GABAA Modulation as a Target for Developing Medications for Methamphetamine Abuse

Methamphetamine dependence is a significant public-health concern. Dopamine plays a prominent role in mediating the behavioral effects of methamphetamine. y-Aminobutync-acid (GABA) systems inhibit dopamine systems. Increasing GABA activity may result in greater inhibition of dopamine systems and thus attenuate the behavioral effects of methamphetamine thought to contribute to its abuse. Preclinical and human laboratory experiments have demonstrated that high-efficacy GABAA receptor modulators attenuate the behavioral effects of stimulants under a variety of behavioral arrangements. These findings suggest that GABAA receptor modulation might be a viable target for the development of medications to manage methamphetamine abuse. The overarching goal of this application is to demonstrate targeting GABA4 receptor modulation is a viable strategy for the development of medications to manage methamphetamine dependence. This goal will be achieved through the conduct of two "proof-of-concept" experiments designed to accomplish two specific aims. The first specific aim is to demonstrate that a GABAA receptor modulator attenuates the reinforcing effects of methamphetamine. To accomplish this aim, we will determine the reinforcing effects of intranasal rnethamphetamine during maintenance on a high-efficacy GABAA receptor modulator using a progressive-ratio procedure (Exp. 1). The reinforcing effects of stimulants are central to their abuse potential. By inference, then, an effective pharmacotherapy for managing stimulant dependence will modify drug self-administration. The second specific aim is to demonstrate that a GABAA receptor modulator attenuates the discriminative-stimulus effects of methamphetamine. To accomplish this aim, we will teach volunteers to discriminate intranasal methamphetamine using a drug-discrimination procedure (Exp. 2). A range of doses of methamphetamine will then be tested during maintenance on a GABAA receptor modulator and placebo. The discriminative effects of methamphetamine may be involved in relapse to drug-taking behavior in that an initial dose (i.e., a lapse) may function as a discriminative stimulus signaling the availability of more drug. Pharmacotherapies that attenuate the discriminative-stimulus effects of methamphetamine may be effective for preventing relapse. The proposed research will provide initial clinical information regarding the viability of targeting GABAA receptor modulation for the development of medications for methamphetamine abuse. In addition to the clinical information, the proposed research will provide basic-science and translational information. First, the inclusion of drug self-administration and discrimination measures, along with subjective-effect questionnaires, will provide information concerning the relationship between the reinforcing, discriminative and subjective effects of methamphetamine. Second, because GABAA receptor modulators have been tested as pharmacotherapies for stimulant dependence in laboratory animals using similar behavioral procedures, the proposed research will determine, albeit indirectly, the extent that findings from preclinical studies generalize to humans.