Psychiatry.

OBJECTIVE: To compare effects of the serotonergic drug clomipramine hydrochloride with those of placebo for treatment of dominance-related aggression in dogs. DESIGN: Randomized, placebo-controlled, double-blind clinical trial. ANIMALS: 28 neutered dogs > 1 year old with dominance-related aggression. PROCEDURE: Dogs displaying > or = 3 aggressive episodes/wk toward > or = 1 human family member in response to identifiable behavioral triggers were included in the study. Owners were instructed not to change patterns of interaction with their dogs during the study. After 2 weeks of baseline observations, dogs were treated for 6 weeks with clomipramine (1.5 mg/kg [0.7 mg/lb] of body weight, q 12 h; n = 15) or placebo (13). Responses to triggers were assigned the following aggression scores: no response, 0; growl or lip curl, 1; snap or bite, 2. Mean scores for responses to triggers were obtained during the 2-week pretreatment period (baseline) and during the first and second weeks, third and fourth weeks, and fifth and sixth weeks of treatment. At the end of the study, owners assigned a score designed to evaluate their overall perceived change in aggressiveness; this was referred to as the global score. RESULTS: Mean aggression scores decreased at the fifth and sixth week of treatment in both groups, compared with baseline scores. However, mean scores between groups were not different. Global scores, assigned by the owner, generally reflected changes in mean aggression scores. CONCLUSIONS AND CLINICAL RELEVANCE: Compared with placebo, clomipramine administered to dogs at the dosage recommended for treatment of separation anxiety did not reduce aggressiveness toward human family members.

Aggression↗

PubMed1999

Developmental exposure to vasopressin increases aggression in adult prairie voles.

Although the biological roots of aggression have been the source of intense debate, the precise physiological mechanisms responsible for aggression remain poorly understood. In most species, aggression is more common in males than females; thus, gonadal hormones have been a focal point for research in this field. Although gonadal hormones have been shown to influence the expression of aggression, in many cases aggression can continue after castration, indicating that testicular steroids are not completely essential for the expression of aggression. Recently, the mammalian neuropeptide arginine vasopressin (AVP) has been implicated in aggression. AVP plays a particularly important role in social behavior in monogamous mammals, such as prairie voles (Microtus ochrogaster). In turn, the effects of social experiences may be mediated by neuropeptides, including AVP. For example, sexually naïve prairie voles are rarely aggressive. However, 24 h after the onset of mating, males of this species become significantly aggressive toward strangers. Likewise, in adult male prairie voles, central (intracerebroventricular) injections of AVP can significantly increase intermale aggression, suggesting a role for AVP in the expression of postcopulatory aggression in adult male prairie voles. In this paper, we demonstrate that early postnatal exposure to AVP can have long-lasting effects on the tendency to show aggression, producing levels of aggression in sexually naïve, adult male prairie voles that are comparable to those levels observed after mating. Females showed less aggression and were less responsive to exogenous AVP, but the capacity of an AVP V(1a) receptor antagonist to block female aggression also implicates AVP in the development of female aggression.

Aggression↗