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Wells AC, Mojica C, Lotfipour S. Hypersensitivity of the nicotinic acetylcholine receptor subunit (CHRNA2 L9'S/L9'S) in female adolescent mice produces deficits in nicotine-induced facilitation of hippocampal-dependent learning and memory. Neurobiol Learn Mem 2024; 213:107959. [PMID: 38964600 DOI: 10.1016/j.nlm.2024.107959] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2024] [Revised: 06/24/2024] [Accepted: 07/01/2024] [Indexed: 07/06/2024]
Abstract
Adolescence is characterized by a critical period of maturation and growth, during which regions of the brain are vulnerable to long-lasting cognitive disturbances. Adolescent exposure to nicotine can lead to deleterious neurological and psychological outcomes. Moreover, the nicotinic acetylcholine receptor (nAChR) has been shown to play a functionally distinct role in the development of the adolescent brain. CHRNA2 encodes for the α2 subunit of nicotinic acetylcholine receptors associated with CA1 oriens lacunosum moleculare GABAergic interneurons and is associated with learning and memory. Previously, we found that adolescent male hypersensitive CHRNA2L9'S/L9' mice had impairments in learning and memory during a pre-exposure-dependent contextual fear conditioning task that could be rescued by low-dose nicotine exposure. In this study, we assessed learning and memory in female adolescent hypersensitive CHRNA2L9'S/L9' mice exposed to saline or a subthreshold dose of nicotine using a hippocampus-dependent task of pre-exposure-dependent contextual fear conditioning. We found that nicotine-treated wild-type female mice had significantly greater improvements in learning and memory than both saline-treated wild-type mice and nicotine-treated CHRNA2L9'S/L9' female mice. Thus, hyperexcitability of CHRNA2 in female adolescent mice ablated the nicotine-mediated potentiation of learning and memory seen in wild-types. Our results indicate that nicotine exposure during adolescence mediates sexually dimorphic patterns of learning and memory, with wild-type female adolescents being more susceptible to the effects of sub-threshold nicotine exposure. To understand the mechanism underlying sexually dimorphic behavior between hyperexcitable CHRNA2 mice, it is critical that further research be conducted.
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Affiliation(s)
- Alicia C Wells
- School of Medicine, University of California, Irvine, CA 92697, USA.
| | - Celina Mojica
- Graduate Division, University of California, Irvine, CA 92697, USA
| | - Shahrdad Lotfipour
- School of Medicine, University of California, Irvine, CA 92697, USA; Department of Emergency Medicine, Pharmaceutical Sciences, Pathology and Laboratory Medicine, University of California, Irvine, CA 92697, USA
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2
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Joglekar R, Cauley M, Lipsich T, Corcoran DL, Patisaul HB, Levin ED, Meyer JN, McCarthy MM, Murphy SK. Developmental nicotine exposure and masculinization of the rat preoptic area. Neurotoxicology 2022; 89:41-54. [PMID: 35026373 PMCID: PMC8917982 DOI: 10.1016/j.neuro.2022.01.005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2021] [Revised: 12/22/2021] [Accepted: 01/06/2022] [Indexed: 11/24/2022]
Abstract
Nicotine is a neuroteratogenic component of tobacco smoke, e-cigarettes, and other products and can exert sex-specific effects in the developing brain, likely mediated through sex hormones. Estradiol modulates expression of nicotinic acetylcholine receptors in rats, and plays critical roles in neurodevelopmental processes, including sexual differentiation of the brain. Here, we examined the effects of developmental nicotine exposure on the sexual differentiation of the preoptic area (POA), a brain region that normally displays robust structural sexual dimorphisms and controls adult mating behavior in rodents. Using a rat model of gestational exposure, developing pups were exposed to nicotine (2 mg/kg/day) via maternal osmotic minipump (subcutaneously, sc) throughout the critical window for brain sexual differentiation. At postnatal day (PND) 4, a subset of offspring was analyzed for epigenetic effects in the POA. At PND40, all offspring were gonadectomized, implanted with a testosterone-releasing capsule (sc), and assessed for male sexual behavior at PND60. Following sexual behavior assessment, the area of the sexually dimorphic nucleus of the POA (SDN-POA) was measured using immunofluorescent staining techniques. In adults, normal sex differences in male sexual behavior and in the SDN-POA area were eliminated in nicotine-treated animals. Using novel analytical approaches to evaluate overall masculinization of the adult POA, we identified significant masculinization of the nicotine-treated female POA. In neonates (PND4), nicotine exposure induced trending alterations in methylation-dependent masculinizing gene expression and DNA methylation levels at sexually-dimorphic differentially methylated regions, suggesting that developmental nicotine exposure is capable of triggering masculinization of the rat POA via epigenetic mechanisms.
