Rv. Searles et al., INTERACTION BETWEEN HEAD-DOWN TILT AND ANTERIOR-CHAMBER INFUSIONS ON INTRAOCULAR-PRESSURE OF ANESTHETIZED RATS, Experimental Eye Research, 62(6), 1996, pp. 621-625
Head-down tilt or infusions of a balanced salt solution into the anter
ior chamber of the eye raise intraocular pressure. Mie measured intrao
cular pressure directly in adult male Sprague-Dawley rats, anesthetize
d with pentobarbital, and subjected to 45 degrees head-down tilt alone
, tilt with an anterior chamber infusion (0.087 mu l min(-1)), or tilt
with an infusion containing arginine vasopressin. The intraocular pre
ssure of the three groups differed during the 1 hr tilt and recovery p
eriods. In the case of tilt alone. intraocular pressure quickly reache
d a peak after tilting, partially decreased during the tilt period, re
covered to baseline immediately after tilt, then a secondary rise occu
rred. Combined infusion and tilt caused a slower rise to peak intraocu
lar pressure, and only a partial recovery occurred during the 1 hr rec
overy period. Combined vasopressin infusion and tilt caused a gradual
rise in intraocular pressure of a lesser magnitude than the other grou
ps, followed by a rapid recovery to baseline pressure and no secondary
rise. Systemic arterial pressure was stable within and between the gr
oups. The underlying mechanism for these differing response patterns i
s unknown. However, some evidence indicates that infusions are indepen
dent of aqueous synthesis rate, and that vasopressin, acting on a V-1
receptor subtype reached from the anterior chamber, exerts a vascular
effect. (C) 1996 Academic Press Limited