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Behavioral Observation and Analysis of PMS Liver-qi Depression Rat Model Established by Chronic Restraint Stress and Resident-Intruder Paradigm
WORLD SCIENCE AND TECHNOLOGY MODERNIZATION OF TRADITIONAL CHINESE MEDICINE AND MATERIA MEDICA
Volume 14, Issue 4, August 2012 Online English edition of the Chinese language journal Cite this article as: Mode Tradit Chin Med Mater Med, 2012, 14(4): 1848–1852
RESEARCH
Behavioral Observation and Analysis of PMS Liver-qi Depression Rat Model Established by Chronic Restraint Stress and Resident-Intruder Paradigm Wei Sheng1, 2, Wang Haiping3, Qiao Mingqi1* 1
Key Laboratory of Traditional Chinese Medicine Classics Theory, Ministry of Education, Shandong University of Traditional Chinese Medicine, Jinan 250355, China 2 Lab of Behavioral Brain Analysis, Shandong University of Traditional Chinese Medicine, Jinan 250355, China 3 Shandong Arura Pharmaceutical Research & Development Company Limited, Jinan 250100, China
Abstract: This study was aimed at investigating the feasibility of establishing premenstrual syndrome (PMS) liver-qi depression rat model with resident-intruder paradigm compared to chronic restraint stress. The PMS liver-qi depression rat model was prepared with chronic restraint stress and resident-intruder paradigm. The effect was systematically evaluated through behavioral methods such as open-field test and tail suspension test. Then, results from both groups were compared. The results showed that both chronic restraint stress and resident-intruder paradigm can effectively simulate the state of premenstrual depression and postmenstrual disappearance. The results of the open-field test suggested that there was no significant difference between these two methods (P > 0.05). It was concluded that as a social psychological stress method the resident-intruder paradigm can preferably simulate the process of clinical PMS liver-qi depression caused by emotional abnormality and overcome the disadvantage of obvious body stress of the chronic restraint stress method. But the success ratio was too low, and further inspection was needed to examine its stability. Key Words: Premenstrual syndrome, liver-qi depression, rat model, chronic restraint stress, resident–intruder paradigm
Our research group encountered a lot of problems, which need to be improved, in the early exploration on the preparation and evaluation of the premenstrual syndrome (PMS) liver-qi depression rat model. Chronic restraint stress, which is widely used as a modeling method, has an obvious physical stimulation on rats and then makes the results fluctuate. Furthermore, this method is unable to comply with animal ethics requirements. Therefore, the experiment was intended to refer to the latest progress abroad. The resident-intruder paradigm was used to prepare the PMS liver-qi depression rat model [1, 2]. Some classic behavioral tests such as openfield test and tail suspension test were applied in the evaluation of the model prepared in this article. And all indexes were contrasted with former ones prepared by chronic restraint stress. This study was aimed at providing a more suitable thought and method for the preparation and evaluation of an emotionally disordered animal model.
A total of 86 SPF SD female rats were chosen with body weights ranging from 180 g to 220 g. A total of 20 healthy SPF Wistar female rats were chosen with body weights ranging from 220 g to 250 g. They were provided by the Experimental Animal Centre of Shandong University of Traditional Chinese Medicine with production license SCXK (Lu) 2005 0015.
1
The estrum of rats was confirmed by observing the vagina cell shape. Vaginal smear was conducted 5-9 times every day for 28 days to confirm the estrous cycle of every experimental rat [3]. Rats with regular estrous cycles were selected for
Materials and methods
1.1 1.1.1
Materials Sample animals
1.1.2
Drugs and instruments
Jingqianshu granules produced by Qinhuangdao Shanhaiguan Medicine Manufacture with production code Z2005 3087; Giemsa stain; OLYMPUS microscope (OLYMPUS China Co., Japan); Panasonic NV-MX7D Digital Video Camera (Matsushita Electric Industrial Co. Ltd, China Co., Japan); open-field box (self-made). 1.2 1.2.1
Experimental methods Method of confirming the estrous cycle of rats
Received date: 27 December 2011 *Corresponding author. E-mail: [email protected] Foundation item: Supported by the National Program of Key Basic Research Project (973 Program, No. 2011CB505102). Copyright © 2012, World Science and Technology Press. Published by Elsevier B.V. All rights reserved.
