title: Time-Dependent Effects of Ethanol on BK Channel Expression and Trafficking in Hippocampal Neurons.
abstract: BACKGROUND
  The large conductance Ca(2+) - and voltage-activated K(+) channel (BK) is an important player in molecular and behavioral alcohol tolerance. Trafficking and surface expression of ion channels contribute to the development of addictive behaviors. We have previously reported that internalization of the BK channel is a component of molecular tolerance to ethanol (EtOH).
  
  
  METHODS
  Using primary cultures of hippocampal neurons, we combine total internal reflection fluorescence microscopy, electrophysiology, and biochemical techniques to explore how exposure to EtOH affects the expression and subcellular localization of endogenous BK channels over time.
  
  
  RESULTS
  Exposure to EtOH changed the expression of endogenous BK channels in a time-dependent manner at the perimembrane area (plasma membrane and/or the area adjacent to it), while total protein levels of BK remain unchanged. These results suggest a redistribution of the channel within the neurons rather than changes in synthesis or degradation rates. Our results showed a temporally nonlinear effect of EtOH on perimembrane expression of BK. First, there was an increase in BK perimembrane expression after 10 minutes of EtOH exposure that remained evident after 3 hours, although not correlated to increases in functional channel expression. In contrast, after 6 hours of EtOH exposure, we observed a significant decrease in both BK perimembrane expression and functional channel expression. Furthermore, after 24 hours of EtOH exposure, perimembrane levels of BK had returned to baseline.
  
  
  CONCLUSIONS
  We report a complex time-dependent pattern in the effect of EtOH on BK channel trafficking, including successive increases and decreases in perimembrane expression and a reduction in active BK channels after 3 and 6 hours of EtOH exposure. Possible mechanisms underlying this multiphasic trafficking are discussed. As molecular tolerance necessarily underlies behavioral tolerance, the time-dependent alterations we see at the level of the channel may be relevant to the influence of drinking patterns on the development of behavioral tolerance.
authors.affiliation: Institute of Neurobiology, University of Puerto Rico, San Juan, Puerto Rico.|Department of Anatomy and Neurobiology, Medical Science Campus, University of Puerto Rico, San Juan, Puerto Rico.
authors.forename: Stephanie
authors.initials: S
authors.lastname: Palacio
authors.affiliation: Institute of Neurobiology, University of Puerto Rico, San Juan, Puerto Rico.
authors.forename: Cristina
authors.initials: C
authors.lastname: Velázquez-Marrero
authors.affiliation: Institute of Neurobiology, University of Puerto Rico, San Juan, Puerto Rico.
authors.forename: Héctor G
authors.initials: HG
authors.lastname: Marrero
authors.affiliation: Institute of Neurobiology, University of Puerto Rico, San Juan, Puerto Rico.
authors.forename: Garrett E
authors.initials: GE
authors.lastname: Seale
authors.affiliation: Institute of Neurobiology, University of Puerto Rico, San Juan, Puerto Rico.|Department of Anatomy and Neurobiology, Medical Science Campus, University of Puerto Rico, San Juan, Puerto Rico.
authors.forename: Guillermo A
authors.initials: GA
authors.lastname: Yudowski
authors.affiliation: Institute of Neurobiology, University of Puerto Rico, San Juan, Puerto Rico.|Department of Anatomy and Neurobiology, Medical Science Campus, University of Puerto Rico, San Juan, Puerto Rico.
authors.forename: Steven N
authors.initials: SN
authors.lastname: Treistman
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D000431:Ethanol / Q000378:metabolism* / Q000494:pharmacology*; D005260:Female; D006624:Hippocampus / Q000187:drug effects / Q000378:metabolism*; D051036:Large-Conductance Calcium-Activated Potassium Channels / Q000378:metabolism*; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D011247:Pregnancy; D021381:Protein Transport / Q000187:drug effects / Q000502:physiology; D051381:Rats; D013997:Time Factors
chemical_list: D051036:Large-Conductance Calcium-Activated Potassium Channels; D000431:Ethanol
keywords: Alcohol; BK Channel; Ethanol; Hippocampus; Tolerance; Trafficking