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Affiliation(s)
- Rashmi Joglekar
- Duke University Nicholas School of the Environment, Durham, NC 27708 USA
| | - Marty Cauley
- Duke University Medical Center, Department of Psychiatry and Behavioral Sciences, Durham, NC 27708 USA
| | - Taylor Lipsich
- Duke University Medical Center, Department of Obstetrics & Gynecology, Durham, NC 27708 USA
| | - David L. Corcoran
- Duke Center for Genomic and Computational Biology, Durham, NC 27708 USA
| | - Heather B. Patisaul
- North Carolina State University, Department of Biological Sciences, Raleigh, NC 27695 USA
| | - Edward D. Levin
- Duke University Medical Center, Department of Psychiatry and Behavioral Sciences, Durham, NC 27708 USA
| | - Joel N. Meyer
- Duke University Nicholas School of the Environment, Durham, NC 27708 USA
| | - Margaret M. McCarthy
- University of Maryland School of Medicine, Department of Pharmacology, Baltimore, MD 21201 USA
| | - Susan K. Murphy
- Duke University Medical Center, Department of Obstetrics & Gynecology, Durham, NC 27708 USA
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3
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Shahraki S, Esmaeilpour K, Shabani M, Sepehri G, Rajizadeh MA, Maneshian M, Joushi S, Sheibani V. Choline chloride modulates learning, memory, and synaptic plasticity impairments in maternally separated adolescent male rats. Int J Dev Neurosci 2021; 82:19-38. [PMID: 34727391 DOI: 10.1002/jdn.10155] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2021] [Revised: 10/19/2021] [Accepted: 10/21/2021] [Indexed: 11/06/2022] Open
Abstract
Maternal separation (MS) is a model to induce permanent alternations in the central nervous system (CNS) and is associated with increased levels of anxiety and cognitive deficiencies. Since Methyl donor choline (Ch) has been shown to play a significant role in learning and memory and enhances synaptic plasticity, the authors hypothesized that Ch may attenuate MS-induced impairments in synaptic plasticity and cognitive performance. Rat pups underwent a MS protocol for 180 min/day from postnatal day (PND) 1 to 21. Ch was administered subcutaneously (100 mg/kg, 21 days) to the Choline chloride and MS + Choline chloride groups from PND 29 to 49. Anxiety-like behavior, recognition memory, spatial and passive avoidance learning and memory were measured in the adolescent rats. In addition, evoked field excitatory postsynaptic potentials (fEPSP) were recorded from the CA1 region of the hippocampus. MS induced higher anxiety-like behavior in the animals. It also impaired learning and memory. However, MS had no effect on locomotor activity. Subcutaneous administration of Ch attenuated MS-induced cognitive deficits and enhanced the learning and memory of MS rats. Ch also decreased anxiety-like behavior in the open field test. The present results showed that long-term potentiation (LTP) was induced in all groups except MS and MS + saline animals. However, Ch injection induced LTP and had maintenance in MS + choline chloride, but it was not statistically significant compared with the MS group. In summary, the present findings indicate that MS can interfere with normal animal's cognition and subcutaneous of Ch may be considered an appropriate therapeutic strategy for promoting cognitive dysfunctions in MS animals.
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Affiliation(s)
- Sarieh Shahraki
- Department of Physiology, Faculty of Medicine, Kerman University of Medical Sciences, Kerman, Iran.,Department of Physiology & pharmacology, school of medicine, Zabol University of Medical Sciences, Zabol, Iran
| | - Khadijeh Esmaeilpour
- Neuroscience Research Center, Institute of Neuropharmacology, Kerman University of Medical Sciences, Kerman, Iran.,Department of Physics and Astronomy, University of Waterloo, Waterloo, Ontario, Canada
| | - Mohammad Shabani
- Neuroscience Research Center, Institute of Neuropharmacology, Kerman University of Medical Sciences, Kerman, Iran
| | - Gholamreza Sepehri
- Neuroscience Research Center, Institute of Neuropharmacology, Kerman University of Medical Sciences, Kerman, Iran
| | - Mohammad Amin Rajizadeh
- Neuroscience Research Center, Institute of Neuropharmacology, Kerman University of Medical Sciences, Kerman, Iran
| | - Marzieh Maneshian
- Neuroscience Research Center, Institute of Neuropharmacology, Kerman University of Medical Sciences, Kerman, Iran
| | - Sara Joushi
- Neuroscience Research Center, Institute of Neuropharmacology, Kerman University of Medical Sciences, Kerman, Iran
| | - Vahid Sheibani
- Department of Physiology, Faculty of Medicine, Kerman University of Medical Sciences, Kerman, Iran.,Neuroscience Research Center, Institute of Neuropharmacology, Kerman University of Medical Sciences, Kerman, Iran
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4
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Nakauchi S, Su H, Trang I, Sumikawa K. Long-term effects of early postnatal nicotine exposure on cholinergic function in the mouse hippocampal CA1 region. Neurobiol Learn Mem 2021; 181:107445. [PMID: 33895349 PMCID: PMC9836228 DOI: 10.1016/j.nlm.2021.107445] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2020] [Revised: 03/30/2021] [Accepted: 04/20/2021] [Indexed: 01/14/2023]
Abstract
In rodent models of smoking during pregnancy, early postnatal nicotine exposure results in impaired hippocampus-dependent memory, but the underlying mechanism remains elusive. Given that hippocampal cholinergic systems modulate memory and rapid development of hippocampal cholinergic systems occurs during nicotine exposure, here we investigated its impacts on cholinergic function. Both nicotinic and muscarinic activation produce transient or long-lasting depression of excitatory synaptic transmission in the hippocampal CA1 region. We found that postnatal nicotine exposure impairs both the induction and nicotinic modulation of NMDAR-dependent long-term depression (LTD). Activation of muscarinic receptors decreases excitatory synaptic transmission and CA1 network activity in both wild-type and α2 knockout mice. These muscarinic effects are still observed in nicotine-exposed mice. M1 muscarinic receptor activity is required for mGluR-dependent LTD. Early postnatal nicotine exposure has no effect on mGluR-dependent LTD induction, suggesting that it has no effect on the function of m1 muscarinic receptors involved in this form of LTD. Our results demonstrate that early postnatal nicotine exposure has more pronounced effects on nicotinic function than muscarinic function in the hippocampal CA1 region. Thus, impaired hippocampus-dependent memory may arise from the developmental disruption of nicotinic cholinergic systems in the hippocampal CA1 region.
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MESH Headings
- Animals
- Animals, Newborn
- CA1 Region, Hippocampal/drug effects
- CA1 Region, Hippocampal/growth & development
- CA1 Region, Hippocampal/metabolism
- Cigarette Smoking
- Excitatory Postsynaptic Potentials/drug effects
- Excitatory Postsynaptic Potentials/physiology
- Female
- Lactation
- Long-Term Synaptic Depression/drug effects
- Long-Term Synaptic Depression/physiology
- Male
- Maternal Exposure
- Memory/drug effects
- Memory/physiology
- Mice
- Mice, Knockout
- Nicotine/pharmacology
- Nicotinic Agonists/pharmacology
- Receptor, Muscarinic M1/drug effects
- Receptor, Muscarinic M1/metabolism
- Receptors, Metabotropic Glutamate/drug effects
- Receptors, Metabotropic Glutamate/metabolism
- Receptors, Muscarinic/drug effects
- Receptors, Muscarinic/metabolism
- Receptors, N-Methyl-D-Aspartate/drug effects
- Receptors, N-Methyl-D-Aspartate/metabolism
- Receptors, Nicotinic/drug effects
- Receptors, Nicotinic/metabolism
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Affiliation(s)
- Sakura Nakauchi
- Department of Neurobiology and Behavior, University of California, Irvine, Irvine, CA 92697-4550, USA
| | - Hailing Su
- Department of Neurobiology and Behavior, University of California, Irvine, Irvine, CA 92697-4550, USA
| | - Ivan Trang
- Department of Neurobiology and Behavior, University of California, Irvine, Irvine, CA 92697-4550, USA
| | - Katumi Sumikawa
- Department of Neurobiology and Behavior, University of California, Irvine, Irvine, CA 92697-4550, USA.
