Introduction

Stress is defined as the non-specific response of the body to any demand imposed upon it ¹. It is known to alter the physiological homeostasis of the organism and complex mechanisms contribute to the breakdown in adaptational processes resulting in various visceral, endocrinal, and behavioural changes ². Stress plays the main role in pathogenesis of mental disorders ^3,4. A host of chronic psychiatric disease states like melancholic depression, anorexia nervosa, panic disorders, anxiety disorders and cognitive dysfunction have been reported to involve abnormality of stress axis ⁵. Anxiety disorders in particular, affect 1/8 ^th of total population worldwide and have become one of important research interest in psychopharmacology during this decade ⁶. The hallmark of anxiety disorders is marked, persistent and excessive or unreasonable fear that is experienced to a degree that significantly interferes with everyday life ⁷.

The prevention and management of these stress disorders remains a major clinical problem. Benzodiazepines (BDZs) appear to be effective against acute stress but fail to prevent the consequences of chronic stress. In addition, the problems of tolerance and physical dependence exhibited by BDZs on prolonged use, limit their utility ⁸. An answer to this vexing problem was first provided when Brekhman and Dardymov ^{reported that some plant-derived agents could induce a state of non specific increase of resistance to affect internal homeostasis. Such agents, named adaptogen have been found to be effective in attenuating stress-induced adverse effects 9. Thus, in the current scenario, finding such adaptogenic agents that possess the ability to combat present day stress disorders along with possessing anxiolytic potential would offer added benefits in psychiatric treatment.}

From the vast array of Materia Medica of the indigenous system so many plants have been reported to have activity against CNS disorders and thus act as very useful remedies for the alleviation of human suffering ¹⁰. Due to the chronic nature of psychiatric and neurological disorders, the therapeutic action of most psychotropic agents is dependent on long-term treatment and the consequent molecular and cellular adaptations that occur over time ¹¹. In this context, administration of herbal plant-based formulation offers an added edge in treatment considering their cost effectiveness and the mild side effect profile compared to prescription alternatives.

The plant Tylophora indica (Burm.f.) family: Asclepiadaceae is distributed in the plains of southern, central and eastern India. Dried root of the plant have been traditionally useful in treatment of dysentery, asthma and bronchitis ¹². Phenanthroindolizidine alkaloids (tylophorine, tylophorinine, and tylophorinidine) present in the roots are the primary bio-active constituents of this plant ¹³. The indole nucleus and highly lipophilic nature of these alkaloids made the roots of this plant an apt contender for testing its psychopharmacological potential. Since, there is no scientific data regarding effect of roots of the plant on CNS activities, it was thought prudent to investigate its anti-stress and anxiolytic potential in animal models of psychiatric disorders.

Material and methods

Collection of plant material

Preparation of the plant extract

Experimental animals

Acute toxicity studies

Anti-stress activity

Anxiolytic activity

Elevated Plus maze Model (EPM)

Light-dark model

Statistical analysis

Results

Anti-stress activity

Anxiolytic activity

Discussion

A wide variety of stresses, both physical and emotional, act via neural pathways to the hypothalamus to increase corticotropin-releasing hormone (CRH) secretion and hence, adrenocorticotropin hormone (ACTH) and cortisol secretion ¹⁹. Release of ACTH in stress stimulates adrenals to increase production of hormones epinephrine, norepinephrine, and corticosteroids ²⁰. These hormones have profound effect on metabolic functions. Adrenaline raises blood sugar, while corticosteroid stimulates glycogenolysis and gluconeogenesis ²¹. Thus, increased cortisol influences mobilization of stored fat and carbohydrate reserve ²², which in turn increases blood glucose, protein, cholesterol, and triglyceride levels.

Chronic cold restraint stress (CCRS) model was used to deliberate the deleterious effect of chronic stress on the entire body system. Organ body weight indices of adrenal and spleen gland were used as vital markers for studying stress response, as involution of the spleen and increase in adrenal gland weight are primary consequences of chronic stress. The individual or combined weight of adrenal glands is likely to double under the influence of ACTH ^23,24. Pretreatment with TI[AE] at all doses reversed increase in adrenal gland weight caused due to stress besides preventing spleen atrophy, thus inhibiting the basic signs of stress response. Likewise, test extract at all doses ameliorated the stress-induced rise in plasma corticosterone, glucose, cholesterol, triglyceride, and total protein levels in CCRS model. Thus, the mitigating effects shown by aqueous extract of T. indica on chronic stress-induced biochemical and physiological perturbations gives a clear indication of its anti-stress activity. Further, this effect of test extract was found to be comparable to that of diazepam, the conventional adaptogenic agent.

The two experimental models of anxiety, elevated plus maze and light and dark arena, are based on the assumption that unfamiliar, non-protective and brightly lit environmental stress provokes inhibition of normal behaviour. This normal behavioural inhibition is further augmented in the presence of fear or anxiety like state ²⁵. In the elevated plus maze, the open arms are more fear provoking than the closed arms. It has been observed that anxiolytic drugs, diazepam-like, increase the number of arm entries and percentage of time spend in the open arms of an elevated plus maze and anxiogenic drugs have opposite effect ²⁶. In the light and dark box paradigm, the brightly lit environment is a noxious environment stressor that inhibits the exploratory behaviour of rodents. Reduction in the number of entries and time spent in the light chamber are regarded as markers of anxiety ²⁷.

Mice pretreated with TI extract at all the doses showed increase in number of entries and total time spent in open arm in elevated plus maze model. In addition, test extract treated group demonstrated increased number of travellings from dark chamber to light chamber in light-dark model. The behavioural changes in both the models indicative of decreased fear and decreased aversion to bright light, suggests the anxiolytic potency of the extract. The validity of both the anxiolytic models was supported by the observation that diazepam, a classical anxiolytic, showed preference to open arm and light chamber in elevated plus maze and light-dark model respectively.

Conclusion

In conclusion, the present study indicated that aqueous extract of roots of Tylophora indica possess significant anti-stress and anxiolytic activities. The plant can thus, be considered as a valuable contribution to the existing armamentarium of very few agents that possess combination of psychopharmacological activities. Further, this dual potential of T. indica extract may bear a potential clinical use in management of stressed patients suffering from anxiety disorders or vice versa.