This transformation is triggered by the withdrawal of testosterone pde5 inhibitor.

Cell death in sparrow brains might provide clues in age-related human diseases A remarkable change occurs in the brains of tiny songbirds every full year, and some day the system controlling that change may help researchers develop treatments for age-related degenerative illnesses of the brain such as Parkinson’s and dementia. This transformation is triggered by the withdrawal of testosterone, a naturally occurring steroid hormone, and is obvious within 12 hours pde5 inhibitor . The analysis may be the first to survey such rapid regression of mind nuclei due to the withdrawal of a hormone and a change in daylight conditions in adult animals. Then, by four days, thousands of HVC neurons are dropped.