Sweating in the intact horse and isolated perfused horse skin.

The research investigates how different substances affect the sweat response in horses, both in the intact organism and in isolated skin samples. The substances examined include adrenaline, isoprenaline, and phenylephrine and it further looks into the cell types involved in this process.

Initial Observations on Sweating in Horses

• The study began with observations on intact horses. It was noted that heat-induced sweating started in pulses but eventually turned into a continuous, synchronised discharge.

Effects of Different Substances on Sweating

• The research further studied the impact of three substances on the sweating process – adrenaline, isoprenaline and phenylephrine.
• Adrenaline, when introduced intravenously, prompted immediate sweating.
• Isoprenaline, on the other hand, induced sweating but with a delayed reaction.
• Phenylephrine was observed to have no effect on the sweating process in intact horses.

Observations on Isolated Perfused Horse Skin

• The researchers also studied isolated perfused horse skin to analyse how the substances affect the sweating process.
• Interestingly, the effect of the substances varied. Phenylephrine, which previously had no effect, prompted a small immediate sweat discharge.
• Isoprenaline induced a more sustained output but at a slower pace.
• Adrenaline initiated a biphasic discharge, meaning that it caused two distinct waves of sweat release.
• Moreover, it was found that alpha- and beta-adrenergic antagonists could block the first and second phases of this biphasic sweat discharge, respectively. This implies that adrenaline’s effect on sweating could be modulated by these antagonists.

Cellular Considerations

• These observations suggest independent activation of two types of cells in the sweat glands – alpha-adrenergic myoepithelium and beta-adrenergic secretory cells.
• This could mean that these cell types are individually responsible for different phases of the sweat response.

Impact of Microcirculatory Changes on Sweating

• The research also observed that changes in the microcirculation, i.e., blood flow through the smallest vessels in the body, also seemed to influence sweat discharge.

In summary, the study highlighted that various substances have different effects on the sweating processes in horses, and how this process involves several bodily responses, including those on a microscopic level.