PPIB and Parkinson disease: Figure 7 shows that hippocampal cAMP levels were significantly decreased in PD compared with control mice. However, administration of B. breve A1 did not show any significant effects on hippocampal cAMP levels in PD mice (Figure 7). Similarly, B. breve A1 did not have any effects on the level in control mice. These results suggest that B. breve A1 improves facilitation of contextual fear extinction in PD mice, but not through the activation of the cAMP-dependent protein kinase signaling pathway in the hippocampus.