining. The effects of caramiphen on NMDA-, AMPA- and GABA-evoked currents were studied in the BLA region of in vitro brain slices from un-treated rats, using whole-cell recordings.
  
  
  RESULTS
  Caramiphen given either 30 min or 60 min after soman, suppressed behavioural seizures within 10 min, but required 1∼4.5 h for complete cessation of seizures. Neuronal loss and degeneration were significantly reduced in the caramiphen-treated, soman-exposed rats. Postsynaptic currents evoked by puff-application of NMDA on BLA principal cells were reduced by caramiphen in a dose-dependent manner (100 µM, 300 µM and 1 mM), while GABA-evoked currents were facilitated by 100 µM and 300 µM, but depressed by 1 mM caramiphen. AMPA-evoked currents were not affected by caramiphen.
  
  
  CONCLUSIONS
  Caramiphen offered partial protection against soman-induced seizures and neuropathology, even when given 60 min after soman. NMDA receptor antagonism and facilitation of GABAergic inhibition in the BLA may play a key role in the anticonvulsive and neuroprotective properties of caramiphen.
authors.affiliation: Department of Anatomy, Physiology and Genetics, F. Edward Hébert School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, MD 20814, USA. mbraga@usuhs.mil
authors.forename: T H
authors.initials: TH
authors.lastname: Figueiredo
authors.forename: V
authors.initials: V
authors.lastname: Aroniadou-Anderjaska
authors.forename: F
authors.initials: F
authors.lastname: Qashu
authors.forename: J P
authors.initials: JP
authors.lastname: Apland
authors.forename: V
authors.initials: V
authors.lastname: Pidoplichko
authors.forename: D
authors.initials: D
authors.lastname: Stevens
authors.forename: T M
authors.initials: TM
authors.lastname: Ferrara
authors.forename: M F M
authors.initials: MF
authors.lastname: Braga
mesh_terms: D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects; D001921:Brain / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D002452:Cell Count; D002619:Chemical Warfare Agents / Q000506:poisoning*; D003517:Cyclopentanes / Q000008:administration & dosage / Q000627:therapeutic use*; D004305:Dose-Response Relationship, Drug; D008297:Male; D009474:Neurons / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D018696:Neuroprotective Agents / Q000008:administration & dosage / Q000627:therapeutic use*; D020258:Neurotoxicity Syndromes / Q000209:etiology / Q000378:metabolism / Q000473:pathology / Q000517:prevention & control*; D018408:Patch-Clamp Techniques; D051381:Rats; D017207:Rats, Sprague-Dawley; D018091:Receptors, AMPA / Q000037:antagonists & inhibitors; D011963:Receptors, GABA-A / Q000378:metabolism; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors; D012640:Seizures / Q000139:chemically induced / Q000378:metabolism / Q000473:pathology / Q000517:prevention & control*; D012999:Soman / Q000506:poisoning*; D055366:Synaptic Potentials / Q000187:drug effects
chemical_list: D002619:Chemical Warfare Agents; D003517:Cyclopentanes; D018696:Neuroprotective Agents; D018091:Receptors, AMPA; D011963:Receptors, GABA-A; D016194:Receptors, N-Methyl-D-Aspartate; D012999:Soman; C004519:caramiphen