The effects of calorie restriction olfactory cues on conspecific anxiety-like behaviour

Olfactory stimuli and calorie restriction (CR) have both been found to reduce anxiety-like behaviour and alter anxiety-related neurochemical mechanisms in rats. The aim of this study was to determine if exposure to olfactory cues from 25% CR male rats leads to anxiolytic-like behaviour in male rats fed ad libitum. Animals were divided into four groups: control (fed ad libitum and given new bedding every 5 days), control olfactory group (fed ad libitum and given the bedding from the control group every 5 days), CR (fed a 25% CR regime and given new bedding every 5 days), and CR olfaction (fed ad libitum and given the bedding from the CR group every 5 days). All animals were assessed on two measures of anxiety-like behaviour: the open field and the elevated plus maze. The CR group demonstrated anxiolytic-like behavioural responses in the open field test, characterised by more time spent in the aversive central zone and a higher frequency of central and middle zone entries compared to all other groups. Intriguingly, the CR olfaction group demonstrated anxiolytic-like behaviour in the elevated plus maze test, characterised by more time spent on the open arms, and a higher ratio of open compared to total arm entries relative to the control and control olfaction groups. After the completion of behavioural testing, serum corticosterone assays were conducted on trunk blood. However, only the CR group demonstrated an increase in corticosterone. Olfactory cues from conspecifics on a CR regime significantly reduced anxiety-like behaviour in rats fed ad libitum, similar to the reduction in anxiety-like behaviour following CR. This may have implications for the development of more efficacious novel treatments for anxiety disorders.