Further evidence to support the alpha 2-adrenergic nature of amitraz-induced decrease in intestinal motility.

Area of Science:

• Pharmacology
• Neurogastroenterology
• Insecticide Toxicology

Background:

• Insecticides can affect non-target organisms, including mammals.
• The gastrointestinal system's motility is regulated by the autonomic nervous system.
• Alpha-adrenoceptors play a role in modulating intestinal function.

Purpose of the Study:

• To investigate the effect of the formamidine insecticide amitraz on in vitro intestinal contractions.
• To determine the specific adrenoceptor subtypes involved in amitraz's action on the gut.

Main Methods:

• Using transmurally-stimulated guinea-pig ileum preparations.
• Administering amitraz in varying concentrations (10(-7) to 10(-6) M).
• Utilizing alpha-adrenoceptor antagonists (idazoxan and prazosin) to probe receptor involvement.

Main Results:

• Amitraz caused a dose-dependent inhibition of electrically-induced intestinal contractions.
• Idazoxan (an alpha 2-adrenoceptor antagonist) blocked and reversed amitraz's inhibitory effect.
• Prazosin (an alpha 1-adrenoceptor antagonist) did not prevent the effect of amitraz.

Conclusions:

• Alpha 2-adrenoceptors mediate the inhibitory effects of amitraz on guinea-pig ileum contractions.
• Amitraz likely decreases intestinal contraction by activating alpha 2-adrenoceptors in the myenteric plexus.
• This activation inhibits parasympathetic tone, leading to reduced gut motility.