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Excitation of the muscularis mucosae is believed to increase gastric acid secretion. This theory was tested by the in vitro characterization of muscularis mucosae responses to substances that moderate acid release. Results show that the muscularis mucosae in the rabbit gastric corpus contracted when treated with ACh, ADP, ATP and histamine and relaxed to vasoactive intestinal polypeptide. The theory was also tested by observing the response to intrinsic nerve stimulation. Results showed that electric field stimulation led to TTX-sensitive responses.

Research shows that airway relaxation via a functional, nonepithelial-dependent sodium-potassium-2Cl cotransporter occurs in newborn guinea pig trachea in the presence of furosemide. Experimental evidence using rubidium-86 in standard or varying low chloride concentration N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid suggests that the sodium-potassium-2Cl cotransporter is an important factor in furosemide-induced airway relaxation.

Sodium nitroprusside (SMP) and S-nitroso-N-acetylpenicillamine (SNAP) both relax phenylephrine-induced contractions in microvessels obtained from the rat mesentery. However, they are less effective in relaxing contractions induced by 40 mM KCl. It appears that SNP stimulates K+ efflux by opening K+ channels via the guanosine 3'-5'-cyclic monophosphate (cGMP)-dependent protein kinase (PKG)-mediated phosphorylation. The vasodilatory effect of nitric oxide (NO) on microvessels is boosted by stimulation of high-conductance Ca2+- and voltage-activated K+ (BKca)-channel activity via cGMP-dependent phosphorylation.

An allometric study of the effect of body size on the pharmacodynamics and pharmacokinetics of the muscle relaxant metocurine reveals that pharmacodynamics is partially dependent on size, while pharmarcokinetics varies with physiological time and size. Individual species data exhibit a bimodal distribution, suggesting a relevance for the receptor density within the endplate. The effect compartment IC(50) in pig, rat and sheep locomotor muscles is equivalent and related to the body size.

Separate gastric and Taenia coli smooth muscle cells show relaxation along with enhanced levels of cAMP and cGMP, or both the protein kinases control the relaxation process. cGK and cAK favor activation by cGMP and cAMP respectively. cGK is activated by cAMP when it is at high concentrations due to its occurrence in larger quantities over cGMP. Activation of cAK and cGK is observed with increased levels of cAMP and cGMP, which influence the relaxation process additively.