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PubMed1957

The action of ergotamine on the intracranial venous pressure and on the cerebral venous outflow of the dog.

The effect of ergotamine and dihydroergotamine on the cerebral circulation was studied in the dog, anaesthetized with chloralose, by recording the intracranial venous pressure and the venous outflow from the superior cerebral vein. Under optimal experimental conditions, ergotamine (5 to 10 mug./kg.) and dihydroergotamine (100 mug./kg.) gave a marked and long-lasting cerebral vasoconstriction accompanied by a slight hypertension. The cerebral vasoconstriction provoked by ergotamine may be very small and was sometimes absent when the cerebral blood-flow was low. This vasoconstrictor effect is more pronounced the higher the initial intracranial venous pressure and hence the cerebral blood-flow. After the induction of a cerebral vasodilatation by 48/80 or strychnine, the vasoconstrictor action of ergotamine was more pronounced. The effect was not observed when CO(2) was employed to modify the intracranial venous pressure. Simultaneous registration of the cerebral, nasal cavity, and kidney vascular responses demonstrated the relative specificity of the action of ergotamine on the cerebral vessels. The small doses of ergotamine used may weaken or abolish the vasoconstrictor action of adrenaline on cerebral vessels. The modification of the responses of the cerebral circulation which such factors as anaesthesia, respiratory acidosis, and operative trauma can produce have been confirmed and emphasized. The results support the view that the vasoconstrictor action of ergotamine on the cerebral vessels might account for the therapeutic value of this drug in migraine.

Animals↗
PubMed1958

Effects of raunescine and isoraunescine on behaviour and on the 5-hydroxytryptamine and noradrenaline contents of brain.

Some behavioural effects of raunescine and isoraunescine on pigeons have been studied; no qualitative difference was detected between their effects and those of reserpine. Isoraunescine is between five and ten times less potent than raunescine, which, in turn, is much less potent than reserpine in producing these effects.Both raunescine (5 mg./kg.) and isoraunescine (50 mg./kg.) were found to cause a reduction in the concentration of noradrenaline in the brains of rats. Raunescine (5 mg./kg.) also caused a reduction in the concentration of 5-hydroxytryptamine in brain; isoraunescine did not do so in the same dose; higher dose levels were not studied.

Animals↗
PubMed1959

Renal effects of veratridine.

Veratridine hydrochloride injected subcutaneously into unanaesthetized rats inhibited water diuresis. A linear relationship between log dose and antidiuretic effect could be established over the dose range 50 to 200 mug./100 g. of body weight. When veratridine hydrochloride was injected intravenously in doses from 10 to 30 mug./100 g., this relationship was also linear. In terms of its antidiuretic action, the alkaloid was approximately five times as effective when given intravenously. Rats anaesthetized with urethane responded to an intravenous injection with a more pronounced inhibition than unanaesthetized animals. Protoveratrine injected intravenously into unanaesthetized rats showed no clear relationship between dose and magnitude of antidiuretic effect. Veratridine hydrochloride injected intravenously had a pronounced hypotensive effect in both anaesthetized and unanaesthetized rats. Treatment with atropine did not affect this hypotensive action significantly. Atropine given subcutaneously 30 min. before an intravenous injection of veratridine hydrochloride abolished or diminished the inhibitory effect of veratridine on water diuresis. Veratridine hydrochloride injected intravenously into unanaesthetized rats caused a marked depression of the clearance of inulin and p-aminohippurate. In unanaesthetized rats with an osmotic diuresis, veratridine hydrochloride produced its usual antidiuretic effect. The urine of rats injected with veratridine hydrochloride produced an antidiuretic effect when injected intravenously into other animals. The antidiuretic potency of such urines was not affected by treatment with thioglycollate. Animals injected with veratridine excreted small amounts of a veratridine-like substance in the urine. These results do not suggest that veratridine in antidiuretic and hypotensive doses stimulated the neurohypophysis in the rat.

Animals↗
PubMed1959

Increase of 5-hydroxytryptamine in the rat brain by raunescine.

The Rauwolfia alkaloid raunescine (5 mg./kg., intraperitoneally) increased the concentration of 5-hydroxytryptamine in the brains of rats after iproniazid pre-treatment. This was evident 3 to 4 hr. after raunescine administration. There was no general increase in the noradrenaline content of the brains. In the intestine, raunescine depleted the 5-hydroxytryptamine content by about 50% within 3 to 4 hr. if the animals had been pre-treated with iproniazid. Iproniazid did not increase the content of noradrenaline in the intestine.

Animals↗