Myogenic Oscillations in Rabbit Ocular Vasculature Are Very Low Frequency

Abstract

Background/Aims: In a previously described model of isolated rabbit eye, we detected myogenic intrinsic vascular tone of unknown origin in the ophthalmic artery. In order to better understand the origin of these low frequency oscillations, we analyzed their spectral characteristics using fast Fourier. Methods: Hybrid New Zealand rabbits of either sex (n = 24) were used; they were divided into 2 groups according to age. The spectral characteristics of the myogenic behaviour of the rabbit external ophthalmic artery were analyzed using the fast Fourier algorithm. Results: The frequency of the oscillations of the myogenic activity seen in the rabbit external ophthalmic artery varied between 0.033 and 0.066 Hz (mean 0.045 ± 0.012 Hz), all in the region of very low frequency (VLF) oscillations (VLF <0.07 Hz for the rabbit). The frequency of spontaneous oscillations was higher in younger animals. Conclusion: Fast Fourier analysis proved to be an adequate mathematical tool to analyze the myogenic tone oscillations, which were all in the range of VLF in the model we used. These results indicate that myogenic vascular function of ocular blood flow is composed of VLF oscillations, and they provide a new explanation for the origin of VLF in arterial spectra. They also suggest that the ocular local myogenic vascular function observed is more efficient in younger animals.