Genetic Heterogeneity of Lymphangiogenesis in Different Mouse Strains

Lymphangiogenesis plays an important role in tumor metastasis, wound healing, and immune reactions, such as after organ transplantation. Furthermore, novel antilymphangiogenic drugs are moving into clinical medicine, but so far nothing is known about a potential genetic heterogeneity influencing lymphangiogenesis. Using the mouse cornea micropocket assay (VEGF-C) and the suture-induced corneal neovascularization model in different inbred and wild–derived mouse strains (Balb/cAnNCrl, C57BL/6NCrl, 129S1/SvImJ, SJL/JCrl, Cast/EiJ, FVB/NCrl), significant differences in the lymphangiogenic response were detected: the lymphvascularized area varied up to 1.9-fold in the micropocket assay and up to 1.7-fold in the suture-induced neovascularization model between the “low-responder” strain BALB/c and the “high-responder” strain FVB in response to the same stimulus. Furthermore, the number of physiological lymphatic vascular extensions into the marginal zone of the normally alymphatic cornea in untreated eyes again showed a difference of 1.6-fold between low- and high-responders. An anti-inflammatory (prednisolone acetate) and a specific anti(lymph)angiogenic therapy (blocking anti–VEGFR-3 antibody) had different effects on the lymphvascularized area in BALB/c mice and FVB mice, suggesting a different responsiveness to antilymphangiogenic treatments. These data for the first time demonstrate significant differences in the lymphangiogenic response of several mouse strains and suggest underlying genetic factors influencing the lymphangiogenic response. These considerations need to be taken into account when using different mouse strains to study lymphangiogenesis and may also explain different success of antilymphangiogenic treatments in tumor patients.Lymphangiogenesis is the formation of novel lymphatic vessels from pre-existing ones. The lymphatic vasculature is spread throughout the whole body with some exceptions like cartilage, central nervous system, and the cornea. It is found in all higher vertebrates as a second vascular system beside the blood vascular system and maintains the fluid balance and blood pressure¹ in the body. In addition, the lymphatic system contributes to the immune surveillance of the body. Via the lymphatic vessels antigen-presenting cells can be transported to the regional lymph nodes and initiate an immune response. This is of special interest in the clinical setting of graft rejection.² Lymphangiogenesis also plays an important role in cancer metastasis³ and is suggested to be involved in the pathogenesis of disorders such as inflammatory arthritis⁴ and chronic airway inflammation.⁵Contrary to angiogenesis, where substantial progress in understanding the molecular mechanisms and regulation-pathways was gained in the last decades, lymphangiogenesis research was long hampered by the absence of specific molecular markers. This changed with the discovery of specific molecular markers, such as LYVE-1,⁶ Podoplanin,⁷ Prox1,⁸ and VEGFR-3⁹ and various in vitro and in vivo models in the last few years.However, available information concerning the field of lymphangiogenesis research still lags behind hemangiogenesis (e.g., in the field of genetic diversity). Genetic heterogeneity of angiogenesis in mice was first reported in 2000 by Rohan et al,¹⁰ who showed that—dependent on the genetic background—the response to growth factor–induced angiogenesis varies significantly between different inbred mouse strains. Strain-dependent differences were also published for the density and surface area of the resting limbal vessels after bFGF-induced neovascularization in the cornea.¹¹ Genetic diversity influencing angiogenesis-regulating genes¹² is implicated in altering the susceptibility to angiogenesis-dependent diseases like cancer, diabetic retinopathy,¹³ psoriasis,¹⁴ and others. In contrast to the evidence for genetic heterogeneity on angiogenesis, to date little is known in this context about lymphangiogenesis.In this study we analyzed the presence of strain-dependent differences in lymphatic vessel growth in a standard corneal neovascularization model, the micropocket assay. We further determined the differences in an inflammatory context, because inflammation is the main trigger for pathological lymphangiogenesis in clinical settings.^15,16 Therefore, in addition we used the murine model of suture-induced inflammatory corneal neovascularization. The normal cornea is devoid of blood and lymph vessels.^2,17 However, due to an inflammatory stimulus the angiogenic privilege can be overcome resulting in a parallel ingrowth of blood and lymphatic vessels.¹⁵ Therefore, the cornea serves as an ideal model to study neovascularization under pathological conditions in vivo.¹⁸ Interindividual differences in lymphangiogenesis may affect the risk for graft/tissue rejection after transplantation and furthermore determine the response to an antilymphangiogenic treatment (e.g., in oncology).     

