The objective of this study is to combine troponin and indicators of cardiac acoustics for synthetically evaluating cardiac fatigue of rabbits, analyzing exercise-induced cardiac fatigue (EICF) and exercise-induced cardiac damage (EICD). New Zealand white rabbits were used to conduct a multi-step swimming experiments with load, reaching an exhaustive state for evaluating if the amplitude ratio of the first to second heart sound (S1/S2) and heart rate (HR) during the exhaustive exercise would decrease or not and if they would be recovered 24-48 h after exhaustive exercise. The experimental end point was to complete 3 times of exhaustions or death from exhaustion. Circulating troponin I (cTnI) were detected from all of the experimental rabbits at rest [(0. 02±0. 01) ng/mL], which, in general, indicated that there existed a physiological release of troponin. After the first exhaustive swim, cTnI of the rabbits increased. However, with 24-hour rest, S1/S2, HR, and cTnI of the tested rabbits all returned toward baseline levels, which meant that the experimental rabbits experienced a cardiac fatigue process. After repeated exhaustion, overloading phenomena were observed, which led to death in 3 out of 11 rabbits, indicating their cardiac damage; the troponin elevation under this condition could be interpreted by pathological release. Evaluation of myocardial damage can not be based on the troponin levels alone, but can only be based on a comprehensive analysis.
Animals ; Fatigue ; Heart ; physiopathology ; Heart Rate ; Myocardium ; pathology ; Rabbits ; Swimming ; Troponin I ; blood

Objective To observe effects of conditioned place preference (CPP) of morphine dependent rats,variation of dopamine neurotransmitter and its receptor 2 of the striatum in rats suffered from 1-tetrabydropalmatine(l-THP).Methods The CPP model was established by morphine injection in rats with a increasing dose for 10 days,with the initial dose of 10 mg · kg-1 and the final dose of 100 mg · kg-1,10 mg · kg-1 was increased each day,thus 100 nmg · kg-1 Was injected by day 10.Treatments with administration of 1-THP(3.76,1.88 and 0.94 mg/kg) were performed respectively for 6 days,and the effects of CPP for psychological dependence in these rats were observed.Striatum samples were taken out and their variable contents of dopamine neurotransmitter and its receptor 2 in striatum were detected by high performance liquid chromatography and immunohistochemisty,respectively.Results Compared with the NS treatment group,the time of animals treated with 1-THP (3.76 and 1.88 mg/kg) staying in drug-paired compartment were reduced (354 ± 58,373 ± 79) (P＜ 0.01) ;the raised of variation contents of dopamine neurotransmitter were reduced in striatum from those rats(5.49 ± 1.95,6.11 ± 1.05),while the expression level of dopamine receptor 2 was increased(0.08 ± 0.02,0.07 ± 0.03) (P ＜ 0.01 or P ＜0.05).Conclusion Reversing dopamine neurotransmitter and its receptor 2 in striatum of morphine dependent rats may be one of the possible mechanisms that 1-THP effectively inhibit the effects of morphine CPP.

Objective To observe the level of dopamine and its receptor in striatum from conditioned place preference (CPP) of rats administrated of morphine.And explore the mechanism of opioid-psychic dependence involving the levels of neurotransmitter and receptor.Methods CPP model was validated in morphine-dependence rats for 10 days.Striatum samples were harvested from two separate groups involving the saline group and morphine treated group (n =10 per experiment).The DA contents in striatum were detected in rats with colorimetry.Immunohistochemistry was applied to detect the differential expression levels of dopamine receptor 2 (DRD2)in samples.Results Compared with the saline group,higher content of neurotransmitter dopamine was observed in the morphine dependent rats (7.63 ±0.98 vs 5.23 ± 1.01,P＜0.01),while the expression level of DRD2 was down regulated (0.06 ± 0.02 vs 0.08 ± 0.02,P ＜ 0.01).Conclusion The increased expression of neurotransmitter dopamine and the decreased of DRD2 may be contributed to morphine-induced psychological dependence in morphine dependent rats.

