Quantitative estimation of putative primary afferent neurons in the myenteric plexus of human small intestine

Abstract

This study aimed at estimating the proportion of human myenteric Dogiel type II neurons, putative intrinsic primary afferent neurons (IPANs), in relation to the entire myenteric neuron population. Since, at present, there is no known single marker, which specifically labels these neurons, we tried to identify the most appropriate marker combination based on the results of an earlier study. For this purpose, 10 wholemounts derived from human small intestinal segments were immunohistochemically triple-stained for calretinin (CALR), somatostatin (SOM) and neurofilaments (NF) and 9 were stained for substance P (SP), SOM and NF. In each wholemount, 15 ganglia selected randomly were evaluated. On the basis of their NF-reactivity, neurons reactive for one or co-reative for both of the other two markers, respectively, were morphologically classified as type II or non-type II neurons. We found that the majorities of neurons co-reactive for CALR/SOM and SP/SOM, respectively, were type II neurons whereas this was not the case for neurons, which were reactive for only one of the two markers. One of the statistical parameters estimated was the positive predictive value, the probability that a neuron displaying CALR/SOM- or SP/SOM-co-reactivity, respectively, is a type II neuron. This value was 97% in case of CALR/SOM- and 95% in case of SP/SOM-co-staining. Although the difference of the statistical parameters between the two stainings was not significant, CALR and SOM were used to estimate indirectly the proportion of type II neurons, in wholemounts co-stained with the pan-neuronal marker neuronal protein HuC/HuD (HU). In these wholemounts, altogether 9.1% of neurons were coreactive for CALR/SOM. We suggest that the proportion of myenteric type II neurons in the human small intestine is related to the proportion of CALR/SOM-co-reactive neurons and may be near to one tenth of the total myenteric neuronal population.

Immunohistochemical analysis of neuron types in the mouse small intestine

“…In the mouse and guinea-pig small intestine, they represent about 25% of neurons (Table 3), whereas in human, they comprise about 10% of the population (Weidmann et al 2007), in pig small intestine about 8% (Brehmer et al 2002), and in sheep small intestine about 6% (Chiocchetti et al 2006). This may reflect the greater bulk of muscle in the larger species and a corresponding greater proportion of motor neurons.…”

Quantitative Estimation and Chemical Coding of Spiny Type I Neurons in Human Intestines

“…Thus, the results of both studies are in mutual accordance and the proportion of spiny neurons in the small intestine appears to be 7%. This proportion is somewhat lower than that of the multiaxonal Dogiel type II, putative primary afferent neurons estimated at 10% based on comparable morphochemical characteristics [Weidmann et al, 2007].…”

“…spiny neurons which probably act as inhibitory motor neurons. Another example is the co-existence of calretinin and somatostatin which points at putative primary afferent neurons in human small intestine [Weidmann et al, 2007]. These particular co-localizations of markers can also be demonstrated on sections and may allow, in the future, to detect changes in proportions of enteric neurons under pathological conditions.…”

Neurophysiologic Mechanisms of Human Large Intestinal Motility

“…253 Dogiel Type II neurons constitute about 30% of all myenteric neurons in the small intestine 115 and a smaller proportion in the distal colon. 30 In human small intestine, it was estimated that Dogiel Type II neurons comprised about 10% of myenteric neurons, 473 but comparable numbers for the human large intestine are not available. 447 Recently, direct evidence for such a role for Dogiel Type II neurons has been provided by recording calcium transients in myenteric nerve cell bodies in murine colon during colonic migrating myoelectric complexes.…”