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Molecular, physiological and behavioral characterization of the heterozygous Df[h15q13]/+ mouse model associated with the human 15q13.3 microdeletion syndrome. Brain Res 2020; 1746:147024. [PMID: 32712126 DOI: 10.1016/j.brainres.2020.147024] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2020] [Revised: 07/13/2020] [Accepted: 07/18/2020] [Indexed: 12/29/2022]
Abstract
The human 15q13.3 microdeletion syndrome (DS) is caused by a heterozygous microdeletion (MD) affecting six genes: FAN1; MTMR10; TRPM1; KLF13; OTUD7A; and CHRNA7. Carriers are at risk for intellectual disability, epilepsy, autism spectrum disorder, and schizophrenia. Here we used the Df[h15q13]/+ mouse model with an orthologous deletion to further characterize molecular, neurophysiological, and behavioral parameters that are relevant to the 15q13.3 DS. First, we verified the expression and distribution of the α7 nicotinic acetylcholine receptor (nAChR), a gene product of the CHRNA7, in cortical and subcortical areas. Results revealed similar mRNA distribution pattern in wildtype (WT) and heterozygous (Het) mice, with about half the number of α7 nAChR binding sites in mutants. Hippocampal recordings showed similar input/output responses of field excitatory post-synaptic potentials and theta-burst induced long-term potentiation in WT and Het mice. Het males exhibited impaired spatial learning acquisition in the Barnes Maze. Indicative of increased seizure susceptibility, Het mice developed secondary seizures after 6-Hz corneal stimulation, and had significantly increased sensitivity to the chemoconvulsant pentylenetetrazol resulting in increased spiking in hippocampal EEG recordings. Basal mRNA expression of brain derived neurotrophic factor and activity regulated immediate early genes (c-fos, Arc, Erg-1 and Npas4) during adolescence, a critical period of brain maturation, was unaffected by genotype. Thus, the MD did not show gross neuroanatomical, molecular, and neurophysiological abnormalities despite deficits in spatial learning and increased susceptibility to seizures. Altogether, our results verify the phenotypic profile of the heterozygous Df[h15q13]/+ mouse model and underscore its translational relevance for human 15q13.3 DS.
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6
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Raghunathan R, Liu CH, Ambekar YS, Singh M, Miranda RC, Larin KV. Optical coherence tomography angiography to evaluate murine fetal brain vasculature changes caused by prenatal exposure to nicotine. BIOMEDICAL OPTICS EXPRESS 2020; 11:3618-3632. [PMID: 33014555 PMCID: PMC7510910 DOI: 10.1364/boe.394905] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/10/2020] [Revised: 06/01/2020] [Accepted: 06/02/2020] [Indexed: 05/03/2023]
Abstract
Maternal smoking causes several defects ranging from intrauterine growth restriction to sudden infant death syndrome and spontaneous abortion. While several studies have documented the effects of prenatal nicotine exposure in development and behavior, acute vasculature changes in the fetal brain due to prenatal nicotine exposure have not been evaluated yet. This study uses correlation mapping optical coherence angiography to evaluate changes in fetal brain vasculature flow caused by maternal exposure to nicotine during the second trimester-equivalent of gestation in a mouse model. The effects of two different doses of nicotine were evaluated. Results showed a decrease in the vasculature for both doses of nicotine, which was not seen in the case of the sham group.
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Affiliation(s)
- Raksha Raghunathan
- Department of Biomedical Engineering, University of Houston, 3517 Cullen Blvd., Houston, TX 77204, USA
| | - Chih-Hao Liu
- Department of Biomedical Engineering, University of Houston, 3517 Cullen Blvd., Houston, TX 77204, USA
| | - Yogeshwari S Ambekar
- Department of Biomedical Engineering, University of Houston, 3517 Cullen Blvd., Houston, TX 77204, USA
| | - Manmohan Singh
- Department of Biomedical Engineering, University of Houston, 3517 Cullen Blvd., Houston, TX 77204, USA
| | - Rajesh C Miranda
- Department of Neuroscience and Experimental Therapeutics, TAMHSC College of Medicine, 8441 Riverside Parkway, Bryan, TX 77807, USA
| | - Kirill V Larin
- Department of Biomedical Engineering, University of Houston, 3517 Cullen Blvd., Houston, TX 77204, USA
- Molecular Physiology and Biophysics, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77206, USA
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7
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Polli FS, Kohlmeier KA. Prenatal nicotine exposure alters postsynaptic AMPA receptors and glutamate neurotransmission within the laterodorsal tegmentum (LDT) of juvenile mice. Neuropharmacology 2018; 137:71-85. [PMID: 29751228 DOI: 10.1016/j.neuropharm.2018.04.024] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2017] [Revised: 04/20/2018] [Accepted: 04/22/2018] [Indexed: 02/06/2023]
Abstract
Despite dissemination of information regarding the harm on fetal development of smoking while pregnant, the number of pregnancies associated with nicotine exposure appears to have stagnated. Presence of nicotine during neural formulation is associated with a higher susceptibility of drug dependence, suggesting an altered development of neurons in circuits involved in saliency and motivation. The laterodorsal tegmental nucleus (LDT) plays a role in coding stimuli valence via afferents to mesolimbic nuclei. Accordingly, alterations in development of neural mechanisms in the LDT could be involved in vulnerability to drug dependency. Therefore, we examined the effect of prenatal nicotine exposure (PNE) on glutamatergic functioning of LDT neurons in mouse brain slices using whole-cell, patch clamp concurrent with fluorescence-based calcium imaging. PNE was associated with larger amplitudes of AMPA-induced currents, and greater AMPA-mediated rises in intracellular calcium. AMPA/NMDA ratios and the AMPA-current rectification index were lower and higher, respectively, consistent with changes in the functionality of AMPA receptors in the PNE, which was substantiated by a greater inhibition of evoked and spontaneous glutamatergic synaptic events by a selective inhibitor of GluA2-lacking AMPA receptors. Paired pulse ratios showed a decreased probability of glutamate release from presynaptic inputs, and fluorescent imaging indicated a decreased action potential-dependent calcium increase associated with PNE. When taken together, our data suggest that PNE alters LDT glutamatergic functioning, which could alter output to mesolimbic targets. Such an alteration could play a role in altered coding of relevancy of drug stimuli that could enhance risk for development of drug dependency.