Objective To observe effect of Compound Ruikangxin Capsula(CRC) on anxiety-like symptoms of morphine-withdrawal rats and investigate its mechanism.Methods The elevating doses were applied to validating anxiety-like behavior in SD male rats with sc morphine for 10 d.Treatments with ig administration of CRC(100,200,and 300 mg/kg) and buspirone(15 mg/kg) were performed during 1—3 d morphine withdrawal(twice every day).The plus elevated maze was applied to validating anxiety-like symptom in rats.The expression levels of synaptophysin were detected on hippocampus in groups by immunohistochemitry 72 h after sc morphine.Results As compared with the control group,animals treated with CRC(200 and 300 mg/kg) and buspirone had higher ratio of entry into open arm (P

Objective To investigate expression level of endoplasmic reticulum stressmarker GRP78 in the testicular tissue in rats with different phases of morphine-dependence. To explore the role of ERS in morphine-de-pendence. Methods SD rats were divided into 6 groups: morphine (mor) -withdrawal group, mor-extinct group, mor-kindling group and their control groups, normal saline (NS)-withdrawal group, NS-extinct group, NS-kindling group. The experimental rats were injected with morphine subcutaneously on increasing dosage to establish the con-ditioned place preference (CPP) model. The rats in control groups were injected NS. Then the rats were suffered from withdrawal for 48 h, extinction and kindling by morphine, separately. The GRP78 expression level in testicular tissues of rats in the time point mentioned above were measured using Western Blot. Results The time of rats in the paired-box was (528.0 ± 81.0) s, which was significantly higher than that in the NS control group (P<0.001). It was (396.8 ± 116.9) s after extinctive phase, which was significantly higher than that the withdrawal phase of rats (P < 0.001). Also it was (396.8 ± 116.9) s after kindling with morphine which was significantly higher than that the extinctive phase of rats (P < 0.001). These changes of the time indicated that the animal models of extinction and kindling were established in the study. The GRP78 levels were down-regulated in 48 h after withdrawal (P <0.05), and increased a bit afterextinctive phase, but up-regulated highly after kindling with morphine (P < 0.01). Conclusion ERS may be related in the morphine dependence and it might play an important role of testicular dys-function in male drugabuser.

This paper presents a preliminary study of rabbit experiment modality incorporating a new indicator for evaluating cardiac function changes, providing a basis for subsequent study of cardiac fatigue. Using only biochemical indicators, such as troponins, is difficult to make a distinction between exercise-induced cardiac fatigue (EICF) and exercise-induced cardiac damage (EICD). Therefore, some new indicators are needed to evaluate cardiac fatigue synthetically. In our study, we used New Zealand white rabbits to conduct a multi-step swimming experiments with load. We made the rabbits reach an exhaustive state to evaluate whether the amplitude ratio of the first to second heart sound (S1/S2) and heart rate (HR) during the exhaustive exercise would be decreased and whether they would be able to recover after the exhaustive exercise for 24 hours. During the first phase of swimming, S1/S2 and HR were increased, and then decreased at exhaustive state. They were recovered after the exhaustive exercise for 24 hours. Overloading led to deaths of three rabbis, and new phenomena from overloading and related to this kind of death were observed. The experiments proved that Multi-steps swimming experiments with loads by using New Zealand white rabbit is useful for studying cardiac fatigue and premonition of sudden cardiac death.
Animals ; Cardiovascular Physiological Phenomena ; Death, Sudden, Cardiac ; Female ; Heart ; physiology ; Heart Rate ; physiology ; Male ; Muscle Fatigue ; physiology ; Myocardial Contraction ; physiology ; Myocardium ; chemistry ; Physical Endurance ; physiology ; Rabbits ; Stress, Physiological ; physiology ; Swimming