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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)
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)
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)
Systemic administration of cannabinoids decreases intraocular pressure (IOP). To determine whether the mechanism of action originates in the central nervous system, we administered various cannabinoids into the cerebral ventricles of conscious New Zealand albino rabbits. When delta 9-tetrahydrocannabinol (delta 9-THC), delta 8-tetrahydrocannabinol,(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)
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)
Luteinizing hormone releasing hormone (LHRH) given intraventricularly caused a delayed, significant decrease of intraocular pressure (IOP) in adult female rabbits for a prolonged period, but only elevated plasma gonadotropins for a few hrs. Intravenous injections of LHRH caused a similar elevation of plasma gonadotropins without any effect on IOP. It(More)
Intravitreal injection of purified human chorionic gonadotropin (hCG) in rabbits decreased intraocular pressure (IOP). A dose-dependent decrease in IOP was observed with intravitreal hCG concentrations at 30 nM and 100 nM. The onset of this effect was later than 10 hr following the injection and it lasted for more than 24 hrs. The purified beta-subunit of(More)
Intramuscular injection of chlorpromazine in rabbits caused a significant decrease in intraocular pressure (IOP). The dose-response curve was generated. The threshold dose was 0.1 mg/kg (approximately 0.35 mg per rabbit) and 10 mg/kg chlorpromazine produced the maximal response which lasted for several hours. This decrease in IOP was not due to the release(More)
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