Action of adrenalin and noradrenalin on gastric secretion

Abstract

We have tried to see in this experiment the influence of the Sympathetic Nervous System upon the gastric secretion, and to this effect we have studied the action of adrenaline and nor-adrenaline upon the basal gastric secretion and upon the constant gastric secretion induced by histamine.

We have used in all cases anesthesized cats with a «total pouch stomach» as experimental animals.

In order to study the action of adrenaline and nor-adrena­ line upon the basal gastric secretion we administered these substances either in subcutaneous injection or intravenously and repeatedly every 10 mins. or intravenous continually. When we wanted to see the influence upon the constant gastric secretion induced by histamine we administered always intrave­ nously. The injection in these cases were sometimes done fractionating the total dosis in 5 parts, injecting one part every two minutes during 10 mins, other times the injection was continuous.

The resultg obtained were the following:

A) Action upon the basal gastric secretion. Adrenaline and nor-adrenaline in subcutaneous injection every ten minutes produce a marked gastric secretion above all when small dosis are employed. We atribute this secretion, based on Baxter's work, to the reactive hiperhemia which would be produced in the gastric mucosa in the intercalary periods of the injections. When the injection is realized in a continuous way intravenously, adrenalin and nor-adrenaline do not act in the same way. Adrenaline In this form does not produce in any of our cases gastric secretion (maybe because the dosis employed were too high) and yet nor-adrenaline did produce gastric secretion eventhaugh only when uséd in small dosis. We atribute this posible difference in the action of these two substances to the fact we have seen that adrenalin in continuos injection is not capable of producing permanent hypertension as nor-adrenaline is capable (graph B) and we know by the works of Chiu (1955) that a raise in the arterial pressure is accompanied by a raise in the blood volume in the stomach, and by Kurtsin (1956) that the raise in the irrigation of the stomach is accompanied by a raise in the secretion of gastric juice. The juice segregated in the different cases by these substances lack always acidity.

B) Action upon the constant secretion induced by hista­ mine. Either adrenaline or nor-adrenaline when injected in fractionated dosis provoke a raise in the volume of the juice segregated by the action of histamine. In this stimulating action the dosage of the substances employed or the volume segregated by the action of histamine does not intervene. We also atribute this raise to the reactive hiperhemia, even if, in these cases the active dosis must be higher, that in order to produce the initial vasoconstriction it is necessary to act upon the vessels already dilated by action of histamine. When the injection of adrenaline and nor-adrenaline is done in a continuous form the results obtained with one and the other hormone are different. Adre­ naline does not provoke in any case modification of the secretion induced by histamine, nor-adrenaline does on the contrary. The modifications produced by nor-adrenaline depend upon the do­ sage employed : if the dosage is low the volume segregated by the action of histamine descends. If the dosis of nor-adrenaline are high the volume augments.

In this case it can also be explained the differences observed for adrenaline and nor-adrenaline by the modifications thatthese substances produce upon the arterial pressure. Adrenaline does not produce persistent raises of the pressure also in this case. Nor-adrenaline only when high dosis are used. The small dosis produce either a persistent raise but not too marked or an abrupt raise but with great oscilations (graph D). The influence of the arterial pressure upon the secretion provoked by nor-adrenaline seems without doubt as when nor-adrenaline is suppressed the arterial pressure descends and the volume of segregated juice diminishes and when the infusión is again renewed both augment almost paralelly (graph E).

When small dosis are injected there is not persistent raise of pressure, this would explain the lack of raise of the volume segregated but not the inhibition, this would have to be attri- buted to a peripheric inhibitory action of the small dosis of nor-adrenaline.