J. G. Waterson

Effect of acetylcholine on the response of the isolated rabbit ear artery to stimulation of the perivascular sympathetic nerves

Abstract In the isolated rabbit ear artery, low concentrations of exogenous acetylcholine inhibited the response of the artery to periarterial electrical stimulation, while much greater concentrations of acetylcholine were required to inhibit the response to exogenous noradrenaline. This action of acetylcholine on periarterial stimulation was suppressed by atropine and potentiated by cholinesterase inhibitors. Neither atropine nor cholinesterase inhibitors, in concentrations which modified the effects of exogenous acetylcholine, altered the response of the artery to periarterial stimulation. The study failed to confirm that either a cholinergic element or endogenous acetylcholine has an effect in the arterial sympathetic nerve response.

MODIFICATION OF AUTOFLUORESCENCE IN THE FORMALDEHYDE-TREATED RABBIT EAR ARTERY BY EVANS BLUE

the contralateral iris was placed in Krebs bicarintensity of color obtained after #{248}ris appreciably weaker than the original Schiff-aldehyde product, thus stuggesting the quinone moiety as the site of attack. The NOr derivative was found to behave as an acid-base indicator, i.e., has bluish shades at acid pH (e.g., dilute acetic acid) amid reddish shades at alkaline pH (Tris). This in turn suggests some kind of chemical equilibrium in the altered molecule since this behavior is not shown by the original Schiff-aldehyde product. It must be noted that the exact nature of the prodtmcts formed between Schiff’s reagent and aldehydes is unknowmi (cf Stoward. J. Histochem. Cytochenu. 14: 681. 1966). That a positive azo coupling reaction occurs in the presemice of a-naphthol (Tris) is indicated by the great increase in intensity and differemit color shades when this phenol is present than when it is omitted from the Tris buffer. The azo dye formed also behaves as a pH imidicator, i.e., changes from an orange-red to a deep brown-violet color in acid media. Both colors are clearly distinguished from the purplish red of theSchiff-reaction. Intensification of color at acid pH can probably be explained by transformation into the qtiinone tautomer. For Feulgen preparations azo cotupling with anaphthol is best visualized at about p11 12 using a saturated solution of sodium carbomiate in 50% ethanol (instead of Tris) since definite color change to orange-red occurs at higher pIT values. It is also interesting that deoxyribonumcleic acid in Feulgen preparations stained deep blue imistead of the brown-violet color of bemizaldehyde-Schiff derivative and PAS-stained cellulose or mucin. The behavior of the deoxyribose sugar itself has not been investigated.

The action of tyramine on the rabbit ear artery

1 The vasoconstrictor potency of extraluminal tyramine on the isolated perfused rabbit ear artery is considerably greater than that of intraluminal tyramine. 2 Chronic denervation, which caused the noradrenergic storage structures in the medial‐adventitial border of the artery to disappear, reduces the potency of extraluminal tyramine more than that of intraluminal tyramine so that the difference in potency for the two routes of administration tends to disappear. Cocaine exerts a greater inhibitory effect on responses to extraluminal tyramine than on those to intraluminal tyramine. 3 It is concluded that the indirect component plays a more prominent part in the responses to extraluminal tyramine than in those to intraluminal tyramine. This conclusion is supported by analysis of the diphasic response of the artery to intraluminal injection of tyramine under perfusion conditions which permit intraluminal fluid to mix with the extraluminal fluid. Evidence is presented that the first phase of the response is mediated by intraluminal tyramine, and the second phase by extraluminal tyramine.

THE INFLUENCE OF REPLACING SODIUM BY POTASSIUM IONS ON UPTAKE OF NORADRENALINE IN THE RABBIT EAR ARTERY

THE INFLUENCE OF REPLACING SODIUM BY POTASSIUM IONS ON UPTAKE OF NORADRENALINE IN THE RABBIT EAR ARTERY