*3.2. Expression Levels of NUCB2B mRNA in the Whole Brain and in the Rostral Intestinal Bulb of Young and Old Animals*

The levels of NUCB2B mRNA varied between the two organs and over age. In the brain, we observed a slight augment of NUCB2B levels in old compared to young animals (*p* = 0.0169). In the rostral intestinal bulb, we did not detect a significant variation in the expression levels of NUCB2B in old animals (Figure 2) compared to young (*p* = 0.0591). Furthermore, we questioned which organ could represent the main source of NUCB2B. At sexual maturity, expression levels of NUCB2B were comparable between the rostral intestinal bulb and brain (*p* = 0.5899), although there was a slight increase in the intestinal bulb; whereas at the old stage, NUCB2B mRNA levels were significantly higher in the rostral intestinal bulb than in the brain (*p* = 0.0001) (Figure 2).

**Figure 2.** Expression levels of mRNA encoding NUCB2B in the brain and rostral intestinal bulb of young and old *N. furzeri.* The graphic was built on ΔΔCT method and data were normalized to the young brain. T-test and p-value were calculated among young (*n* = 12) and old (*n* = 10) brains and young (*n* = 12) and old (*n* = 10) rostral intestinal bulbs. Furthermore, T-test and *p*-value were also calculated for young brains versus young intestinal bulbs and old brains versus old intestinal bulbs. (*p* brain old versus young = 0.0169; *p* rostral intestine bulb old versus young = 0.0591; *p* young rostral intestinal bulb versus brain = 0.5899; *p* old rostral intestinal bulb versus brain = 0.0001). (\*) indicates the level of significance.
