Main and accessory olfactory bulbs and their projections in the brain anticipate feeding in food-entrained rats

Abstract

The olfactory bulb (OB) has a circadian clock independent of the suprachiasmatic nucleus, but very little is known about the functional significance of its oscillations. The OB plays a major role in food intake as it contributes to the evaluation of the hedonic properties of food, it is necessary for a normal pattern of locomotor behavior and their ablation disrupts feeding patterns. Previously we demonstrated that OB of rabbit pups can be entrained by periodic nursing but it was not clear whether food was the entraining signal. Here we hypothesized that OB can be entrained by a food pulse during the day in adult rats under a restricted feeding schedule. Then we expect that OB will have a high activation before food presentation when animals show food anticipatory activity (FAA). To this aim we determined by immunohistochemistry the expression of FOS protein, as an indicator of neural activation, in the mitral and granular cell layers of the main and accessory OB. Additionally we also explored two of the OB brain targets, the piriform cortex (PC) and bed nuclei of the accessory olfactory tract (BAOT), in three groups: ad libitum (ALF), restricted feeding (RF), and fasted rats after restricted feeding (RF-F). In ALF group FOS levels in both main and accessory OB were low during the day and high during the night at the normal onset of the increase of activity, in agreement with previous reports. On the contrary in RF and RF-F groups FOS was high at the time of FAA, just before food presentation, when animals are in a state of high arousal and during food consumption but was low during the night. In their brain targets, we observed a similar pattern as OB in all groups with the only difference being that FOS levels remained high during the night in RF-F group. We conclude that the OB is entrained by food restriction by showing high activation at the time of food presentation, which persists during fasting and impose a similar FOS pattern to the two brain targets explored only in fed animals.

Differential regulation of the immune system in a brain-liver-fats organ network during short term fasting

“…Samples from OB and psWAT grouped only in two clusters (Phases I and III), which seemingly cycle throughout the 22 hours. This cyclical transcriptomic pattern is reminiscent and consistent with other cyclical physiological or metabolic responses occurring in these organs during fasting [24][25][26]. In contrast with these results, we failed to identify robust clusters using the samples from pgWAT (thus excluding it from our downstream analyses).…”

The Neuronal and Peripheral Expressed Membrane-Bound UNC93A Respond to Nutrient Availability in Mice

“…The increase in transcript levels of Unc93a observed in vitro and in vivo might indicate that it is involved in autophagy to provide the body with needed macronutrients during starvation, and it is possible that Unc93a is involved in the initiation of autophagy. Furthermore, the alterations observed for Unc93a expression in hypothalamus and olfactory bulb, two organs important for feeding ( van den Top et al, 2004 ; Caba et al, 2014 ; Betley et al, 2015 ) further highlight its role in metabolism.…”

Brain Activity during Methamphetamine Anticipation in a Non-Invasive Self-Administration Paradigm in Mice

“…However, anticipatory activity does not appear in the absence of a circadian injection schedule ( Iijima et al, 2002 ), indicating that entrainment of the circadian timing system is required for the anticipation to develop. More evidence of a circadian component to anticipation is available in changes in c-FOS expression in anticipation of a daily meal, with studies in rats ( Challet et al, 1997 ; Angeles-Castellanos et al, 2004, 2007 ; Mendoza et al, 2005 ; Escobar et al, 2007 ; Poulin and Timofeeva, 2008 ; Acosta-Galvan et al, 2011 ; Mitra et al, 2011 ; Caba et al, 2014 ), mice ( Begriche et al, 2012 ; Blum et al, 2012 ; Gallardo et al, 2014 ; Dattolo et al, 2016 ; Luna-Illades et al, 2017 ), and hamsters ( Dantas-Ferreira et al, 2015 ; Ruby et al, 2017 ), or in anticipation of a palatable treat in rats or mice ( Mendoza et al, 2005 ; Mitra et al, 2011 ; Gallardo et al, 2012 ; Blancas et al, 2014 ).…”