The use of menthol cigarettes is especially high among African-American smokers, and research has shown a higher rate of lung cancer in African American smokers, compared with other smokers.
“The issue may be that menthol in the presence of nicotine may reduce the irritation enough that a smoker can inhale more deeply, bringing not just nicotine but toxic smoke products farther into the lungs,” said Gerald Ahern, PhD, an Associate Professor of Pharmacology at GUMC. “While beyond the scope of this study, it is possible that such deeper inhalation of menthol cigarettes, to the extent it occurs, increases the already substantial health harms from smoking.”
The study provides a better understanding of how menthol affects the function of the α3β4 receptor, one of the most prevalent nicotinic acetylcholine receptors expressed in the peripheral nervous system, said the researchers. These receptors are expressed in airway sensory nerves as well as other neurons.
“These receptors are also found in the brain, but we don’t know yet what effect menthol has on those receptors, or whether they contribute in any way to nicotine addiction,” said Dr. Kellar.
Childhood Maltreatment May Alter Brain Circuits Regulating Emotions and Impulses
Childhood neglect and abuse may alter the development of brain circuitry in adolescents, especially in the prefrontal cortex, a part of the brain that is important in emotion and impulse regulation, according to findings presented.
“We gained a rare window into how childhood neglect and abuse, both physical and emotional, alter the patterns of brain circuits during adolescence,” said lead author Elizabeth Cox Lippard, PhD, Postdoctoral Fellow in Psychiatry at Yale University. “These findings can help guide the development of early detection and intervention strategies for disorders such as depression and addiction.”
Adolescence is a critical period in brain development, especially for the brain circuits that help to regulate emotions and impulses. It is also a time when disorders such as depression and substance abuse often develop.
The researchers conducted clinical and behavioral assessments and brain scans of adolescents who had been neglected or abused during childhood. They assessed the adolescents twice: first when the adolescents were approximately 15 years old and second at about two and a half years later. Both times, MRI scans provided information on brain structure and connectivity.
The findings suggest that maltreatment alters the brain circuitry within the prefrontal cortex and from that region to other brain regions that are important in emotion and impulse control, potentially altering the function of the circuits that connect these regions.
Researchers also found preliminary evidence that the consequences of maltreatment differ between females and males, supporting earlier research that suggested females exposed to childhood maltreatment have a higher risk of developing depression, while males are more likely to struggle with substance abuse.
Presence of Caregiver Improves Children’s Regulation of Their Emotions
The presence of a caregiver may influence the function of children’s brain circuits that are responsible for emotional regulation. With a caregiver present, those brain circuits act in a more mature fashion that resembles a pattern observed in adolescents. In contrast, during adolescence, the presence of a caregiver has little effect on the function of these brain circuits, which have likely already matured.
“Our research indicates a critical ‘sensitive period’ in the development of circuits responsible for emotional regulation,” said Dylan Gee, a graduate student at the University of California, Los Angeles. “The children in this study were all between 4 and 10 years of age. This appears to be a time when the outside environment is particularly influential in shaping development.”
The brain’s amygdala plays a key role in emotional reactions, and the prefrontal cortex regulates the amygdala. The researchers investigated sensitive periods in the development of amygdala–prefrontal cortex circuitry. The investigators used functional MRI to scan the brains of children and adolescents while the subjects viewed either their mother or a stranger. The researchers also measured how well participants could regulate their responses to emotional stimuli while they were sitting with their mother, compared with when they were sitting with a stranger. Twenty-three children (ages 4 to 10) and 30 adolescents (ages 11 to 17) participated in the study.
The results showed that viewing their mother reduced amygdala reactivity in children and resulted in stronger communication between the amygdala and prefrontal cortex. Children also had better regulatory behavior in the presence of their mothers. In addition, children whose mothers had greater effects on their amygdala–prefrontal circuitry had lower anxiety and more secure parent–child attachment. In contrast, for adolescents, the presence of their mother had little impact on the function of these brain circuits, which have likely already matured.