Protein kinase Cγ mediates ethanol withdrawal hyper‐responsiveness of NMDA receptor currents in spinal cord motor neurons

Abstract

1 The present studies were designed to test the hypothesis that neuronal-specific protein kinase Cg (PKCg) plays a critical role in acute ethanol withdrawal hyper-responsiveness in spinal cord. 2 Patch-clamp studies were carried out in motor neurons in neonatal rat spinal cord slices. Postsynaptic currents were evoked by brief pulses of 2 mM N-methyl-D-aspartic acid (NMDA) in the presence of bicuculline methiodide 10 mM; strychnine 5 mM and tetrodotoxin 0.5 mM. 3 Both ethanol depression and withdrawal hyper-responsiveness of NMDA-evoked currents are dependent on increases in intracellular Ca 2 þ . Blocking intracellular increase in Ca 2 þ by 30 mM 1,2-bis(2-aminophenoxy)-ethane-N,N,N 0 ,N 0 -tetraacetic acid (BAPTA) not only decreased the ethanolinduced depression of NMDA-evoked currents (3375% in control vs 2073% in BAPTA, Po0.05) but also eliminated acute ethanol withdrawal hyper-responsiveness. 4 Immunohistochemistry studies revealed that neonatal spinal cord motor neurons contain an abundance of nuclear PKCg. 5 Exposure to ethanol (100 mM) induced PKCg translocation from the nucleus to cytoplasm in motor neurons. Pretreatment with the g-isozyme-specific peptide PKC inhibitor, gV5-3, blocked ethanol-induced translocation and also blocked withdrawal hyper-responsiveness. 6 The results show that PKCg mediates ethanol withdrawal hyper-responsiveness in spinal motor neurons; the results may be relevant to some symptoms of ethanol withdrawal in vivo.

Ethanol Induces Long-Term Facilitation of NR2B-NMDA Receptor Activity in the Dorsal Striatum: Implications for Alcohol Drinking Behavior

“…This result is consistent with other long-lasting effects of ethanol on NMDARs reported in acute spinal cord slices (Li et al, 2005). This finding also resembles the enhancement in NMDAR-mediated currents we recently observed in the ventral tegmental area after washout of cocaine (Schilstrom et al, 2006).…”

Protein kinase C as a stress sensor

“…Pain sensitivity after alcohol administration is associated with altered levels of PKCγ in the cytoplasm of rat motor neurons [71]. In related work, withdrawal-induced hyperalgesia was reversibly inhibited with PKCε oligodeoxynucleotide antisense [72].…”

Acute Ethanol Administration Rapidly Increases Phosphorylation of Conventional Protein Kinase C in Specific Mammalian Brain Regions in Vivo

“…In agreement with these data showing loss of ethanol sensitivity, PKCγ null mice voluntarily consume significantly more ethanol than wild-type controls . Ethanol also alters association of PKCγ with GABA A receptors in the cerebral cortex (Kumar et al, 2002) and mediates the effects of ethanol withdrawal on N-methyl-D-aspartate receptor currents in the spinal cord (Li et al, 2005). Moreover, ethanol prevents translocation of the βII isoform of PKC, another member cPKC subgroup (Ron et al, 2000).…”

“…Ethanol has been shown to activate phospholipase C, which initiates intracellular signaling responses including formation of inositol-1,4, 5-trisphosphate, the release of intracellular Ca 2+ , and formation of DAG, which leads to stimulation of cPKC (Hoek and Rubin, 1990). Evidence also indicates that ethanol (100 mM) induces translocation of PKCγ from the nucleus to the cytoplasm in neonatal spinal cord motor neurons (Li et al, 2005). However, to be catalytically active, cPKC isoforms also require a series of phosphorylations (Newton, 2003).…”