Abstract
Abstract: :
Purpose:Ketamine, a dissociative anesthetic, has been used as the traditional agent of choice for in vivo rodent ERG studies. In spite of the good success experienced by investigators using ketamine anesthesia, the method is not without problems. For example, mutant mouse strains may exhibit different levels of sensitivity to ketamine when compared to the background strain. We have found some strains that are susceptible to sudden death under ketamine anesthesia, whereas others are resistant to its anesthetic effects. Inasmuch as rodents are obligate nose–breathers, it is possible to administer inhalation anesthetics without the need for intubation, making these drugs a viable alternative for anesthesia. We compared the effects of isoflurane and ketamine anesthesia on the parameters of the murine scotopic and photopic ERGs. Methods:Scotopic and photopic ERGs were performed on C57BL/6J mice anesthetized with either the standard subcutaneous mouse ketamine/xylazine cocktail or with inhaled isoflurane. A cross–over study design was utilized in which each animal was exposed to each of the anesthetic agents in random order and separated by a one week interval. Pair–wise comparisons of the ERG parameters, measured with each anesthetic in a given animal, were made for twelve male and twelve female mice. Results:There were no significant differences in the amplitudes of the b–waves or oscillatory potentials between the two anesthetic agents for scotopic ERGs. In contrast, although there were no significant differences in the amplitudes of the photopic ERG b–waves or oscillatory potentials between the two anesthetic agents for male mice, female mice had significantly smaller b–wave and oscillatory peak amplitudes with isoflurane as opposed to the ketamine anesthesia (p<0.05). Conclusions:Isoflurane is an effective alternative to ketamine anesthesia for studying the murine ERG, and provides a viable option for studying animals that exhibit differential toleratance to an anesthetic agent when compared to animals from the background strain. In addition to its ease of use, the more rapid recovery from isoflurane anesthesia (generally less than 5 min) as compared to ketamine (on the order of 30–45 min) is another potential advantage.
Keywords: electroretinography: non–clinical • electrophysiology: non–clinical