Doctor Larry Young discusses how vasopressin and oxytocin contribute to the reward system, which can promote behavior such as bonding and drug addiction.

One of the areas that we know is really important in terms of the social bonding in prairie voles is the nucleus accumbens and its output the ventral pallidum. These are two areas that are part of the brain’s reward circuitry. They are critically involved in things like addiction, so it’s not surprising that they may also be involved in the social bond formation; maybe a social bond is very similar to an addiction. In the prairie voles oxytocin acts in the nucleus accumbens where there are lots of receptors to promote that pair bonding. It actually acts to activate the reward circuitry so that the social interaction itself becomes very pleasant and the individual associates that pleasant, rewarding aspect of the social interaction with the particular individual that they are interacting with, so that in the future they want to be with that individual. It’s sort of a self perpetuating process that draws the animals into a stronger and stronger bond. Oxytocin is acting in females to promote that bond in the nucleus accumbens. In males vasopressin is acting in the ventral pallidum, which is just below the nucleus accumbens [and is] part of the same circuitry. In both cases, the males and the females, you have these two molecules acting in the same circuitry to promote this behavior, which has remarkable parallels to addiction.

nucleus accumbens, ventral pallidum, globus pallidus, prairie voles, reward, social interaction, oxytocin, vasopressin, larry, young