Oral Presentation ANZOS Annual Scientific Meeting 2021

Sucrose intake by rats affected by both intraperitoneal oxytocin administration and time of day (#108)

Simone Rehn 1 , Robert Boakes 1 , Joel Raymond 2 , Michael Bowen 2
  1. University of Sydney, Camperdown, NSW, Australia
  2. Brain and Mind Centre, University of Sydney, Camperdown, NSW, Australia

Daily limited access to a palatable food or drink at a fixed time is commonly used in rodent models of bingeing. Under these conditions, entrainment may modulate intake patterns but has received little attention. Oxytocin is involved in circadian patterns of intake and when administered peripherally, reduces sucrose intake. However, oxytocin’s effects on intake under limited-access conditions and its potential interaction with entrainment have not been explored. This study examined the role of entrainment on intake patterns, oxytocin’s effects on sucrose intakes and locomotor activity and whether oxytocin’s effects were mediated by its actions at oxytocin or vasopressin V1a receptors. Sated rats received daily 1-h access to 10% sucrose solution either at a fixed or varied time of day. Rats received intraperitoneal oxytocin (0, 0.3, 1, 3 mg/kg) prior to sucrose access and spontaneous locomotor activity was assessed in an open-field test. Rats were then pre-treated with an oxytocin receptor antagonist, L368,899 or a vasopressin V1a receptor antagonist, SR49059 prior to oxytocin before sucrose access. Intake patterns did not differ between fixed- or varied-time presentations, rats consumed more sucrose solution in the middle as opposed to early dark phase. Oxytocin dose-dependently reduced sucrose intakes, but also reduced locomotor activity. There was some evidence of partial blockade of oxytocin-induced sucrose intake reductions by both L368,899 and SR49059, but the results were unclear. Time of day and oxytocin impact sucrose solution intake under daily limited access in rats, and the sedative-like effects of oxytocin should be considered in future studies on oxytocin and food intake.