Chemical Coding of Neurons in the Myenteric Plexus and External Muscle of the Small and Large Intestine of the Mouse

Immunohistochemical techniques were used to examine the presence and co-localisation of a range of putative neurotransmitters and other neuronal markers in the myenteric plexus of the small and large intestine of the mouse. Distinct sub-populations of myenteric neurons were identified, based on the combinations of substances they contained and the distribution of their fibres. In the small intestine, there were two major classes of circular muscle motor neurons; one class was characterised by the presence of nitric oxide synthase, vasoactive intestinal peptide plus neuropeptide Y (NOS/VIP/NPY), and the second class contained calretinin plus substance P (CalR/SP). There were seven classes of neurons that innervated myenteric ganglia; these contained nos, vip, nos/vip, npy, calr/calbindin (calb), sp or 5-ht. In the large intestine, there were five major classes of motor neurons that contained nos, nos/vip, gaba, sp, or calr/sp, and seven major classes of neurons that innervated myenteric ganglia and contained nos, vip, calr/calb, calr, sp, gaba or 5-ht. Although some aspects of the patterns of co-localisation are similar to those in other species, this study re-inforces recent analyses that indicate significant species differences in neurochemical patterns in the enteric neurons of different species.