The Neuronal Nitric Oxide Synthase Gene Is Critically Involved in Neurobehavioral Effects of Alcohol

Abstract

In the present study, we describe a new role of the neuronal nitric oxide synthase (nNOS) gene in the regulation of alcohol drinking behavior. Mice deficient in the nNOS gene (nNOS Ϫ/Ϫ) and wild-type control mice were submitted to a two-bottle free-choice procedure with either water or increasing concentrations of alcohol (2-16%) for 6 weeks. nNOS Ϫ/Ϫ mice did not differ in consumption and preference for low alcohol concentrations from wild-type animals; however, nNOS Ϫ/Ϫ mice consumed sixfold more alcohol from highly concentrated alcohol solutions than wild-type mice. Taste studies with either sucrose or quinine solutions revealed that alcohol intake in nNOS Ϫ/Ϫ and wild-type mice is associated, at least in part, with sweet solution intake but not with the taste of bitterness. When compared with wild-type mice, the nNOS Ϫ/Ϫ mice were found to be less sensitive to the sedative effects of ethanol as measured by shorter recovery time from ethanol-induced sleep and did not develop rapid tolerance to ethanol-induced hypothermia, although plasma ethanol concentrations were not significantly different from those of controls. Our findings contrast with previous reports that showed that nonselective NOS inhibitors decrease alcohol consumption. However, because alcohol consumption was suppressed in wild-type as well as nNOS Ϫ/Ϫ mice by the NOS inhibitor N G -nitro-L-arginine methyl ester, we conclude that the effect of nonselective NOS inhibitors on alcohol drinking is not mediated by nNOS. Other NOS isoforms, most likely in the periphery or other splice variants of the NOS gene, might contribute to the effect of nonselective NOS inhibitors on alcohol drinking. In summary, the nNOS gene is critically involved in the regulation of neurobehavioral effects of alcohol.

PRECLINICAL STUDY: Circadian regulation of central ethanol sensitivity by the mPer2 gene

“…Furthermore, LORR measurements in rodents have been frequently utilized as a mean to assess the sensitivity of the CNS to the depressant effects of ethanol (e.g. Harris et al 1995;Spanagel et al 2002;Rimondini, Sommer & Dall 2008). Moreover, in line with the present results, brain sensitivity has been demonstrated to display circadian rhythmicity by the longer LORR durations in the animals' active or dark phase, as opposed to much shorter ones in the resting or light phase (Deimling & Schnell 1980;Sato et al 2005).…”

“…Body temperature and hypothermia in wild-type and Per mutant mice were measured as described by Spanagel et al (2002). Thus, by using an infrared thermometer (Infratherm, Boston, MA, USA), ventral surface temperature was measured.…”

Acute ethanol modulates glutamatergic and serotonergic phase shifts of the mouse circadian clock in vitro

“…NMDA receptors are one of the principal targets of ethanol in the brain (Lovinger et al, 1989;Abrous et al, 2005;Krystal et al, 2003;Chandler, 2003). Acute ethanol exposure both in vivo and in vitro suppresses NMDA receptor-induced ion currents, Ca 2+ influx, and downstream cellular events (Wirkner et al, 2000;Roberto et al, 2004;Spanagel et al, 2002).…”

“…NMDA receptors are one of the principal targets of ethanol in the brain (Lovinger et al, 1989;Abrous et al, 2005;Krystal et al, 2003;Chandler, 2003). Acute ethanol exposure both in vivo and in vitro suppresses NMDA receptor-induced ion currents, Ca 2+ influx, and downstream cellular events (Wirkner et al, 2000;Roberto et al, 2004;Spanagel et al, 2002).Non-photic stimuli also regulate SCN circadian clock phase. Arousal or behavioral activity during the daytime (for nocturnal rodents) induce robust phase advances (Mrosovsky, 1988;Reebs et al, 1989;Antle and Mistlberger, 2000) that may involve neuropeptide Y (Biello et al, 1994;Golombek et al, 1996;Marchant et al, 1997) and/or serotonin (5-HT) (Prosser, 2003;Tominaga et al, 1992;Horikawa and Shibata, 2004;Marchant et al, 1997;Glass et al, 2003) signaling in the SCN.…”

A Molecular Mechanism of Ethanol Dependence: The Influence of the Ionotropic Glutamate Receptor Activated by N-Methyl-D-Aspartate

“…NO is an intracellular and extracellular messenger which is produced by nitric oxide synthase (NOS) (Bredt et al, 1990). The stimulation of NMDARs leads to a calcium influx within the cell and the binding of calcium to calmodulin activates neuronal NOS (nNOS) activity (Spanagel et al, 2002). Other studies have also implicated NOS activity in the modulation of alcohol mediated effects on the CNS (Spanagel et al, 2002;Deng & Deitrich, 2007).…”