( bind properly with the neurotransmitter...)Nicotine exposure during development leads to hearing problems

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.

"While verbal function cannot be measured in an animal, this establishment of a causal relationship between prenatal nicotine exposure and auditory-cognitive deficits is an important step forward in reinforcing these previous findings in humans," Metherate said.

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 sou
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Source:University of California - Irvine