Survival of Swiss-Webster mouse cerebellar granule neurons is promoted by a combination of potassium channel blockers.
Cultured cerebellar granule neurons (CGN) are commonly used to assess neurotoxicity, but are routinely maintained in supraphysiological (25 mM) extracellular K(+) concentrations [K(+)](o). We investigated the effect of potassium channel blockade on survival of CGN derived from Swiss-Webster mice in supraphysiological (25 mM) and physiological (5.6 mM) [K(+)](o). CGN were cultured for 5 days in 25 mM K(+), then in 5.6 mM K(+) or 25 mM K(+) (control). Viability, assayed 24 h later by 3-(4,5-dimethylthiazolyl-2)-2,5-diphenyltetrazolium bromide (MTT) reduction and by lactate dehydrogenase (LDH) release, was approximately 50% in 5.6 mM K(+) versus 25 mM K(+) (p<.001). Potassium channel blockers, 2 mM 4-aminopyridine (4-AP), 2 mM tetraethylammonium (TEA) or 1 mM Ba(2+), individually afforded limited protection in 5.6 mM K(+). However, survival in 5.6 mM K(+) with a combination of 4-AP, TEA and Ba(2+) was similar to survival in 25 mM K(+) without blockers (p<.001 versus 5.6 mM K(+) alone). CGN survival in 25 mM K(+) was attenuated 25% by 2 microM nifedipine (p>.001), but nifedipine did not attenuate neuroprotection by K(+) channel blockers. Together, these results suggest that the survival of CGN depends on the K(+) permeability of the membrane rather than the activity of a particular type of K(+) channel, and that the mechanism of neuroprotection by K(+) channel blockers is different from that of elevated [K(+)](o).
Collins
Anthony
A
Department of Pharmaceutical Sciences, College of Pharmacy, Oregon State University, Corvallis, OR 97331, USA.
Larson
Maureen K
MK
Pfaff
Jilleen E
JE
Ishmael
Jane E
JE
D015761:4-Aminopyridine / Q000494:pharmacology; D000818:Animals; D001464:Barium / Q000494:pharmacology; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D002531:Cerebellum / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007093:Imidazoles / Q000494:pharmacology; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D051379:Mice; D009474:Neurons / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D009543:Nifedipine / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology*; D026902:Potassium Channel Blockers / Q000494:pharmacology*; D012430:Ruthenium Red / Q000494:pharmacology; D019789:Tetraethylammonium / Q000494:pharmacology; D013997:Time Factors
D002121:Calcium Channel Blockers; D004791:Enzyme Inhibitors; D007093:Imidazoles; D026902:Potassium Channel Blockers; D012430:Ruthenium Red; D001464:Barium; D019789:Tetraethylammonium; C029899:imidazole; D015761:4-Aminopyridine; D007770:L-Lactate Dehydrogenase; D009543:Nifedipine; D011188:Potassium