Wei Sheng / Mode Tradit Chin Med Mater Med, 2012, 14(4): 1848–1852
the experiment as follows: The estrous cycle of a rat generally contains non-receptive period (anestrous, metoestrous 1 and metoestrous 2; every stag lasts for about one day) and receptive period (proestrus, estrous; altogether lasts for about one day). The non-receptive period is equivalent to the premenstrual period of human females [1]. 1.2.2
Grouping and rearing
Open-field test was used to select 62 SD rats whose scores were close to each other as the invasion model group. They were marked and weighed and then randomly divided into five groups: normal control group, model 1 group (restraint model group), model 1 administered group (restraint model group with medication), model 2 group (intruder model group) and model 2 administered group (intruder model group with medication), with 8 rats in each group. Meanwhile, 20 Wistar rats were reared as resident rats. The intruder rats were reared in a group, 8 rats in every cage. The resident rat was reared in a single cage. The resident rat and intruder rats were reared in different rooms. The feeding conditions of all rats were identical: day and night reversed (turn on the lights at 21:00, turn off the lights at 9:00 every day). Rats had free access to food and water in addition to the experimental period. 1.2.3
Model and drug administration
1.2.3.1 Chronic restraint stress Selected rats from model 1 group and model 1 administration group, tied the forefoot and lateral foot by sterile gauze, interfere with their freedom of movement with little rat activity, appropriate feeding. Rats were suffered from stress mentioned above for 10 days [3]. The selected rat model was successfully made from model 1 administration group after 5 days, gavaged with Jingqianshu granules at 9:00 every day (equivalent to 8 times the human clinical dose [4], concentration 1:1, 1 mL of liquid containing 1 g of native medicine). Rats from model 1 group were gavaged with sterilized water once a day for 5 days. The administration dosage for rats was 1 mL per 100 g of the rats’ weight. 1.2.3.2 Resident-intruder paradigm Rats from model 2 group and model 2 administration group were selected as intruder rats. Rats were transferred into the resident rat cage for 15 min at 12:00, once a day for 10 days. The experiment was conducted under red light (< 2 lux). To guarantee that each intruder rat suffered uniform homogeneous attacks, the Latin square design was used in the selection of resident rats [5]. Rat models from model 2 administration group were selected after 5 days of modeling and drug administration. The drug administration methods were the same as those described for the chronic restraint stress experiment. 1.2.4
Behavioral determination
Determination of behavior began in the second cycle (day 6 to day 10) after the completion of a rat model of stress. The behavioral indicators of rats in each group were collected se-
parately in the non-receptive period and the receptive period of the estrous cycle. 1.2.4.1 Open-field test Count the open-field test scores immediately after the last resident-intruder paradigm of each intruder rat. The specific operation was as follows: The tail of the rat was gripped at 1/3 of the root by the runner and was put into an open-field box (100 cm × 100 cm × 50 cm). The open-field box was painted with black lacquer, and the undersurface was partitioned into 25 areas with the same size by white lines. The areas along wall were called periphery grilles (including 16 areas). The rest were called central grilles. The rat’s behavior changes were recorded by a photographic recording system for three minutes. After each test, the open-field box was emptied and cleaned with 75% ethanol solution. Crossing score was recorded as the number of times that animals cross undersurface grilles. All four claws must enter the grille. Rearing score was recorded as the number of times that animals make a perpendicular act. The total score is the crossing score added to the rearing score. 1.2.4.2 Tail suspension test Rats were fixed in barrels with twine and tape at 2 cm of the root of the tail after 1 hour of completing the open-field test. They were in the upside-down state. Their heads were about 30 cm from the bottom of the barrels. Behavioral changes of rats were recorded by a photographic recording system for three minutes. Further, 6 minutes of immobility time was recorded. 1.2.4.3 Statistical analysis The experimental data were analyzed by Graphpad Prism 5.0 with one-factor analysis of variance. The experimental data were expressed by x r s .
