Survival and neurotransmitter plasticity in cultured rat colonic myenteric neurons

The enteric nervous system is of great importance for maintenance and proper function of the gastrointestinal tract. The aim of this study was to quantify myenteric neuronal subpopulations expressing calcitonin gene-related peptide (CGRP), galanin, neuropeptide Y (NPY), somatostatin, vasoactive intestinal peptide (VIP) and nitric oxide synthase (NOS) in rat colon in vivo and after culturing. Further we investigated if culturing in the presence of CGRP, galanin, VIP, S-nitroso-N-acetyl-D,L-penicillamine (SNAP, a NO donor) or N-nitro-L-arginine methyl ester (L-NAME, a NOS inhibitor) affect neuronal survival. After 4 days of culturing the proportions of neurons expressing CGRP, NPY, somatostatin or VIP increased as compared to in vivo, while the proportions of neurons expressing galanin or NOS did not change. Neuronal survival was unaffected after culturing in media enriched with CGRP, galanin, VIP, SNAP or L-NAME. Neither did addition of CGRP, galanin nor VIP to the cultures affect the relative numbers of neurons expressing CGRP, galanin or VIP respectively. Addition of SNAP or L-NAME did not change the percentage of neurons expressing NOS. In conclusion, cultured rat colonic myenteric neurons increase their expression of CGRP, NPY, somatostatin and VIP, suggesting that these neuropeptides are of importance for neuronal survival.