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Affiliation(s)
- Filip S Polli
- Department of Drug Design and Pharmacology, Faculty of Health Sciences, University of Copenhagen, Copenhagen 2100, Denmark
| | - Kristi A Kohlmeier
- Department of Drug Design and Pharmacology, Faculty of Health Sciences, University of Copenhagen, Copenhagen 2100, Denmark.
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8
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Mojica C, Bai Y, Lotfipour S. Maternal nicotine exposure effects on adolescent learning and memory are abolished in alpha(α)2* nicotinic acetylcholine receptor-null mutant mice. Neuropharmacology 2018; 135:529-535. [PMID: 29677582 DOI: 10.1016/j.neuropharm.2018.04.010] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2018] [Revised: 03/13/2018] [Accepted: 04/09/2018] [Indexed: 11/17/2022]
Abstract
The objective of the current study is to test the hypothesis that the deletion of alpha(α)2* nicotinic acetylcholine receptors (nAChRs) (encoded by the Chrna2 gene) ablate maternal nicotine-induced learning and memory deficits in adolescent mice. We use a pre-exposure-dependent contextual fear conditioning behavioral paradigm that is highly hippocampus-dependent. Adolescent wild type and α2-null mutant offspring are exposed to vehicle or maternal nicotine exposure (200 μg/ml, expressed as base) in the drinking water throughout pregnancy until weaning. Adolescent male offspring mice are tested for alterations in growth and development characteristics as well as modifications in locomotion, anxiety, shock-reactivity and learning and memory. As expected, maternal nicotine exposure has no effects on pup number, weight gain and only modestly reduces fluid intake by 19%. Behaviorally, maternal nicotine exposure impedes extinction learning in adolescent wild type mice, a consequence that is abolished in α2-null mutant mice. The effects on learning and memory are not confounded by alternations in stereotypy, locomotion, anxiety or sensory shock reactivity. Overall, the findings highlight that the deletion of α2* nAChRs eliminate the effects of maternal nicotine exposure on learning and memory in adolescent mice.
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Affiliation(s)
- Celina Mojica
- University of California, Los Angeles, Department of Psychiatry, United States; University of California, Irvine, Graduate Division, United States
| | - Yu Bai
- University of California, Irvine, School of Biological Sciences, United States
| | - Shahrdad Lotfipour
- University of California, Los Angeles, Department of Psychiatry, United States; University of California, Irvine, Department of Emergency Medicine and Pharmacology, United States.
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9
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Zeid D, Kutlu MG, Gould TJ. Differential Effects of Nicotine Exposure on the Hippocampus Across Lifespan. Curr Neuropharmacol 2018; 16:388-402. [PMID: 28714396 PMCID: PMC6018186 DOI: 10.2174/1570159x15666170714092436] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2017] [Revised: 06/09/2017] [Accepted: 07/12/2017] [Indexed: 01/01/2023] Open
Abstract
BACKGROUND Nicotine exposure affects the hippocampus through activation of hippocampal nicotinic acetylcholine receptors (nAChRs), which are present throughout excitatory and inhibitory hippocampal circuitry. The role of cholinergic functioning in the hippocampus varies across developmental stages so that nicotine exposure differentially affects this region depending upon timing of exposure, producing developmentally distinct changes in structure, function, and behavior. METHODS We synthesize findings across literature in this area to comprehensively review current understanding of the unique effects of nicotine exposure on the hippocampus throughout the lifespan with a focus on hippocampal morphology, cholinergic functioning, and hippocampusdependent learning and memory. CONCLUSIONS Chronic and acute nicotine exposure differentially affect hippocampus structure, functioning, and related learning and memory in the perinatal period, adolescence, and aging. Age-related differences in sensitivity to nicotine exposure should be considered in the research of nicotine addiction and the development of nicotine addiction treatments.
