Link between the ciliary process and lens equatorial current.

Circadian and seasonal rhythmic changes in the intraocular pressure are modulated by the nervous system and expressed in the eye by the release of norepinephrine at adrenergic nerve endings. This study links seasonal changes and the effects of the topical application of norepinephrine with changes in the equatorial current of the lens in frogs. A vibrating probe and microelectrodes were used to study the segment of the K+ electrical loop extending between the internal microelectrode, used for measuring potential difference (PD), and the external vibrating electrode, measuring the equatorial current (J). Changes were noted in the electrophysiological parameters of 270 normal frog lenses (Rana pipiens) at different times of the year. Threefold seasonal variations were observed in the amplitude of equatorial current (J) and the resistance associated with the equatorial current (RJ). J was greatest in the winter and RJ was greatest in late spring. Norepinephrine applied directly to the lens did not affect the equatorial current. Norepinephrine applied topically, increased the equatorial current of the lens. It is concluded that the magnitude of the equatorial current of the lens is mediated in part by the ciliary process epithelium.