Brain research

A thalamus region controls how Siberian hamsters respond to day length changes

Circadian Biology Weekly Brief ↗PubMed ↗DOI ↗

Updated

Abstract

Neurochemical lesions of the intergeniculate leaflet (IGL) alter the circadian entrainment and photoperiodic responsiveness of Siberian hamsters to a simulated natural photoperiod.

  • Siberian hamsters use changes in day length to time their reproductive efforts.
  • The suprachiasmatic nucleus (SCN) in the hypothalamus is crucial for measuring and responding to day length.
  • Two pathways transmit light information to the SCN: the retinohypothalamic tract (RHT) and the geniculohypothalamic tract (GHT).
  • Ablating the IGL/GHT leads to modest changes in entrainment to static day lengths but does not affect seasonal responses to shifts between long and short day lengths.
  • Lesions of the IGL affect both circadian entrainment patterns and the ability to respond to a simulated natural photoperiod.
  • Both IGL-intact and IGL-lesioned hamsters showed testicular regression in response to shortening day lengths, but only IGL-intact hamsters molted seasonally.

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