Effect of Electrical Stimulation of Cervical Sympathetic Ganglia on Intraocular Pressure Regulation According to Different Circadian Rhythms in Rats

Abstract

The purpose of this study was to investigate the relationship between circadian rhythm and intraocular pressure (IOP), and to explore whether electrical stimulation of cervical sympathetic ganglia (SCG) can regulate IOP via neurotransmitter distribution around the Schlemm's canal (SC) in rats. METHODS. Sprague Dawley rats were housed under normal (N-normal), constant dark (N-dark), and constant light (N-light) rhythms (n = 6 per group). Electrical stimulation (intermittent wave [20 hertz {Hz}, 2 mA, 10 minutes]) was used to stimulate the SCG. Atropine sulfate eye gel was applied three times a day. DiI was injected into the SCG and anterior chamber. The cross-sectional area and circumference of SC were evaluated using hematoxylin-eosin staining. Immunofluorescence staining was used to evaluate dopamine-β-hydroxylase (DβH) expression in SC endothelial (SCE) cells. RESULTS. N-Dark increased the IOP, decreased the cross-sectional area of SC, and increased DβH levels in SCE cells. Nerve projection between SC and SCG was detected, and electrical stimulation of SCG upregulated DβH expression in SCE cells. Under normal and constant light rhythms, electrical stimulation of SCG increased DβH and decreased the cross-sectional area and circumference of SC, while simultaneously increasing IOP and decreasing IOP fluctuations. After paralyzing the ciliary muscles, electrical stimulation of SCG decreased the cross-sectional area and circumference of SC under normal and constant light rhythms. CONCLUSIONS. N-Dark increased DβH in SCE cells, reduced the cross-sectional area of SC, and increased IOP. Under the normal and light rhythms, electrical stimulation of SCG increased DβH in SCE cells, reduced the cross-sectional area and circumference of SC, and in turn elevated IOP and decreased IOP fluctuations.

A portable feedback-controlled pump for monitoring eye outflow facility in conscious rats

“…The eye presumably must remain connected to circulatory and neural signals from the suprachiasmatic nucleus, which has been shown to regulate IOP rhythmicity [ 33 , 34 ]. Observed changes in outflow resistance may reflect sympathetic shrinkage of Schlemm’s canal [ 35 ], suppression of trabecular meshwork phagocytosis [ 36 ], or other processes under circadian control.…”

Paraventricular Hypothalamic Nucleus Upregulates Intraocular Pressure Via Glutamatergic Neurons

“… 61 – 63 The diameter of Schlemm's canal is reduced when the superior cervical ganglion is stimulated, followed by a rise in IOP, suggesting that local sympathetic stimulation can increase IOP. 64 – 66 Nocturnal IOP is lower, which correlates with a decreased sympathetic tone. 67 Clinically, drugs of sympathetic inhibition are used to treat glaucoma.…”

Ocular Autonomic Nervous System: An Update from Anatomy to Physiological Functions

“…NOS in the endothelium mediates pressure-dependent drainage, which may form a negative feedback pathway [ 197 ]. A previous study has suggested that under electric stimulation of SCG in rats, the expression of DβH in the SC endothelium is increased, and the cross-sectional area and perimeter of the SC are reduced [ 198 ]. This may explain the elevated IOP [ 199 ].…”