Manchester. Daily rhythmicity in physiology, metabolism and behaviour is controlled by a master clock located in the hypothalamic suprachiasmatic nuclei (SCN). SCN neurons were shown not only to be directly photosensitive but also their responses strongly dependent on the stimulus irradiance. That type of ‘irradiance response’ is believed to reflect the SCN’s use of retinal input to track 24 h light-dark cycle. However, most of our knowledge about photic sensitivity of the SCN came from nocturnal species and far less is known about diurnal mammals. Thus, we set out here to provide a detailed comparison of hypothalamic light responses between a diurnal murid rodent, Rhabdomys pumilio, and nocturnal mice by performing in viva acute multielectrode recordings. We find that overall the visual response properties of SCN cells were very similar between species. Majority of neurons were excited by light stimulation and responding in either classic sustained or transient manner. In both species, sustained neurons followed increments and decrements in irradiance presented either as simple light steps or when more naturalistic stimuli (such as temporal white noise or chirp) were superimposed. On the other hand, light responsive cells were muchemical more common in Rhabdomys in the peri-SCN area. These peri-SCN responses were mostly transient responses to the appearance and/or disappearance of light, which are generally associated with rods and cones signals. Our data show that, regardless of the temporal niche, most of SCN neurons are specialized to read the time of the day by coding irradiance in their maintained firing rate. On the other hand, high light-responsiveness of peri-SCN area in diurnal Rhabdomys suggest processing of more complex visual information
About the speaker
PhD in Biological Sciences (2014) from the Jagiellonian University Postdoc researcher at Jagiellonian University (2015-2019). Awarded in 2019 a Bekker Fellowship (NAWA, Poland) to join the Lucas group at Manchester University, subsequently obtained a Marie Sklodowska-Curie Individual Fellowship (European Commission) to stay in
