A Survey of Recent Results concerning Glycyrrhizic Acid in Stress and Adaptation

Glycyrrhizic acid (GCA) the active component of liquorice acts by inhibiting the enzyme 11-hydroxysteroid dehydrogenase (11HSD) which is a microsomal enzyme catalysing the reversible conversion of corticosterone to 11-dehydrocorticosterone. On repeated exposure to ether stress, there was a significant reduction in tail blood pressure during the second exposure followed by adaptation on the fifth to seventh exposure. This stress-induced hypotension was blocked by prior treatment with opioid antagonist Naloxone, mineralocorticoid deoxycorticosterone and GCA. It is not mediated by the -endorphins containing neurons at the paraventricular nucleus of the hypothalamus. The 11HSD type 1 bioactivity is reduced in the anterior pituitary of rats exposed to ether stress suggesting it could be involved in blocking stress-induced hypotension. Rats exposed to restraint stress demonstrated similar pattern, that is, a significant decrease in the locomotor activity on the second exposure and adaptation on the seventh exposure. This decrease in locomotor activity was partially blocked and adaptation to the repetitive stress was enhanced in rats given GCA. It thus appears that GCA acts in reducing stress by increasing the body's corticosterone level by blocking the enzyme which breaks it down.