Herbal Products and GABA Receptors

This article profiles ten examples of chemicals derived from herbal preparations that influence ionotropic receptors for the brain’s major inhibitory neurotransmitter g-aminobutyric acid (GABA). Many herbal medicines are used to influence brain function in order to treat anxiety, cognitive disorders, and insomnia. Such disorders are considered likely to involve GABA receptors, particularly ionotropic receptors that are responsible for fast synaptic transmission via ion channels. The evidence of efficacy, or otherwise, in the use of herbal medicines to treat central nervous system (CNS) disorders remains to be established unequivocally in many cases. There is no doubt, however, that these products contain chemicals that in their pure form can be shown to influence brain function in specific ways. The structural diversity of these chemicals provides valuable leads for the development of new therapeutic agents and tools with which to investigate nervous system function. Herbal medicines are usually complex mixtures of chemicals. The combined actions of these chemicals may contribute to the overall effects of the medicines. Thus, it is important to study interactions among the individual chemicals.With respect to ionotropicGABA receptors, there are examples of synergistic interactions between two chemicals and examples of what has been termed second-order modulation, in which a second modulator enhances the action of a first-order modulator. Thismay represent a new formof drug action and lead to the identification of new drug targets. Investigating the complex ways in which these chemicals interact could lead to a better understanding of the function of ionotropic GABA receptors. GABA itself is an important plant constituent, and thus it should not be surprising that plants contain a range of other chemicals that can influence GABA function. In addition, there are examples of plantderived GABA mediating some form of communication among animals, bacteria, fungi, and plants. Thus, GABA may represent a conserved and ubiquitous biological signaling molecule. Quality control of herbal medicines is a significant problem. Identification of key active ingredients in herbal medicines and the interactions among them