INS and dementia: In this examination, SAMP8 and SAMR1 (33–38 weeks old) were used as dementia model mice with progressive cognitive dysfunction and normal (control) mice, respectively, which were repeatedly administered exendin-4 solution (1 mg/mL) containing L-penetratin (2 mM) with or without insulin (8 IU/mL) for 30 days.