Pituitary adenylate cyclase-activating polypeptide (
PACAP) and its receptors occur throughout the nervous system, including the retina.
PACAP exerts diverse actions in the eye: it influences ocular blood flow, contraction of the ciliary muscle, and has retinoprotective effects. This has been proven in different models of
retinal degeneration. The in vivo protective effects of
PACAP have been shown in
retinal degeneration induced by
kainic acid,
optic nerve transection and
ischemia. We have previously shown by morphological, morphometrical and immunohistochemical analyses that intravitreal
PACAP administration protects against
monosodium glutamate (
MSG)-induced damage in neonatal rats. The question was raised whether these apparent morphological improvements by
PACAP administration also lead to functional amelioration in
MSG-induced
retinal damage. The aim of the present study was to investigate the functional consequences of
MSG treatment and the subsequent
PACAP administration using electroretinographic measurements. The histological and morphometrical analyses supported the earlier findings that
PACAP protected the retina in
MSG-induced excitotoxicity. ERG recordings revealed a marked decrease in both the b- and a-wave values, reflecting the function of the inner
retinal layers and the photoreceptors, respectively. In retinas receiving intravitreal
PACAP treatment, these values were significantly increased. Thus, the functional outcome, although not parallel with the morphology, was significantly improved after
PACAP treatment. The present observations are important from the clinical point of view showing, for the first time, that
PACAP treatment is able to improve the functional properties of the retina in excitotoxic damage.