Kriegsfeld L J, Dawson T M, Dawson V L, Nelson R J, Snyder S H
Department of Psychology, The Johns Hopkins University, Baltimore, MD 21205, USA.
Brain Res. 1997 Sep 19;769(1):66-70. doi: 10.1016/s0006-8993(97)00688-4.
Nitric oxide acts as a neural messenger in both the central and peripheral nervous systems. Mice with targeted disruption of the neuronal isoform of nitric oxide synthase (nNOS - / -) are extremely aggressive relative to wild-type (WT) mice. Male nNOS - / - mice exhibit an increase in the number and duration of aggressive encounters compared to WT animals when tested in a variety of paradigms used to test rodent aggression. This inappropriate aggressive behavior has only been observed in male nNOS - /- mice; nNOS - /- females, like female WT mice, exhibit little or no aggression. The present study sought to test the dependence of increased aggressive behavior in nNOS - / - males on testosterone. Intact nNOS - / - males exhibited elevated levels of aggression relative to intact WT males. Castration reduced aggression in both WT and nNOS - /- males to equivalent low levels. Testosterone replacement restored aggression to precastration levels in both genotypes. These data provide evidence that increased aggressive behavior of nNOS - /- mice, like aggression in WT mice, is testosterone-dependent.
