| Popis: |
Understanding of the mammalian c-wave is enhanced by recent clarification of the role of the cells of the pigment epithelium. Profound between and within human variability is reported by Hock and Marmor (1982), while the classical literature exhibits a confusing number of citations to species variation for c-wave amplitude and latency. Among others, the canine eye has been reported to have no c-wave (Rodieck, 1973). We report here that this view is incorrect although DC-recorded canine c-waves are highly breed dependent and exhibit sensitivity to both inhalation and parenteral anesthetics. For example, in the pure breed beagle, normally large c-waves were eliminated by end-tidal halothane concentrations of 2%. More sensitive English setters lost 70% of c-wave amplitude with end-tidal halothane concentrations of 0.1%. Setters also show significant c-wave reductions with graded pentobarbital concentrations up to 10 mg/kg. One mixed breed dog showed potentiation of the c-wave in the presence of 2% halothane. An overview of performance across breeds disclosed moderate or mild a-, b-wave sensitivities, while c-wave reductions up to 100% were recorded. Species, breed, anesthetic and general physiological state probably account for the varied results in the classical c-wave literature. |
