Antidromic vasodilatation and blood flow in the rabbit's ear

Sympathetic vasodilatation in the rabbit ear

Changes in the blood content of a 1 cm(2) portion of the intact rabbit's ear were studied with transillumination and a photocell. Stimulation of the post-ganglionic sympathetic nerves produced a decrease in blood content, attributable to vasoconstriction, followed by an increased blood content, attributable to vasodilatation. The vasodilatation was enhanced by eserine and decreased by atropine. Guanethidine abolished the vasoconstriction but not the vasodilatation. After the ganglion had been decentralized by degeneration of the pre-ganglionic sympathetic nerves the vessels had an increased sensitivity to acetylcholine and the vasodilatation in response to sympathetic stimulation was enhanced. It is concluded that sympathetic stimulation results in the liberation of acetylcholine which causes vasodilatation.

Absorption and ester cleavage of methyl salicylate by skin of single-pass perfused rabbit ears

1. Rabbit ears were single-pass perfused with a cell-free medium. Arterial pressure, oxygen consumption, and lactate production increased with flow rate. 2. Methyl salicylate was hydrolysed with an apparent Vmax of 1.5 nmol/min per cm2 surface area, a rate about 25 times greater than after arterial administration. 3. Estimation of the Km was not possible, due to oedema developing at arterial concentrations greater than 100 microM methyl salicylate. 4. The model appears suitable to compare absorption, as well as metabolic rates, of xenobiotics in rabbit skin.

Dorsal root vasodilatation in cat skeletal muscle

1. A study has been made, in the cat anaesthetized with chloralose, of the effects of antidromic stimulation of dorsal roots L6-S1 on the blood flow through the gastrocnemius muscle. 2. Stimulation of the peripheral ends of the ligated dorsal roots with current pulses of 0.3-0.5 msec duration and at intensities most effective in activating the smaller afferent fibres, for periods of 15-20 sec, produced a 50-60% increase in muscle vascular conductance which was slow in onset and long outlasted the stimulus. 3. This muscle vasodilatation could be evoked in the paralysed animal and was unaffected by guanethidine or atropine. It was, however, greatly reduced or even abolished by the prostaglandin synthetase inhibitors, indomethacin or acetylsalicylic acid, in doses which had no effect on the dilatation produced by a local injection of acetylcholine or the functional hyperaemia induced by muscle contraction. 4. It is concluded that activity in the smaller myelinated or unmyelinated afferent fibres of skeletal muscle produces an increase in muscle blood flow which is mediated, at least in part, by prostaglandins locally synthesized within the muscle.