Vaso-depressor

A II II CILCILCII, NH // ciLSr NIL Strong vaso-depressor action 909... 

Vanadium complexes, 157, 158 Vapor phase chromatography, see Gas-liquid chromatography Vaso-depressor, 149 Vasodilator, 150 Veterinary applications, 138 Vinylchloride, 438... 

The most important natural sources of minor tobacco alkaloids are from Nicotiana species, and at least eight minor tobacco alkaloids are shown in Figure 1. Since the chemical structures and physical properties of these minor tobacco alkaloids are similar to that of nicotine, some of them are shown to exhibit similar pharmacological activities as those of nicotine, although with a much lower potency. Table 2 shows their relative molar potency in some pharmacological systems. When nornicotine or anabasine was applied to the cat cervical ganglion, initial stimulation was followed by paralysis. On the autonomic ganglion and neuromuscular junction, nornicotine is only one-fifth to one-tenth as active as nicotine. Both nornicotine and anabasine have vaso-depressor action and affect the respiratory system. 

Like-wise angiotensin II (9 or 30 rat units per mouse) failed to augment erythropoiesis in polycythemic mice (25). However, similar quantities of both renin and angiotensin II increased blood pressure when administered intravenously to normal rats and mice (Fig. lO). Neither the REF nor the incubation mixture of REF and serum produced any vasopressor action. On the contrary, a slight drop in blood pressure was observed with the REF-serum mixture. This mild vaso-depressor action of the mixt-ure of REF and serum noted in rats and the report of a kinin-forming enzyme in the light-mitochondrial fraction of rat kidneys (2) led us to test the effect of bradykinin on erythropoiesis. Intravenous injections of 2.0 and 20 ug of bradykinin triacetate evoked no demonstrable erythropoietic response in polycythemic mice (Fig. lO). This agent did, however, produce the expected drop in blood pressure of rats. 

Ihe mechanism of the pressure fall is probably different in the various animal species.In the dog,hypotension is certainly due,at least to a great extent,to a direct depressor action on the vascular smooth musole with consequent vaso-dilatation in the oat,cholinergic mechanisms seem to play a major role,as shown by the reversal of the action of oaerulein from hypotensive to hypertensive,produced by atropine. 

For many years it has been known that simple extracts of animal tissues, when injected intravenously, may cause a profound fall in blood pressure in experimental animals, especially carnivora. This depressor effect is essentially a vaso-dilatation, although cardiac and respiratory phenomena may be involved also. At one time it was believed that the depressor effect was due to choline, but this was disproved when Vincent and others showed that the effect was not inhibited by a previous injection of atropine, the pharmacological antagonist of choline. The histamine is not derived from infective or post-mortem changes in the tissues, as it can be obtained when living lung tissue is taken from an anaesthetised animal, and... 

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