ADAPTOGENIC (MODULATES STRESS RESPONSE)
Siberian ginseng appears to alter the levels of different neurotransmitters and hormones involved in the stress response, chiefly at the HPA axis. It degrades the enzyme (catechol-O-methyl transferase), and increases levels of noradrenaline and serotonin in the brain and adrenaline in the adrenal glands, according to animal studies (Abramova et al 1972). Eleutherosides have also been reported to bind to Ginseng_Siberian 577
receptor sites for progestin, oestrogen, mineralocorticoids and glucocorticoids in vitro
and therefore may theoretically exert numerous pharmacological actions important for the body's stress response (Pearce et al 1982).
Owing to such actions, herbalists and naturopaths describe the herb's overall action as 'adaptogenic', whereby the body is better able to adapt to change and homeostasis is more efficiently restored. More recently, the term 'allostasis' is being adopted in the medical arena to describe 'the ability to achieve stability through change'.
Clinical note — Allostasis
Allostasis is the body's adaptation to stress. Allostatic (adaptive) systems are critical to survival and enable us to respond to changes in our physical state (such as asleep, awake, standing, sitting, eating, exercising, infection) and psychological states (such as anticipation, fear, isolation, worry and lack of control). The consumption of tobacco, alcohol and our dietary choices also induce allostatic responses (McEwan 1998). These systems are complex and have broad boundaries, in contrast to the body's homeostatic systems (e.g. blood pH and body temperature), which are maintained within a narrow range.
Most commonly, allostatic responses involve the sympathetic nervous system and the HPA axis. Upon activation (e.g. a challenge is perceived), catecholamines are released from nerves and the adrenal medulla, corticotrophin is secreted from the pituitary and Cortisol is released from the adrenal cortex. Once the threat has passed (e.g. environment is more comfortable or infection is controlled), the system is inactivated and levels of Cortisol and catecholamine secretion return to baseline.
Chronic exposure to stress can lead to allostatic load, a situation resulting from chronic overactivity or underactivity of allostatic systems. The situation is characterised by maladaptive responses whereby systems become inefficient or do not turn off appropriately. Currently, there is much interest in understanding the association between numerous diseases such as cardiovascular disease and overwhelming allostatic load.
One measure that is used to gauge an individual's allostatic response is the Cortisol response to a variety of stressors. As such, Cortisol is seen as the classical 'stress' hormone.
Although the mechanism of action responsible is still unclear, several theories have been proposed to explain the effect of Siberian ginseng on allostatic systems, largely based on the pharmacological actions observed in test-tube and animal studies.
Siberian ginseng increases levels of noradrenaline, serotonin, adrenaline and Ginseng—Siberian 578
Cortisol that are able to induce both positive and negative feedback responses
(Abramova et al 1972, Gaffney et al 2001a). Therefore, for example, If allostatlc load Is such that responses have become Inadequate, then the resulting Increase In hormone levels would theoretically Induce a more efficient response. Alternatively, situations of chronic overactivity, also due to allostatic load, would respond to Siberian ginseng in a different way, with negative feedback systems being triggered to inactivate the stress response (Gaffney et al 2001 a). As a result, Siberian ginseng could theoretically induce quite different effects, largely dependent on whether allostatic responses were underactive or overwhelmed.
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