1. Figure 2 The brainstem neurocircuit comprising vagovagal reflexes
Figure 2 | The brainstem neurocircuit comprising vagovagal reflexes. Vagal afferent fibres relay sensory information from the upper gastrointestinal tract, entering the CNS via the TS and transmitting sensory information to neurons of the NTS using glutamate as their main neurotransmitter5,13. The NTS neurons integrate this visceral sensory information, which is then conveyed to higher centres, such as the PVN, as well to the adjacent neurons of the DMV. Although a large array of neurotransmitters are used by NTS neurons, the main neurotransmitters are GABA, Glu and NE. Of these neurotransmitters, GABA seems to play a major part in controlling DMV neuronal firing rate and, by consequence, regulates vagal efferent outflow and modulation of gastric tone and motility45,46. Preganglionic parasympathetic neurons of the DMV use ACh, which interacts with nicotinic receptors, to excite postganglionic myenteric neurons and/or interstitial cells of Cajal. Vagal motor activation can induce both excitatory and inhibitory effects via stimulation of postganglionic neurons, which either release ACh onto excitatory muscarinic receptors or release inhibitory NANC neurotransmitters such as nitric oxide or vasoactive intestinal polypeptide onto gastric smooth muscles. Notably, NANC neurotransmission has an effect on gastric tone and motility, but not secretion. Ach, acetylcholine; AP, area postrema; DMV, dorsal motor nucleus of the vagus; GABA, γ-aminobutyric acid; Glu, glutamate; NANC, non-adrenergic non-cholinergic; NE, noradrenaline; NTS, nucleus tractus solitaries; PVN, paraventricular nucleus of the hypothalamus; TS, tractus solitarius.
Travagli, R. A. & Anselmi, L. (2016) Vagal neurocircuitry and its influence on gastric motility
Nat. Rev. Gastroenterol. Hepatol. doi: /nrgastro