不同纯系小鼠免疫球蛋白分泌细胞的检测

本文介绍用反向溶血空斑技术对三种纯系小鼠的脾和骨髓中自然免疫球蛋白分泌细胞(IgSC)数的检测,其结果如下:在8周龄时,C57BL小鼠,BALB/c小鼠及BALB/c裸小鼠脾中每10~5个有核细胞的IgSC数分别为81.8±51.6,71±47与178±42,这三纯系小鼠骨髓中每10~5个有核细胞的IgSC数分别为20.4±10.3、8.0±4.9与7.8±2.2。这些结果表明:(1)在出生8周左右,三种纯系小鼠脾中的IgSC数皆多于各自骨髓中的IgSC数。(2)C57BL小鼠体内IgSC数多于BALB/c小鼠的IgSC数,两系鼠骨髓中IgSC数的差别有显著性。(3)与预料的相反,裸小鼠睥中的IgSC数多于MHC基因相同的正常小鼠的水平。这提示,有关裸小鼠B细胞增殖与分化的调控机制有待进一步研究。     

广州管圆线虫对不同宿主感染性的比较研究

目的比较广州管圆线虫在褐云玛瑙螺和福寿螺螺体内的发育情况及对BALB／c小鼠和昆明鼠的毒力,寻找适宜的实验室易感宿主。方法连续7d分别用感染大鼠的粪便喂食福寿螺和褐云玛瑙螺．1个月后解剖感染螺,观察螺体内广州管圆线虫幼虫的发育情况及虫数;从褐云玛瑙螺和福寿螺分离广州管圆线虫Ⅲ期幼虫（L3）分别感染昆明鼠;而感染BALB／c小鼠的Ⅲ期幼虫来自于褐云玛瑙螺。通过观察感染小鼠的死亡率、体重变化、mmp-9活性、脑组织的病理变化、脑内虫体数及脑脊液总蛋白含量等指标评价不同来源幼虫对不同小鼠的致病力。结果广州管圆线虫在褐云玛瑙螺及福寿螺中的发育无显著性差异．但褐云玛瑙螺感染的幼虫数量高于福寿螺。BALB／c小鼠感染广州管圆线虫后其死亡率、mmp-9活性、脑内虫体数及脑脊液总蛋白含量等明显高于昆明小鼠,其体重减轻、病理变化也更明显。用不同螺来源的Ⅲ期幼虫感染的小鼠其mmp-9活性、脑内虫体数、脑脊液总蛋白含量、体重减轻及脑组织病变程度均无显著差异。结论BALB／c小鼠、褐云玛瑙螺与福寿螺对广州管圆线虫易感,BALB／c小鼠是较好的实验室易感宿主,褐云玛瑙螺与福寿螺来源的广州管圆线虫Ⅲ期幼虫对小鼠的毒力无差异,从环保角度考虑褐云玛瑙螺更适合于实验室应用。     

