title: In vivo and in vitro effects of pilocarpine: relevance to ictogenesis.
abstract: OBJECTIVE
  A common experimental model of status epilepticus (SE) utilizes intraperitoneal administration of the cholinergic agonist pilocarpine preceded by methyl-scopolamine treatment. Currently, activation of cholinergic neurons is recognized as the only factor triggering pilocarpine SE. However, cholinergic receptors are also widely distributed systemically and pretreatment with methyl-scopolamine may not be sufficient to counteract the effects of systemically injected pilocarpine. The extent of such peripheral events and the contribution to SE are unknown and the possibility that pilocarpine also induces SE by peripheral actions is yet untested.
  
  
  METHODS
  We measured in vivo at onset of SE: brain and blood pilocarpine levels, blood-brain barrier (BBB) permeability, T-lymphocyte activation and serum levels of IL-1beta and TNF-alpha. The effects of pilocarpine on neuronal excitability was assessed in vitro on hippocampal slices or whole guinea pig brain preparations in presence of physiologic or elevated [K+](out).
  
  
  RESULTS
  Pilocarpine blood and brain levels at SE were 1400 +/- 200 microM and 200 +/- 80 microM, respectively. In vivo, after pilocarpine injection, increased serum IL-1beta, decreased CD4:CD8 T-lymphocyte ratios and focal BBB leakage were observed. In vitro, pilocarpine failed to exert significant synchronized epileptiform activity when applied at concentrations identical or higher to levels measured in vivo. Intense electrographic seizure-like events occurred only in the copresence of levels of K+ (6 mM) mimicking BBB leakage.
  
  
  CONCLUSIONS
  Early systemic events increasing BBB permeability may promote entry of cofactors (e. g. K+) into the brain leading to pilocarpine-induced SE. Disturbance of brain homeostasis represents an etiological factor contributing to pilocarpine seizures.
authors.affiliation: Department of Cerebrovascular Research, The Cleveland Clinic Foundation, Cleveland, Ohio 44195, USA.
authors.forename: Nicola
authors.initials: N
authors.lastname: Marchi
authors.forename: Emily
authors.initials: E
authors.lastname: Oby
authors.forename: Ayush
authors.initials: A
authors.lastname: Batra
authors.forename: Laura
authors.initials: L
authors.lastname: Uva
authors.forename: Marco
authors.initials: M
authors.lastname: De Curtis
authors.forename: Nadia
authors.initials: N
authors.lastname: Hernandez
authors.forename: Anette
authors.initials: A
authors.lastname: Van Boxel-Dezaire
authors.forename: Imad
authors.initials: I
authors.lastname: Najm
authors.forename: Damir
authors.initials: D
authors.lastname: Janigro
mesh_terms: D000818:Animals; D001812:Blood-Brain Barrier / Q000187:drug effects* / Q000502:physiology; D001921:Brain / Q000187:drug effects* / Q000503:physiopathology*; D004195:Disease Models, Animal; D004569:Electroencephalography / Q000706:statistics & numerical data; D006168:Guinea Pigs; D006624:Hippocampus / Q000737:chemistry / Q000187:drug effects / Q000503:physiopathology; D066298:In Vitro Techniques; D007274:Injections, Intraperitoneal; D053583:Interleukin-1beta / Q000097:blood; D008297:Male; D018721:Muscarinic Agonists / Q000008:administration & dosage / Q000494:pharmacology; D018727:Muscarinic Antagonists / Q000494:pharmacology; D010275:Parasympathetic Nervous System / Q000187:drug effects / Q000503:physiopathology; D010539:Permeability / Q000187:drug effects; D010862:Pilocarpine / Q000008:administration & dosage / Q000032:analysis / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011976:Receptors, Muscarinic / Q000187:drug effects / Q000502:physiology; D012601:Scopolamine / Q000494:pharmacology; D013226:Status Epilepticus / Q000097:blood / Q000139:chemically induced* / Q000503:physiopathology*; D013601:T-Lymphocytes / Q000187:drug effects; D014409:Tumor Necrosis Factor-alpha / Q000097:blood; D014743:Videotape Recording
chemical_list: D053583:Interleukin-1beta; D018721:Muscarinic Agonists; D018727:Muscarinic Antagonists; D011976:Receptors, Muscarinic; D014409:Tumor Necrosis Factor-alpha; D010862:Pilocarpine; D012601:Scopolamine