Background Strain Mice Research Articles

Effects of nicotine + morphine on reward‐related behavior and nicotinic acetylcholine receptor regulation in mouse midbrain.

In the United States about 480,000 deaths/year are caused by cigarette smoking and about 50,000 due to opioid abuse. Co‐use of more than one drug is common, therefore, it is vital to study the effects of drug combinations to understand how co‐use alters the brain. Especially given that in America, > 90% of opioid dependents are heavy smokers. The objective for this study is to determine how combined nicotine + morphine alters reward‐related behavior and nicotinic acetylcholine receptor (nAChR) expression in the midbrain. Our hypothesis is that co‐use of nicotine + morphine leads to enhanced GABA neuron disinhibition of VTA dopamine neurons. Female and male (3–5 months old) C57BL/6J background strain mice with or without α4‐mCherryα6‐GFP nAChRs were used in conditioned place (CPP) preference assays to examine reward‐related behavior with nicotine + morphine. We used confocal microscopy to analyze the density of α4‐containing (α4*), α6*, and α4α6* nAChRs in ventral tegmental area (VTA), substantia nigra pars compacta (SNc), and substantia nigra pars reticulata (SNr). In our CPP assays, a Two‐way ANOVA (factors: treatment and sex) showed a significant effect of sex (F (1, 42) = 5.75; p = 0.02) on reward‐related behavior, suggesting a sex‐dependent dose effect with morphine. In our microscopy assays, nicotine + morphine treatment downregulated α4* nAChRs on SNr GABA cells. Our CPP data supports that sex is an important variable in the effects of drugs on reward‐related behavior. Our receptor regulation data suggests that downregulation of α4* nAChRs on SNr GABA cells is important to the combined effects of nicotine + morphine.Support or Funding InformationSupport: Funding was provided through start‐up funds through the Marshall University Research Corporation.

Effects of Treadmill Running on Oxidative Stress and Heat Shock Protein in Early Stage of 3xTg-AD Mice

PURPOSE The mechanisms underlying the protective effects of exercise training against cognitive decline are not fully understood. This study aimed to investigate the effects of treadmill running on oxidative stress and heat shock protein levels in a mouse model of early stage triple transgenic Alzheimer’s disease (3xTg-AD). METHODS We divided 5-month old 3xTg-AD mice (N=20) into the control (AD+CON, n=10) and exercise training (AD+EX, n=10) groups. Background strain mice were included as wild-type controls (WT, n=10). AD+EX mice were subjected to treadmill running at a speed of 15 m/min, 50 min/day, 5 days/week for 12 weeks. RESULTS Treadmill running protected 3xTg-AD mice from cognitive decline and significantly suppressed the increase in soluble Aβ1-42 protein levels (AD+CON vs AD+EX, p=0.015) and the progression of oxidative damage. This was evidenced by significant increase in anti-oxidative protein levels such as superoxide dismutase-1 (SOD-1), heme oxygenase (HO-1) and heat shock protein 70 (HSP70) in the hippocampus of AD+EX mice compared to AD+CON mice. Moreover, the brain-derived neurotrophic factor (BDNF) and synaptic proteins such as PSD95 and synaptophysin were upregulated in AD+EX mice compared to AD+CON mice. CONCLUSIONS Our findings support and extend previous studies reporting the preventive effects of exercise training on the pathological processes of the Alzheimer’s disease in the 3xTg AD mouse model. 색인어: ì•Œì¸ í•˜ì´ë¨¸ 병, íŠ¸ë ˆë“œë°€ 운동, 산화성 ìŠ¤íŠ¸ë ˆìŠ¤, 열쇼크 단백질, 3xTg-AD Keywords: Alzheimer’s disease, treadmill running, oxidative stress, heat shock protein, 3xTg-AD

Cosinor Analysis Reveals Non‐dipping Hypertension in Mixed Background Strain Mice Lacking the Circadian Clock Protein PER1