Convergent Replication of Mouse Synthetic Prion Strains

Prion diseases are neurodegenerative disorders characterized by the aberrant folding of endogenous proteins into self-propagating pathogenic conformers. Prion disease can be initiated in animal models by inoculation with amyloid fibrils formed from bacterially derived recombinant prion protein. The synthetic prions that accumulated in infected organisms are structurally distinct from the amyloid preparations used to initiate their formation and change conformationally on repeated passage. To investigate the nature of synthetic prion transformation, we infected mice with a conformationally diverse set of amyloids and serially passaged the resulting prion strains. At each passage, we monitored changes in the biochemical and biological properties of the adapting strain. The physicochemical properties of each synthetic prion strain gradually changed on serial propagation until attaining a common adapted state with shared physicochemical characteristics. These results indicate that synthetic prions can assume multiple intermediate conformations before converging into one conformation optimized for in vivo propagation.See related Commentary on page 623.In prion diseases, for example, Creutzfeldt-Jakob disease in humans, scrapie in sheep, and bovine spongiform encephalopathy in cattle, an aberrantly folded conformer of the prion protein (PrP) propagates by catalyzing a posttranslational conversion reaction, using cellular PrP (PrP^C) as substrate.^1,2 This conversion reaction transforms endogenous PrP^C to the pathogenic conformer PrP^Sc.^3–5 Although self-replication of protein conformations was previously thought to be a unique feature of PrP prion diseases, in recent experiments, aggregates of proteins that cause other neurodegenerative diseases, for example, Aβ,^6–8 α-synuclein,^9–11 tau,^12,13 and huntingtin,¹⁴ stimulated the formation of pathogenic conformations in vivo. Thus, it is likely that elucidating the mechanisms of PrP^Sc prion propagation will provide important insights into the pathogenic properties of a broad range of neurodegenerative disorders.An important advance in prion biology was the creation of infectious synthetic prion strains formed exclusively from bacterially derived recombinant (rec) PrP.^15–18 The ability to create de novo synthetic strains has provided indisputable evidence for the prion hypothesis and has facilitated structural studies with the objective of elucidating the structural basis of protein-based infectivity. However, an enigmatic feature of synthetic prion strains is that the conformations that ultimately accumulate in infected organisms are structurally distinct from recombinant amyloids used to initiate their formation.^19–21 In contrast, specific biochemical features of the amyloid inocula, such as their conformational stabilities, correlate with the prion strains induced in vivo.¹⁶ Thus, the mechanisms by which amyloid preparations are transformed into transmissible prion strains in vivo remain under investigation.^22–24In an earlier investigation into the transformation of prion strains, we studied the mouse synthetic prion strain MoSP1,²⁵ which was generated by inoculating transgenic (Tg) mice expressing truncated mouse PrP(Δ23–88), which were denoted as Tg9949 mice,²⁶ with recPrP(Δ23–88) refolded into β-rich amyloid fibrils.¹⁵ After >500 days, the inoculated Tg9949 mice amassed protease-resistant infectious prions (rPrP^Sc).¹⁵ The accumulated MoSP1 strain had two biochemical features that differentiated it from naturally occurring prion strains such as the mouse-adapted Rocky Mountain Laboratory (RML; Golden, CO) scrapie strain. First, MoSP1 PrP^Sc had a high conformational stability, requiring >4 mol/L guanidine hydrochloride (GdnHCl) to unfold the prion aggregate and render it susceptible to proteolysis.²⁷ Second, the unglycosylated protease-resistant core had a molecular weight of ∼19 kDa.²⁵ By comparison, RML requires ∼1.5 mol/L GdnHCl to unfold and has a protease-resistant core of ∼21 kDa. We showed that the difference in molecular weights of the protease-resistant cores of MoSP1 and RML was due to conformational differences at their N-termini. When MoSP1 was continually passaged in mice, its physicochemical properties transformed in three ways: i) the unglycosylated protease-resistant core shifted from a molecular weight of ∼19 kDa to ∼21 kDa; ii) MoSP1 became conformationally less stable; and iii) the incubation period of the strain decreased to ∼150 days. We were able to recapitulate these transformations by propagating MoSP1 in cell culture.²⁵ We hypothesized that the mechanism of this transformation involved rare conformational conversion events followed by competitive selection among the resulting pool of conformers.After our previous study, it remained uncertain whether the observed MoSP1 transition constituted a strain-specific transformation or a common pathway for the in vivo adaptation of all mouse synthetic prion strains. To address this, we created a conformationally diverse set of amyloids by refolding recPrP under various denaturing conditions.¹⁶ These preparations were inoculated intracerebrally into Tg mice overexpressing full-length PrP, denoted as Tg4053 mice.²⁸ After the initially infected mice developed prion disease, we serially passaged the resulting PrP^Sc strains (MoSP5, MoSP6, MoSP7, and MoSP9) and monitored changes in their biological and biochemical characteristics including incubation period, rPrP^Sc banding patterns, conformational stability, and ability to seed amyloid formation in vitro. On initial infection, the synthetic prion strains accumulated as a diverse set of conformations. However, on repeated passage, all four synthetic prion strains acquired the same set of physicochemical characteristics including short incubation periods, low conformational stabilities, 21-kDa banding patterns for unglycosylated rPrP^Sc, and diminished abilities to seed amyloid formation in vitro. In addition, we tested the infectivity of MoSP7 in three different cell lines and found an increased ability to induce the cellular formation of rPrP^Sc on passage. Together, these results show that synthetic prions can assume different intermediate conformations before achieving a conformation that is optimized for in vivo propagation.     