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Affiliation(s)
- Dana Zeid
- Department of Biobehavioral Health, Penn State University, University Park, PA, USA
| | - Munir Gunes Kutlu
- Department of Biobehavioral Health, Penn State University, University Park, PA, USA
| | - Thomas J. Gould
- Department of Biobehavioral Health, Penn State University, University Park, PA, USA
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10
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Cross SJ, Linker KE, Leslie FM. Sex-dependent effects of nicotine on the developing brain. J Neurosci Res 2017; 95:422-436. [PMID: 27870426 DOI: 10.1002/jnr.23878] [Citation(s) in RCA: 62] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2016] [Revised: 07/08/2016] [Accepted: 07/14/2016] [Indexed: 02/06/2023]
Abstract
The use of tobacco products represents a major public health concern, especially among women. Epidemiological data have consistently demonstrated that women have less success quitting tobacco use and a higher risk for developing tobacco-related diseases. The deleterious effects of nicotine are not restricted to adulthood, as nicotinic acetylcholine receptors regulate critical aspects of neural development. However, the exact mechanisms underlying the particular sensitivity of women to develop tobacco dependence have not been well elucidated. In this mini-review, we show that gonadal hormone-mediated sexual differentiation of the brain may be an important determinant of sex differences in the effects of nicotine. We highlight direct interactions between sex steroid hormones and ligand-gated ion channels critical for brain maturation, and discuss the extended and profound sexual differentiation of the brain. We emphasize that nicotine exposure during the perinatal and adolescent periods interferes with normal sexual differentiation and can induce long-lasting, sex-dependent alterations in neuronal structure, cognitive and executive function, learning and memory, and reward processing. We stress important age and sex differences in nicotine's effects and emphasize the importance of including these factors in preclinical research that models tobacco dependence. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Sarah J Cross
- Department of Anatomy and Neurobiology, School of Medicine, University of California, Irvine, California
| | - Kay E Linker
- Department of Anatomy and Neurobiology, School of Medicine, University of California, Irvine, California
| | - Frances M Leslie
- Department of Anatomy and Neurobiology, School of Medicine, University of California, Irvine, California.,Department of Pharmacology, School of Medicine, University of California, Irvine, California
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11
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Kleeman E, Nakauchi S, Su H, Dang R, Wood MA, Sumikawa K. Impaired function of α2-containing nicotinic acetylcholine receptors on oriens-lacunosum moleculare cells causes hippocampus-dependent memory impairments. Neurobiol Learn Mem 2016; 136:13-20. [PMID: 27660076 DOI: 10.1016/j.nlm.2016.09.010] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2016] [Revised: 09/14/2016] [Accepted: 09/18/2016] [Indexed: 01/22/2023]
Abstract
Children of mothers who smoked during pregnancy are at significantly greater risk for cognitive impairments including memory deficits, but the mechanisms underlying this effect remain to be understood. In rodent models of smoking during pregnancy, early postnatal nicotine exposure results in impaired long-term hippocampus-dependent memory, functional loss of α2-containing nicotinic acetylcholine receptors (α2∗ nAChRs) in oriens-lacunosum moleculare (OLM) cells, increased CA1 network excitation, and unexpected facilitation of long-term potentiation (LTP) at Schaffer collateral-CA1 synapses. Here we demonstrate that α2 knockout mice show the same pattern of memory impairment as previously observed in wild-type mice exposed to early postnatal nicotine. However, α2 knockout mice and α2 knockout mice exposed to early postnatal nicotine did not share all of the anomalies in hippocampal function observed in wild-type mice treated with nicotine during development. Unlike nicotine-treated wild-type mice, α2 knockout mice and nicotine-exposed α2 knockout mice did not demonstrate increased CA1 network excitation following Schaffer collateral stimulation and facilitated LTP, indicating that the effects are likely adaptive changes caused by activation of α2∗ nAChRs during nicotine exposure and are unlikely related to the associated memory impairment. Thus, the functional loss of α2∗ nAChRs in OLM cells likely plays a critical role in mediating this developmental-nicotine-induced hippocampal memory deficit.
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Affiliation(s)
- Elise Kleeman
- Department of Neurobiology and Behavior, University of California Irvine, Irvine, CA 92697-4550, USA
| | - Sakura Nakauchi
- Department of Neurobiology and Behavior, University of California Irvine, Irvine, CA 92697-4550, USA
| | - Hailing Su
- Department of Neurobiology and Behavior, University of California Irvine, Irvine, CA 92697-4550, USA
| | - Richard Dang
- Department of Neurobiology and Behavior, University of California Irvine, Irvine, CA 92697-4550, USA
| | - Marcelo A Wood
- Department of Neurobiology and Behavior, University of California Irvine, Irvine, CA 92697-4550, USA
| | - Katumi Sumikawa
- Department of Neurobiology and Behavior, University of California Irvine, Irvine, CA 92697-4550, USA.
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12
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Chung BYT, Bignell W, Jacklin DL, Winters BD, Bailey CDC. Postsynaptic nicotinic acetylcholine receptors facilitate excitation of developing CA1 pyramidal neurons. J Neurophysiol 2016; 116:2043-2055. [PMID: 27489367 DOI: 10.1152/jn.00370.2016] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2016] [Accepted: 08/01/2016] [Indexed: 11/22/2022] Open
Abstract
The hippocampus plays a key role in learning and memory. The normal development and mature function of hippocampal networks supporting these cognitive functions depends on afferent cholinergic neurotransmission mediated by nicotinic acetylcholine receptors. Whereas it is well-established that nicotinic receptors are present on GABAergic interneurons and on glutamatergic presynaptic terminals within the hippocampus, the ability of these receptors to mediate postsynaptic signaling in pyramidal neurons is not well understood. We use whole cell electrophysiology to show that heteromeric nicotinic receptors mediate direct inward currents, depolarization from rest and enhanced excitability in hippocampus CA1 pyramidal neurons of male mice. Measurements made throughout postnatal development provide a thorough developmental profile for these heteromeric nicotinic responses, which are greatest during the first 2 wk of postnatal life and decrease to low adult levels shortly thereafter. Pharmacological experiments show that responses are blocked by a competitive antagonist of α4β2* nicotinic receptors and augmented by a positive allosteric modulator of α5 subunit-containing receptors, which is consistent with expression studies suggesting the presence of α4β2 and α4β2α5 nicotinic receptors within the developing CA1 pyramidal cell layer. These findings demonstrate that functional heteromeric nicotinic receptors are present on CA1 pyramidal neurons during a period of major hippocampal development, placing these receptors in a prime position to play an important role in the establishment of hippocampal cognitive networks.