Cardiovascular disease is the leading cause of death among Americans. Hypertension is the leading risk factor for cardiovascular disease, thus blood pressure (BP) regulation is imperative for maintaining cardiovascular health. BP exhibits a circadian rhythm that is regulated through many mechanisms. Humans experience a BP rhythm resulting in a 10–20% dip in BP during their resting period. Individuals who fail to maintain this dip, termed non‐dippers, are associated with worse cardiovascular outcomes. The circadian clock mechanism, which includes the transcription factors PERIOD, BMAL1, CLOCK, and CRYPTOCHROME, is necessary to maintain this rhythm. Past studies in our lab have shown that global loss of PER1 leads to non‐dipping hypertension in male C57BL/6 mice in response to high salt diet plus an aldosterone analogue desoxycorticosterone pivalate‐salt (DOCP) (Solocinski et al. 2017). The goal of this study was to determine the BP phenotype of Per1 knockout (KO) mice on a salt‐sensitive 129/sv/s1s4 background strain. 129/sv/s1s4 mice were implanted with radiotelemetry devices and maintained in a normal 12‐hour light/dark period. BP was monitored continuously while the mice were subjected to a control diet, a high salt (HS) diet, or a HS diet plus treatment with an aldosterone analogue DOCP. BP rhythms were analyzed through the program Cosinor (www.circadian.org) to determine the mesor, amplitude, and acrophase. When evaluating a cosine wave, the mesor is the midline between the peak and the trough, the amplitude is the measure of the mesor to the peak, and the acrophase is the time point of the peak. These values were then used to discern whether the mice maintained a BP rhythm. The 129/sv/s1s4 Per1 KO experienced a 9‐mmHg increase in BP in response to HS/DOCP (P<0.01, n=8). In contrast, the wild type (WT) mice (n=5) did not experience a significant increase in BP after HS/DOCP. Furthermore, the KO mice had a 2.4‐mmHg decrease in amplitude (P=0.01), whereas the WT mice did not exhibit a significant decrease in amplitude. The WT mice on control diet exhibited a 12.8% dip in BP during their inactive period compared to their active period, which insignificantly decreased to an 11.5% dip on HS/DOCP diet. However, the KO mice on control diet had an 11% dip, which decreased to 5.4% dip on HS/DOCP diet (P<0.05, n=5–8). These data demonstrate that loss of Per1 in male 129/sv/s1s4 mice leads to a non‐dipping phenotype in response to HS/DOCP treatment. Importantly, these findings represent the reproducibility of the non‐dipping hypertension phenotype we previously observed in C57BL/6 mice in a distinct strain on a mixed background.Support or Funding InformationAmerican Physiological Society Undergraduate Summer Fellowship Program; American Society of Nephrology Foundation for Kidney ResearchThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Treadmill Running Reverses Cognitive Declines due to Alzheimer Disease.

This study investigated the effect of treadmill running on cognitive declines in the early and advanced stages of Alzheimer disease (AD) in 3xTg-AD mice. At 4 months of age, 3xTg-AD mice (N = 24) were assigned to control (AD + CON, n = 12) or exercise (AD + EX, n = 12) group. At 24 months of age, 3xTg-AD mice (N = 16) were assigned to AD + CON (n = 8) or AD + EX (n = 8) group. The AD + EX mice were subjected to treadmill running for 12 wk. At each pathological stage, the background strain mice were included as wild-type control (WT + CON, n = 8-12). At the early stage of AD, 3xTg-AD mice had impaired short- and long-term memory based on Morris water maze along with higher cortical Aβ deposition, higher hippocampal and cortical tau pathology, and lower hippocampal and cortical PSD-95 and synaptophysin. A 12-wk treadmill running reversed the impaired cognitive declines and significantly improved the tau pathology along with suppression of the decreased PSD-95 and synaptophysin in the hippocampus and cortex. At the advanced stage of AD, 3xTg-AD mice had impaired short- and long-term memory along with higher levels of Aβ deposition, soluble Aβ1-40 and Aβ1-42, tau pathology, and lower levels of brain-derived neurotrophic factor, PSD-95, and synaptophysin in the hippocampus and cortex. A 12-wk treadmill running reversed the impaired cognitive declines and significantly improved the Aβ and tau pathology along with suppression of the decreased synaptic proteins and brain-derived neurotrophic factor in the hippocampus and cortex. The current findings suggest that treadmill running provides a nonpharmacological means to combat cognitive declines due to AD pathology.

HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP)-like disease and toxic epidermal necrolysis (TEN)-like disease in HTLV-1 Tax transgenic mice

Human T-cell leukemia virus type 1 (HTLV-1) can cause an aggressive malignancy known as adult T-cell leukemia/lymphoma (ATLL), as well as inflammatory diseases such as HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). We created a transgenic mouse model of HTLV-1 infection by using the distal promoter of Lck to express tax in mature thymocytes and peripheral T lymphocytes. Major phenotypes of disease in this model were mature T cell leukemia/lymphoma similar to ATLL and an inflammatory arthropathy. While expanding the transgenic mouse colony, we also found 2.7% of transgenic mice developed a HAM/TSP-like disease and 2.4% of transgenic mice developed a toxic epidermal necrolysis (TEN)-like disease. The HAM/TSP-like disease with symmetrical paraparesis of the hind limbs in transgenic mice was not inflammatory, unlike that found in HAM/TSP patients, but instead involved the invasion of histiocytic sarcoma cells into the lumbar spinal cord from the bone marrow where they had undergone extensive proliferation. Mice with the HAM/TSP-like disease showed abnormal expression of cytokines and chemokines, including TNF and IL-6. There are no reports of spontaneous symmetrical paraparesis caused by histiocytic sarcoma in mice. TEN is characterized by a rash, bullae, and diffuse exfoliation of wide cutaneous surface areas, as seen in second-degree burns. Massive keratinocyte apoptosis is the hallmark of TEN. The TEN-like disease in transgenic mice occurred mainly in C57BL/6 background strain mice. These mice showed a skin detachment rate of greater than 30%. The pathology in transgenic mice with a TEN-like disease is currently under study and will be discussed.

Obesity‐induced diabetes and lower urinary tract fibrosis promote urinary voiding dysfunction in a mouse model

Progressive aging- and inflammation-associated fibrosis effectively remodels the extracellular matrix (ECM) to increase prostate tissue stiffness and reduce urethral flexibility, resulting in urinary flow obstruction and lower urinary tract symptoms (LUTS). In the current study, we sought to test whether senescence-accelerated mouse prone (SAMP)6 mice, which were reported to develop prostatic fibrosis, would also develop LUTS, and whether these symptoms would be exacerbated by diet-induced obesity and concurrent Type 2 Diabetes Mellitus (T2DM). To accomplish this, SAMP6 and AKR/J background strain mice were fed regular mouse chow, low fat diet chow, or high fat diet chow for 8 months, then subjected to glucose tolerance tests, assessed for plasma insulin levels, evaluated for urinary voiding function, and assessed for lower urinary tract fibrosis. The results of these studies show that SAMP6 mice and AKR/J background strain mice develop diet-induced obesity and T2DM concurrent with urinary voiding dysfunction. Moreover, urinary voiding dysfunction was more severe in SAMP6 than AKR/J mice and was associated with pronounced prostatic and urethral tissue fibrosis. Taken together, these studies suggest that obesity, T2DM, lower urinary tract fibrosis, and urinary voiding dysfunction are inextricably and biologically linked.

Rostroventral caudate putamen involvement in ethanol withdrawal is influenced by a chromosome 4 locus

Physiological dependence and associated withdrawal episodes are thought to constitute a motivational force that sustains alcohol use and abuse and may contribute to relapse in dependent individuals. Although no animal model duplicates alcoholism, models for specific factors, like withdrawal, are useful for identifying potential genetic and neural determinants of liability in humans. Previously, we identified a quantitative trait locus (QTL) and gene (Mpdz, which encodes the multi-PDZ domain protein) on chromosome 4 with a large effect on alcohol withdrawal in mice. Using congenic mice that confirm this QTL and c-Fos expression as a high-resolution marker of neuronal activation, we report that congenic mice show significantly less neuronal activity associated with alcohol withdrawal in the rostroventral caudate putamen (rvCP), but not other parts of the striatum, compared with background strain mice. Moreover, bilateral rvCP lesions significantly increase alcohol withdrawal severity. Using retrograde (fluorogold) and anterograde (Texas Red conjugated dextran amine) tract tracing, we found that ∼25% of c-Fos immunoreactive rvCP neurons project to caudolateral substantia nigra pars reticulata (clSNr), which we previously found is crucially involved in withdrawal following acute and repeated alcohol exposure. Our results expand upon work suggesting that this QTL impacts alcohol withdrawal via basal ganglia circuitry associated with limbic function, and indicate that an rvCP-clSNr projection plays a critical role. Given the growing body of evidence that the syntenic region of human chromosome 9p and human MPDZ gene are associated with alcohol abuse, our results may facilitate research on alcohol dependence and associated withdrawal in clinical populations.

