Tolerance, described as the loss of drug effectiveness over time, is an important component of addiction. The degree of acute behavioral tolerance to alcohol exhibited by a naïve subject can predict the likelihood of alcohol abuse. Thus, the determinants of acute tolerance are important to understand. Calcium-and voltage-gated (BK) potassium channels, consisting of pore forming ␣ and modulatory ␤ subunits, are targets of ethanol (EtOH) action. Here, we examine the role, at the molecular, cellular, and behavioral levels, of the BK ␤4 subunit in acute tolerance. Single channel recordings in HEK-293 cells show that, in the absence of ␤4, EtOH potentiation of activity exhibits acute tolerance, which is blocked by coexpressing the ␤4 subunit. BK channels in acutely isolated medium spiny neurons from WT mice (in which the ␤4 subunit is well-represented) exhibit little tolerance. In contrast, neuronal BK channels from ␤4 knockout (KO) mice do display acute tolerance. Brain slice recordings showed tolerance to EtOH's effects on spike patterning in KO but not in WT mice. In addition, ␤4 KO mice develop rapid tolerance to EtOH's locomotor effects, whereas WT mice do not. Finally, in a restricted access ethanol self-administration assay, ␤4 KO mice drink more than their WT counterparts. Taken together, these data indicate that the ␤4 subunit controls ethanol tolerance at the molecular, cellular, and behavioral levels, and could determine individual differences in alcohol abuse and alcoholism, as well as represent a therapeutic target for alcoholism.electrophysiology ͉ knockout mice ͉ striatum ͉ addiction ͉ plasticity A lcohol abuse is the third largest cause of preventable mortality in the world. Tolerance, described as the gradual loss of drug effectiveness over time, is a hallmark of abused drugs. This phenomenon is particularly important in the response to acute alcohol because the degree of tolerance exhibited by a naïve subject can predict the likelihood to develop alcohol abuse (1-4). Thus, identifying the mechanistic and molecular underpinnings of tolerance is essential for understanding the pathophysiology of alcoholism, as well as determining potential therapeutic targets for alcohol abuse. The neurobiology of tolerance is thought to involve several types of adaptation, ranging from alteration in membrane lipid composition (5) to neuroadaptative changes in target proteins (6, 7).In recent years, large conductance calcium-and voltage-gated potassium (BK) channels have emerged as one of the key targets of ethanol action, yet their role in the physiological and behavioral response to alcohol are unknown. Invertebrate studies suggest that BK channels may be important for the development of tolerance to ethanol (8, 9). In mammals, BK channels exist as a complex formed by the association of the pore-forming ␣ subunit with the auxiliary ␤ subunit. The ␣ subunit is encoded by only one gene (slo) with several splice variants (STREX, P27, insertless, etc.), whereas the ␤ subunit is the product of four distinct genes (␤1-␤4)...

Chromatin remodeling, including histone modification, is involved in stimulant-induced gene expression and addiction behavior. To further explore the role of dopamine D 1 receptor signaling, we measured cocaine-related locomotor activity and place preference in mice pretreated for up to 10 days with the D 1 agonist SKF82958 and/or the histone deacetylase inhibitor (HDACi), sodium butyrate. Cotreatment with D 1 agonist and HDACi significantly enhanced cocaine-induced locomotor activity and place preference, in comparison to single-drug regimens. However, butyrate-mediated reward effects were transient and only apparent within 2 days after the last HDACi treatment. These behavioral changes were associated with histone modification changes in striatum and ventral midbrain: (1) a generalized increase in H3 phosphoacetylation in striatal neurons was dependent on activation of D 1 receptors; (2) H3 deacetylation at promoter sequences of tyrosine hydroxylase (Th) and brain-derived neurotrophic factor (Bdnf) in ventral midbrain, together with upregulation of the corresponding gene transcripts after cotreatment with D 1 agonist and HDACi. Collectively, these findings imply that D 1 receptor-regulated histone (phospho)acetylation and gene expression in reward circuitry is differentially regulated in a region-specific manner. Given that the combination of D 1 agonist and HDACi enhances cocaine-related sensitization and reward, the therapeutic benefits of D 1 receptor antagonists and histone acetyl-transferase inhibitors (HATi) warrant further investigation in experimental models of stimulant abuse.

Phosphorylation at murine Serine 18 (human Serine 15) is a critical regulatory process for the tumor suppressor function of p53. p53Ser18 residue is a substrate for ataxia-telangiectasia mutated (ATM) and ATM-related (ATR) protein kinases. Studies of mice with a germ-line mutation that replaces Ser18 with Ala (p53S18A mice) have demonstrated that loss of phosphorylation of p53Ser18 leads to the development of tumors, including lymphomas, fibrosarcomas, leukemia and leiomyosarcomas. The predominant lymphoma is B-cell lymphoma, which is in contrast to the lymphomas observed in Atm−/− animals. This observation and the fact that multiple kinases phosphorylate p53Ser18 suggest Atm-independent tumor suppressive functions of p53Ser18. Therefore, in order to examine p53Ser18 function in relationship to ATM, we analyzed the lifespan and tumorigenesis of mice with combined mutations in p53Ser18 and Atm. Surprisingly, we observed no cooperation in survival and tumorigenesis in compound p53S18A and Atm−/− animals. However, we observed embryonic lethality in the compound mutant animals. In addition, the homozygous p53Ser18 mutant allele impacted the weight of Atm−/− animals. These studies examine the genetic interaction of p53Ser18 and Atm in vivo. Furthermore, these studies demonstrate a role of p53Ser18 in regulating embryonic survival and motor coordination.