Monoterpenoids (thymol, carvacrol and S-(+)-linalool) with anesthetic activity in silver catfish (Rhamdia quelen): evaluation of acetylcholinesterase and GABAergic activity

Abstract

This study evaluated the anesthetic potential of thymol and carvacrol, and their influence on acetylcholinesterase (AChE) activity in the muscle and brain of silver catfish (Rhamdia quelen). The AChE activity of S-(+)-linalool was also evaluated. We subsequently assessed the effects of thymol and S-(+)-linalool on the GABAergic system. Fish were exposed to thymol and carvacrol (25, 50, 75, and 100 mg/L) to evaluate time for anesthesia and recovery. Both compounds induced sedation at 25 mg/L and anesthesia with 50–100 mg/L. However, fish exposed to carvacrol presented strong muscle contractions and mortality. AChE activity was increased in the brain of fish at 50 mg/L carvacrol and 100 mg/L thymol, and decreased in the muscle at 100 mg/L carvacrol. S-(+)-linalool did not alter AChE activity. Anesthesia with thymol was reversed by exposure to picrotoxin (GABAA antagonist), similar to the positive control propofol, but was not reversed by flumazenil (antagonist of benzodiazepine binding site), as observed for the positive control diazepam. Picrotoxin did not reverse the effect of S-(+)-linalool. Thymol exposure at 50 mg/L is more suitable than carvacrol for anesthesia in silver catfish, because this concentration did not cause any mortality or interference with AChE activity. Thymol interacted with GABAA receptors, but not with the GABAA/benzodiazepine site. In contrast, S-(+)-linalool did not act in GABAA receptors in silver catfish.

Anesthetic potential of the essential oils of Lippia alba and Lippia origanoides in Tambaqui juveniles

“…The time required to induce sedation with EOLO-Ca in tambaqui was similar to that reported for silver catfish, however the time required to induce deep anesthesia was longer . The anesthetic effect of EOLO-Ca on silver catfish was similar to carvacrol, its main compound (BIANCHINI et al, 2017;. Recovery time of tambaqui from anesthesia with EOLO-Ca was much longer than that observed for silver catfish .…”

Application of herbal anaesthetics in aquaculture

“…Silver catfish anaesthetized with 135 mg L −1 linalool showed no change in acetylcholine esterase activity in muscle and brain (Bianchini et al . ).…”

“…It was found to anaesthetize silver catfish within >1800–170 s, with recovery time of 919 to >1800 s at the concentrations of 25–100 mg L −1 (Bianchini et al . ). Thymol at the concentration of 100 mg L −1 increases silver catfish brain acetylcholine esterase activity (Bianchini et al .…”

“…Thymol at the concentration of 100 mg L −1 increases silver catfish brain acetylcholine esterase activity (Bianchini et al . ).…”

“…In silver catfish, carvacrol induced anaesthesia within >1800–299 s at the concentrations of 25–100 mg L −1 ; recovery time was in general >1800 s (Bianchini et al . ). At 50 mg L −1 concentration, carvacrol significantly increases brain acetylcholine esterase activity, whereas at 100 mg L −1 concentration a significant inhibition was observed in muscle acetylcholine esterase activity (Bianchini et al .…”