A new neuroscience research has found that nicotine has a similar initial impact on the brain as cocaine, explaining why both are highly addictive substances.
In the new experiments, Danyan Mao, postdoctoral researcher at the University of Chicago Medical Center monitored the electrical activity of VTA dopamine neurons in slices of brain dissected from adult rats.
Each slice was bathed for 15 minutes in a concentration of nicotine similar to the amount that would reach the brain after smoking a single cigarette.
After 3-5 hours, Mao conducted electrophysiology experiments to detect the presence of synaptic plasticity and determine which neurotransmitter receptors were involved in its development.
Mao discovered that nicotine-induced synaptic plasticity in the VTA is dependent upon one of the drug`s usual targets, a receptor for the neurotransmitter acetylcholine located on the dopamine neurons.
But another element found necessary for nicotine`s synaptic effects was a surprise: the D5 dopamine receptor, a component previously implicated in the action of cocaine.
Blocking either of these receptors during nicotine exposure eliminated the drug`s ability to cause persistent changes in excitability.
"We found that nicotine and cocaine employ similar mechanisms to induce synaptic plasticity in dopamine neurons in VTA," Mao said.
The results suggest that nicotine and cocaine hijack similar mechanisms of memory on first contact to create long-lasting changes in a person`s brain.
The study has been published in The Journal of Neuroscience.