Adult levels of testosterone alter catecholamine innervation in an animal model of attention-deficit hyperactivity disorder

The spontaneously hypertensive rat (SHR) has been used as an animal model o f attention-deficit hyperactivity disorder (ADHD), This disorder, which is most preva lent in males during childhood, persists in adulthood more frequ ently in females. Since other work has shown that neonatal testosterone lev els may be a contributing factor in the expression of ADHD-like behavior, t he present study was designed to determine whether androgen levels also alt ered the neurobiology of adult SHRs compared to Wistar (WKY) controls. Male s castrated on postnatal day 45 were implanted with testosterone, and the d ensity of tyrosine-hydroxylase-immunoreactive (TH-ir) fibers (an indicator of catecholamine in nervation) in the frontal cortex was compared between a nimals. The data show that testosterone-treated SHRs were associated with h igher levels of TH immunoreactivity in the frontal cortex and hippocampus t han WKY rats. These results may explain why high circulating levels of test osterone during adulthood do not support an increase in ADHD-like behavior in noth the animal model and human males. Copyright (C) 2000 S. Karger AG, Basel.