2
Results
2.1 Scores of tail suspension test and open-field test (non-receptive period, Fig. 1) Compared with the control group, the crossing score, rearing score and total score of rats in model 1 and model 2 groups were remarkably decreased (P < 0.05, P < 0.01). The immobility time of tail suspension test was remarkably increased (P < 0.01). There was no significant difference between the two groups (P > 0.05). The crossing score, rearing score and total score of rats in model 1 and model 2 administration groups were remarkably increased (P < 0.05, P < 0.01). The immobility time of tail suspension test was remarkably decreased (P < 0.01). 2.2 Scores of tail suspension test and open-field test (receptive period, Fig. 2) Compared with the control group, the crossing score, rearing score and total score of rats from model 1 and model 2 groups in the receptive period showed no significant difference (P > 0.05).
Wei Sheng / Mode Tradit Chin Med Mater Med, 2012, 14(4): 1848–1852
Thus, the resident-intruder paradigm was used in this study [7]. The resident-intruder paradigm as a kind of social stress modeling method was first introduced in the successful establishment of premenstrual dysphoric disorder model in 2001 by Hoi-Por Ho et al. [1]. Then, in 2005 Rafal Rygula et al. [2] improved the method and successfully prepared the rat model of depression. Methods used in this experiment were referred to the methods by Hoi-Por Ho and Rafal Rygula. Female Wistar rats were selected and reared individually as intruders. Further, SD rats were selected and reared as residents, which were easily defeated by aggressive ones. As reported in the literature, PMS rat models prepared by the re-
Fig.1 Comparison of scores in the behavioral experiment during the non-receptive period of estrous cycle in rats of each group ( x r s ) Notes: A. Crossing score comparison of each group; B. Rearing score comparison of each group; C. Total score comparison of each group; D. Immobility time comparison of each group. Compared with the control group *P < 0.05, **P < 0.01; compared to the model 1 group, #P < 0.05, ## P < 0.01; compared to the model 2 group, &&P < 0.01.
But the immobility time of tail suspension test was remarkably increased (P < 0.01). Compared with the corresponding model group, the immobility time of tail suspension test from administration group in the receptive period was remarkably decreased (P < 0.01).
3
Discussion
Chronic restraint stress, which is used in the preparation of the depression (equivalent to liver-qi depression) rat model, is a classic method [6]. But in recent years, some people have thought that this approach inevitably mixes the physical stress component and is unable to conduct the purification exploration of emotional psychological stress.
Fig.2 Comparison of scores in the behavioral experiment during the receptive period of estrous cycle in rats of each group ( x r s ) Note: A. Crossing score comparison of each group; B. Rearing score comparison of each group; C. Total score comparison of each group; D. Immobility time comparison of each group. Compared with the control group, **P < 0.01; compared to the model 1 group, ##P < 0.01; compared to the model 2 group, &&P < 0.01.
