The hippocampal N-methyl-D-aspartate receptor (NMDAR) activity plays important roles in cognition and is a major substrate for ethanol-induced memory dysfunction. This receptor is a glutamate-gated ion channel, which is composed of NR1 and NR2 subunits in various brain areas. Although homomeric NR1 subunits form an active ion channel that conducts Na ϩ and Ca 2ϩ currents, the incorporation of NR2 subunits allows this channel to be modulated by the Src family of kinases, phosphatases, and by simple molecules such as ethanol. We have found that short-term ethanol application inhibits the NMDAR activity via striatal enriched protein tyrosine phosphatase (STEP)-regulated mechanisms. The genetic deletion of the active form of STEP, STEP61, leads to marked attenuation of ethanol inhibition of NMDAR currents. In addition, STEP61 negatively regulates Fyn and p38 mitogen-activated protein kinase (MAPK), and these proteins are members of the NMDAR super molecular complex. Here we demonstrate, using wholecell electrophysiological recording, Western blot analysis, and pharmacological manipulations, that neurons exposed to a 3-h, 45 mM ethanol treatment develop an adaptive attenuation of short-term ethanol inhibition of NMDAR currents in brain slices. Our results suggest that this adaptation of NMDAR responses is associated with a partial inactivation of STEP61, an activation of p38 MAPK, and a requirement for NR2B activity. Together, these data indicate that altered STEP61 and p38 MAPK signaling contribute to the modulation of ethanol inhibition of NMDARs in brain neurons.

High abstinence rates characterize alcohol-dependent liver graft recipients. The immunosuppressants cyclosporine A (CsA) and tacrolimus (TRL) also inhibit calcineurin (CLN) in the brain. Previously, we found that CsA reduces alcohol consumption in C57BL/6J mice. The goals of the present study were: 1) to compare the ethanol preference effects of CsA against TRL, as well as sirolimus (SRL), an immunosuppressant without CLN inhibition and 2) to establish that reduction of alcohol consumption is not caused by caloric reinforcement from these ligands. C57BL/6J mice trained to imbibe ethanol consumed ethanol or sucrose in a modified limited-access drinking-in-the-dark paradigm; test groups received vehicle or doses of CsA (5-50 mg/kg), TRL (0.5-2.5 mg/kg), or SRL (1.0 -5.0 mg/kg) for 5 consecutive days, 30 min before each 2-h limited-access session. Brain CsA, TRL, and SRL concentrations were measured. CsA (p Ͻ 0.001) and TRL (p Ͻ 0.01) each decreased ethanol consumption, whereas SRL showed no significant effects at any dose. Effective doses included CsA at 10 mg/kg and above and TRL at 2.5 mg/kg. CsA (50 mg/kg) did not reduce sucrose consumption. Both CsA and TRL reached significant brain concentrations compared with very low values of SRL. These data suggest that CsA and TRL may reduce alcohol preference through central CLN inhibition rather than by immunosuppression.

The endogenous substrate proteins of rat cardiac protein kinase C type I, II, and III isozymic forms were studied in rat cardiac sarcolemma. The 19-, 21-, 29-, 35-, and 95-kDa proteins were phosphorylated by both types II and III, but not type I. The extent of phosphorylation by individual protein kinase C isozymic forms was additive and equal to the extent of phosphorylation observed when a mixture of isozymic forms was employed. The extent of phosphorylation of the 21-kDa protein by type III was much higher than that by type II. These results suggest that the protein kinase C isozymes have preferences for specific endogenous substrate proteins. The phosphorylation of these endogenous substrate proteins by protein kinase C isozymes probably plays a role in cardiac cell functions.