GABAergic modulation of serotonergic neurons in the dorsal raphe nucleus

The dorsal raphe nucleus (DRN), located in the brainstem, is involved in several functions such as sleep, temperature regulation, stress responses, and anxiety behaviors. This nucleus contains the largest population of serotonin expressing neurons in the brain. Serotonergic DRN neurons receive tonic γ-aminobutyric acid (GABA)inhibitory inputs from several brain areas, as well as from interneurons within the same nucleus. Serotonergic and GABAergic neurons in the DRN can be distinguished by their size, location, pharmacological responses, and electrophysiological properties. GABAergic neurons regulate the excitability of DRN serotonergic neurons and the serotonin release in different brain areas. Also, it has been shown that GABAergic neurons can synchronize the activity of serotonergic neurons across functions such as sleep or alertness. Moreover, dysregulation of GABA signaling in the DRN has been linked to psychiatric disorders such as anxiety and depression. This review focuses on GABAergic transmission in the DRN. The interaction between GABAergic and serotonergic neurons is discussed considering some physiological implications. Also, the main electrophysiological and morphological characteristics of serotonergic and GABAergic neurons are described.