Anatomical Variation of the Tarsus in Common Inbred Mouse Strains

Rodent models are used for a variety of orthopedic research applications; however, anatomy references include mostly artistic representations. Advanced imaging techniques, including micro‐computed tomography (microCT), can provide more accurate representations of subtle anatomical characteristics. A recent microCT atlas of laboratory mouse (Mus musculus) anatomy depicts the central and tarsal bone III (T3) as a single bone, differing from previous references. Fusion of tarsal bones is generally characterized as pathological secondary to mutations associated with growth factors, and normal variation has not been documented in the mouse tarsus. Therefore, it is unclear if this fusion is a normal or a pathological characteristic. The aim of this study is to characterize the tarsus of the laboratory mouse and compare it to the rat and selected outgroup species (i.e., white‐footed mouse) via microCT and histology to determine if the central and T3 are separate or fused into a single bone. Laboratory mice (C57/Bl6 [n = 17] and BalbC [n = 2]) and rats (n = 5) were scanned with microCT. A representative laboratory mouse from each strain was evaluated histologically via serial sagittal sections through the mid‐tarsus. General pedal anatomy was similar between all species; however, the central and T3 bones were fused in all laboratory mice but not the rat or white‐footed mouse. A band of hyaline cartilage was identified within the fused bone of the laboratory mice. We conclude that the fusion found is a normal characteristic in laboratory mice, but timing of the fusion remains ambiguous. Anat Rec, 300:450–459, 2017. © 2016 Wiley Periodicals, Inc.     

Immunity Parameters in Mice of Different Strains

Quantitative composition and functional activity of immunocompetent cells differ in mice of different strains. The counts of T cells in the bone marrow and spleen, proliferative activity of T cells in the spleen, levels of IL-2 and IL-10 production by splenic T cells, number of antigen-specific T cells and their functional activity are low in C57Bl/6, BALB/c, and CC57W mice and high in CBA/CaLac, DBA/2, and C3H animals. Low phagocytic activity of peritoneal macrophages was detected in BALB/c and CC57W mice and high activity in C3H animals. The content of antibody-producing cells in the spleens of C57Bl/6, BALB/c, and CC57W mice is higher than in CBA/CaLac, DBA/2, C3H, A/SN, and AKR/JY mice. Functional activity of B cells is lower in BALB/c and CC57W compared to CBA/CaLac and DBA/2 mice. __________ Translated from Byulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 140, No. 8, pp. 189–191, August, 2005     

Degradation of Serum Amyloid A in Amyloid-Susceptible and Amyloid-Resistant Mouse Strains

Degradation of serum amyloid A (apoSAA) by resident peritoneal cells (RPCS) and conditioned medium (CDM), prepared with RPCS, from amyloid-susceptible CBA/J mice, amyloid-resistant CE/J mice and their amyloid-resistant CBA/J × CE/J F₁ progeny was investigated in vitro . Serum amyloid A was derived from murine acute phase (AP) plasma and associated with high density lipoprotein (HDL). Degradation of apoSAA by RPCS and CDM from CBA/J mice was complete while degradation by RPCS and CDM from CE/J mice did not occur. Degradation of apoSAA by RPCS and CDM from CBA/J × CE/J F₁ hybrid mice was indistinguishable from that by RPCS and CDM from the CBA/J parent. Intermediate fragments were not detected with either RPCS or CDM from CBA/J mice or CBA/J × CE/J F₁ hybrid mice. Degradation of apoSAA was inhibited by phenylmethanylsulfonyl fluoride (PMSF) indicating that the enzyme, secreted into the fluid phase, was a serine esterase. Unlike apoSAA, HDL-associated apoA-1 remained intact. It was thus concluded that while selective degradation of HDL-associated apoSAA (apoSAA-HDL) by RPCS from the CBA/J and CE/J mice was significantly different, the genetic study did not support the hypothesis that there was direct linkage between impaired degradation of apoSAA-HDL in the CE/J mouse strain and protection against amyloid fibril formation. As amyloid resistance in CBA/J × CE/J F₁ hybrid mice is not attributable to failure to express the amyloidogenic isoform apoSAA₂, the study supports the original hypothesis that amyloid resistance may be linked to expression of apoSAA_cej     

Amphotericin B Selectively Stimulates Macrophages from High Responder Mouse Strains

Lymphoid cells from most inbred mouse strains respond to amphotericin B (AmB)-induced immunostimulation. However, C57BL/6 mice and related strains display low or absent lymphoid cell stimulation by AmB and enhanced susceptibility to AmB toxicity. Experiments reported here show that in vitro incubation with AmB can stimulate AKR (AmB-high responder strain) macrophage proliferation. Intraperitoneal injection of AKR mice with AmB also elicits a population of macrophages primed for enhanced oxidative burst activity after triggering by zymosan particles. Under the same experimental conditions, AmB elicits a population of very weakly responsive macrophages from C57BL/6 mice. the low responsiveness of C57BL/6 macrophages correlates with previous observations that AmB is a potent immunoadjuvant and B cell mitogen in most inbred strains, but it selectively lacks immunoadjuvant effects in C57BL/6 mice and it also fails to induce polyclonal B cell stimulation in their spleen cell suspensions. Similarly, in measurements of protein synthesis in vitro, high concentrations of AmB produce a greater inhibition of protein synthesis in C57BL/6 peritoneal macrophages than in parallel cultures of AKR macrophages. These findings support the hypothesis that the macrophage is an important target cell in the mediation of AmB-induced immunomodulation.     

