(Title stolen from the Science Now blurb)
One of the powerful attractions of cocaine is that the drug activates the reward centers in the brain, giving rise to a sense of elation and reduced fatigue, among lots of other things. These reward centers probably evolved to confer reinforcement for behaviors that are especially important for survival of the species. Cocaine and other drugs hijack this reinforcement property, and the seeking of cocaine becomes the reinforced behavior. Pretty poweful stuff.
Thus it's very interesting to see in Science Now a week or so ago, that nursing rats show the same activation of the reward pathways as virgin rats on cocaine. In fact, mom rats with babies under 8 days' age prefer nursing over a dose of cocaine; and when suckling moms are given cocaine, it actually causes a dip in the electrical activity of the reward center.
I can see where the anti-fatigue effects might come in handy....
Subscription link (Journal of Neuroscience) is here. .