Endothelin-1 effects on spontaneous oscillations in choroidal arterioles.
OBJECTIVE
This study characterizes the effects of endothelin-1 (ET-1) on the perfusion pressure of the choroidal vasculature using in situ perfused isolated rabbit eyes.


METHODS
Rabbit external ophthalmic arteries (n = 12) in a head-mounted preparation were cannulated and perfused with warmed tyrode. The three-way polypropylene catheter was further connected to a pressure transducer and the effect of intraluminal pressure as a measure of total vascular resistance was assessed. Response curves to intra-arterial injections of ET-1 (group A; n = 6) and to an intravitreal injection followed by an intra-arterial injection of ET-1 (group B; n = 6) were obtained. Data were studied using paired t-test and fast Fourier transform.


RESULTS
Before any drugs were administered, spontaneous oscillations were observed in the 12 rabbit models. In group A, ET-1 induced a short and weak vasodilating effect followed by a strong and long-lasting vasoconstrictor tone. Vasomotion became more evident, showing a higher frequency and shorter amplitude of oscillations. In group, B the intravitreal injection produced no significant changes in registered pressure or vasomotion characteristics. The intra-arterial injection produced effects similar to those observed in group A.


CONCLUSIONS
Our study has three main findings: (i) the choroidal vasculature demonstrated spontaneous oscillations in perfusion pressure in basal conditions in all rabbit eye models; (ii) ET-1 applied intra-arterially induced a short drop in perfusion pressure followed by a long withstanding contraction; and (iii) intra-arterial ET-1 modulated the frequency and amplitude of the spontaneous oscillations, causing a faster rate of pulsatility.
Delgado
Esmeralda
E
Clinics Department, Centre for Interdisciplinary Investigation into Animal Health, Alameda da Universidade Técnica, Lisbon, Portugal. esmeralda@fmv.utl.pt
Marques-Neves
Carlos
C
Rocha
Isabel
I
Sales-Luís
José
J
Silva-Carvalho
Luis
L
D000818:Animals; D001160:Arterioles / Q000187:drug effects* / Q000502:physiology*; D002829:Choroid / Q000098:blood supply*; D019332:Endothelin-1 / Q000008:administration & dosage*; D005260:Female; D005583:Fourier Analysis; D066298:In Vitro Techniques; D007269:Injections, Intra-Arterial; D056965:Injections, Intraocular; D008297:Male; D009991:Oscillometry; D011673:Pulsatile Flow / Q000187:drug effects; D011817:Rabbits; D013997:Time Factors; D014655:Vascular Resistance / Q000187:drug effects; D014661:Vasoconstriction / Q000187:drug effects; D014664:Vasodilation / Q000187:drug effects; D014822:Vitreous Body
D019332:Endothelin-1