Exploration of animal models to assess Shrama (Fatigue) with reference to Weight Loaded Forced Swimming Test

INTRODUCTION

Ayurveda is not only a system of medicine, it emphasises on the culture, behaviour and huge heritage of India regarding individual life style. It is a time tested science. Evidence-based medicine (EBM) is a form of medicine that aims to optimize decision-making by emphasizing the use of evidence from well designed and conducted research. For globalization of Ayurveda, there is need to create evidence. In an attempt of this the present article throws light on it. In modern sciences many methods were used to assess the anti fatigue effect in animals, out of those Weight Loaded Forced Swimming Test (WFST) can be utilized to objectivise the shrama in an animal experiment model. Shramahara dashemani (Group of 10 drugs performs same action) is explained in the Charaka samhita to alleviate Shrama.

Shrama: The word meaning of Shrama is Fatigue, Weariness, Tired, Exhausted, Exertion and Effort either bodily or mentally etc. Shrama, is a action that produces perspiration. It is mentioned as a symptom in many diseases. It is of two types, viz Sharirika (Physical) and Manasika (Psychological) Shrama¹ .

Shramahara dashemani: In Charaka samhita acharya charaka mentioned Shramahara Mahakashaya having 10 drugs to alleviate Shrama or to increase the physical endurance capacity. viz. Draksha, Kharjura, Priyala, Badara, Dadima, Phalgu, Parushaka, Ikshu, Yava and Shastika2 . [Table no 1 & 2].

Fatigue: Fatigue is known to be accompanied by a feeling of extreme physical or mental tiredness resulting from severe stress. Fatigue can also be defined as the reversible decline in skeletal muscle contractile performance due to intense muscle activity. It can be divided into two categories: physical fatigue caused by such things as over exercises or heavy movement of muscle for a long time and it can effect in deterioration of physical performance, mental fatigue caused by sleep deprivation or mental stress. It is a physiological phenomenon that appears with physical stress or exhaustive exercises, which reduces the physical endurance capacity³ .

Theories of Fatigue: The ‘‘exhaustion theory” suggests that during exercise, many energy sources, such as glucose and liver glycogen, will be exhausted, thus leading to physical fatigue. Several reports showed that post-exercise nutrition through the administration of proteins, peptides or amino acids can facilitate recovery from fatigue (Wang et al., 2008). Compared with proteins, peptides, as nutrition supplements, not only are absorbed quickly and easily without competition from amino acids, but also promote the use of amino acids, proteins and glucose. Therefore, peptides may be useful in assisting in counteracting and ameliorating physical fatigue.

The ‘‘clogging theory’’, the over accumulation of serum lactic acid (LA) and blood urea nitrogen (BUN) will also result in metabolic disorders leading to fatigue.

Among the fatigue mechanisms, the ‘‘radical theory” has been attracting more interest. Harman’s classical ‘‘radical theory’’ suggests that intense exercise can produce an imbalance between the body’s oxidation system and its anti-oxidation system. The accumulation of reactive free radicals will put the body in a state of oxidative Stress and bring injury to the body by attacking large molecules and cell organs. Muscle cells contain complex endogenous cellular defense mechanisms to eliminate reactive oxygen species, such as superoxide dismutase (SOD), glutathione peroxidase (GPx) and catalase (CAT), and to protect among other things against exerciseinduced oxidative injury⁴ .

Oxidative stress in Physical Performance:

Physical exercises by means of contracting skeletal muscles generate free radicals and that prolonged and intense exercise can result in oxidative damage to cell constituents. Free radicals can be generated as products of homolytic, heterolytic or redox reactions, producing either charged or uncharged radical species. The primary free radicals generated in cells are superoxide (O2.-) and nitric oxide (NO). O2.- is generated through either incomplete reduction of oxygen in electron transport system or as a specific product of enzymatic system, while NO is generated by a series of enzymes.

