Projections and neurochemical coding of motor neurones to the circular and longitudinal muscle of the guinea pig gastric corpus

Abstract

The present study identified projection and neurochemical coding patterns of intrinsic circular (CMN) and longitudinal muscle motor neurones (LMN) in the guinea pig stomach by using the retrograde tracer DiI (1,1'-didodecyl-3,3,3',3'-tetramethylindocarbocya-nine perchlorate) in combination with the immunohistochemical demonstration of choline acetyltransferase (ChAT), enkephalin (ENK), neuropeptide Y (NPY), nitric oxide synthase (NOS) and substance P (SP). Populations of LMN and CMN had similar neurochemical coding and a clear polarity of projection. Taking all DiI-labeled cell bodies as 100%, ascending pathways exhibited the coding ChAT/- (CMN:14.7%/LMN: 18.3%), ChAT/ENK (15.7%/10.1%), ChAT/SP/+/-ENK (19.2%/16.4%), or ChAT/NPY (4.4%/7.6%); descending pathways had the coding NOS/- (13.8%/16.9%), NOS/NPY (9.9%/17%), NOS/ENK (4.4%/1.2%) or NOS/NPY/ENK (13.0%/5.5%). The relative contributions of these populations were not different between CMN and LMN. However, target-specific projection patterns were revealed: most LMN (82%) had longitudinal whereas most CMN (58%) had circumferential projection preferences. The results indicate that gastric circular and longitudinal muscle layers are innervated by ascending excitatory and descending inhibitory pathways in the myenteric plexus. The projection patterns of CMN and LMN were different and followed the orientation of the muscle layers. It is suggested that the specific muscle motor pathways in the gastric myenteric plexus coordinate the reflex-mediated phasic and tonic activity of gastric muscle layers.

Distribution and trafficking of the μ-opioid receptor in enteric neurons of the guinea pig

“…atory motor neurons. These neurons are relatively lower in abundance in the gastric corpus relative to other regions (38).…”

“…MOR-IR neurons were mostly NOS-IR (88%, 232 of 263 neurons; Fig. 3A), suggesting expression by inhibitory motor neurons innervating both the circular and longitudinal muscle layers (38). The mucosa of the gastric corpus receives innervation from the myenteric plexus in the absence of submucosal neurons; therefore, the detection of secretomotor peptides such as neuropeptide Y (NPY) in choline acetyltransferase (ChAT)-and NOSpositive neuronal populations can be used to identify mucosally projecting myenteric neurons (42).…”

Enteric pathways in the stomach

“…Motor neurones of the myenteric plexus projecting to the mucosa or the circular muscle or the longitudinal muscle of the gastric corpus were identified by retrograde tracing with the dye DiI (1,1Ј-didodecyl-3,3,3Ј,3Ј-tetramethylindocarbocyanine perchlorat) as previously described in detail Pfannkuche et al, 1998a,b;Michel et al, 2000). For mucosa preparations most of the mucosa was removed except a 400 mm 2 mucosa patch onto which the DiI bead (50 -100m) was placed.…”

“…The neurochemical coding is now well characterised in various regions of the guinea-pig gut and it is clear that there are region specific transmitter co-localisation patterns Furness et al, 1995;Costa et al, 1996;Neunlist et al, 1999a). In combination with retrograde tracing techniques it was possible to investigate relations between the neurochemical codes and the functions of enteric neurones in the stomach (Michel et al, 1997;Pfannkuche et al, 1998a,b;Brookes et al, 1998;Michel et al, 2000).…”

Neuronal activation of brain vagal-regulatory pathways and upper gut enteric plexuses by insulin hypoglycemia

“…The role of vagal afferent signaling in the Fos induction in the brain, and the role of the extrinsic vagal efferent innervation in Fos expression in the gastric/duodenal myenteric plexus in response to insulin hypoglycemia were investigated by vagotomy. We also partly examined the biochemical coding of the brain and myenteric Fos-IR cells in insulin-hypoglycemic rats by use of double labeling of Fos with choline acetyltransferase (ChAT) (39), tyrosine hydroxylase (TH) (27), or vasoactive intestinal peptide (VIP) or with nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d), an established marker for nitric oxide (NO)-synthesizing neurons (12,69). Part of this study has been published in abstract form (74).…”