Vasodilatory actions of four atropine-like drugs on the rat foot-pad

The minimal ip doses of scopolamine,anisodine,anisodamine, atropine that significantly raised the foot-pad skin temperature (MDRT) were 0.08,0.10,0.20 and 0.10 mg/kg respectively. The corresponding LD50/MDRT ratios were 14400, 14050, 3405, and 2560, respectively. Atropine showed a stronger vasodilatory action on the denervated limb than that on the intact limb. In cross-perfused hind-limb preparations, when atropine was given to donor iv, the skin temperature rose both on donor and perfused limb of recipient, but not on non-perfused limb. When atropine was injected to the recipient, except the nonperfused side recipient, it raised the skin temperature neither on donor nor on perfused limb recipient. The rise of temperature and reddening of skin after iv atropine were antagonized by ACh and Adr. Hence atropine-like drugs exert a direct action on the vascular bed of the rat foot-pad and both muscarinic and adrenergic mechanisems may be involved.