Rat Model Of Chronic Exposure Research Articles

A Multimodal MR Imaging Study of the Effect of Hippocampal Damage on Affective and Cognitive Functions in a Rat Model of Chronic Exposure to a Plateau Environment

Prolonged exposure to high altitudes above 2500 m above sea level (a.s.l.) can cause cognitive and behavioral dysfunctions. Herein, we sought to investigate the effects of chronic exposure to plateau hypoxia on the hippocampus in a rat model by using voxel-based morphometry, creatine chemical exchange saturation transfer (CrCEST) and dynamic contrast-enhanced MR imaging techniques. 58 healthy 4-week-old male rats were randomized into plateau hypoxia rats (H group) as the experimental group and plain rats (P group) as the control group. H group rats were transported from Chengdu (500 m a.s.l.), a city in a plateau located in southwestern China, to the Qinghai–Tibet Plateau (4250 m a.s.l.), Yushu, China, and then fed for 8 months there, while P group rats were fed in Chengdu (500 m a.s.l.), China. After 8 months of exposure to plateau hypoxia, open-field and elevated plus maze tests revealed that the anxiety-like behavior of the H group rats was more serious than that of the P group rats, and the Morris water maze test revealed impaired spatial memory function in the H group rats. Multimodal MR imaging analysis revealed a decreased volume of the regional gray matter, lower CrCEST contrast and higher transport coefficient Ktrans in the hippocampus compared with the P group rats. Further correlation analysis found associations of quantitative MRI parameters of the hippocampus with the behavioral performance of H group rats. In this study, we validated the viability of using noninvasive multimodal MR imaging techniques to evaluate the effects of chronic exposure to a plateau hypoxic environment on the hippocampus.

Cigarette smoke exposure induced pulmonary artery pressure increase through inhibiting Kv1.5 and Kv2.1 mRNA expression in rat pulmonary artery smooth muscles

To investigate the effect of cigarette smoke exposure on Kv1.5 and Kv2.1 mRNA expression in rat pulmonary arterial smooth muscle cells (PASMCs), and further to clarify the possible mechanism of cigarette smoking induced pulmonary arterial hypertension. Primary cell culture and animal experiments were used in this study. Rat distal PASMCs were isolated and cultured by collagenase digestion. PASMCs were treated by nicotine 100 nmol/L. After 48 h, Kv1.5 and Kv2.1 mRNA expression were detected by real-time quantitative PCR and compared with the control group. Rat model of chronic exposure to cigarette smoke was established. Thirty-six male SD rats were randomly divided equally into 6 groups: (1) 1 month control group; (2) 1 month cigarette exposure group; (3) 3 month control group; (4) 3 month cigarette exposure group; (5) 6 month control group; (6) 6 month cigarette exposure group. Direct right heart manometry, HE staining and real-time quantitative PCR were used to detect the effect of smoke exposure on rat right ventricular systolic pressure (RVSP), mean pressure (mPAP), right ventricular hypertrophy index [RV/(LV + S)] as well as Kv1.5 and Kv2.1 mRNA expression on pulmonary artery smooth muscle at different time points (1 month, 3 months and 6 months). The mPAP and RVSP in cigarette smoke exposure 6 month group were (13.08 ± 0.64) mm Hg and (29.73 ± 0.83) mm Hg, slightly higher than those in the control 6 month group [(10.16 ± 0.44) mm Hg and (22.56 ± 0.64) mm Hg] (P < 0.01). The ratio of Kv1.5 mRNA expression in distal pulmonary arteries in 1 month, 3 month, 6 month cigarette exposure group to that in control groups was (52 ± 11)%, (64 ± 19)% and (75 ± 11)% (P < 0.05). The ratio of Kv2.1 mRNA expression in distal pulmonary arteries in 1 month, 3 month, 6 month cigarette exposure groups to that in control groups was (51.0 ± 18.6)%, (78.7 ± 10.1)% and (71.4 ± 2.3)% (P < 0.01); Chronic exposure to cigarette smoke significantly decreased Kv1.5 and Kv2.1 mRNA expression in rat pulmonary arterial smooth muscle at each time point. The ratio of Kv1.5 and Kv2.1 mRNA expression in rat distal PASMCs treated with nicotine (100 nmol/L, 48 h) to control group were (62 ± 14)% (P < 0.05) and (72 ± 15)% (P < 0.01), respectively. Nicotine inhibited Kv1.5 and Kv2.1 mRNA expression in rat distal PASMCs. Cigarette smoke exposure may be involved in pulmonary hypertension by downregulating potassium channels Kv1.5 and Kv2.1 mRNA expression in rat pulmonary artery smooth muscles.

Involvement of endogenous hydrogen sulfide in cigarette smoke-induced changes in airway responsiveness and inflammation of rat lung

Hydrogen sulfide (H 2S), recently considered the third endogenous gaseous transmitter, may have an important role in systemic inflammation. We investigated whether endogenous H 2S may be a crucial mediator in airway responsiveness and airway inflammation in a rat model of chronic exposure to cigarette smoke (CS). Rats randomly divided into control and CS-exposed groups were treated with or without sodium hydrosulfide (NaHS, donor of H 2S) or propargylglycine (PPG, inhibitor of cystathionine-γ-lyase [CSE], an H 2S-synthesizing enzyme) for 4-month exposure. Serum H 2S level and CSE protein expression in lung tissue were higher, by 2.04- and 2.33-fold, respectively, in CS-exposed rats than in controls ( P < 0.05). Exogenous administration of NaHS to CS-exposed rats alleviated airway reactivity induced by acetylcholine (Ach) or potassium chloride (KCl) by 17.4% and 13.8%, respectively, decreased lung pathology score by 32.7%, inhibited IL-8 and TNF- α concentrations in lung tissue by 34.2% and 31.4%, respectively, as compared with CS-exposed rats (all P < 0.05). However, blocking endogenous CSE with PPG in CS-exposed rats increased airway reactivity induced by Ach or KCl, by 24.1% and 24.5%, respectively, and aggravated lung pathology score, by 44.8%, as compared with CS-exposed rats (all P < 0.01). Incubation in vitro with NaHS, 1–3 mmol/L, relaxed rat tracheal smooth muscle precontracted by Ach or KCl. However, the NaHS-induced relaxation was not blocked by glibenclamide (10 −4 mol/L), L-NAME (10 −4 mol/L), or ODQ (1 μmol/L) or denudation of epithelium. Endogenous H 2S may have a protective role of anti-inflammation and bronchodilation in chronic CS-induced pulmonary injury.