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Affiliation(s)
- Beryl Y T Chung
- Department of Biomedical Sciences, Ontario Veterinary College, University of Guelph, Guelph, Ontario, Canada; and
| | - Warren Bignell
- Department of Biomedical Sciences, Ontario Veterinary College, University of Guelph, Guelph, Ontario, Canada; and
| | - Derek L Jacklin
- Department of Psychology, College of Social and Applied Human Sciences, University of Guelph, Guelph, Ontario, Canada
| | - Boyer D Winters
- Department of Psychology, College of Social and Applied Human Sciences, University of Guelph, Guelph, Ontario, Canada
| | - Craig D C Bailey
- Department of Biomedical Sciences, Ontario Veterinary College, University of Guelph, Guelph, Ontario, Canada; and
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13
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Nakauchi S, Malvaez M, Su H, Kleeman E, Dang R, Wood MA, Sumikawa K. Early postnatal nicotine exposure causes hippocampus-dependent memory impairments in adolescent mice: Association with altered nicotinic cholinergic modulation of LTP, but not impaired LTP. Neurobiol Learn Mem 2014; 118:178-88. [PMID: 25545599 DOI: 10.1016/j.nlm.2014.12.007] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2014] [Revised: 12/15/2014] [Accepted: 12/16/2014] [Indexed: 12/17/2022]
Abstract
Fetal nicotine exposure from smoking during pregnancy causes long-lasting cognitive impairments in offspring, yet little is known about the mechanisms that underlie this effect. Here we demonstrate that early postnatal exposure of mouse pups to nicotine via maternal milk impairs long-term, but not short-term, hippocampus-dependent memory during adolescence. At the Schaffer collateral (SC) pathway, the most widely studied synapses for a cellular correlate of hippocampus-dependent memory, the induction of N-methyl-D-aspartate receptor-dependent transient long-term potentiation (LTP) and protein synthesis-dependent long-lasting LTP are not diminished by nicotine exposure, but rather unexpectedly the threshold for LTP induction becomes lower after nicotine treatment. Using voltage sensitive dye to visualize hippocampal activity, we found that early postnatal nicotine exposure also results in enhanced CA1 depolarization and hyperpolarization after SC stimulation. Furthermore, we show that postnatal nicotine exposure induces pervasive changes to the nicotinic modulation of CA1 activity: activation of nicotinic receptors no longer increases CA1 network depolarization, acute nicotine inhibits rather than facilitates the induction of LTP at the SC pathway by recruiting an additional nicotinic receptor subtype, and acute nicotine no longer blocks LTP induction at the temporoammonic pathway. These findings reflect the pervasive impact of nicotine exposure during hippocampal development, and demonstrate an association of hippocampal memory impairments with altered nicotinic cholinergic modulation of LTP, but not impaired LTP. The implication of our results is that nicotinic cholinergic-dependent plasticity is required for long-term memory formation and that postnatal nicotine exposure disrupts this form of plasticity.
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Affiliation(s)
- Sakura Nakauchi
- Department of Neurobiology and Behavior, University of California, Irvine, Irvine, CA 92697-4550, USA
| | - Melissa Malvaez
- Department of Neurobiology and Behavior, University of California, Irvine, Irvine, CA 92697-4550, USA
| | - Hailing Su
- Department of Neurobiology and Behavior, University of California, Irvine, Irvine, CA 92697-4550, USA
| | - Elise Kleeman
- Department of Neurobiology and Behavior, University of California, Irvine, Irvine, CA 92697-4550, USA
| | - Richard Dang
- Department of Neurobiology and Behavior, University of California, Irvine, Irvine, CA 92697-4550, USA
| | - Marcelo A Wood
- Department of Neurobiology and Behavior, University of California, Irvine, Irvine, CA 92697-4550, USA
| | - Katumi Sumikawa
- Department of Neurobiology and Behavior, University of California, Irvine, Irvine, CA 92697-4550, USA.
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14
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Damborsky JC, Griffith WH, Winzer-Serhan UH. Neonatal nicotine exposure increases excitatory synaptic transmission and attenuates nicotine-stimulated GABA release in the adult rat hippocampus. Neuropharmacology 2014; 88:187-98. [PMID: 24950455 DOI: 10.1016/j.neuropharm.2014.06.010] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2013] [Revised: 06/02/2014] [Accepted: 06/09/2014] [Indexed: 01/22/2023]
Abstract
Developmental exposure to nicotine has been linked to long-lasting changes in synaptic transmission which may contribute to behavioral abnormalities seen in offspring of women who smoke during pregnancy. Here, we examined the long-lasting effects of developmental nicotine exposure on glutamatergic and GABAergic neurotransmission, and on acute nicotine-induced glutamate and GABA release in the adult hippocampus, a structure important in cognitive and emotional behaviors. We utilized a chronic neonatal nicotine treatment model to administer nicotine (6 mg/kg/day) to rat pups from postnatal day (P) 1-7, a period that falls developmentally into the third human trimester. Using whole-cell voltage clamp recordings from CA1 pyramidal neurons in hippocampal slices, we measured excitatory and inhibitory postsynaptic currents in neonatally control- and nicotine-treated young adult males. Neonatal nicotine exposure significantly increased AMPA receptor-mediated spontaneous and evoked excitatory signaling, with no change in glutamate release probability in adults. Conversely, there was no increase in spontaneous GABAergic neurotransmission in nicotine-males. Chronic neonatal nicotine treatment had no effect on acute nicotine-stimulated glutamate release in adults, but acute nicotine-stimulated GABA release was significantly attenuated. Thus, neonatal nicotine exposure results in a persistent net increase in excitation and a concurrent loss of nicotinic acetylcholine receptor (nAChR)-mediated regulation of presynaptic GABA but not glutamate release, which would exacerbate excitation following endogenous or exogenous nAChR activation. Our data underscore an important role for nAChRs in hippocampal excitatory synapse development, and suggest selective long-term changes at specific presynaptic nAChRs which together could explain some of the behavioral abnormalities associated with maternal smoking.
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Affiliation(s)
- Joanne C Damborsky
- Department of Neuroscience & Experimental Therapeutics, College of Medicine, Health Science Center, Texas A&M University, USA
| | - William H Griffith
- Department of Neuroscience & Experimental Therapeutics, College of Medicine, Health Science Center, Texas A&M University, USA
| | - Ursula H Winzer-Serhan
- Department of Neuroscience & Experimental Therapeutics, College of Medicine, Health Science Center, Texas A&M University, USA.
