Immunohistochemical demonstration of GABAB receptors in the rat gastrointestinal tract

Abstract

Immunohistochemical localization of GABA(B)-receptors was demonstrated in the rat gastrointestinal tract using a monoclonal antibody (GB-1) raised against the purified GABA(B)-receptor. Immunoreactive staining for GABA(B)-receptors was found in some populations of endocrine, muscular and neuronal components in the stomach and gut wall. Positive mucosal epithelial, probably endocrine, cells were distributed throughout the stomach and intestine. Double immunostaining indicated that such positive cells for GABA(B)-receptors often co-possessed serotonin in the small intestine but not in the gastric body. In the muscular layer of the digestive canal, positive staining was seen as dotty granules punctuated on the surface of muscle fibers. In the enteric nervous system, positive neuronal somata were found in both submucosal and myenteric ganglia throughout the entire canal extending from the stomach to the rectum. This is the first report to visualize the cellular localization of GABA(B)-receptors in the gastrointestinal system of the rat, and should provide a fundamental basis for future studies on gastrointestinal functions regulated by GABA(B)-receptors.

Probiotics function mechanistically as delivery vehicles for neuroactive compounds: Microbial endocrinology in the design and use of probiotics

“…The amount of a neurochemical, such as GABA for example, found within, or produced by, probiotics is most likely sufficient to influence localized immune and neurophysiological process in the gut as both immune and neuronal cells have been well documented to respond to nanomolar concentrations of GABA [31,32,[37][38][39]. The delivery of neurochemicals by probiotics may therefore either be in the amount already contained in the bacterium at time of ingestion or that which is actively produced once inside the gastrointestinal tract.…”

Neuroimmune aspects of food intake

“…While this does not prove that GABA was not involved in the anti-nociceptive effects of oral ingestion of lactobacilli, since we have no way of determining how much GABA was synthesized in situ in the intestine, it does nevertheless cast some doubt on this being the mechanism of analgesic effect we have seen. Nevertheless, GABA is synthesized within the intestinal lumen, and some bacteria even have the capacity to selectively take up GABA from the environment through a GABA-like receptor (Guthrie & Nicholson-Guthrie, 1989) and others have shown that GABA, as well as its receptor are routinely expressed within the intestinal epithelium (Nakajima, Tooyama, Kuriyama, & Kimura, 1996), so it is reasonable to assume that local effects of locally synthesized neurotransmitters are playing some physiological roles, in all aspects of interkingdom signaling, bacteria-bacteria communication and also bacteria to host interactions.…”

The Neuro-endocrinological Role of Microbial Glutamate and GABA Signaling

“…GABA and its ionotropic and metabotropic receptors are widely distributed throughout the ENS, in both submucosal and myenteric neurons, from the stomach to the ileum (Auteri et al, 2015). In addition, Nakajima et al (1996) reported the expression of GABA B receptors in cells morphologically similar to EECs, where they co-localized with cells containing somatostatin (in the stomach) or serotonin (in the duodenum). However, a later study failed to detect any positive EEC for GABA B receptors (Casanova et al, 2009).…”