Effect of nervous excitation on acid secretion in horses.

This research article investigates how nervous excitation, induced by a variety of methods, affects acid secretion in horses.

Methods and Findings

• The study involved horses that were already equipped with a gastric cannula – a tube inserted into the stomach.
• Nervous excitation in the horses was induced by several methods for the purpose of this study.
• The researchers observed that insulin hypoglycaemia (low blood sugar levels due to insulin) greatly inhibited the basic or ‘basal’ secretions of acid and the volume of these secretions from the stomach.
• Bethanechol, a drug often used to help recover normal bowel function among other uses, was administered to the horses. Though the researchers expected it to potentially impact acid secretion levels, they observed no clear effect, proposedly because copious amounts of saliva, another digestive secretion was produced as well.
• When the horses were given Atropine – a medication used to treat certain types of nerve agent and pesticide poisonings, heart rhythm problems, and to decrease saliva production during surgery – the basal acid output was dramatically reduced almost to non-existence.
• Sensoric stimulation initiated by teasing caused a slight, but deemed statistically non-significant, increase in total acid output.

Interpretations and Conclusions

• From these observations, the study postulates that cholinergic excitation (excitation related to the neurotransmitter acetylcholine) could play a role in stimulating both the volume and acid secretion in horses.
• The inhibitory effect that was apparent on both these parameters after inducing insulin hypoglycaemia, is hypothetically ascribed to inhibitory impulses carried in peptide neurons of the vagal nerves (nerves that innervate the stomach) or inhibitory impulses in adrenergic nerves (nerves that release adrenaline/noradrenaline) which might act directly or indirectly on the parietal cells (stomach lining cells responsible for producing gastric acid).

Overall, the research suggests potentially complex interactions between the nervous system and the digestive system of horses, particularly in relation to acid production. However, the complexity of interactions and the variety of methods of nervous system excitement used means that further research is likely necessary to fully understand the mechanisms at play.