ORAL PRESENTATION: Sympathetic innervation modulates daily rhythms and metabolism homeostasis

PLANO SANTIAGO; MUL FEDELE MALENA L.; GALIANA MARIA D.; GOLOMBEK DIEGO; MUÑOZ ESTELA M.

COLONIA

Simposio; XV Latin American Symposium on Chronobiology; 2019

Mammalian circadian rhythms are synchronized to the environment by photic and nonphotic stimuli. The SCN set temporal variations in peripheral oscillators to control physiology and metabolism homeostasis. One of the major time cues to the periphery is the nocturnal melatonin, which is synthesized and secreted by the pineal gland. Under SCN control, arylalkylamine N-acetyltransferase (AA-NAT)?the main enzyme regu- lating melatonin synthesis in vertebrates?is activated at night by sympathetic innervation that includes the superior cervical ganglia (SCG). Bilateral surgical removal of the superior cervical ganglia (SCGx) is consid- ered a reliable procedure to completely prevent the nocturnal AA-NAT activation, irreversibly suppressing melatonin rhythmicity. In the present work, we studied the effects of SCGx on rat metabolic parameters and diurnal rhythms of feeding and locomotor activity. We found a significant difference between SCGx and sham-operated rats in metabolic variables such as an increased body weight/food intake ratio, increased adi- pose tissue, and decreased glycemia with a normal glucose tolerance. An analysis of locomotor activity and feeding rhythms showed an increased daytime (lights on) activity (including food consumption) in the SCGx group. These alterations suggest that superior cervical ganglia-related feedback mechanisms play a role in SCN-periphery phase coordination and that SCGx is a valid model without brain-invasive surgery to explore how sympathetic innervation affects daily (24 h) patterns of activity, food consumption and, ultimately, its role in metabolism homeostasis.