Mouse Virulence of Human, Systemic, Pathogenic Escherichia coli Strains

Strains of Escherichia coli isolated from systemic infections of humans exhibited marked intraperitoneal and intracerebral virulence for mice. This marked virulence was not exhibited by enteropathogenic strains.     

The Effects of Novelty and Behavioral Stereotype on the Development of Amnesia in Mice

The aim of the present study was to analyze the significance of the interaction between the basic behavioral strategy, the extinction of the novelty of information, and the efficacy of amnesia-inducing influences. Using a combination of training to passive avoidance with holding the animal in the unsafe sector of the apparatus, comparative analysis was performed of the reproduction of a memory trace in aggressive and submissive mice of line C57BL/6J with and without six sessions of familiarization with the apparatus. These experiments showed that preliminary habituation prevented the development of amnesia in submissive but not aggressive individuals. The cause of these differences in the effects of preexposure on the development of amnesia involves the selectivity of the process of extinction of information novelty characteristic for the behavioral stereotype.     

Bacterial Lipopolysaccharides Bind Selectively to Lymphocytes from Lipopolysaccharide High-responder Mouse Strains

Three different concentrations of horseradish peroxidase-labelled lipopolysaccharide (LPS-HRP) were added in vitro to spleen cells from the LPS high-responder strain C3H/Tif and to cells from the low-responder strain C3H/HeJ. After being washed and fixed the cells were exposed to the substrate and prepared for electron microscopy. After addition of 7 and 0.7 microgram/ml of labelled LPS only lymphocytes from the high-responder strain were labelled. About 5-10% of the cells from C3H/Tif bound LPS, which is in accordance with the known frequency of B cells possessing the genetically determined LPS receptor. At the highest dose of labelled LPS (70 microgram/ml) a large proportion of lymphocytes from the low-responder strain also bound LPS. Erythrocytes from both strains bound LPS at all concentrations. It is concluded that LPS-HRP allows the detection at the cellular level of LPS binding to the genetically controlled membrane receptor for LPS.     

Differential Effects of Morphine and Naltrexone on the Antibody Response in Various Mouse Strains

Morphine treatment has been shown to suppress several immunologic parameters. In this study, we examined the effects of morphine pellet implantation in vivo on the primary antibody response measured in vitro in various mouse strains. Effects of mouse strain and sex on morphine-induced suppression of the plaque-forming cell response, as well as spleen weight and mortality were determined. Morphine suppressed the primary antibody response in C3HeB/FeJ, C3H/HeJ and C57BI/6 mice, while Balb/cByJ and the (i-receptor-deficient strain CxBk/ByJ mice were not affected. There was no difference in the response to morphine between male and female C3HeB/FeJ mice. Naltrexone reversed the morphine-induced suppression in the C3H strains, but not in C57BI/6 mice. In addition, naltrexone caused significant mortality in Balb/cByJ mice. Spleen weight was decreased by morphine treatment in all the strains, but only the C3H strains were sensitive to the lethal effects of morphine. Thus, immune suppression did not correlate with splenic atrophy or mortality. The strain differences in response to chronic morphine and naltrexone treatment suggest that morphine may be acting through both opioid and non-classical opioid (e.g., not blocked by naltrexone) mechanisms.     

不同小鼠品系对天花粉蛋白诱导免疫抑制易感性的差异

为了解不同品系小鼠对天花粉蛋白 (Tk )诱导的免疫抑制应答能力的差异 ,应用OVA特异性T细胞体外增殖抑制试验 ,发现 8种近交系小鼠对Tk相关免疫抑制的敏感性不同。根据抑制幅度 ,C5 7BL/ 6 (H 2 b)被判为高易感品系 (HS ,highsusceptible ) ,同属H 2 k 的C3H/He和AKR为低易感品系 (LS ,lowsusceptible)。Tk浓度为 5 0ng/ml时的T细胞增值抑制百分率对HS为 4 7 8%± 3 4 % ;对两个LS分别为 15 9%± 3 0 %和 18 9%± 3 5 % ,两组间差异显著 (P <0 0 0 1)。这一差异可持续出现在 5 0～ 2 0 0ng/ml的Tk剂量范围内。其余 5个品系 (BALB/c、 6 15、T739、A、DBA/ 2 )的抑制幅度介于HS和LS之间。这一结果有助于研究相应免疫抑制的基因调控。     

