Aggressive behavior in male mice lacking the gene for neuronal nitric oxide synthase requires testosterone

Lance J. Kriegsfeld, Ted M Dawson, Valina Dawson, Randy J. Nelson, Solomon H Snyder

Research output: Contribution to journalArticle


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.

Original languageEnglish (US)
Pages (from-to)66-70
Number of pages5
JournalBrain Research
Issue number1
StatePublished - Sep 19 1997



  • Agonistic behavior
  • Androgen
  • Behavioral neuroendocrinology
  • Gonadectomy
  • Knockout
  • Sex steroid

ASJC Scopus subject areas

  • Neuroscience(all)

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