Development of receptoral responses in pigmented and albino guinea-pigs (Cavia porcellus) |
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Authors: | Bang Viet Bui Algis Jonas Vingrys |
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Institution: | (1) Department of Optometry and Vision Sciences, University of Melbourne, 3010 Victoria, Australia |
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Abstract: | We describe the postnatal development of the electroretinogram (ERG) receptoral response in the guinea pig. In addition, the
time course and nature of maturation was compared between albino and pigmented strains to consider the role that melanogenesis
might have in this process. Electroretinograms were collected on groups of albino and pigmented animals from postnatal day
(PD) PD1 to PD60. A-wave amplitudes and implicit times were extracted from filtered data (0–75 Hz). Receptoral components
were modelled using the delayed gaussian model of Hood and Birch 1] fitted as an ensemble to the raw data. Guinea pigs show
saturated amplitudes (RmP3) that are 50% of adult values at birth, these mature by PD12. Receptoral delay (td) also undergoes some postnatal maturation, while phototransduction gain (log S) is adult-like at birth. Albino animals had
significantly (p<0.05) larger RmP3 and log S across all ages. Guinea pigs have significant postnatal development in their receptoral response. Maturation of
RmP3 implies a postnatal increase in rod outer segment length. Whereas the adult values of log S implies a mature phototransduction
process at birth. We argue that the likely cause for the larger log S of albino eyes is compatible with theories of increased
levels of internal light. Whereas the larger RmP3, even after allowing for increased light effectiveness, may reflect a lower ocular resistance in albino eyes due to their
lower levels of melanin. Furthermore, decreased RmP3 and log S with age is observed in the pigmented group only and is consistent with increased ocular resistance due to melanin
development in this strain.
This revised version was published online in July 2006 with corrections to the Cover Date. |
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Keywords: | electroretinogram ERG melanin neonate neuronal growth receptor physiology |
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