Sodium channel blocking activity of AM-36 and sipatrigine (BW619C89): in vitro and in vivo evidence.
Sodium channel blockers are neuroprotective against cerebral ischemia in animal models. A novel neuroprotective compound AM-36, when screened for activity at the most common receptor and ion channel binding sites, revealed activity at site 2 Na+ channels. Studies then investigated this Na+ channel blocking activity in vitro and in vivo relative to other Na+ channel blockers, including the neuroprotective agent sipatrigine (BW619C89). AM-36 inhibited batrachotoxinin (BTX)-sensitive Na+ channel binding in rat brain homogenates with an IC50 of 0.28 microM. Veratridine (100 microM)-induced neurotoxicity in murine cerebellar granule cells was completely inhibited by AM-36 (1.7 microM) compared to only partial inhibition by sipatrigine (26 microM). Veratridine-stimulated glutamate release, as measured through a microdialysis probe in the cortex of anesthetised rats, was inhibited by 90% by superfusion of AM-36 (1000 microM). In the endothelin-1 (ET-1) model of middle cerebral artery occlusion (MCAo) in conscious rats, both AM-36 (6 mg/kg i.p.) and sipatrigine (10 mg/kg i.p.) 30 min post-MCAo significantly reduced cortical, but not striatal infarct volume. As the refractiveness of the striatum is likely to be dependent on the route and time of drug administration, AM-36 (1 mg/kg i.v.) was administered 3 or 5 h after MCAo and significantly reduced both cortical and striatal infarct volumes. The present studies demonstrate Na+ channel blocking activity of AM-36 both in vitro and in vivo, together with significant neuroprotection when administration is delayed up to 5 h following experimental stroke.
Callaway
J K
JK
Department of Physiology, Monash University, Clayton, Vic. 3800, Australia. j.callaway@hfi.unimelb.edu.au
Castillo-Melendez
M
M
Giardina
S F
SF
Krstew
E K
EK
Beart
P M
PM
Jarrott
B
B
D000818:Animals; D001496:Batrachotoxins / Q000494:pharmacology; D006168:Guinea Pigs; D008297:Male; D051379:Mice; D018696:Neuroprotective Agents / Q000494:pharmacology; D010879:Piperazines / Q000494:pharmacology*; D011743:Pyrimidines / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011956:Receptors, Cell Surface / Q000037:antagonists & inhibitors / Q000502:physiology; D017981:Receptors, Neurotransmitter / Q000037:antagonists & inhibitors / Q000502:physiology; D026941:Sodium Channel Blockers / Q000494:pharmacology*; D015222:Sodium Channels / Q000187:drug effects / Q000502:physiology*; D013574:Synaptosomes / Q000187:drug effects / Q000502:physiology*
D001496:Batrachotoxins; D018696:Neuroprotective Agents; D010879:Piperazines; D011743:Pyrimidines; D011956:Receptors, Cell Surface; D017981:Receptors, Neurotransmitter; D026941:Sodium Channel Blockers; D015222:Sodium Channels; C401121:AM 36; C081980:sipatrigine