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15
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Yetnikoff L, Reichard RA, Schwartz ZM, Parsely KP, Zahm DS. Protracted maturation of forebrain afferent connections of the ventral tegmental area in the rat. J Comp Neurol 2014; 522:1031-47. [PMID: 23983069 PMCID: PMC4217282 DOI: 10.1002/cne.23459] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2013] [Revised: 07/30/2013] [Accepted: 08/14/2013] [Indexed: 01/21/2023]
Abstract
The mesocorticolimbic dopamine system has long attracted the interest of researchers concerned with the unique gamut of behavioral and mental health vulnerabilities associated with adolescence. Accordingly, the development of the mesocorticolimbic system has been studied extensively, but almost exclusively with regard to dopaminergic output, particularly in the nucleus accumbens and medial prefrontal cortex. To the contrary, the ontogeny of inputs to the ventral tegmental area (VTA), the source of mesocorticolimbic dopamine, has been neglected. This is not a trivial oversight, as the activity of VTA neurons, which reflects their capacity to transmit information about salient events, is sensitively modulated by inputs. Here, we assessed the development of VTA afferent connections using the β subunit of cholera toxin (Ctβ) as a retrograde axonal tracer in adolescent (postnatal day 39) and early adult (8-9-week-old) rats. After intra-VTA injections of Ctβ, adolescent and early adult animals exhibited qualitatively similar distributions of retrogradely labeled neurons in the sense that VTA-projecting neurons were present at all of the same rostrocaudal levels in all of the same structures in both age groups. However, quantitation of retrogradely labeled neurons revealed that adolescent brains, compared with early adult brains, had significantly fewer VTA-projecting neurons preferentially within an interconnected network of cortical and striatopallidal forebrain structures. These findings provide a novel perspective on the development of the mesocorticolimbic dopamine system and may have important implications for age-dependent specificity in the function of this system, particularly with regard to adolescent impulsivity and mental health vulnerabilities.
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Affiliation(s)
- Leora Yetnikoff
- Department of Pharmacological and Physiological Science, St. Louis University School of Medicine, St. Louis, Missouri 63104
| | - Rhett A. Reichard
- Department of Pharmacological and Physiological Science, St. Louis University School of Medicine, St. Louis, Missouri 63104
| | - Zachary M. Schwartz
- Department of Pharmacological and Physiological Science, St. Louis University School of Medicine, St. Louis, Missouri 63104
| | - Kenneth P. Parsely
- Department of Pharmacological and Physiological Science, St. Louis University School of Medicine, St. Louis, Missouri 63104
| | - Daniel S. Zahm
- Department of Pharmacological and Physiological Science, St. Louis University School of Medicine, St. Louis, Missouri 63104
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16
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Balsevich G, Poon A, Goldowitz D, Wilking JA. The effects of pre- and post-natal nicotine exposure and genetic background on the striatum and behavioral phenotypes in the mouse. Behav Brain Res 2014; 266:7-18. [PMID: 24607511 DOI: 10.1016/j.bbr.2014.02.038] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2013] [Revised: 02/07/2014] [Accepted: 02/25/2014] [Indexed: 02/03/2023]
Abstract
Maternal tobacco use increases the risk of complications in pregnancy and also the risk of adverse fetal outcomes. Studies have established nicotine as the principal component of tobacco smoke that leads to the majority of negative reproductive outcomes associated with maternal tobacco use. It appears the neuroteratogenicity of nicotine is mediated by complex gene-environment interactions. Genetic background contributes to individual differences in nicotine-related phenotypes. The aim of the current study was to investigate the interaction between pre- and post-natal nicotine exposure and genetic background on the histology of the striatum and behavioral measures using DBA/2J (D2) and C57BL/6J (B6) inbred mice. Alterations in neuronal cell populations, striatal brain volume, and behavior - open field (OF) activity, novel object recognition (NOR), elevated plus maze (EPM), and passive avoidance (PA) - were evaluated on post-natal day (PN) 24 and PN75. Histological data showed that pre- and post-natal nicotine exposure resulted in decreased striatal volume among preadolescent B6 and reduced neuronal number within the striatum of preadolescent B6 mice. Behavioral data showed that pre- and post-natal nicotine exposure promoted hyperactivity in D2 female mice and disrupted NOR and PA memory. Specifically, NOR deficits were significant amongst adult male mice whereas PA deficits were seen across genetic background and sex. These data suggest that nicotine treatment, genetic background, developmental stage, and sex effect striatal morphology can lead to neurobehavioral alterations.
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Affiliation(s)
- Georgia Balsevich
- Department of Neuroscience, University of British Columbia, 950 W. 28th Ave, Vancouver, BC, Canada V5Z 4H4; Centre for Molecular Medicine & Therapeutics, University of British Columbia, 950 W. 28th Ave, Vancouver, BC, Canada V5Z 4H4; Child and Family Research Institute, University of British Columbia, 950 W. 28th Ave, Vancouver, BC, Canada V5Z 4H4
| | - Anna Poon
- Department of Medical Genetics, University of British Columbia, 950 W. 28th Ave, Vancouver, BC, Canada V5Z 4H4; Centre for Molecular Medicine & Therapeutics, University of British Columbia, 950 W. 28th Ave, Vancouver, BC, Canada V5Z 4H4; Child and Family Research Institute, University of British Columbia, 950 W. 28th Ave, Vancouver, BC, Canada V5Z 4H4
| | - Dan Goldowitz
- Department of Medical Genetics, University of British Columbia, 950 W. 28th Ave, Vancouver, BC, Canada V5Z 4H4; Centre for Molecular Medicine & Therapeutics, University of British Columbia, 950 W. 28th Ave, Vancouver, BC, Canada V5Z 4H4; Child and Family Research Institute, University of British Columbia, 950 W. 28th Ave, Vancouver, BC, Canada V5Z 4H4
| | - Jennifer A Wilking
- Department of Medical Genetics, University of British Columbia, 950 W. 28th Ave, Vancouver, BC, Canada V5Z 4H4; Centre for Molecular Medicine & Therapeutics, University of British Columbia, 950 W. 28th Ave, Vancouver, BC, Canada V5Z 4H4; Child and Family Research Institute, University of British Columbia, 950 W. 28th Ave, Vancouver, BC, Canada V5Z 4H4.
