Abstract
Calbindin (CALB) is well established as immunohistochemical marker for intrinsic primary afferent neurons in the guinea pig gut. Its expression by numerous human enteric neurons has been demonstrated but little is known about particular types of neurons immunoreactive for CALB. Here we investigated small and large intestinal wholemount sets of 26 tumor patients in order to evaluate (1) the proportion of CALB+ neurons in the total neuron population, (2) the colocalization of CALB with calretinin (CALR), somatostatin (SOM) and vasoactive intestinal peptide (VIP) and (3) the morphology of CALB+ neurons. CALB+ neurons represented a minority of myenteric neurons (small intestine: 31%; large intestine: 25%) and the majority of submucosal neurons (between 72 and 95%). In the submucosa, most CALB+ neurons co-stained for CALR and VIP (between 69 and 80%) or for SOM (between 20 and 3%). In the myenteric plexus, 85% of CALB+ neurons did not co-stain with the other markers investigated. An unequivocal correlation between CALB reactivity and neuronal morphology was found for myenteric type III neurons in the small intestine: uniaxonal neurons with long, slender and branched dendrites were generally positive for CALB. Since also other neurons displayed occasional CALB reactivity, this protein is not suited as an exclusive marker for type III neurons.
Highlights
The combined application of various neuroscientific methods has enabled the identification and characterization of different types of enteric neurons primarily in the guinea pig [1,2]
We have shown that human myenteric type II neurons, the putative myenteric IPANs, are immunohistochemically characterized by the colocalization of calretinin (CALR) with somatostatin (SOM) [10,11]
This staining combination allows for an estimation of the proportion of CALB+ neurons in relation to the whole enteric neuron population (Figure 1, Table 1)
Summary
The combined application of various neuroscientific methods has enabled the identification and characterization of different types of enteric neurons primarily in the guinea pig [1,2]. One of these methods was the immunohistochemical distinction between several enteric neuron types by different markers that deciphered their chemical codes. The value of these chemical codes consists of the relatively simple possibility of representing neuron types in gut tissue samples, e.g., under experimental or pathological conditions. We have shown that human myenteric type II neurons, the putative myenteric IPANs, are immunohistochemically characterized by the colocalization of calretinin (CALR) with somatostatin (SOM) [10,11]
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