Dopamine and opioid systems interact within the nucleus accumbens to maintain monogamous pair bonds

摘要

The bond between parents is one of the most important social relationships that humans have. Prairie voles are one of the few other mammals whose individuals also form long-term social bonds after having offspring together, so they have frequently been used to study the brain mechanisms that underlie such bonding. However, most previous studies have focused only on how the bond between a pair of mating partners is formed little is known about how this bond is then maintained over months and years. When a prairie vole forms a bond with a mate, it will then aggressively reject other prairie voles. This “selective aggression” only happens once a social bond between two mating prairie voles is formed, so this behavior can be used as a proxy to confirm that the social bond exists. In order to study how prairie voles maintain bonds with a mate, Resendez et al. tracked what happens in the brain of a prairie vole during selective aggression. The experiments showed that this aggressive behaviour coincides with changes in gene expression and brain chemistry that make it unpleasant for a prairie vole to be exposed to voles that are not its partner. For male prairie voles – but not females – these changes only happened if the female mating partner became pregnant during the cohabitation period. The changes that occur in the brain as a result of bonding with a partner also mean that drugs that are normally addictive are no longer pleasant and rewarding to the prairie vole. Indeed, forming a social bond between mating animals alters the brain in similar ways to the effects produced by addictive drugs. Thus, in a sense, each member of the mating pair becomes ‘addicted’ to their partner. The results presented by Resendez et al. also have implications for humans. They suggest that having a strong social support network is a powerful way of preventing casual drug use from developing into compulsive drug addiction. This may also mean that positive social relationships could help to treat people with drug addiction problems.