Figure 10. Immunoreactivity of nerve fibres innervating choroidal arterioles in the guinea-pig to αPGP9.5, αTH, αVIP, αNOS and αSP.

A, a preparation treated with αPGP9.5, a marker used to identify all neuronal elements. Numerous, dense nerve fibres immunoreactive to αPGP9.5 were identified surrounding guinea-pig choroidal arterioles (arrows). B and C, same preparation double labelled with αTH (B) and αVIP (C). Choroidal arterioles were densely innervated with αTH immunoreactive fibres, which often formed a plexus around the arterioles (B). Choroidal arterioles were also innervated by nerve fibres immunoreactive to αVIP (C). In preparations double labelled with both αTH and αVIP, nerve fibres immunoreactive to αTH formed a separate population from those fibres which expressed immunoreactivity to αVIP (longer arrows in B indicate fibres immunoreactive to αTH but not to αVIP and longer arrows in C indicate those fibres expressing immunoreactivity to αVIP only). However, even though nerve fibres immunoreactive to αTH were separate from those immunoreactive to αVIP, they were often found running alongside one another, possibly in the same nerve bundle (arrowed in B and C). Choroidal arterioles were also innervated by numerous αNOS-containing nerve fibres, which appeared to be varicose (arrow, D). In separate preparations, varicose nerve fibres expressing immunoreactivity to αSP were also identified (arrow, E), although innervation by αSP immunoreactive fibres were sparse. Scale bars: A, 100 μm; B-E, 50 μm.