An Interesting Molecule: γ-Aminobutyric Acid. What Can We Learn from Hydra Polyps?

Neuronal excitability is controlled primarily by gamma-aminobutyric acid (GABA) in the central and peripheral nervous systems of vertebrate as well as invertebrate organisms. Besides its recognized neurotransmitter functions, GABA also plays a fundamental role in neurogenesis and synaptogenesis during embryonic development. In addition, GABAergic mechanisms are also involved in disorders of various peripheral tissues, ranging from diabetes to hypothyroidism to inflammatory responses. The discovery of the molecule and the history of its biosynthetic pathways in vertebrate and invertebrate phyla are summarized here. The occurrence and distribution of GABA, GABA-synthesizing enzymes, and receptors to GABA in the freshwater polyp Hydra vulgaris (Cnidaria: Hydrozoa), endowed with an early evolved nervous system, are discussed in relation to possible interactions with the microbiota, a stable component of Hydra polyps; their contribution to the evolution of nervous systems through microbe-neuronal interactions is proposed.

Automated summary

GABA plays a crucial role in controlling neuronal excitability in vertebrate and invertebrate organisms, as well as in neurogenesis and synaptogenesis during embryonic development. In addition, GABA is implicated in various peripheral tissue disorders. The presence of GABA and its interactions with microbiota in freshwater polyps suggest a potential contribution to the evolution of nervous systems through microbe-neuronal interactions.