Wei Sheng / Mode Tradit Chin Med Mater Med, 2012, 14(4): 1848–1852
sident-intruder paradigm have a low success ratio of about 30% [1]. Thus, this experiment selected 62 rats suffering from resident-intruder stress. A total of 16 rats were selected for further experimentation after 5 days of modeling procedure. So the experiment had a success ratio of 25.8%. Although the clinical symptoms of PMS liver-qi depression were complex, its core symptom was the occurrence of depression mood and behavior during the premenstrual period, and symptoms diminished or disappeared after menstruation [89]. In this study, we selected receptive period (equivalent to the postmenstrual period of humankind) and non-receptive period (equivalent to the premenstrual period of humankind) during the estrous cycle in rats exposed to stress. Data of open-field test and tail suspension test were collected. Openfield test can effectively evaluate the animal’s environment excitability, adaptability, exploration, nervousness, memory and other acts. The crossing score reflects the animal’s excitability, and the rearing score reflects its exploration trends in an unfamiliar environment [2]. Thus, the open-field test score reflects overall animal exploratory behavior and excitability. The tail suspension test was used to reflect the degree of physical and psychological fatigue of rats in overcoming outside negative stimulus [10]. The tail suspension immobility time was regarded as the core index, which mainly reflects psychological requirements and emotional states of rats to change the status. The behavioral evaluation results of the experiment showed that compared with the rats in control group the rats of two model types had significantly low scores, including crossing, rearing and total scores. Further, all changes returned to normal levels after Jingqianshu granule administration. There was no significant difference between rats of the two model groups and the control group on all scores mentioned above during the receptive period (P > 0.05). Similarities between appearances were observed on the rats of the two model groups and the symptoms of PMS liver-qi depression patients. This indicated that two modeling methods can approximately induce the characteristic appearance of PMS liver-qi depression on rat models. Further, the symptoms of rats can be reversed by formulas that were proved effective for PMS liver-qi depression patients. Tail suspension test results showed that compared with rats in the control group the immobility time of two model groups were significantly increased in both the receptive and the non-receptive periods (P < 0.01). The results showed that tail suspension test may not be suitable for the evaluation of the PMS liver-qi depression rat model, although it was widely used as a classic depression modeling and behavioral evaluation method. In addition to the behavioral tests mentioned above, experiments such as sucrose prefer-
ence test, forced swimming test, etc., should be confirmed as to whether they are suitable or not for the evaluation of the PMS qi-depression rat model. The results of this experiment showed that model rats prepared by two methods can effectively simulate the symptoms of PMS liver-qi depression patients, and open-field test results showed no significant difference between the two methods (P > 0.05). This experiment used the resident-intruder paradigm as a social psychological stress modeling method. It can simulate the pathogenesis of abnormal emotion triggering PMS liver-qi depression in the clinic. This seems to be better than using chronic restraint stress. However, this modeling method has a low success ratio. Moreover, the stability of this model still requires further evaluation.
References [1]
Hoi-Por Ho, Marie O, Lars W et al. The serotonin reuptake inhibitor fluoxetine reduces sex steroid-related aggression in female rats: an animal model of premenstrual irritability. Neuropsychopharmacology 2001, 24(2): 502-510.
[2]
Rygula R, Abumaria N, Flügge G et a1. Anhedonia and motivational deficits in rats: Impact of chronic social stress. Behavioural Brain Research 2005, 14(7): 127-134.
[3]
Wei S, Zhang HY. Establishment of premenstrual syndrome liver-qi invasion, depression rats model and macroevaluation. Laboratory Animal and Comparative Medicine 2009, 29(3): 142-146.
[4]
Xu SY, Bian RL, Chen X. Pharmacological Experiments Methodology. Beijing: People’s Medical Publishing House 2002: 202-203.
[5]
Rygula R, Abumaria N, Domenici E et al. Effects of fluoxetine on behavioral deficits evoked by chronic social stress in rats. Behavioual Brain Research 2006, 174(1): 188-192.
[6]
O’Mahony SM, Myint AM, van den Hove D et al. Gestational stress leads to depressive-like behavioural and immunological changes in the rat. Neuroimmunomodulation 2006, 13(2): 82-88.
[7]
Zhang HM, Liu XW, Qu HD et al. Establishment and behavioural evaluation of animal model with psycological stress of anger. Chinese Journal of Behavioral Medical Science 2005, 14(2): 188-190.
[8]
Grady-Weliky TA. Clinical practice. Premenstrual dysphoric disorder. N Eng J Med 2003, 348(5): 433-438.
[9]
Kessel B. Premenstrual syndrome. Advances in diagnosis and treatment. Obstet Gynecol Clin North Am 2000, 27(6): 25-39.
