Cervical ganglionectomy alters the circadian rhythm of intraocular pressure in New Zealand White rabbits

Abstract

A circadian rhythm of intraocular pressure in rabbits could provide a useful model for understanding the daily rhythm of intraocular pressure in humans and for studying mechanisms which regulate intraocular pressure. Our results confirm earlier work showing that New Zealand White rabbits housed in an environment with a lighting cycle of 12 hours light and 12 hours dark have a rhythm of intraocular pressure, and that this rhythm persists in constant dark. We show further that the cycle of light and dark is the zeitgeber for entrainment of the rhythm of intraocular pressure, and therefore persistence of this rhythm in constant dark establishes it as a circadian rhythm. Cervical ganglionectomy demonstrated that intact sympathetic innervation to the eye is required for maintenance of the normal circadian rhythm of intraocular pressure in rabbits. Intraocular pressure in sympathectomized eyes is no different from control eyes during the light, but is significantly reduced during the dark.

Rabbit Diurnal Ocular Tension Variations

“…Rowland et al [5] made the interesting observation, as did Gregory et al [9], that the diurnal variation is unchanged by continuous 24-hour darkness, but is converted by contin uous 24-hour light into a plateau of unvarying pressure with a value intermediate between 374 T sukahara/Phillips/Gore Diurnal Variations in Rabbit Intraocular Pressure the low 'illuminated' level and the higher 'non-illuminated' values. In human glaucoma patients there is a cor relation between diurnal variations in ocular tension (and also outflow facility) and plasma glucorticoid levels, with a time lag of 3-4 h [10].…”

“…In human glaucoma patients there is a cor relation between diurnal variations in ocular tension (and also outflow facility) and plasma glucorticoid levels, with a time lag of 3-4 h [10]. A fall in rabbit plasma corticosterone levels has been observed in the dark [7], Adrenergic and other mechanisms are impor tant in the circadian cycle of rabbit intraocu lar pressure [8][9][10][11], As mentioned in 'Materials and Methods', we have studied only pressure changes rela tive to the baseline. However, we performed several calibration studies, both open and closed stopcock, with surprisingly variable re sults (as also occurred in another quite sepa rate study), probably because needles in the anterior chamber became blocked by plasmoid aqueous.…”

Reduction of Enhanced Rabbit Intraocular Pressure by Instillation of Pyroglutamic Acid Eye Drops

“…[27][28][29][30][31][32][33] The enhancement of IOP in dark phase was caused an increase of norepinephrine, the adrenergic neurotransmitter and cyclic adenosine monophosphate, the second messenger for beta-adrenergic signal transduction in aqueous humor.…”

Lack of circadian change of concentration of C-type natriuretic peptide in rabbit aqueous humor

“…ABSTRACT the dark and therefore that sympathetic tone is important at night (11) . Aqueous humor production, like the rhythm of IOP, is greater during the dark (12) .…”