Metabolic and physiological effects of adrenoceptor agonists and antagonists in the horse.

The research explores the effects of various adrenergic agonists and antagonists on horses, determining physiological responses linked to both beta and alpha adrenoceptors.

About the Experiment

• The researchers performed experimental tests on horses to observe the metabolic and physiological effects of certain adrenergic agonists – adrenaline, phenylephrine, and salbutamol.
• They measured changes in the horse’s hematocrit, plasma free fatty acid, glycerol, and lactate levels, along with observing effects on the horse’s heart rate, sweating, and muscle tremor.

Administration of Antagonists

• Following this, the adrenoceptor antagonists – propranolol, metoprolol, H35/25, and acepromazine – were administrated to study their effects on adrenaline-induced changes.

Observations and Results

• The observed results suggest lipolysis (the breakdown of fats to release fatty acids) and hyperglycemia (high glucose levels in blood) are mediated via beta-adrenoceptors.
• Both Beta1 and Beta2 subtypes of receptors appear to be involved in these processes.
• Muscle glycogenolysis (the breakdown of glycogen to glucose in muscles), muscle tremor, and sweating were found to be mediated via beta2-adrenoceptors.
• Even though administration of salbutamol elevated the hematocrit, other results supported the alpha-mediation of adrenaline-induced increases in hematocrit.

Implications of the Study

• This research reflects the significant role of adrenoceptors in key metabolic processes in horses, and potentially other species as well.
• It sheds light on how different categories of adrenoceptors mediate various physiological responses, a crucial understanding for pharmacological purposes.
• The study’s findings could potentially aid in the development of more effective drugs or treatments for disorders related to these adrenergic responses.