The use of anesthesia during evoked potential audiometry in goldfish (Carassius auratus)

Abstract

Auditory evoked potentials (AEPs) have become a widely utilized measure of hearing sensitivity. Most investigators use pharmacological paralysis to reduce myogenic noise and immobilize the animal for stable electrical recordings, but additional anesthesia is generally not used because the most commonly available fish anesthetic, the cholinergic antagonist tricane methanosulfate (MS222), is known to disrupt hair cell and primary afferent physiology. Anesthetic agents that do not interfere with auditory function would be a useful adjunctant to paralytic immobilization and would reduce any possible distress incurred by prolonged immobilization. In this report we tested the opiate anesthetic Fentanyl and compared hearing thresholds in immobilized versus immobilized and anesthetized animals. Short-term effects of mild MS222 anesthesia were also measured via evoked potential audiometry. Animals were tested before and after Fentanyl injection (100, 500 and 2500 μg g −1 fish body-weight) using standard evoked potential audiometry. Tone pips, 0.2 to 3 kHz, from an aerial loudspeaker served as stimuli. Fentanyl altered evoked potential waveforms slightly, but did not alter estimated threshold sensitivity. These results suggest Fentanyl be considered as a possible addition to AEP techniques in goldfish (Carassius auratus) and poikilothermic vertebrates generally.

Auditory evoked potential audiometry in fish.

“…Comparisons among other species (see below) for which these data exist could tell us whether or not this hypothetical 'factor' is universal among fish, or is species-specific. The baseline hearing abilities of goldfish have been investigated by numerous investigators applying different behavioral (Enger 1966;Fay 1969;Jacobs and Tavolga 1967;Offutt 1968;Popper 1971;Weiss 1966) or electrophysiological (e.g., Amoser and Ladich 2003;Cordova and Braun 2007) techniques in different labs.…”

“…After Wysocki et al (2009b) used, different numbers of AEPs averaged, signal-tonoise ratio in the electrophysiological recordings, and genetic differences between fish populations can add to the variation in hearing thresholds published for goldfish. Cordova and Braun (2007) investigated if immobilization agents affect hearing thresholds. They compared auditory thresholds in goldfish after intramuscular injection of gallamine triethiodide (Flaxedil-a paralytic agent) or in combination with an injection of fentanyl (an anesthetic).…”

Dopaminergic-induced changes in Mauthner cell excitability disrupt prepulse inhibition in the startle circuit of goldfish

“…The fish was stabilized in the recording chamber by two pins, one on each side of the head, and ventilated through the mouth with aerated conditioned water at 18°C. Water contained the general anesthetic MS-222 at a concentration of 20 mg/l, which does not interfere with auditory processing at the dosage used (Cordova and Braun 2007).…”

Objective threshold estimation and measurement of the residual background noise in auditory evoked potentials of goldfish

“…It has now become widely used in clinical and basic hearing research in both human and diverse vertebrate animal models ͓mammals ͑e.g., Boettcher, 2002͒, birds ͑e.g., Brittan-Powell et al, 2002͒, reptiles ͑e.g., Higgs et al, 2002͒, amphibians ͑e.g., Katbamna et al, 2006͒, and fishes ͑e.g., Kenyon et al, 1998͔͒. Most recently, AEP audiometry has been used to statistically test a wide variety of hypotheses on the function, development, and evolution of audition. Examples include the effect of chemical and noise exposure on auditory sensitivity ͑e.g., Lu and Tomchik, 2002;Le Prell et al, 2004;Popper et al, 2005;Porter et al, 2006;Cordova and Braun, 2007͒, ontogenetic changes in hearing abilities ͑e.g., Boettcher, 2002;Higgs et al, 2003;Song et al, 2006͒, or com-parative studies of closely related species ͑e.g., Ramcharitar and Popper, 2004;Ramcharitar et al, 2006͒. The vast majority of publications reporting AEP threshold estimates ͑in animals͒ in this and three other prominent journals over the last 10 years used subjective response determinations to estimate thresholds ͑Table I͒.…”