Genetic Mapping of Social Interaction Behavior in B6/MSM Consomic Mouse Strains

Genetic studies are indispensable for understanding the mechanisms by which individuals develop differences in social behavior. We report genetic mapping of social interaction behavior using inter-subspecific consomic strains established from MSM/Ms (MSM) and C57BL/6J (B6) mice. Two animals of the same strain and sex, aged 10 weeks, were introduced into a novel open-field for 10 min. Social contact was detected by an automated system when the distance between the centers of the two animals became less than ~12 cm. In addition, detailed behavioral observations were made of the males. The wild-derived mouse strain MSM showed significantly longer social contact as compared to B6. Analysis of the consomic panel identified two chromosomes (Chr 6 and Chr 17) with quantitative trait loci (QTL) responsible for lengthened social contact in MSM mice and two chromosomes (Chr 9 and Chr X) with QTL that inhibited social contact. Detailed behavioral analysis of males identified four additional chromosomes associated with social interaction behavior. B6 mice that contained Chr 13 from MSM showed more genital grooming and following than the parental B6 strain, whereas the presence of Chr 8 and Chr 12 from MSM resulted in a reduction of those behaviors. Longer social sniffing was observed in Chr 4 consomic strain than in B6 mice. Although the frequency was low, aggressive behavior was observed in a few pairs from consomic strains for Chrs 4, 13, 15 and 17, as well as from MSM. The social interaction test has been used as a model to measure anxiety, but genetic correlation analysis suggested that social interaction involves different aspects of anxiety than are measured by open-field test.     

Differential Effects of Morphine and Naltrexone on the Antibody Response in Various Mouse Strains

Abstract

Morphine treatment has been shown to suppress several immunologic parameters. In this study, we examined the effects of morphine pellet implantation in vivo on the primary antibody response measured in vitro in various mouse strains. Effects of mouse strain and sex on morphine-induced suppression of the plaque-forming cell response, as well as spleen weight and mortality were determined. Morphine suppressed the primary antibody response in C3HeB/FeJ, C3H/HeJ and C57BI/6 mice, while Balb/cByJ and the (i-receptor-deficient strain CxBk/ByJ mice were not affected. There was no difference in the response to morphine between male and female C3HeB/FeJ mice. Naltrexone reversed the morphine-induced suppression in the C3H strains, but not in C57BI/6 mice. In addition, naltrexone caused significant mortality in Balb/cByJ mice. Spleen weight was decreased by morphine treatment in all the strains, but only the C3H strains were sensitive to the lethal effects of morphine. Thus, immune suppression did not correlate with splenic atrophy or mortality. The strain differences in response to chronic morphine and naltrexone treatment suggest that morphine may be acting through both opioid and non-classical opioid (e.g., not blocked by naltrexone) mechanisms.     

Gustatory,Trigeminal, and Olfactory Aspects of Nicotine Intake in Three Mouse Strains

Studies of nicotine consumption in rodents often intend to investigate nicotine’s post-absorptive effects, yet little is known about the pre-absorptive sensory experience of nicotine drinking, including gustatory, trigeminal, and olfactory influences. We conditioned taste aversion (CTA) to nicotine in males of 3 inbred mouse strains: C57BL/6J, DBA/2J, and 129X1/SvJ by repeatedly pairing 150 μg/ml nicotine drinking with lithium chloride injections. Generalization to a variety of bitter, sour, sweet, salty, and irritant solutions and to nicotine odor was then examined. Nicotine CTA generalized to the bitter stimulus quinine hydrochloride and the chemosensory irritant spilanthol in all strains. It also showed strain specificity, generalizing to hydrogen peroxide (an activator of TRPA1) in C57BL/6J mice and to the olfactory cue of nicotine in DBA/2J mice. These behavioral assays demonstrate that the sensory properties of nicotine are complex and include multiple gustatory, irritant, and olfactory components. How these qualities combine at the level of perception remains to be assessed, but sensory factors clearly exert an important influence on nicotine ingestion and their contribution to net intake of nicotine should not be neglected in animal or human studies.