Direct photosensitivity of chick pinealocytes as demonstrated by visinin immunoreactivity.
Level 5 - mechanism / opinion, no new human data
Preclinical animal and organ culture laboratory experiment
PubMed 2078852 · doi:10.1007/BF00305245
What was done
Chicks were exposed to either continuous environmental light or continuous darkness for 3 days to evaluate changes in pineal visinin immunoreactivity. Pineal visinin protein abundance was measured by semi-quantitative dot-immunoblotting. Eye-enucleation and pineal organ culture experiments were conducted to determine if photoreception was mediated directly by the pineal organ or through retinal neural pathways.
What was found
Continuous light increased the population density of visinin-immunoreactive pinealocytes. Dot-immunoblotting showed that visinin levels in pineal organs were 4- to 8-fold higher after 3 days of continuous light compared with 3 days of continuous darkness. Eye-enucleation and organ culture demonstrated that this response occurred directly at the pineal organ through the skull without involving the retinohypothalamic pathway.
Why it matters
The findings demonstrate direct, intrinsic photosensitivity of avian pinealocytes and suggest visinin is involved in extraretinal photoreception.
Limits
The abstract reports no sample sizes, variance measures, or statistical test values. Findings in chick pineal tissue cannot be generalized to mammals, which lack direct pineal photosensitivity.
Cited by
- supports Avian species have a pineal gland capable of detecting light directly through the skull.