[10] Porsolt RD, Pichon ML, Jalfre M. Depression: a new animal model sensitive to antidepressant treatments. Nature 1977, 266(5604): 730-732.
Volume 14, Issue 4, August 2012 Online English edition of the Chinese language journal Cite this article as: Mode Tradit Chin Med Mater Med, 2012, 14(4): 1848–1852
RESEARCH
Behavioral Observation and Analysis of PMS Liver-qi Depression Rat Model Established by Chronic Restraint Stress and Resident-Intruder Paradigm Wei Sheng1, 2, Wang Haiping3, Qiao Mingqi1* 1
Key Laboratory of Traditional Chinese Medicine Classics Theory, Ministry of Education, Shandong University of Traditional Chinese Medicine, Jinan 250355, China 2 Lab of Behavioral Brain Analysis, Shandong University of Traditional Chinese Medicine, Jinan 250355, China 3 Shandong Arura Pharmaceutical Research & Development Company Limited, Jinan 250100, China
Abstract: This study was aimed at investigating the feasibility of establishing premenstrual syndrome (PMS) liver-qi depression rat model with resident-intruder paradigm compared to chronic restraint stress. The PMS liver-qi depression rat model was prepared with chronic restraint stress and resident-intruder paradigm. The effect was systematically evaluated through behavioral methods such as open-field test and tail suspension test. Then, results from both groups were compared. The results showed that both chronic restraint stress and resident-intruder paradigm can effectively simulate the state of premenstrual depression and postmenstrual disappearance. The results of the open-field test suggested that there was no significant difference between these two methods (P > 0.05). It was concluded that as a social psychological stress method the resident-intruder paradigm can preferably simulate the process of clinical PMS liver-qi depression caused by emotional abnormality and overcome the disadvantage of obvious body stress of the chronic restraint stress method. But the success ratio was too low, and further inspection was needed to examine its stability. Key Words: Premenstrual syndrome, liver-qi depression, rat model, chronic restraint stress, resident–intruder paradigm
Our research group encountered a lot of problems, which need to be improved, in the early exploration on the preparation and evaluation of the premenstrual syndrome (PMS) liver-qi depression rat model. Chronic restraint stress, which is widely used as a modeling method, has an obvious physical stimulation on rats and then makes the results fluctuate. Furthermore, this method is unable to comply with animal ethics requirements. Therefore, the experiment was intended to refer to the latest progress abroad. The resident-intruder paradigm was used to prepare the PMS liver-qi depression rat model [1, 2]. Some classic behavioral tests such as openfield test and tail suspension test were applied in the evaluation of the model prepared in this article. And all indexes were contrasted with former ones prepared by chronic restraint stress. This study was aimed at providing a more suitable thought and method for the preparation and evaluation of an emotionally disordered animal model.
A total of 86 SPF SD female rats were chosen with body weights ranging from 180 g to 220 g. A total of 20 healthy SPF Wistar female rats were chosen with body weights ranging from 220 g to 250 g. They were provided by the Experimental Animal Centre of Shandong University of Traditional Chinese Medicine with production license SCXK (Lu) 2005 0015.
1
The estrum of rats was confirmed by observing the vagina cell shape. Vaginal smear was conducted 5-9 times every day for 28 days to confirm the estrous cycle of every experimental rat [3]. Rats with regular estrous cycles were selected for
Materials and methods
1.1 1.1.1
Materials Sample animals
1.1.2
Drugs and instruments
Jingqianshu granules produced by Qinhuangdao Shanhaiguan Medicine Manufacture with production code Z2005 3087; Giemsa stain; OLYMPUS microscope (OLYMPUS China Co., Japan); Panasonic NV-MX7D Digital Video Camera (Matsushita Electric Industrial Co. Ltd, China Co., Japan); open-field box (self-made). 1.2 1.2.1
Experimental methods Method of confirming the estrous cycle of rats
Received date: 27 December 2011 *Corresponding author. E-mail: [email protected] Foundation item: Supported by the National Program of Key Basic Research Project (973 Program, No. 2011CB505102). Copyright © 2012, World Science and Technology Press. Published by Elsevier B.V. All rights reserved.
