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A unique circadian rhythm of intraocular pressure (IOP) occurs in laboratory rabbits housed in a light-dark environment. The IOP is low in the light and high in the dark. In 32 rabbits studied, the IOP was 18.7 +/- 0.3 mm Hg (mean +/- the standard error of the mean) at 2 hr before the onset of dark and 24.9 +/- 0.6 mm Hg at 2 hr into the dark. The changes(More)
Intravenous injections of 1-100 micrograms thyrotropin releasing hormone (TRH) in rabbits elevated intraocular pressure (IOP). The 2-5 mm Hg increase of IOP lasted for less than 2 hr. No change of pupil size was observed. This IOP elevation was not due to a direct effect of TRH on ocular tissues since intravitreal injections of 0.1 and 1 micrograms TRH did(More)
Intracerebroventricular (ICV) injection of carbachol into the third ventricle of conscious rabbits increased pupil size and intraocular pressure (IOP). A significant increase of pupil size by 0.6-1.3 mm for 60-90 min was observed with the dose of 1 microgram and an increase of IOP by 1.1-1.9 mmHg for 15-60 min was observed with doses over 10 ng. These(More)
Stimulation of the ocular sympathetic nerves is essential for the circadian elevation of intraocular pressure (IOP) in rabbits. Adrenergic mechanisms that participate in this elevation of IOP around the onset of darkness were investigated using selective adrenergic agents. Unilateral topical administration of 0.0001-0.1% prazosin, an alpha-1-adrenergic(More)
Rabbits entrained in a daily light-dark environment show a circadian elevation of intraocular pressure (IOP) around the onset of dark. It was reported that concentration of cyclic AMP (cAMP) in aqueous humor increases significantly during this time period. Whether or not the increase of ocular cAMP-mediated activities is related to the circadian elevation(More)
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