title: Cav 2.3 (R-type) calcium channels are critical for mediating anticonvulsive and neuroprotective properties of lamotrigine in vivo.
abstract: OBJECTIVE
  Lamotrigine (LTG) is a popular modern antiepileptic drug (AED); however, its mechanism of action has yet to be fully understood, as it is known to modulate many members of several ion channel families. In heterologous systems, LTG inhibits Cav 2.3 (R-type) calcium currents, which contribute to kainic-acid (KA)-induced epilepsy in vivo. To gain insight into the role of R-type currents in LTG drug action in vivo, we compared the effects of LTG to two other AEDs in Cav 2.3-deficient mice and controls on KA-induced seizures.
  
  
  METHODS
  Behavioral seizure rating and quantitative electrocorticography were performed after injection of 20 mg/kg (and 30 mg/kg) KA. One hour before KA injection, mice were pretreated with 30 mg/kg LTG, 50 mg/kg topiramate (TPM), or 30 mg/kg lacosamide (LSM).
  
  
  RESULTS
  Ablation of Cav 2.3 reduced total seizure scores by 28.6% (p = 0.0012), and pretreatment with LTG reduced seizure activity of control mice by 23.2% (p = 0.02). In Cav 2.3-deficient mice, LTG pretreatment increased seizure activity by 22.1% (p = 0.018) and increased the percentage of degenerated CA1 pyramidal neurons (p = 0.02). All three AEDs reduced seizure activity in control mice; however, only the non-calcium channel modulating AED, LSM, had an anticonvulsive effect in Cav 2.3-deficient mice. Furthermore, LTG altered electrocorticographic parameters differently in the two genotypes: decreasing relative power of ictal spikes in control mice but increasing relative power of high frequency fast ripple discharges during seizures in Cav 2.3-deficient mice.
  
  
  CONCLUSIONS
  These findings provided the first in vivo evidence for an essential role for Cav 2.3 in LTG pharmacology and shed light on a paradoxical effect of LTG in their absence. Furthermore, LTG appears to promote ictal activity in Cav 2.3-deficient mice by increasing high frequency components of seizures, resulting in increased neurotoxicity in the CA1. This paradoxical mechanism, possibly reflecting rebound hyperexcitation of pyramidal CA1 neurons after increased inhibition, may be key in understanding LTG-induced seizure aggravation observed in clinical practice.
authors.affiliation: Institute for Neurophysiology, University of Cologne, Cologne, Germany. maxine.dibue@med.uni-duesseldorf.de
authors.forename: Maxine
authors.initials: M
authors.lastname: Dibué
authors.forename: Marcel A
authors.initials: MA
authors.lastname: Kamp
authors.forename: Serdar
authors.initials: S
authors.lastname: Alpdogan
authors.forename: Etienne E
authors.initials: EE
authors.lastname: Tevoufouet
authors.forename: Wolfram F
authors.initials: WF
authors.lastname: Neiss
authors.forename: Jürgen
authors.initials: J
authors.lastname: Hescheler
authors.forename: Toni
authors.initials: T
authors.lastname: Schneider
mesh_terms: D000081:Acetamides / Q000627:therapeutic use; D000818:Animals; D000927:Anticonvulsants / Q000627:therapeutic use*; D020908:Calcium Channels, R-Type / Q000378:metabolism*; D027682:Cation Transport Proteins / Q000378:metabolism*; D004195:Disease Models, Animal; D004569:Electroencephalography / Q000379:methods; D005632:Fructose / Q000031:analogs & derivatives / Q000627:therapeutic use; D006624:Hippocampus / Q000187:drug effects; D000078334:Lacosamide; D000077213:Lamotrigine; D051379:Mice; D012640:Seizures / Q000188:drug therapy*; D000077236:Topiramate; D014227:Triazines / Q000627:therapeutic use*
chemical_list: D000081:Acetamides; D000927:Anticonvulsants; C498916:Cacna1e protein, mouse; D020908:Calcium Channels, R-Type; D027682:Cation Transport Proteins; D014227:Triazines; D000077236:Topiramate; D005632:Fructose; D000078334:Lacosamide; D000077213:Lamotrigine
keywords: Antiepileptic drugs; Cav2.3; Lamotrigine; Quantitative electroencephalography; R-type; Toxicity