Judith E. Grisel - US grants

tranquilizer; behavioral habituation /sensitization; ethanol; endorphins; genetic models; behavioral /social science research tag; gene targeting; laboratory mouse;

Adaption to chronic opiate exposure leads to tremendous health and social problems for addicts and pain patients, and thus imposes great costs for society in general. Despite years of intensive research directed toward understanding opiate tolerance and dependence, mechanisms of these changes remain unclear. Orphanin FQ is the recently identified endogenous ligand for the orphan opioid receptor (OFQ-R). OFQ-R was discovered by virtue of its high sequence homology to the family of opiate receptors, and OFQ also was found to be structurally related to members of the opioid family. Perhaps surprisingly, given these and other similarities (e.g., negative coupling to adenylate cyclase and overlapping central nervous system distribution), OFQ, acting at its receptor, appears to function as an endogenous antiopioid. Recent evidence suggests that changes in activity of this peptide may underlie processes associated with the neuroadaptation that ensues from chronic exposure to opiates. Most notably, OFQ administration blocks both opioid-mediated stress-induced analgesia and morphine analgesia, and there is an upregulation in both OFQ peptide and its receptor following repeated morphine administration. Furthermore, the development of opiate tolerance is reduced in transgenic mice that lack the OFQ-R (Ueda et al., 1997). The following studies are proposed to investigate the effect of OFQ on changes resulting from chronic exposure to opiates. Because coadministration of OFQ with morphine will block morphine effects without affecting morphine receptor occupancy, we propose to test whether such coadministration will alter the development of morphine tolerance, withdrawal, and place preference. Information from these studies will help determine whether morphine-receptor interactions are sufficient for such changes and thus help to answer the question of whether neuroadaption following chronic exposure to opiates results from cellular or systemic phenomena. Clinical applications of this work might include the development of novel treatment strategies and pharmacotherapies for opiate addicts and pain sufferers.

DESCRIPTION (provided by applicant): The influence of opioid peptides on alcohol sensitivity has been studied for a number of years, and the endogenous opioid system is hypothesized to be an important substrate for alcohol actions. The experiments proposed in this application will utilize transgenic mice that differ in their ability to synthesize B-endorphin in order to study the way that B-endorphin affects the response to alcohol. We have shown that these mice differ with respect to self-administration of alcohol. Other preliminary data indicate that mice lacking B-endorphin have an enhanced alcohol-mediated reduction in anxiety - in spite of the fact that under basal conditions anxiety increases as B-endorphin levels decrease. In addition, B-endorphin deficient mice show increased sensitivity to EtOH-induced ataxia and analgesia. These data support the hypothesis, deriving from both clinical and basic research, that B-endorphin affects sensitivity to alcohol. The overarching aim of these studies is to more fully characterize alcohol's differential effect on behavior in mice possessing varying amounts of B-endorphin. Moreover, we are hopeful that a better understanding of the relationship between alcohol and B-endorphin levels will lead to studies in which the mechanism of interaction can be elucidated. Because this peptide appears to differ between humans with varying genetic risk for alcoholism, a greater understanding of its relationship to alcohol sensitivity will contribute to our knowledge of the mechanisms underlying excessive alcohol use.

[unreadable] DESCRIPTION (provided by applicant): Opioid peptides contribute to the effects of ethanol and play a role in the development of alcoholism. For example, human populations with a genetic propensity toward alcohol abuse and dependence are reported to differ with respect to ethanol- stimulated release of b-endorphin, and these differences may affect the pharmacological properties of alcohol to contribute toward the disease state. The experiments in this proposal utilize an animal model to investigate the relationship between b-endorphin and alcohol sensitivity. We've found that genetically engineered mice that lack the ability to synthesize the peptide b-endorphin differ markedly in several measures of alcohol sensitivity, including ethanol-mediated reward, aversion and neural adaptation. Mirroring epidemiological findings from alcoholic populations, the effects of b-endorphin on alcohol response often appears to be sex- dependent. Moreover, we have found that gonadal hormones such as testosterone regulate the effect of b-endorphin on alcohol sensitivity. Despite the clear evidence linking alcohol response and b-endorphin, to date, studies reported in the literature have been correlational. In order to elucidate the mechanisms underlying this differential sensitivity we plan a series of comprehensive behavioral studies in mice with varying levels of b-endorphin. These will systematically vary ethanol exposure, b-endorphin level and sex/hormone status. In addition, neurochemical assays will be used to begin uncovering the neural consequences of low or absent b-endorphin that result in modified alcohol sensitivity. Finally, the effect of gonadal steroid hormones in modulating the ethanol's action on brain substrates will be explored. It is hoped that these studies will lead to a greater understanding of the relationship between b-endorphin and alcohol and thereby contribute to our knowledge of the mechanisms underlying human alcohol dependence. Although alcoholism and its consequences have devastating implications throughout the world and on virtually all aspects of human society, the causes are still largely unknown. The opioid peptide system is thought to be one important biological factor contributing to a liability for developing alcoholism and we use an animal model to better understand the mechanisms by which opioids modulate this risk. [unreadable] [unreadable] [unreadable]

DESCRIPTION (provided by applicant): The goal of this research is to better understand the influence of sex-dependent factors on the development of alcoholism. The overarching hypothesis is that there are sex differences in the liability toward alcohol abuse. More specifically, we hypothesize that sex differences partially derive from the effects of gonadal hormones and heritable levels of b-endorphin to influence the neural and behavioral stress response and modify the pleasure derived from alcohol (EtOH) administration. In Specific Aim 1, we will use mouse models to characterize the role of male versus female gonadal hormones in the effects of stress on EtOH self-administration. Our hypothesis here is that stress will increase the self-administration of EtOH, dependent upon gonadal hormones, such that an ovariectomy of female mice will counter this effect and that castration of male mice will promote it. Specific Aim 2 will focus on the role of b-endorphin (b-E) and endogenous opioid peptide in the sex-dependent effect of stress on the self-administration of EtOH. As differences in coping behavior and vulnerability to stress have a biological basis in HPA axis function and are modulated by b-E, we will use transgenic mice deficient in the capacity to synthesize b-E to test the hypothesis that behavioral responses contributing to allostasis of the stress response (i.e., EtOH self-administration) will vary as a function of this peptide. Finally, Specific Aim 3 is to employ at lest a dozen undergraduates, including female and underrepresented minority students, to work with the principle investigator on these research projects in a highly mentored environment. As an HHMI Distinguished Mentor with an exemplary record of collaborating with undergraduate students in the laboratory, the PI has a longstanding commitment to the educational benefit that these hands-on skills provide to future neuroscientists.