Wei Sheng / Mode Tradit Chin Med Mater Med, 2012, 14(4): 1848–1852
the experiment as follows: The estrous cycle of a rat generally contains non-receptive period (anestrous, metoestrous 1 and metoestrous 2; every stag lasts for about one day) and receptive period (proestrus, estrous; altogether lasts for about one day). The non-receptive period is equivalent to the premenstrual period of human females [1]. 1.2.2
Grouping and rearing
Open-field test was used to select 62 SD rats whose scores were close to each other as the invasion model group. They were marked and weighed and then randomly divided into five groups: normal control group, model 1 group (restraint model group), model 1 administered group (restraint model group with medication), model 2 group (intruder model group) and model 2 administered group (intruder model group with medication), with 8 rats in each group. Meanwhile, 20 Wistar rats were reared as resident rats. The intruder rats were reared in a group, 8 rats in every cage. The resident rat was reared in a single cage. The resident rat and intruder rats were reared in different rooms. The feeding conditions of all rats were identical: day and night reversed (turn on the lights at 21:00, turn off the lights at 9:00 every day). Rats had free access to food and water in addition to the experimental period. 1.2.3
Model and drug administration
1.2.3.1 Chronic restraint stress Selected rats from model 1 group and model 1 administration group, tied the forefoot and lateral foot by sterile gauze, interfere with their freedom of movement with little rat activity, appropriate feeding. Rats were suffered from stress mentioned above for 10 days [3]. The selected rat model was successfully made from model 1 administration group after 5 days, gavaged with Jingqianshu granules at 9:00 every day (equivalent to 8 times the human clinical dose [4], concentration 1:1, 1 mL of liquid containing 1 g of native medicine). Rats from model 1 group were gavaged with sterilized water once a day for 5 days. The administration dosage for rats was 1 mL per 100 g of the rats’ weight. 1.2.3.2 Resident-intruder paradigm Rats from model 2 group and model 2 administration group were selected as intruder rats. Rats were transferred into the resident rat cage for 15 min at 12:00, once a day for 10 days. The experiment was conducted under red light (< 2 lux). To guarantee that each intruder rat suffered uniform homogeneous attacks, the Latin square design was used in the selection of resident rats [5]. Rat models from model 2 administration group were selected after 5 days of modeling and drug administration. The drug administration methods were the same as those described for the chronic restraint stress experiment. 1.2.4
Behavioral determination
Determination of behavior began in the second cycle (day 6 to day 10) after the completion of a rat model of stress. The behavioral indicators of rats in each group were collected se-
parately in the non-receptive period and the receptive period of the estrous cycle. 1.2.4.1 Open-field test Count the open-field test scores immediately after the last resident-intruder paradigm of each intruder rat. The specific operation was as follows: The tail of the rat was gripped at 1/3 of the root by the runner and was put into an open-field box (100 cm × 100 cm × 50 cm). The open-field box was painted with black lacquer, and the undersurface was partitioned into 25 areas with the same size by white lines. The areas along wall were called periphery grilles (including 16 areas). The rest were called central grilles. The rat’s behavior changes were recorded by a photographic recording system for three minutes. After each test, the open-field box was emptied and cleaned with 75% ethanol solution. Crossing score was recorded as the number of times that animals cross undersurface grilles. All four claws must enter the grille. Rearing score was recorded as the number of times that animals make a perpendicular act. The total score is the crossing score added to the rearing score. 1.2.4.2 Tail suspension test Rats were fixed in barrels with twine and tape at 2 cm of the root of the tail after 1 hour of completing the open-field test. They were in the upside-down state. Their heads were about 30 cm from the bottom of the barrels. Behavioral changes of rats were recorded by a photographic recording system for three minutes. Further, 6 minutes of immobility time was recorded. 1.2.4.3 Statistical analysis The experimental data were analyzed by Graphpad Prism 5.0 with one-factor analysis of variance. The experimental data were expressed by x r s .