Animal Models of Physical Stress:

Stress undoubtedly has become an integral part of human life. Stressful conditions have a derogative effect on normal physiological functions leading to a variety of disease states. Many of the most prevalent diseases of the modern era like hypertension, diabetes, behavioural disorders, etc. have been implicated as one of the many ill-effects of chronic stress. Experimental models are required to better understand the progression of the disease and elaborate new therapy. An ideal model should be able to reproduce each of the aspects of stress response and should be able to mimic the natural progression of the disease. Different animal models of stress that have been used are able to evaluate many biochemical or physiological parameters that get altered as a response to stress, however these models are unable to fully mimic the pathophysiological changes caused by stress.

Since long, these animal models i.e. rat/mice models to evaluate effect of stress and its mechanism have been developed and used frequently with anti-stress compounds from natural and synthetic origin. An ideal animal model should be able to reproduce each of the aspects of stress response and should be able to mimic the natural progression of the disease.

However, none of the models available is able to entirely reproduce stress response. Some models reproduce physical stress and associated neuroendocrine changes, whereas others better reproduce the psychological stress and associated behavioral changes. Acute models do not reproduce the neuroendocrine dysfunction whereas a chronic model might be able to do so. Therefore, a correct model should be used to evaluate specific aspects of the stress response5. Each model has inherent limitations including lack of stability, lack of predictability of tissue damage, and lack of adjustability. The commonly used animal models for different types of stress have been illustrated below (Table No.03).

Weight Loaded Forced Swimming Test (WFST): The acute weight-loaded forced swimming test (AWLFS) was used as described previously with some modifications6 (Jung et al., 2007). The rats of Test drug administered groups and control group were taken for swimming exercise with support of constant loads (attached to the tails) corresponding to 5% of their body weight. The swimming exercise was carried out in small tank with 30cm deep with water maintained at 25 ±2 °C. Exhaustion was determined by observing loss of coordinated movements and failure to return to the surface within 10s7 (Wang et al., 2006). This experiment was repeated every alternate day for a period over two weeks. After two weeks Animals were sacrificed under mild anaesthesia. Blood samples were collected immediately after the last exercise.

Parameters of the assessment

• Blood biochemical parameters- Glucose, Lactic Acid, Blood Urea Nitrogen (BUN), Creatinine kinase (CK) will be studied by Spectrophotometric method and using biochemical kits.

• Tissue biochemical parameters- Liver and Muscle tissues will be collected after animal sacrifice, and will be stored in -80 C for further biochemical parameters study like Glycogen, Lactic Acid and Lipid Peroxidase (MDA) will be studied by using various biochemical procedures.

• Anti-Oxidant Enzyme Assays - Supra Oxide Dismutase (SOD), Catalase (CAT) and Glutathione Peroxidase (GPx) will be studied be spectrophotometric method

DISCUSSION

Shrama vis~à~vis Fatigue: Shrama is determined by Swedagama, Karmendriya Akshamatva etc features8, Fatigue is a subjective feeling of tiredness that can be alleviated by periods of rest. Based on the physiology, pathology and treatment, Shrama is co related to fatigue. Their similarities are as follows,(Table no 4)

Weight Loaded Forced Swimming Test : It is one of the commonly used animal models of behavioural despair that has been used extensively for the evaluation of anti fatigue properties of novel compounds⁹ . In order to clarify mechanism, blood biochemical parameters can measured in the weight loaded forced swimming test. The swimming exercise is known to induce biochemical changes in blood. Parameters of assessment

a) Tissue Biochemical Parameters

Based on the exhaustion theory – Tissue glycogen content was estimated,

Clogging theory- Lactic Acid content was estimated,

Radical theory- Lipid peroxidase/ TBARS, SOD, CAT and GPx Anti oxidants were evaluated from the liver samples.

These theories explain the involvement of these parameters on muscle and liver tisuues in fatigue.

b) Serum Biochemical Parameters

Based on the exhaustion theory – Serum glucose content was estimated,

Clogging theory- Creatin kinase and BUN were estimated,

These theories explain the involvement of these parameters on serum in fatigue.

CONCLUSION

Shrama is an important concept explained in Ayurveda literature, it holds good with concept of fatigue. Weight Loaded Forced Swimming Test is one of the commonly used animal models for Fatigue. Hence can be used to quantify the Shrama induced in an animal and to test the anti fatigue action of herbs mentioned in Ayurvedic texts.