Publication: ldentification of extraretinal
photoreceptors in the teleost Phoxinus phoxinus
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Date
2004
Authors
Álvarez-Viejo, M. ; Cernuda-Cernuda, R. ; Álvarez-López, C. ; García-Fernández, J.M.
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Publisher
Murcia : F. Hernández
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DOI
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info:eu-repo/semantics/article
Description
Abstract
The existence of cells capable of detecting
changes of the photoperiod within the deep brain, the socalled
deep brain photoreceptors, was proposed in the
early years of the twentieth century.
By using immunocytochemistry with antisera
against phototransductory proteins on paraffin and
vibratome sections, we have localized severa1 positive
areas in the brain of the teleost Phoxinus phoxinus.
These areas were restricted to two encephalic regions:
the epithalamus and the hypothalamus. Immunopositive
(rod-opsin- and a-transducin-like) pinealocytes and
parapinealocytes, as well as some sparse neurons in the
habenula, were seen in the epithalamus. The
irnmunoreaction of the hypothalamus was represented by
a-transducin-like positive (magnocellular and
parvicellular) neurons of the Nucleus Preopticus, as well
as by a-transducin- and arrestin-like positive fibers
corresponding to the hypothalamic-hypophyseal tract
and a few fibers running towards the basa1
telencephalon.
These findings corroborate the data published on
other teleost fish and fully support the hypothesis of the
presence of photosensitive cells in the encephalon of
lower vertebrates. The labelling with antisera against
different components of the phototransductory cascade
also strengthens the idea that such cells employ a
biochemical mechanism similar to that in the retinal
visual photoreceptor cells, rods and cones. Although the
function is still unclear, the detection of the photoperiod
seems to be the most likely role for these extraretinal
photoreceptors.
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