Involvement of the Limbic Basal Ganglia in Ethanol Withdrawal Convulsivity in Mice Is Influenced by a Chromosome 4 Locus

Physiological dependence and associated withdrawal episodes are thought to constitute a motivational force that sustains ethanol (alcohol) use/abuse and may contribute to relapse in alcoholics. Although no animal model duplicates alcoholism, models for specific factors, like the withdrawal syndrome, are useful for identifying potential genetic and neural determinants of liability in humans. We generated congenic mice that confirm a quantitative trait locus (QTL) on chromosome 4 with a large effect on predisposition to alcohol withdrawal. Using c-Fos expression as a high-resolution marker of neuronal activation, congenic mice demonstrated significantly less neuronal activity associated with ethanol withdrawal than background strain mice in the substantia nigra pars reticulata (SNr), subthalamic nucleus (STN), rostromedial lateral globus pallidus, and ventral pallidum. Notably, neuronal activation in subregions of the basal ganglia associated with limbic function was more intense than in subregions associated with sensorimotor function. Bilateral lesions of caudolateral SNr attenuated withdrawal severity after acute and repeated ethanol exposures, whereas rostrolateral SNr and STN lesions did not reduce ethanol withdrawal severity. Caudolateral SNr lesions did not affect pentylenetetrazol-enhanced convulsions. Our results suggest that this QTL impacts ethanol withdrawal via basal ganglia circuitry associated with limbic function and that the caudolateral SNr plays a critical role. These are the first analyses to elucidate circuitry by which a confirmed addiction-relevant QTL influences behavior. This mouse QTL is syntenic with human chromosome 9p. Given the growing body of evidence that a gene(s) on chromosome 9p influences alcoholism, our results can facilitate human research on alcohol dependence and withdrawal.

Radiation-Induced Lung Response of AcB/BcA Recombinant Congenic Mice

The genetic factors that influence the development of radiotherapy-induced lung disease are largely unknown. Herein we identified a strain difference in lung response to radiation wherein A/J mice developed alveolitis with increased levels of pulmonary mast cells and cells in bronchoalveolar lavage while the phenotype in C57BL/6J mice was fibrosis with fewer inflammatory cells. To identify genomic loci that may influence these phenotypes, we assessed recombinant congenic (RC) mice derived from the A/J and C57BL/6J strains for their propensity to develop alveolitis or fibrosis after 18 Gy whole-thorax irradiation. Mouse survival, lung histopathology and bronchoalveolar lavage cell types were recorded. Informative strains for each of mast cell influx, bronchoalveolar cell numbers, alveolitis and fibrosis were identified. In mice with the A/J strain background, the severity of alveolitis correlated with increased mast cell numbers while in C57BL/6J background strain mice fibrosis was correlated with the percentage of neutrophils in lavage. The data for RC mice support the association of specific inflammatory cells with the development of radiation-induced lung disease and provide informative strains with which to dissect the genetic basis of these complex traits.

Effect on Diurnal Intraocular Pressure Variation of Eliminating the α-2 Adrenergic Receptor Subtypes in the Mouse

To investigate the effect on circadian variation of intraocular pressure (IOP) of eliminating the alpha2A-, alpha2B-, or the alpha2C-adrenergic receptor subtypes in the mouse. A microneedle method was used to measure IOP in knockout mice lacking the alpha2A-, alpha2B-, or the alpha2C-receptor (alpha2A-R(-/-), alpha2B-R(-/-), alpha2C-R(-/-)), in wild-type mice of the alpha2B knockout strain (alpha2B-R(+/+)), and in the background strain mice, C57BL/6. All mice were maintained in a 12-hour light-dark cycle commencing at 0600 hours. IOP was measured at 0900 and 2100 hours in the five groups: C57BL/6 (n = 8), alpha2A-R(-/-) (n = 10), alpha2B-R(-/-) (n = 8), alpha2B-R(+/+) (n = 8), and alpha2C-R(-/-) (n = 10). In parallel experiments, eyes from the alpha2A-R(-/-), alpha2B-R(-/-), alpha2C-R(-/-), and C57BL/6 mice were embedded in epoxy resin, and semithin sections were stained with toluidine blue. IOP at 0900 hours in B6, alpha2A-R(-/-), alpha2B-R(-/-), alpha2B-R(+/+), and alpha2C-R(-/-) mice was 17.1 +/- 1.8, 17.7 +/- 1.4, 17.1 +/- 2.1, 17.6 +/- 1.3, and 17.3 +/- 0.9 mm Hg, respectively (mean +/- SD). IOP at 2100 hours in the same eyes was 19.6 +/- 1.9, 19.2 +/- 2.2, 20.5 +/- 1.5, 19.7 +/- 0.8, and 21.3 +/- 2.7 mm Hg, respectively. There was no significant difference among these genotypes in IOP measured at either time point (P > 0.05, ANOVA). Within each genotype, IOP at 2100 hours was significantly higher than IOP at 0900 hours (C57BL/6, alpha2B-R(-/-), alpha2B-R(+/+), and alpha2C-R(-/-): P < 0.01; alpha2A-R(-/-): P < 0.05, paired t-test). Differences in the diurnal IOP change among the different genotypes were insignificant (P > 0.05, ANOVA). Histopathologic assessment found minimal differences in the structural organization of the anterior segment among the alpha2A-R(-/-), alpha2B-R(-/-),alpha2C-R(-/-), or C57BL/6 mice. These results indicate that IOP magnitude and circadian variation are minimally altered by the absence of the alpha2A-, alpha2B-, or alpha2C-receptor subtypes in transgenic mice.

