Apomorphine-induced vomiting in rainbow trout (Salmo gairdneri)

Area of Science:

• Pharmacology
• Toxicology
• Comparative Physiology

Background:

• Apomorphine is a dopamine receptor agonist with known emetic effects in mammals.
• The emetic (vomiting) response in fish, particularly rainbow trout, is not well-characterized.
• Understanding fish vomiting mechanisms can inform ecotoxicology and animal welfare studies.

Purpose of the Study:

• To determine the median lethal dose (LD50) of apomorphine hydrochloride in rainbow trout.
• To characterize the emetic and other toxicological effects of apomorphine hydrochloride in rainbow trout.
• To investigate potential similarities between trout and mammalian vomiting control mechanisms.

Main Methods:

• Rainbow trout were administered intraperitoneal injections of apomorphine hydrochloride at varying doses.
• The 7-day median lethal dose (LD50) was calculated.
• Vomiting was induced using plastic balls as a physical stimulus, and behavioral and physiological responses were recorded.

Main Results:

• The 7-day LD50 for apomorphine hydrochloride in rainbow trout was determined to be 158 mg/kg.
• Doses of 60 mg/kg or higher induced vomiting of ingested plastic balls.
• Observed effects included emesis, toxicity, increased respiration, impaired motor control, and enhanced aggression.

Conclusions:

• Apomorphine hydrochloride is acutely toxic to rainbow trout, with a calculated LD50 of 158 mg/kg.
• The emetic response in rainbow trout to apomorphine hydrochloride is dose-dependent and pronounced.
• The findings suggest that the neurobiological mechanisms controlling vomiting in trout may share similarities with those in mammals.