(Ivanhoe Newswire) — New research from the University of Chicago Medical Center has given new insight into just what makes cocaine and nicotine so addictive. According to the research, the effects of nicotine on the regions of the brain associated with addiction are similar to those of cocaine””both create lasting changes in a person’s brain by affecting similar mechanisms of memory on first contact.
Scientists have already established that learning and memory are connected to one another via “synaptic plasticity”””the long-term strengthening and weakening of connections between neurons. The more often two neurons are activated together, the stronger the bond between them becomes. This leads to an increased ability for one neuron to excite the other.
Previous research by Daniel McGehee, Ph.D., at the University of Chicago Medical Center has also shown that nicotine can promote plasticity in the region of the brain called the ventral tegmental area, or VTA. Neurons originating from the VTA release dopamine, a neurotransmitter that plays a role in rewards, such as food and sex, and addictions. In a series of new experiments, Danyan Mao, Ph.D., also of the University of Chicago Medical Center, monitored the electrical activity of VTA dopamine neurons in slices of brain taken from adult rats. Every slice was soaked for 15 minutes in a concentration of nicotine that equaled the amount that would reach the brain after smoking one cigarette. After 3 to 5 hours, experiments were conducted in order to detect the presence of synaptic plasticity and find out which neurotransmitter receptors were involved in the development of the synaptic plasticity.
As a result of the experiment, Mao discovered two receptors necessary for synaptic plasticity in the VTA: the acetylcholine receptor located on the dopamine neurons, and the D5 dopamine receptor””a component previously associated with the consumption of cocaine. If either of these receptors were blocked during nicotine exposure, the drug’s ability to cause lasting changes in excitability was eliminated.
The findings from the experiment suggest a reason for why both cocaine and nicotine are such highly addictive substances. Daniel McGehee, Ph.D., neuroscientist and associate professor in the Department of Anesthesia & Critical Care at the Medical Center, was quoted as saying,
“We know without question that there are big differences in the way these drugs affect people. But the idea that nicotine is working on the same circuitry as cocaine does point to why so many people have a hard time quitting tobacco, and why so many who experiment with the drug end up becoming addicted.”
While the results of the experiment also pose possible strategies for preventing or treating cocaine and nicotine addictions, the use of D5 blockers to treat addiction may be further in the future””currently all known blockers of the D5 receptor also block the D1 dopamine receptor, which is important for healthy motivation and movement.
Source: Journal of Neuroscience, May 4, 2011
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