Gastric distension causes changes in heart rate and arterial blood pressure by affecting the crosstalk between vagal and splanchnic systems in anesthetised rats

Various hindbrain nuclei have been demonstrated to be involved in the control of the cardiovascular reflexes elicited by both non-noxious and noxious gastric distension, through parasympathetic and sympathetic activation. The different role played by the branches of autonomic nervous system in exerting these effects and their crosstalk in relation to low-/high-pressure distension rate has not been examined yet. Therefore, in the present work, monolateral and bilateral vagotomy and splanchnicotomy were performed in anesthetised rats to analyse the involvement of hindbrain nuclei in haemodynamic changes caused by gastric distension at high (80 mmHg) and low (15 mmHg) pressure. The analysis of c-Fos expression in neuronal areas involved in cardiovascular control allowed us to examine their recruitment in response to various patterns of gastric distension and the crosstalk between vagal and splanchnic systems. The results obtained show that the low-pressure (non-noxious) gastric distension increases both heart rate and arterial blood pressure. In addition, the vagus nerve and hindbrain nuclei, such as nucleus ambiguous, ventrolateral medulla and lateral reticular nucleus, appear to be primarily involved in observed responses. In particular, we have found that although vagus nerve plays a central role in exerting those cardiovascular reflex changes at low gastric distension, for its functional expression an intact splanchnic system is mandatory. Hence, the absence of splanchnic input attenuates pressor responses or turns them into depressor responses. Instead at high-pressure (noxious) gastric distension, the splanchnic nerve represents the primary component in regulating the reflex cardiovascular effects.