Urocortin 1 and 3 impair maternal defense behavior in mice.

Lactating female mice fiercely defend offspring while exhibiting decreased fear and anxiety. Recent work (J. S. Lonstein & S. C. Gammie, 2002) found that intracerebroventricular (icv) injections of corticotropin releasing factor (CRF), a putative anxiogenic peptide, inhibit maternal defense behavior. This study examines effects of CRF-related peptides, urocortin (Ucn) 1 and Ucn 3, on maternal aggression in mice. Intracerebroventricular injections of both Ucn 1 (0.2 microg) and Ucn 3 (0.5 microg) reduced aggression but not pup retrieval. c-Fos levels were elevated by intracerebroventricular injections of Ucn 1 (0.2 microg) and Ucn 3 (0.5 microg) in 2 and 6 brain regions, respectively; however, both triggered increases in bed nucleus of the stria terminalis dorsal (BNSTd) and lateral septum (LS). These findings suggest that CRF-related peptides similarly modulate maternal aggression and that BNSTd/LS may be critical sites for negative regulation of maternal aggression.