The children of addicts: what do they inherit?

Are genes coding for dopamine receptors implicated in alcoholism?

Part of the familial factor of alcoholism is associated with the existence of genetic vulnerability. Genetic factors which interact with the pathogenesis of alcoholism are nevertheless complex, partial and for the moment partly unknown at the biological level. Recently, many association studies have been published concerning alcohol-dependence and genes coding for the second dopamine receptor. These associations, which have had positive replications, raise many questions. First of all, should the inheritance of alcoholism be regarded as a definitive fact? Secondly what is inherited? It could be alcoholism in general, a component of this disease (for instance, dependence on, sensitivity to or the seeking-process for alcohol), a specific pattern of drinking, presence of complications linked to alcohol abuse, or more general features, common to many addiction diseases. Thirdly, how could dopamine be linked to alcoholism? Furthermore, how should these positive associations be considered, given that two of these studies were negative, and that all linkage studies were negative. Lastly, are there other clues and ways of finding genetic vulnerability factors for alcohol abuse?

Is the Nociception Mechanism Altered in Offspring of Morphine-Abstinent Rats?

To investigate the effect of parental drug abuse on children, nociception, electrophysiological alteration, mRNA expression of opioid receptors, and expression of certain intracellular proteins in offspring of morphine-abstinent rats were studied. Adult male and female animals received water-soluble morphine for 21 days. Ten days after the last morphine administration, animals were placed for mating in 4 groups as follows: healthy (drug naive) female and male, morphine-abstinent female and healthy male, morphine-abstinent male and healthy female, morphine-abstinent male and morphine-abstinent female. Their adult male offspring were tested for nociception, neuronal discharge in nucleus accumbens (NAC) and prefrontal cortex (PFC). Our results showed that nociception in male offspring of all morphine-abstinent parent(s) groups was significantly reduced, compared with the control group. In the offspring of morphine-abstinent parent(s) groups, sensitivity to the antinociceptive effect of morphine was enhanced in chronic as well as in acute phases of the formalin test. Neuronal electrical activity reduced in the offspring of the morphine-exposed parent(s) in NAC as well as PFC regions. Moreover, our findings show that opioid receptors' expressions (µ, κ, and δ) increased in NAC of the litter of morphine-abstinent parent(s), compared with the control group. In addition, the expression of κ receptors was remarkably increased in the PFC in morphine-abstinent parent group, relative to the control group. The phosphorylated levels of extracellular regulated kinase 1/2 and cyclic adenosine monophosphate responsive element binding protein were significantly higher in the offspring of the morphine-abstinent parent(s) than the control group in the NAC. Our results indicated that endogenous opioid is altered in offspring of the morphine-exposed parent(s) and that heritage has a major role.

PERSPECTIVE

This study showed that nociception was reduced in offspring of morphine-abstinent rat(s) and also these litters had a low level of neuronal firing rate, and enhanced opioid receptors expression, especially in the NAC. Because these offspring are more sensitive to the analgesic effect of morphine, clinicians should consider this issue to manage the dosage of morphine for treating pain in children with an abstinent parent(s).

Alcoholism: toward understanding genetic and social factors

This study uses prospective data to assess the interaction of environmental and genetic contributions to alcoholism. Families of men whose genetic loading included fathers who were alcoholics were compared with men whose fathers were not alcoholics. Alcoholism among the former appeared to be promoted by mothers who held the alcoholic fathers in high esteem. The analyses suggested that genetic loading together with covert acceptance of alcoholism increases risk, as does absence of maternal control.

Neurogenetic adaptive mechanisms in alcoholism

Clinical, genetic, and neuropsychopharmacological studies of developmental factors in alcoholism are providing a better understanding of the neurobiological bases of personality and learning. Studies of the adopted-away children of alcoholics show that the predisposition to initiate alcohol-seeking behavior is genetically different from susceptibility to loss of control after drinking begins. Alcohol-seeking behavior is a special case of exploratory appetitive behavior and involves different neurogenetic processes than do susceptibility to behavioral tolerance and dependence on the antianxiety or sedative effects of alcohol. Three dimensions of personality have been described that may reflect individual differences in brain systems modulating the activation, maintenance, and inhibition of behavioral responses to the effects of alcohol and other environmental stimuli. These personality traits distinguish alcoholics with different patterns of behavioral, neurophysiological, and neuropharmacological responses to alcohol.