Effects of Pacemaker Lesions on the Temporal Organization in Mammals
Many physiological, biochemical and behavioural processes show functionally significant circadian rhythms. A host of recent experiments mainly in rats and hamsters have led to the recognition of the suprachiasmatic nuclei (SCN) of the hypothalamus as a major regulator of circadian rhythmicity (1). The natural starting point of the search for the central pacemaker has been to trace the pathway for entrainment, as in the hierarchical multi-oscillator model the pacemaker interacts with the entrainment mechanism. Since in mammals the light-dark cycle is the predominant synchronizing agent, the Zeitgeber can be assumed to enter the organism via the retina. The possibility that extraretinal photoreception plays any significant role in the process of photic entrainment in adult mammals can at present be considered very unlikely.
KeywordsLithium Dopamine Serotonin Retina Peri
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