Cocaine and morphine trump food and water in brain’s reward hierarchy: Study

Researchers from Rockefeller University and the Icahn School of Medicine at Mount Sinai have made a discovery regarding the effects of addictive drugs like cocaine and morphine on our brains. They analysed the brain's reward pathway, and tried to answer why these substances can takeover our natural desires for essential needs such as food and water.

Lead researcher Jeffrey Friedman said, "We've known for decades that natural rewards, like food, and drugs can activate the same brain region. But what we've just learned is that they impact neural activity in strikingly different ways."

"One of the big takeaways here is that addictive drugs have pathologic effects on these neural pathways, that's distinct from, say, the physiologic response to eating a meal when you are hungry or drinking a glass of water when you are thirsty," he added.

Add WION as a Preferred Source

How did they perform this study?

Using mouse models, the research team employed a comprehensive approach to study the impact of cocaine and morphine on the brain's reward circuits. By mapping brain activity, imaging neurons, and analysing genetic activity, they tried to understand how these drugs influence neural pathways.

The study reveals the crucial role of the nucleus accumbens (NAc) in both typical brain functions and drug rewards. Neurons projecting to the NAc from the orbitofrontal cortex are implicated in reducing natural reward responses when activated by drug use.

"The NAc is a key node where the underlying dopaminoceptive neurons direct and refine animals' behaviours towards their goals," neuroscientist Bowen Tan told Science Alert. "What we hadn't been able to understand is how repeated exposure to drugs corrupts these neurons, resulting in escalated drug-seeking behaviors and a shift away from healthy goals," he added.

How do cocaine and morphine affect our brain differently?

While cocaine and morphine activate specific subsets of neurons in the NAc, their effects differ. Cocaine, a potent stimulant, and morphine, an opioid, elicit unique responses in the brain, ultimately altering behaviour and preference for these drugs over basic needs.

"By tracking these cells, we show that not only are similar cells activated across reward classes, but also that cocaine and morphine elicit initially stronger responses than food or water, and this actually magnifies with increasing exposure," neuroscientist Caleb Browne said. "After withdrawal from the drugs, these same cells exhibit disorganized responses to natural rewards in a manner that may resemble some of the negative affective states seen in withdrawal in substance use disorder," he added.

Repeated exposure to cocaine and morphine leads to a shift in behaviour, with mice exhibiting increased interest in drugs and decreased interest in food and water. This change is accompanied by alterations in neuron communication, affecting how the brain processes rewards from natural stimuli.

The study identifies a protein encoded by the Rheb gene that interferes with typical neuron communication, contributing to addiction-related behaviors. Understanding these pathways opens avenues for developing targeted therapies to combat addiction.