Technique for reversible vagal blockade in the standing conscious pony.

This research study presents a new surgical method used to create temporary vagal blockades in ponies. Changes in heart rate, blood pressure and respiratory rates were observed when the vagus nerve was cooled by circulating methanol, and the effects were quickly reversed when the cooling stopped.

Technique Description

• The research paper describes a surgical procedure designed to establish chronic cervical vagal loops in ponies. This involves surgically manipulating the vagus nerve of the pony in a manner that allows for temporary blockages.
• The blockage of the nerve, or vagal blockade, is induced by cooling the nerve. This is done by circulating methanol, a chemical, at a temperature of -2 degrees Celsius through coils that enclose the nerve loops. This cooldown leads to the temporary cessation of the nerve’s functions.
• The surgery has been developed to be performed on standing, conscious ponies, which adds to the significance of the procedure.

Observations and Effects

• When the vagal blockade is induced, there were noticeable increases in the ponies’ tidal volume, heart rate, and systemic blood pressure. Conversely, their respiratory rate was observed to decrease. Tidal volume refers to the normal volume of air displaced between normal inhalation and exhalation when extra effort is not applied.
• The increase in heart rate and systemic pressure was also observed when the ponies were given Atropine, a type of medication. However, Atropine did not alter their respiratory variables, suggesting that the cooling of the vagus nerve caused a blockade in both incoming (afferent) and outgoing (efferent) nerve signals.
• The effects of the vagal blockade could be quickly reversed. When the refrigerated coils that were cooling the nerve were removed, the nerve rapidly returned to its usual functioning.

Implications of the Research

• The practical applications of the research could be extensive, particularly in certain areas of veterinary science. The technique demonstrated a way to control some physiological variables like heart rate, respiratory rate, and blood pressure, by a reversible blockade of the vagus nerve.
• This surgery and its methods could also possibly be adapted for use in various forms of medical research, treatment of certain diseases and improving the understanding of the role the vagus nerve plays in various physiological processes.