2
Results
2.1 Scores of tail suspension test and open-field test (non-receptive period, Fig. 1) Compared with the control group, the crossing score, rearing score and total score of rats in model 1 and model 2 groups were remarkably decreased (P < 0.05, P < 0.01). The immobility time of tail suspension test was remarkably increased (P < 0.01). There was no significant difference between the two groups (P > 0.05). The crossing score, rearing score and total score of rats in model 1 and model 2 administration groups were remarkably increased (P < 0.05, P < 0.01). The immobility time of tail suspension test was remarkably decreased (P < 0.01). 2.2 Scores of tail suspension test and open-field test (receptive period, Fig. 2) Compared with the control group, the crossing score, rearing score and total score of rats from model 1 and model 2 groups in the receptive period showed no significant difference (P > 0.05).
Wei Sheng / Mode Tradit Chin Med Mater Med, 2012, 14(4): 1848–1852
Thus, the resident-intruder paradigm was used in this study [7]. The resident-intruder paradigm as a kind of social stress modeling method was first introduced in the successful establishment of premenstrual dysphoric disorder model in 2001 by Hoi-Por Ho et al. [1]. Then, in 2005 Rafal Rygula et al. [2] improved the method and successfully prepared the rat model of depression. Methods used in this experiment were referred to the methods by Hoi-Por Ho and Rafal Rygula. Female Wistar rats were selected and reared individually as intruders. Further, SD rats were selected and reared as residents, which were easily defeated by aggressive ones. As reported in the literature, PMS rat models prepared by the re-
Fig.1 Comparison of scores in the behavioral experiment during the non-receptive period of estrous cycle in rats of each group ( x r s ) Notes: A. Crossing score comparison of each group; B. Rearing score comparison of each group; C. Total score comparison of each group; D. Immobility time comparison of each group. Compared with the control group *P < 0.05, **P < 0.01; compared to the model 1 group, #P < 0.05, ## P < 0.01; compared to the model 2 group, &&P < 0.01.
But the immobility time of tail suspension test was remarkably increased (P < 0.01). Compared with the corresponding model group, the immobility time of tail suspension test from administration group in the receptive period was remarkably decreased (P < 0.01).
3
Discussion
Chronic restraint stress, which is used in the preparation of the depression (equivalent to liver-qi depression) rat model, is a classic method [6]. But in recent years, some people have thought that this approach inevitably mixes the physical stress component and is unable to conduct the purification exploration of emotional psychological stress.
Fig.2 Comparison of scores in the behavioral experiment during the receptive period of estrous cycle in rats of each group ( x r s ) Note: A. Crossing score comparison of each group; B. Rearing score comparison of each group; C. Total score comparison of each group; D. Immobility time comparison of each group. Compared with the control group, **P < 0.01; compared to the model 1 group, ##P < 0.01; compared to the model 2 group, &&P < 0.01.
