Receptors and transmission in the brain-gut axis: Potential for novel therapies - V. Fast and slow extrinsic modulation of dorsal vagal complex circuits

Vago-vagal reflex circuits in the medulla are responsible for the smooth co ordination of the digestive processes carried out from the oral cavity to t he transverse colon. In this themes article, we concentrate mostly on elect rophysiological studies concerning the extrinsic modulation of these vago-v agal reflex circuits, with a particular emphasis on two types of modulation , i.e., by "fast" classic neurotransmitters and by "slow" neuromodulators. These examples review two of the most potent modulatory processes at work w ithin the dorsal vagal complex, which have dramatic effects on gastrointest inal function. The reader should be mindful of the fact that many more diff erent inputs from other central nervous system (CNS) loci or circulating hu moral factors add to this complex mix of modulatory inputs. It is likely th at similar long-term modulations of synaptic transmission occur with other neurotransmitters and may represent an important mechanism for the integrat ion and regulation of neuronal behavior. Of course, this fact strongly mili tates against the success of any single drug or approach in the treatment o f motility disorders having a CNS component.