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Title: Photic and non-photic inputs to the suprachiasmatic nucleus of the hypothalamus : an electrophysiological perspective
Author: González, J. A.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2005
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Photic information reaches the SCN by a direct neural projection from the retina but non-photic cues are also important. In this context, the projection from the thalamic intergeniculate leaflet (IGL) to the SCN is of particular interest, since the IGL receives both photic inputs and non-photic information from other parts of the brain. In previous studies, the IGL has been implicated both in photic and non-photic regulation of the SCN. The hormone melatonin, secreted by the pineal gland during the night, may also have a modulatory effect on the activity of the SCN by mechanisms that are not fully understood. The aim of the present work was to evaluate the influence of melatonin on the electrical activity of the SCN, and to characterise physiologically the projections from the IGL and the retina to the SCN in intact and melatonin-deficient animals. The techniques used involved extracellular single-cell recordings from the SCN of intact and pinealectomised rats in vivo under anaesthesia. The work presented shows that there was a daily rhythm in the electrical activity of the SCN in intact animals, measured by oscillations in the entropy of the logarithmic interval histogram and in mean spike frequency. These rhythms were not seen in pinealectomised animals. In addition, a significantly lower proportion of SCN cells were responsive to stimulation of the optic nerve in pinealectomised than in intact animals at night, although no difference were seen following IGL stimulation between intact and pinealectomisd animals. These results suggest that melatonin affects the daily rhythms of activity that are seen in the SCN. Moreover, the hormone seems to modify the inputs carrying photic information to the SCN from the retina but the inputs from the IGL to the SCN do not appear to be affected by it.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available