Impaired nitrergic relaxations in the gastric fundus of dystrophic (mdx) mice

Relaxant responses to electrical field stimulation (EFS) were investigated in the gastric longitudinal fundus strips from young normal and mdx dystrop hic mice, an animal model of Duchenne muscular dystrophy. in carbachol (CCh ) precontracted strips from normal mice, EFS elicited brisk relaxant respon ses that, depending on stimulation frequency, could be followed by a sustai ned relaxation. In strips from mdx mice the brisk relaxation was impaired. Smooth muscle responses to direct stimulating agents did not differ in ampl itude between the two groups of animals. In strips from both normal and mdx mice, N-G-nitro-L-arginine (L-NNA) abolished the brisk phase of relaxation , without affecting the sustained response. alpha-chymotrypsin abolished, i n both preparations, the sustained relaxant response to EFS as well as rela xation to vasoactive intestinal polypeptide. Results suggest that, in strip s from mdx mice, a defective production/ release of the neurotransmitter re sponsible for the brisk relaxation, likely nitric oxide, occurs. (C) 2000 E lsevier Science Ireland Ltd. All rights reserved.