Stimulation of the dorsal PAG evokes defensive behavior and physiological responses (tachycardia and increased blood pressure) (Paul et al., 2014). Cholecystokinin peptide CCK-4 can enhance this response (Paul et al., 2014). Both the cholecystokinin precursor (Cck) and the Cck B receptor (Cckbr) had decreased expression, suggesting reduced autonomic response to threat. Decreased expression of two NPY receptors, Npy5r and Npy1r could increase anxiety-like behavior.
