GALANIN AND SOMATOSTATIN INHIBITION OF SUBSTANCE-P-INDUCED AIRWAY MUCUS SECRETION IN THE RAT

Substance P is present in several neurons innervating the lung. Tachykinin receptors are expressed on submucosal gland cells. Substance P is known to be a potent stimulator of airway mucus secretion. In the present study we characterized the effects of galanin and somatostatin on basal and substance P-induced mucus secretion. The stimulatory effect of substance P was concentration-dependent (100 mu mol/l: 112%, 1 nmol/l: 120%, 10 nmol/l: 153%, 100 nmol/l: 223%, 1 mu mol/l: 275%, 10 mu mol/l: 172%) and was inhibited by galanin and somatostatin (1 mu mol/l substance P: 277%; 1 mu mol/l substance P+1 mu mol/l somatostatin: 190%, p < 0.01; 1 mu mol/l substance P+1 mu mol/l galanin: 206%, p < 0.05). In the presence of lower concentrations of substance P1 mu mol/l somatostatin and 1 mu mol/l galanin did not modify mucus secretion. Lower concentrations of galanin and somatostatin did not significantly change mucus secretion stimulated by 1 mu mol/l substance P. Both, galanin and somatostatin at 1 mu mol/l left basal airway mucus secretion unaltered. These data suggest that mucus secretion into airways is regulated by a complex network of peptidergic stimulators and inhibitors including substance P, somatostatin and galanin.