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Melanopsin – a unique photopigment

Melanopsin – a unique photopigment. Problem. In addition to giving is relatively immediate information about visual scenes, light is involved in regulating certain kinds of bodily processes One important such process is regulation of diurnal (daily) rhythms

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Melanopsin – a unique photopigment

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  1. Melanopsin – a unique photopigment

  2. Problem • In addition to giving is relatively immediate information about visual scenes, light is involved in regulating certain kinds of bodily processes • One important such process is regulation of diurnal (daily) rhythms • Experiments involving gene knockouts have shown that neither rods nor cones are necessary for visual regulation of rhythms

  3. Melanopsin • Some animals (birds, reptiles) have photoreceptive tissue in places other than the eye – the skin, the pineal gland • Is melanopsin present in mammals?

  4. Yes! In their eyes! Melanopsin in the retina of the rat: Notice where it is relative to the photoreceptor layer

  5. Melanopsin is distributed in discrete little puffs

  6. Melanopsin-positive retinal ganglion fibres leaving the eye

  7. Most melanopsin RGC’s land in the hypothalamus -the suprachiasmatic nucleus

  8. Transduction is not the same as in other opsins. Isolated cell bodies produce electrical events in response to light

  9. One puzzle • Knocking out melanopsin does not abolish diurnal rhythms • But knocking out rods, cones AND melanopsin does • Likely, this means that there is convergent input from rods and/or cones onto melanopsin RGCs.

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