1 Changes in isometric tension were recorded from circular muscle strips of rat pyloric sphincter in vitro, in response to electrical field stimulation and exogenously applied muscle relaxants. 2 Concentration-response relationships were studied for relaxations to exogenously applied adenosine 5'-triphosphate (ATP) and two analogues, 2-methylthioATP (2-MeSATP) and a,p-methylene ATP (a,. These drugs evoked concentration-dependent relaxation of rat pyloric sphincter with an order of potency 2-MeSATP> ATP >>a,-MeATP, indicating the presence of P2y-purinoceptors. The IC50 value of each nucleotide was: 2-MeSATP, 5.0 x 10-8 M; ATP, 7.9 x 10-6 M; a,P-MeATP showed only slight activity at a concentration of 0.1 mM. 3 Frequency-response relationships for relaxations evoked by electrical field stimulation (EFS) were studied in the absence and presence of 10 gAM NG-nitro-L-arginine methyl ester (L-NAME, an inhibitor of nitric oxide (NO) synthesis) and 20 JAM reactive blue 2 (a P2y-purinoceptor antagonist). It was found that these substances significantly reduced the relaxant response of rat pyloric sphincter to EFS by 40% and 50% respectively. In the presence of both L-NAME and reactive blue 2 the responses were reduced by 75%. 4 Concentration-response relationships were studied for ATP and 2-MeSATP in the presence of L-NAME. It was found that L-NAME did not significantly inhibit the relaxant responses to these drugs. 5 Concentration-response relationships for ATP and noradrenaline were studied in the presence of reactive blue 2 (20 JM); the P2y-antagonist significantly inhibited the relaxant response to ATP, but not that to noradrenaline. 6 The distribution of nitric oxide synthase in rat pyloric sphincter was investigated immunohistochemically, with immunoreactive nerve fibres found throughout the circular muscle layer and myenteric plexus of the sphincter.

Background-The response of the oesophagus to refluxed gastric contents is likely to depend on intact neural mechanisms in the oesophageal mucosa. The epithelial innervation has not been systematically evaluated in health or reflux disease. Aims-To study oesophageal epithelial innervation in controls, and also inflamed and non-inflamed mucosa in patients with reflux oesophagitis and healed oesophagitis. Patients-Ten controls, nine patients with reflux oesophagitis, and five patients with healed oesophagitis. Methods-Oesophageal epithelial biopsy specimens were obtained at endoscopy. The distribution of the neuronal marker protein gene product 9.5 (PGP), and the neuropeptides calcitonin gene related peptide (CGRP), neuropeptide Y (NPY), substance P (SP), and vasoactive intestinal peptide (VIP) were investigated by immunohistochemistry. Density of innervation was assessed by the proportion of papillae in each oesophageal epithelial biopsy specimen containing immunoreactive fibres (found in the subepithelium and epithelial papillae, but not penetrating the epithelium). Results-The proportion of papillae positive for PGP immunoreactive nerve fibres was significantly increased in inflamed tissue when compared with controls, and non-inflamed and healed tissue. There was also a significant increase in VIP immunoreactive fibres within epithelial papillae. Other neuropeptides showed no proportional changes in inflammation. Conclusions-Epithelial biopsy specimens can be used to assess innervation in the oesophagus. The innervation of the oesophageal mucosa is not altered in non-inflamed tissue of patients with oesophagitis but alters in response to inflammation, where there is a selective increase (about three-to fourfold) in VIP containing nerves. (Gut 1999;44:317-322)

It is suggested that the increase in density of protein gene product 9.5- and neuropeptide Y-immunoreactive nerves, part of the sympathetic contractile system of the bladder neck, may exacerbate bladder outlet obstruction and thus play a role in the pathogenesis of BND.