A comparative quantitative study of the effects of dihydroergotamine (DHE)and noradrenaline (NA) on the precapillary and postcapillary resistance vessels, the precapillary 'sphincters', and the capacitance vessels was performed in a skeletal muscle and a skin region in healthy humans and in patients with orthostatic symptoms; further, the vascular effects of the drugs were analysed in muscle, skin, intestine and kidney in cats before and after sympathectomy.2. The two drugs evoked a similar pattern of response in the cutaneous vascular bed, i.e. they both constricted resistance and capacitance vessels, increased the ratio of pre-/post-capillary resistance, but did not significantly influence precapillary sphincters. The reactions were similar in skeletal muscle for NA and also for DHE, with the important exception that the latter drug usually elicited a moderate dilator response in the muscle resistance vessels.3. The average constrictor responses of the capacitance vessels were significantly larger for DHE than NA in skin and also in muscle despite the fact that DHE did not much affect the resistance vessels in muscle.4. The effects of DHE on the intestinal and renal vascular circuits in the cat were comparatively small. 5. Since the constrictor effect of DHE seems confined mainly to the capacitance vessels, the drug may have beneficial effects in circulatory disorders characterized by impaired venomotor regulation.A thorough description of the effects on the peripheral circulation of a vasoactive drug cannot be made unless quantitative information is available about the reactions evoked in the functionally differentiated consecutive sections of the vascular beds (see Mellander & Johansson, 1968). Drug induced changes of tone in the resistance vessels influence regional blood flow, and changes of activity in the precapillary 'sphincters' determine the number of patent capillaries and therefore, the size of the functional capillary surface area available for exchange.

Reference values for exercise tests with continuous increase in load are presented. The exercise tests were performed on an electrically braked bicycle ergometer by 188 randomly selected Swedes of both sexes who were between 20 and 79 years of age. The reference values are related to sex, age (in decades) and weight and classified in decreasing levels of exercise capacity. Reference values for systolic blood pressure at different work loads are also given.

Choline acetylase activity was demonstrated in the normally innervated salivary glands of the cat and rabbit. The submaxillary glands were found to have an activity about double that of the parotids, while the enzyme activity of rabbit glands was found to be more than three times that of the corresponding glands in the cat.Chronic preganglionic parasympathetic denervation of the submaxillary gland of the cat and rabbit reduced the concentration and total choline acetylase activity in each gland. The total activity per gland fell to almost half of that of the contralateral gland. Partial postganglionic denervation of the cat's submaxillary diminished the activity in the whole gland to about 15 per cent of the contralateral control gland.An even greater reduction of enzyme was produced in the parotid gland of the two species by postganglionic denervation but some measurable activity usually remained for several weeks after the operation.

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Summary. Secretion from the submaxillary and parotid glands has been studied in rabbits under urethane anaesthesia. The submaxillary gland, but not the parotid, shows a continuous secretion, which probably occurs spontaneously. The secretory responses of the glands to various drugs have been investigated. The parotid gland of the rabbit seems to be a valuable substrate for experiments on supersensitivity to chemical agents. Supersensitivity has been produced by extirpation of the superior cervical ganglion or treatment with the parasympathicolytic agent Hoechst 9980.

The choline acetylase activity of the cat's submaxillary and parotid glands has been found to increase after excision of the superior cervical ganglion. Both concentration and total activity were significantly changed. The enzyme increase did not occur if only the preganglionic sympathetic trunk had been sectioned. The increase of choline acetylase was found to be dependent on the presence of intact pre-and postganglionic parasympathetic neurones. The enzyme change appeared, however, even if the glandular cells were made inactive with the atropine-like substance Hoechst 9980.

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