THE EFFECT OF VASOACTIVE-INTESTINAL-PEPTIDE ON DEVELOPMENT OF FORM DEPRIVATION MYOPIA IN THE CHICK - A PHARMACOLOGICAL AND IMMUNOCYTOCHEMICAL STUDY

The role of vasoactive intestinal peptide (VIP) in the development of form deprivation myopia (FDM) was examined. Daily intravitreal injecti on of porcine VIP reduced, but did not eliminate FDM at a maximal dail y dose of 1 x 10(-5) mol/injection, A VIP analogue reported to be rela tively hydrolysis-resistant in vivo, had no effect on development of F DM at any dose tested. Two VIP antagonists completely abolished FDM. T he one reported to be selective for central nervous system VIP recepto rs was 100 times more potent than one reported to be selective for per ipheral nervous system receptors (ED(50)=2 x 10(-10) and 2 x 10(-8) mo l/injection respectively). By immunofluorescence using antiserum to po rcine VIP, VIP-like immunoreactivity was localized to a subset of amac rine cells (AC) acid in three parallel layers in the inner plexiform l ayer (IPL) (10%, 40% and 70% of IPL thickness from the AC layer). Immu noreactive nerve fibres were also seen in the choroid, the ciliary bod y and the iris. These results suggest that VIP may play a role in both normal development of the refractive properties of the eye, and in th e development of FDM.