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Chrna5 genotype determines the long-lasting effects of developmental in vivo nicotine exposure on prefrontal attention circuitry.

ABSTRACT: Maternal smoking during pregnancy repeatedly exposes the developing fetus to nicotine and is linked with attention deficits in offspring. Corticothalamic neurons within layer VI of the medial prefrontal cortex are potential targets in the disruption of attention circuitry by nicotine, a process termed teratogenesis. These prefrontal layer VI neurons would be likely targets because they are developmentally excited and morphologically sculpted by a population of nicotinic acetylcholine receptors (nAChRs) that are sensitive to activation and/or desensitization by nicotine. The maturational effects of these ?4?2* nAChRs and their susceptibility to desensitization are both profoundly altered by the incorporation of an ?5 subunit, encoded by the chrna5 gene. Here, we investigate nicotine teratogenesis in layer VI neurons of wildtype and ?5(-/-) mice. In vivo chronic nicotine exposure during development significantly modified apical dendrite morphology and nAChR currents, compared with vehicle control. The direction of the changes was dependent on chrna5 genotype. Surprisingly, neurons from wildtype mice treated with in vivo nicotine resembled those from ?5(-/-) mice treated with vehicle, maintaining into adulthood a morphological phenotype characteristic of immature mice together with reduced nAChR currents. In ?5(-/-) mice, however, developmental in vivo nicotine tended to normalize both adult morphology and nAChR currents. These findings suggest that chrna5 genotype can determine the effect of developmental in vivo nicotine on the prefrontal cortex. In wildtype mice, the lasting alterations to the morphology and nAChR activation of prefrontal layer VI neurons are teratogenic changes consistent with the attention deficits observed following developmental nicotine exposure.

SUBMITTER: Bailey CD

PROVIDER: S-EPMC4633297 | biostudies-literature | 2014 Feb

REPOSITORIES: biostudies-literature

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Chrna5 genotype determines the long-lasting effects of developmental in vivo nicotine exposure on prefrontal attention circuitry.

Bailey Craig D C CD Tian Michael K MK Kang Lily L O'Reilly Ryan R Lambe Evelyn K EK

Neuropharmacology 20130918

Maternal smoking during pregnancy repeatedly exposes the developing fetus to nicotine and is linked with attention deficits in offspring. Corticothalamic neurons within layer VI of the medial prefrontal cortex are potential targets in the disruption of attention circuitry by nicotine, a process termed teratogenesis. These prefrontal layer VI neurons would be likely targets because they are developmentally excited and morphologically sculpted by a population of nicotinic acetylcholine receptors ( ...[more]

PMID: 24055499

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Project description:Introduction. Environmental exposure of the developing offspring to cigarette smoke or nicotine is an important predisposing factor for many chronic respiratory conditions, such as asthma, emphysema, pulmonary fibrosis, and so forth, in the exposed offspring. Studies showed that electroacupuncture (EA) applied to maternal "Zusanli" (ST36) acupoints during pregnancy and lactation protects against perinatal nicotine exposure- (PNE-) induced lung damage. However, the most effective time period, that is, prenatal vs. postnatal, to attain this effect has not been determined. Objective:To determine the most effective developmental timing of EA's protective effect against PNE-induced lung phenotype in the exposed offspring. Methods:Pregnant rats were given (1) saline ("S" group); (2) nicotine ("N" group); (3) nicotine?+?EA, exclusively prenatally ("Pre-EA" group); (4) nicotine?+?EA, exclusively postnatally ("Post-EA," group); and (5) nicotine?+?EA, administered both prenatally and postnatally ("Pre- and Post-EA" group). Nicotine was injected once daily (1?mg/kg, 100??l) and EA was administered to bilateral ST36 acupoints once daily during the specified time-periods. At the end of the experimental periods, key hypothalamic pituitary adrenal (HPA) axis markers in pups and dams, and lung function, morphometry, and the central molecular markers of lung development in the offspring were determined. Results:After nicotine exposure, alveolar mean linear intercept (MLI) increased, but mean alveolar number (MAN) decreased and lung PPAR? level decreased, but glucocorticoid receptor (GR) and serum corticosterone (Cort) levels increased, in line with the known PNE-induced lung phenotype. In the nicotine exposed group, maternal hypothalamic corticotropin releasing hormone (CRH) level decreased, but pituitary adrenocorticotropic hormone (ACTH) and serum Cort levels increased. In the "Pre- and Post-EA" groups, PNE-induced alterations in lung morphometry, lung development markers, and HPA axis were blocked. In the "Pre-EA" group, PNE-induced changes in lung morphometry, GR, and maternal HPA axis improved; lung PPAR? level decreased, but glucocorticoid receptor (GR) and serum corticosterone (Cort) levels increased, in line with the known PNE-induced lung phenotype. In the nicotine exposed group, maternal hypothalamic corticotropin releasing hormone (CRH) level decreased, but pituitary adrenocorticotropic hormone (ACTH) and serum Cort levels increased. In the "Pre- and Post-EA" groups, PNE-induced alterations in lung morphometry, lung development markers, and HPA axis were blocked. In the "Pre-EA" group, PNE-induced changes in lung morphometry, GR, and maternal HPA axis improved; lung PPAR. Conclusions:Maternal EA applied to ST36 acupoints during both pre- and postnatal periods preserves offspring lung structure and function despite perinatal exposure to nicotine. EA applied during the "prenatal period" affords only limited benefits, whereas EA applied during the "postnatal period" is ineffective, suggesting that the EA's effects in modulating PNE-induced lung phenotype are limited to specific time-periods during lung development.

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Chrna5 genotype determines the long-lasting effects of developmental in vivo nicotine exposure on prefrontal attention circuitry.

Publications

Chrna5 genotype determines the long-lasting effects of developmental in vivo nicotine exposure on prefrontal attention circuitry.

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