Effect of antibodies to the neuropeptide GRP on distention-induced gastric acid secretion in the rat

The present study examined and compared the effects of muscarinic blockade, β-adrenergic blockade and immunoneutralization of the neuropeptide gastrin-releasing peptide (GRP) on distention-induced gastric acid secretion and gastrin release. In response to distention of rat stomachs with 0.9% NaCl, acid output rose from 3.5 ± 0.5 μmol H⁺/30 min to 15.4 ± 2.5 μmol H⁺/30 min (P < 0.01). Intravenous administration of 4 mg/kg propranolol did not affect the acid secretory response to distention, however both 2 mg/kg atropine and 6 mg/kg pirenzepine significantly decreased gastric acid secretion by 44.8 ± 7.8% and 40.9 ± 5.7% (P < 0.05), respectively. When specific antibodies to GRP were infused intravenously, the acid secretory response to distention was nearly abolished, decreasing to 5.1 ± 0.8 μmol H⁺/30 min (P < 0.01). In contrast to the effects on acid secretion, GRP antiserum did not significantly alter the gastrin release observed following distention. Results of these studies indicate that, under the conditions of these experiments, the acid secretory response to gastric distention may be independent of its effect on gastrin release. Although distention-induced gastric acid secretion may be partially governed by muscarinic pathways, the acid secretory response to distention in the rat appears to involve GRP-containing neurons.