5-HT 2C and GABA B receptors influence handling-induced convulsion severity in chromosome 4 congenic and DBA/2J background strain mice

Progress towards elucidating the underlying genetic variation for susceptibility to complex central nervous system (CNS) hyperexcitability states has just begun. Genetic mapping analyses suggest that a gene(s) on mid-chromosome 4 has pleiotropic effects on multiple CNS hyperexcitability states in mice, including alcohol and barbiturate withdrawal and convulsions elicited by chemical and audiogenic stimuli. We recently identified Mpdz within this chromosomal region as a gene that influences alcohol and barbiturate withdrawal convulsions. Mpdz encodes the multi-PDZ domain protein (MPDZ). Currently, there is limited information available about the mechanism by which MPDZ influences drug withdrawal and/or other CNS hyperexcitability states, but may involve its interaction with 5-HT 2C and/or GABA B receptors. One of the most useful tools we have developed thus far is a congenic strain that possesses a segment of chromosome 4 from the C57BL/6J (donor) mouse strain superimposed on a genetic background that is > 99% from the DBA/2J strain. The introduced segment spans the Mpdz gene. Here, we demonstrate that handling-induced convulsions are less severe in congenic vs. background strain mice in response to either a 5-HT 2C receptor antagonist (SB242084) or a GABA B receptor agonist (baclofen), but not a GABA A receptor channel blocker (pentylenetetrazol). These data suggest that allelic variation in Mpdz, or a linked gene, influences SB242084- and baclofen-enhanced convulsions. Our results are consistent with the hypothesis that Mpdz's effects on CNS hyperexcitability, including alcohol and barbiturate withdrawal, involve MPDZ interaction with 5-HT 2C and/or GABA B receptors. However, additional genes reside within the congenic interval and may also influence CNS hyperexcitability.

Prostaglandin FP Receptors Do Not Contribute to 24-hour Intraocular Pressure Variation in Mice

It is not known whether the prostaglandin FP receptor plays an important role in endogenous 24-hour regulation of intraocular pressure. The purpose of this study was to compare 24-hour intraocular pressure (IOP) in FP receptor-knockout mice with that of wild-type mice that have normal FP receptor expression. The 24-hour IOP profile was determined by rebound tonometry in FP-knockout and wild-type mice. Peak and trough IOP was then measured by microneedle cannulation of the anterior chamber in homozygous (FP(-/-); n = 8), heterozygous (FP(+/-); n = 14), and C57BL/6 background strain mice (FP(+/+); n = 11). To confirm any differences in baseline IOP between genotypes, midafternoon IOP was also measured in a larger, separate group of FP(-/-) mice (n = 20), FP(+/-) mice (n = 49), and FP(+/+) (n = 23) wild-type littermates. Trough IOPs were measured between 10 AM and 12 PM, peak IOPs were measured between 8 and 10 PM. For FP(+/+), FP(+/-), and FP(-/-) mice trough IOP was 16.2, 15.3, and 15.1 mm Hg and peak IOPs were 18.2, 18.4, and 17.7 mm Hg, respectively. There was no significant difference among genotypes for mean peak or mean trough IOP or for peak-trough difference in IOP among genotypes (P > 0.05, ANOVA). In addition, there was no significant difference in midafternoon IOP between genotypes in a larger population (n = 92) of FP-knockout and wild-type mice. An intact FP receptor does not appear to be critical for normal 24-hour IOP regulation in the mouse eye.