Cardioacceleratory and myostimulatory activity of allatotropin in Triatoma infestans

Haematophagous insects incorporate a large quantity of blood with each meal, producing a big quantity of urine in a few hours. The activity of the Malpighian tubules (MTs) is facilitated by the increase of the circulation of the haemolymph produced by the increase of the aorta contractions as well as, of the peristaltic waves of the anterior midgut. MTs of Triatoma infestans secrete an allatotropin-like peptide, which has a myostimulatory effect on the hindgut, inducing the mixing and voiding of the content during post-prandial diuresis. We are reporting now the activity of allatotropin (AT) as a cardioacceleratory and a myostimulatory peptide at the level of the anterior midgut. The peptide induced the increase of the rate of contractions of the anterior midgut and the aorta in a wide range of concentrations. The cardioacceleratory effect of AT was dependent on the feeding state of the insects and on the presence of serotonin. The response showed the existence of a differential behavior between sexes, inducing a higher increase on the frequency of contractions, as well as, the width of the aorta in males than in females. Finally, our results suggest that AT interacts with serotonin to facilitate the circulation of haemolymph during post-prandial diuresis.