In this study, we evaluate the effect of bilateral superior cervical ganglionectomy on albino rabbit choroidal blood flow (CBF) in changes of perfusion pressure (PP). Twenty albino rabbits of either sex weighing between 2.0 and 3.0 kg were randomly divided into two groups. The experimental group (group S) included 10 rabbits (20 eyes) that received bilateral superior cervical ganglionectomy one week prior to the study. The other 10 rabbits (20 eyes) served as a control (group N): each received the same procedure as group S except that the superior cervical ganglion was preserved. By means of a laser Doppler flowmeter (Perimed PF4001), blood cell flux (PF), velocity (V), and concentration of moving blood cells (CMBC) were recorded simultaneously while intraocular pressure was increased linearly by a syringe pump. Blood pressure and intraocular pressure were continuously monitored. The laser beam focused on the posterior pole away from major retinal vessels. When PP decreased from 75 to 0 mm Hg, in group N, PF, V and CMBC decreased from 100% to 6.94 ± 0.91%, 8.41 ± 0.87%, and 19.38 ± 1.11%; in group S, it was 17.75 ± 2.58%, 16.78 ± 1.48%, and 34.58 ± 4.42%, respectively. Group S poses higher PF, V, and CMBC than group N while PP decreased gradually. These results indicate that the superior cervical ganglion plays a role in CBF regulation. Bilateral sympathectomy led to a higher PF in the group S rabbits, indicating increased CBF. PF, V, and CMBC remained constant until PP <55 mm Hg demonstrated the existence of CBF autoregulation within a limited perfusion range in both groups. This autoregulation did not change after sympathectomy.

In this study we demonstrate the existence of sympathetic innervation and compare the effect of unilateral or bilateral superior cervical sympathectomy on albino rabbit choroidal blood flow (CBF) during changes in perfusion pressure (PP). Forty albino rabbits weighing between 2.0 and 3.0 kg were randomly divided into three groups. The bilateral sympathectomy group (group S) included 10 rabbits (20 eyes) that received bilateral sympathectomy 1 week prior to the study. The unilateral sympathectomy group (group U) included 20 rabbits (20 eyes) that received unilateral sympathectomy 1 week prior to the study. Only the eyes ipsilateral to sympathectomy were utilized. The other 10 rabbits (20 eyes) served as controls (group N), each received the same procedure as the experimental groups except that the superior cervical ganglion (SCG) was preserved. The blood cell flux (PF), velocity (V), and concentration of moving blood cells (CMBC) were recorded simultaneously by means of a laser Doppler flowmeter (Perimed PF4001), while the intraocular pressure was increased linearly with a syringe pump. When the PP decreased steadily, the PF, V, and CMBC remained constant until PP <55 mm Hg, then decreased proportionally to the PP. When the PP decreased from 75 to 0 mm Hg, the PF, V and CMBC decreased from 100 to 6.87 ± 0.97%, 8.44 ± 0.92%, and 18.67 ± 0.91% in group N, to 18.56 ± 1.62%, 19.30 ± 1.84%, and 38.02 ± 9.10% in group U, and to 18.38 ± 2.89%, 16.78 ± 1.48%, and 34.58 ± 4.42% in group S. The changes in PF, V, and CMBC were similar in groups S and U. Both group S and U had higher PF, V, and CMBC values than group N at comparable PPs below 55 mm Hg. These results indicate that the SCG plays a role in CBF regulation. Both unilateral and bilateral sympathectomy led to a higher PF in both groups S and U rabbits, indicating increased CBF while PP decreased gradually. This suggests that the rabbit choroid does not receive crossed innervation. The plateau response in each curve demonstrates the presence of autoregulation. This autoregulation was unchanged by either unilateral or bilateral sympathetic denervation.