Maternal deprivation specifically enhances vulnerability to opiate dependence

Abstract

Maternal deprivation has been shown to increase vulnerability to morphine dependence and to disturb the enkephalinergic system in adulthood. To study whether or not this vulnerability to opiates is a specific feature, we examined oral self-administration behaviour of various reinforcing substances. Experiments were performed with morphine (25 mg/l), ethanol (10%), amphetamine (25 mg/l) and cocaine (100 mg/l). Drugs were available in a continuous free choice paradigm during 3 months. Cocaine and ethanol consumption and preference were similar in both deprived and control rats. Deprived rats greatly increased their morphine consumption and 78% of them showed a progressive decrease in morphine aversion. Only a slight, but significant, increase in oral amphetamine consumption was observed in deprived rats when compared with control rats. The difference in amphetamine self-administration in control and deprived rats cannot be explained by a modification of dopamine transporter expression measured by immunoautoradiography. Altogether, we conclude that maternal deprivation worsens inherent susceptibility to dependence, specifically for opiates, and therefore represents a highly valuable model to study environmentally triggered interindividual vulnerability to opiate addiction.

Adolescent Exposure to Chronic Delta-9-Tetrahydrocannabinol Blocks Opiate Dependence in Maternally Deprived Rats

“…This indicates that dronabinol treatment did not affect the ability to sense the aversive taste of morphine. There is not always a concordance in the ability of opioids to produce CPP and engender self-administration in rats (for review, see Bardo and Bevins, 2000;Vazquez et al, 2006). Context-drug associative learning (CPP) is likely fundamentally distinct from the acquisition of a drug-reward or -reinforced response at least in part because they are subserved by distinct neuropharmacological circuitry (for review, see Bardo and Bevins, 2000).…”

“…The measurement of morphine solution consumption was performed during 12 weeks using a two-bottle choice paradigm as described (Vazquez et al, 2005(Vazquez et al, , 2006. The rats were first trained to consume water for 5 days to habituate the rats to the free choice.…”

“…Enduring neurobiological changes have been described with basal hypoactivity of the enkephalinergic system in deprived (D) rats, which could explain their sensitivity to opiate dependence (Vazquez et al, 2005). Maternal deprivation specifically enhances vulnerability to opiate dependence (Vazquez et al, 2006), representing a highly valuable model to study the hypothesis that cannabis intake during adolescence may enhance or not the addictive effect of opiates and facilitate or not the progression to their consumption.…”

Possible involvement of endocannabinoids in the increase of morphine consumption in maternally deprived rat

“…cannabinoid receptor agonist CP-55940 either post-natally (Singh et al, 2006) or during adolescence (Biscaia et al, 2008). We reported that exposing neonatal male rats to an episode of 3 h per day of maternal deprivation (deprivation of new born pups from their mothers as well as littermates from each other) from postnatal days 1e14 induces long-term behavioral and biochemical alterations that resemble opiate dependence, with an escalation behavior in morphine consumption test and an increase of weight gain after morphine removal (Vazquez et al, 2005a(Vazquez et al, , 2006. Interestingly, adolescent exposure to chronic THC blocks morphine dependence in maternally deprived (D) rats (Morel et al, 2009).…”

Individual Differences and Social Influences on the Neurobehavioral Pharmacology of Abused Drugs

“…In males, maternal separation increases intake of oral amphetamine (Vazquez et al (2006) and i.v. cocaine (Kosten et al, 2000(Kosten et al, , 2004Zhang et al, 2005;Moffett et al, 2006), although one study using a 24-h discrete trial reinforcement schedule found no effect of maternal separation in cocaine self-administration in either male or female rats (Lynch et al, 2005).…”