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17
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Dušková M, Hruškovičová H, Šimůnková K, Stárka L, Pařízek A. The effects of smoking on steroid metabolism and fetal programming. J Steroid Biochem Mol Biol 2014; 139:138-43. [PMID: 23685014 DOI: 10.1016/j.jsbmb.2013.05.003] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/30/2012] [Revised: 04/20/2013] [Accepted: 05/06/2013] [Indexed: 02/01/2023]
Abstract
Tobacco addiction is a serious psychosocial and health problem. A pregnant woman who smokes not only influences the maternal organism, but also passes health risks on to the unborn child. A fetus exposed to maternal smoking is not only directly influenced, but is also endangered by a wide range of diseases up to his or her adult years. The components of tobacco smoke play a significant role in the development of a number of diseases for a large proportion of the smoking population, as well as among those pregnant. This article summarizes findings regarding the impacts on the production of steroid hormones - first describing the smoking-related changes in steroidogenesis in women, and then focusing on the influence of maternal smoking on the fetus's developing steroidogenesis. We assume that if during prenatal development the fetus has already been exposed to the effect of endocrine disruptors at the time fetal steroidogenesis begins fetal programming, this exposure can have serious pathophysiological effects both in the pregnancy as well as later in life. An example of such effects might be a delay in the creation of kidney adrenal androgens, which could also be evident on the level of steroid neuroactive metabolites that may influence the individual's psychological state and lead to later addictions.
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Affiliation(s)
- M Dušková
- Institute of Endocrinology, Narodní 8, 116 94, Prague 1, Czech Republic; First Faculty of Medicine, Katerinska 32, 121 08, Praha 2, Czech Republic.
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18
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Cao X, Huang S, Cao J, Chen T, Zhu P, Zhu R, Su P, Ruan D. The timing of maternal separation affects morris water maze performance and long-term potentiation in male rats. Dev Psychobiol 2013; 56:1102-9. [DOI: 10.1002/dev.21130] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2012] [Accepted: 03/29/2013] [Indexed: 02/05/2023]
Affiliation(s)
- Xiujing Cao
- Department of Child and Maternal Health Care; School of Public Health, Anhui Medical University; Hefei, Anhui 230032, P.R. China
| | - Shenghai Huang
- Department of Microbiology; Anhui Medical University; Hefei, Anhui 230032, P.R. China
| | - Jiejie Cao
- Department of Child and Maternal Health Care; School of Public Health, Anhui Medical University; Hefei, Anhui 230032, P.R. China
| | - Tingting Chen
- Department of Child and Maternal Health Care; School of Public Health, Anhui Medical University; Hefei, Anhui 230032, P.R. China
| | - Ping Zhu
- Department of Child and Maternal Health Care; School of Public Health, Anhui Medical University; Hefei, Anhui 230032, P.R. China
| | - Rui Zhu
- Department of Child and Maternal Health Care; School of Public Health, Anhui Medical University; Hefei, Anhui 230032, P.R. China
| | - Puyu Su
- Department of Child and Maternal Health Care; School of Public Health, Anhui Medical University; Hefei, Anhui 230032, P.R. China
| | - Diyun Ruan
- School of Life Science; University of Science and Technology of China; Hefei, Anhui 230027, P.R. China
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19
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Damborsky JC, Winzer-Serhan UH. Effects of sex and chronic neonatal nicotine treatment on Na²⁺/K⁺/Cl⁻ co-transporter 1, K⁺/Cl⁻ co-transporter 2, brain-derived neurotrophic factor, NMDA receptor subunit 2A and NMDA receptor subunit 2B mRNA expression in the postnatal rat hippocampus. Neuroscience 2012; 225:105-17. [PMID: 22982626 DOI: 10.1016/j.neuroscience.2012.09.002] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2012] [Revised: 08/27/2012] [Accepted: 09/01/2012] [Indexed: 12/01/2022]
Abstract
Chronic exposure to nicotine during the first postnatal week in rats, a developmental period that corresponds to the third trimester of human gestation, results in sexually dimorphic long-term functional defects in the adult hippocampus. One potential cause could be the sex-specific differences in the maturation of GABA(A) receptor-mediated responses from excitatory to inhibitory, which depends on the expression of the Na(2+)/K(+)/Cl(-) co-transporter 1 (NKCC1) and the K(+)/Cl(-) co-transporter 2 (KCC2). In the rat hippocampus, this switch occurs during the first and second postnatal week in females and males, respectively, and is regulated by nicotinic receptor activation. Excitatory GABAergic signaling can increase brain-derived neurotrophic factor (BDNF) expression, which might exacerbate sex differences by impacting synaptogenesis. We hypothesized that chronic neonatal nicotine (CNN) exposure differentially regulates the expression of these co-transporters and BDNF in males and females. We use quantitative isotopic in situ hybridization to examine the expression of mRNAs for NKCC1, KCC2, BDNF, and NMDA receptor subunit 2A (NR2A) and NMDA receptor subunit 2B (NR2B) in the postnatal day (P) 5 and 8 rat hippocampi in both sexes that were either control-treated or with 6mg/kg/day nicotine in milk formula (CNN) via gastric intubation starting at P1. In line with prolonged GABAergic excitation, we found that at P5 males had significantly higher mRNA expression of NKCC1 and BDNF than females. CNN treatment resulted in a significant increase in KCC2 and BDNF mRNA expression in male but not female hippocampus (p<0.05). Males also had higher expression of NR2A and lower expression of NR2B at P5 compared to females (p<0.05). At P8, there were neither sex nor treatment effects on mRNA expression, indicating the end of a critical period for sensitivity to nicotine. These results suggest that differential maturation of GABA(A)R-mediated responses result in sex-specific sensitivity to nicotine during early postnatal development, potentially explaining the differential long-term effects of CNN on hippocampal function.
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Affiliation(s)
- J C Damborsky
- Department of Neuroscience and Experimental Therapeutics, Texas A&M University System Health Science Center, Medical Research and Education Building, 8447 State Highway 47, Bryan, TX 77807-3260, USA
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