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Effects of Developmental Nicotine Exposure on Frontal Cortical GABA-to-Non-GABA Neuron Ratio and Novelty-Seeking
Melissa M Martin1, Deirdre M McCarthy1, Chris Schatschneider2
1Center for Brain Repair, Department of Biomedical Sciences, Florida State University College of Medicine, Tallahassee, FL 32306-4300, USA.
Insights
Developmental nicotine exposure in mice alters brain signaling, increasing risks for behavioral issues like novelty-seeking. This research highlights the impact of prenatal smoking on offspring brain development and function.
Area of Science:
- Neuroscience
- Developmental Biology
- Public Health
Background:
- Prenatal exposure to cigarette smoke is a significant public health issue.
- Nicotine exposure during development is linked to adverse behavioral outcomes in children, including attention deficits and risk-taking.
- These behavioral changes may stem from an imbalance in brain neurotransmitter systems, specifically glutamate and GABA signaling in the frontal cortex.
Purpose of the Study:
- To investigate the effects of developmental nicotine exposure on GABAergic neuron populations in the mouse frontal cortex.
- To determine if nicotine exposure alters the ratio of GABA to non-GABA neurons in specific cortical regions.
- To assess the impact of developmental nicotine exposure on behavioral phenotypes related to novelty-seeking and risk-taking.
Main Methods:
- Utilized a GAD67-GFP knock-in mouse model for visualizing GABA neurons.
- Administered nicotine (100 or 200 μg/mL) to female mice in drinking water from pre-breeding through postpartum.
- Examined offspring at 60 days of age, analyzing prefrontal and medial prefrontal cortices for neuron ratios and assessing behavior using an approach-avoidance paradigm.
Main Results:
- Nicotine exposure resulted in dose-dependent reductions in the GABA to non-GABA neuron ratio in the prefrontal cortex.
- No significant changes were observed in cortical thickness or the laminar distribution of GABA/non-GABA neurons.
- Offspring exhibited increased exploratory behavior and a heightened "approach" response in the approach-avoidance test.
Conclusions:
- Developmental nicotine exposure shifts the excitation-inhibition balance in the frontal cortex towards excitation.
- These neurobiological changes are associated with behavioral alterations consistent with increased novelty-seeking behavior.
- The findings underscore the detrimental effects of prenatal nicotine exposure on offspring neurodevelopment and behavior.
Abstract:
Cigarette smoking during pregnancy is a major public health concern, resulting in detrimental health effects in the mother and her offspring. The adverse behavioral consequences for children include increased risk for attention deficit hyperactivity disorder, working memory deficits, epilepsy, novelty-seeking, and risk-taking behaviors. Some of these behavioral conditions are consistent with an imbalance in frontal cortical excitatory (glutamate) and inhibitory (GABA) neurotransmitter signaling. We used a GAD67-GFP knock-in mouse model to examine if developmental nicotine exposure alters frontal cortical GABA neuron numbers, GABA-to-non-GABA neuron ratio and behavioral phenotypes. Female mice were exposed to nicotine (100 or 200 μg/mL) in drinking water beginning 3 weeks prior to breeding and until 3 weeks postpartum. Male and female offspring were examined beginning at 60 days of age. The nicotine exposure produced dose-dependent decreases in GABA-to-non-GABA neuron ratios in the prefrontal and medial prefrontal cortices without perturbing the intrinsic differences in cortical thickness and laminar distribution of GABA or non-GABA neurons between these regions. A significant increase in exploratory behavior and a shift toward "approach" in the approach-avoidance paradigm were also observed. Thus, developmental nicotine exposure shifts the cortical excitation-inhibition balance toward excitation and produces behavioral changes consistent with novelty-seeking behavior.