Wei Sheng / Mode Tradit Chin Med Mater Med, 2012, 14(4): 1848–1852
sident-intruder paradigm have a low success ratio of about 30% [1]. Thus, this experiment selected 62 rats suffering from resident-intruder stress. A total of 16 rats were selected for further experimentation after 5 days of modeling procedure. So the experiment had a success ratio of 25.8%. Although the clinical symptoms of PMS liver-qi depression were complex, its core symptom was the occurrence of depression mood and behavior during the premenstrual period, and symptoms diminished or disappeared after menstruation [89]. In this study, we selected receptive period (equivalent to the postmenstrual period of humankind) and non-receptive period (equivalent to the premenstrual period of humankind) during the estrous cycle in rats exposed to stress. Data of open-field test and tail suspension test were collected. Openfield test can effectively evaluate the animal’s environment excitability, adaptability, exploration, nervousness, memory and other acts. The crossing score reflects the animal’s excitability, and the rearing score reflects its exploration trends in an unfamiliar environment [2]. Thus, the open-field test score reflects overall animal exploratory behavior and excitability. The tail suspension test was used to reflect the degree of physical and psychological fatigue of rats in overcoming outside negative stimulus [10]. The tail suspension immobility time was regarded as the core index, which mainly reflects psychological requirements and emotional states of rats to change the status. The behavioral evaluation results of the experiment showed that compared with the rats in control group the rats of two model types had significantly low scores, including crossing, rearing and total scores. Further, all changes returned to normal levels after Jingqianshu granule administration. There was no significant difference between rats of the two model groups and the control group on all scores mentioned above during the receptive period (P > 0.05). Similarities between appearances were observed on the rats of the two model groups and the symptoms of PMS liver-qi depression patients. This indicated that two modeling methods can approximately induce the characteristic appearance of PMS liver-qi depression on rat models. Further, the symptoms of rats can be reversed by formulas that were proved effective for PMS liver-qi depression patients. Tail suspension test results showed that compared with rats in the control group the immobility time of two model groups were significantly increased in both the receptive and the non-receptive periods (P < 0.01). The results showed that tail suspension test may not be suitable for the evaluation of the PMS liver-qi depression rat model, although it was widely used as a classic depression modeling and behavioral evaluation method. In addition to the behavioral tests mentioned above, experiments such as sucrose prefer-
ence test, forced swimming test, etc., should be confirmed as to whether they are suitable or not for the evaluation of the PMS qi-depression rat model. The results of this experiment showed that model rats prepared by two methods can effectively simulate the symptoms of PMS liver-qi depression patients, and open-field test results showed no significant difference between the two methods (P > 0.05). This experiment used the resident-intruder paradigm as a social psychological stress modeling method. It can simulate the pathogenesis of abnormal emotion triggering PMS liver-qi depression in the clinic. This seems to be better than using chronic restraint stress. However, this modeling method has a low success ratio. Moreover, the stability of this model still requires further evaluation.
References [1]
Hoi-Por Ho, Marie O, Lars W et al. The serotonin reuptake inhibitor fluoxetine reduces sex steroid-related aggression in female rats: an animal model of premenstrual irritability. Neuropsychopharmacology 2001, 24(2): 502-510.
[2]
Rygula R, Abumaria N, Flügge G et a1. Anhedonia and motivational deficits in rats: Impact of chronic social stress. Behavioural Brain Research 2005, 14(7): 127-134.
[3]
Wei S, Zhang HY. Establishment of premenstrual syndrome liver-qi invasion, depression rats model and macroevaluation. Laboratory Animal and Comparative Medicine 2009, 29(3): 142-146.
[4]
Xu SY, Bian RL, Chen X. Pharmacological Experiments Methodology. Beijing: People’s Medical Publishing House 2002: 202-203.
[5]
Rygula R, Abumaria N, Domenici E et al. Effects of fluoxetine on behavioral deficits evoked by chronic social stress in rats. Behavioual Brain Research 2006, 174(1): 188-192.
[6]
O’Mahony SM, Myint AM, van den Hove D et al. Gestational stress leads to depressive-like behavioural and immunological changes in the rat. Neuroimmunomodulation 2006, 13(2): 82-88.
[7]
Zhang HM, Liu XW, Qu HD et al. Establishment and behavioural evaluation of animal model with psycological stress of anger. Chinese Journal of Behavioral Medical Science 2005, 14(2): 188-190.
[8]
Grady-Weliky TA. Clinical practice. Premenstrual dysphoric disorder. N Eng J Med 2003, 348(5): 433-438.
[9]
Kessel B. Premenstrual syndrome. Advances in diagnosis and treatment. Obstet Gynecol Clin North Am 2000, 27(6): 25-39.
[10] Porsolt RD, Pichon ML, Jalfre M. Depression: a new animal model sensitive to antidepressant treatments. Nature 1977, 266(5604): 730-732.