Motor stimulant effects of ethanol and acetaldehyde injected into the posterior ventral tegmental area of rats: role of opioid receptors

Abstract

The posterior VTA is another brain region involved in the locomotor activation after the intracerebroventricular administration of ethanol or acetaldehyde. Our data indicate that opioid receptors, particularly the micro-opioid receptors, could be the target of the actions of these compounds in the VTA. These results are consistent with the hypothesis that acetaldehyde could be a mediator of some ethanol effects.

Locomotor stimulant effects of acute and repeated intrategmental injections of salsolinol in rats: role of μ-opioid receptors

“…The profile of this plot is similar to those obtained in the posterior VTA for Sal (Rodd et al 2008), ethanol (Rodd et al 2004a, b), and ACH (Rodd et al 2004b;Rodd-Henricks et al 2002) in ICSA experiments and for ethanol in the substantia nigra pars reticulata (Arizzi-LaFrance et al 2006) in locomotor activity studies in rats. It is important to realize that the maximum effect on motor activity was obtained in our present study with the 30.0-pmol dose, which is clearly lower than that previously reported by our group for ethanol (150 nmol) and ACH (250 nmol; Sánchez-Catalán et al 2009). In our experimental conditions therefore, the dose of Sal producing the maximum effect was 5,000 and 8,300 times lower than that of ethanol and ACH, respectively.…”

“…The addition of the control group aCSF + Sal (30 pmol) would have allowed to know, in a direct manner, if the nonincrease in activity is an effect due to the two successive intra-VTA injections. However, in the experiment 3 (and also in our previous paper of Sánchez-Catalán et al 2009), the administration of successive microinjections into the VTA does not affect the responsiveness of the VTA neurons, so finally we decided not to plan this group in order to diminish the number of animals used in the present study.…”

The antero-posterior heterogeneity of the ventral tegmental area

“…1, Table 1). Indeed, rats self-administer ethanol into the pVTA but not into the aVTA (Rodd-Henricks et al, 2000Rodd et al, 2004bRodd et al, , 2005dDing et al, 2014), and the infusion of ethanol into the pVTA also increases the rat locomotor activity (Sanchez-Catalan et al, 2009). Considering data obtained in a strain of alcohol-preferring rats, the preferential sensitivity of the pVTA may be relevant to the vulnerability to alcohol.…”

“…in rats, which is prevented by an intra-pVTA pre-treatment with a l-opioid receptor antagonist (Sanchez-Catalan et al, 2009). The critical role of acetaldehyde in pVTA ethanol action is demonstrated by the pharmacological use of an acetaldehyde sequestering agent, D-penicillamine.…”

“…The endogenous opioid system is intimately associated with ethanol addiction (Gianoulakis, 2009), and opioid antagonists are even used as a treatment for alcoholism (Spanagel and Kiefer, 2008). The intra-pVTA administration of an opioid antagonist prevents the locomotor-activating effects of intra-pVTA ethanol in rats (Sanchez-Catalan et al, 2009), and decreases ethanol-induced conditioned place preference in mice (Bechtholt and Cunningham, 2005). Various intra-pVTA 5-HT 3 antagonists can also reduce the pVTA ethanol self-administration (Rodd-Henricks et al, 2003;Rodd et al, 2005d), the pVTA self-administration of a mixture of ethanol and cocaine (Ding et al, 2012c) and the oral self-administration of ethanol (Rodd et al, 2010), while the 5-HT 3 antagonists had no effect on oral ethanol self-administration when delivered into the aVTA (Rodd et al, 2010).…”