Scientists know that children of women who smoke during pregnancy can develop hearing-related cognitive deficits. For the first time, researchers believe they have evidence that not only implicates nicotine as the culprit, but also shows what the substance does to the brain to cause these deficits.
In a study using rats, Raju Metherate, associate professor of neurobiology and behavior, and colleagues from UC Irvine, showed that nicotine exposure during the equivalent of a human’s third trimester led to hearing-related cognitive problems. This is the first time a study has demonstrated this causal link. Further tests then revealed that the probable cause of the deficits was damage to the receptors in the brain that are sensitive to nicotine, which seems to occur when humans or animals are exposed to the substance during development. The study appears this week in the early online issue of the European Journal of Neuroscience.
They may have difficulty understanding speech in a noisy environment, not understand information that is presented verbally, and may not be able to tell the difference between similar sound
Chemicals known as neurotransmitters act as message carriers between cells and bind with receptors on the cells’ surfaces, much like a key fits into the lock. If the receptors are damaged, they can no longer bind properly with the neurotransmitter. Nicotine shares a receptor with the neurotransmitter acetylcholine, which is important for a number of cognitive functions.
Researchers believe that when people are paying attention to something, such as an important sound, acetylcholine is released into the brain. It then interacts with the nicotinic-acetylcholine receptor and, the UCI study showed, thereby enhances sensitivity to that sound. If that receptor is damaged due to prenatal exposure to nicotine, acetylcholine cannot bind with it and increased sensitivity to the important sound is lost.
According to the researchers, given the importance of acetylcholine to a number of brain functions, a loss of nicotinic-acetylcholine receptors may have a negative effect on other higher cognitive functions and may also impair vision and other senses.
Nicotine does seem to actually enhance cognitive processing when administered to adults, a finding that has also been shown in previous studies. The researchers found that in this study, nicotine appeared to enhance auditory function in the adult rats, but only if they had not been exposed to the substance during development.
Researchers placed electrodes in the animals’ auditory cortex, then exposed them to different frequencies of sound. They found that nicotine made the cortex much more responsive to sound if the rats had not had exposure to nicotine during their early development. In the case of previous exposure, there was no increased sensitivity to sound. According to Metherate, this occurs most likely because the nicotine is mimicking the action of acetylcholine on their shared receptors and increasing responsiveness to sound if those receptors had not been previously damaged.
Collaborators on this study from UCI were Norman Weinberger, research professor of neurobiology and behavior; Frances Leslie, professor of pharmacology; Kevin Liang, graduate student researcher in neurobiology and behavior; Bonnie Sue Poytress, laboratory assistant in neurobiology and behavior; and Yiling Chen, associate specialist in pharmacology. The study was funded by the National Institute on Drug Abuse and the National Institute on Deafness and Other Communication Disorders, both parts of the National Institutes of Health.
Source: universityofcalifornia.edu
Related posts:
- Nicotine May Have More Profound Impact Than Previously Thought
- Study in Rats May Lead to Treatment for Nicotine Addiction in Humans
- How Nicotine Changes Brain
- Harmful effects of Physical and Social Exposure of Children to Tobacco Smoke
- Why Address Exposure to Tobacco Smoke?
Tags: development leads, Drug Testing, Drug Testing guides, hearing problems, nicotine abuse, nicotine effect, nicotine exposure, testing guides, woman smoking
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