Sildenafil counteracts the inhibitory effect of social subordination on competitive aggression and sexual motivation in male mice

• Published in: Behavioural brain research 2011, Vol.216 (1), p.193-199
• Main Authors: Dadomo, Harold, Volpi, Riccardo, Ferrari, Massimiliano, Vignali, Alessandro, Bartolomucci, Alessandro, Palanza, Paola, Parmigiani, Stefano
• Format: Article
• Language: English
• Subjects: Aggression - drug effects; Analysis of Variance; Animals; Behavioral psychophysiology; Biological and medical sciences; Body weight; Competitive aggression; Dominance-Subordination; Fundamental and applied biological sciences. Psychology; Male; Mice; Motivation - drug effects; Piperazines - pharmacology; Psychology. Psychoanalysis. Psychiatry; Psychology. Psychophysiology; Purines - pharmacology; Sexual Behavior, Animal - drug effects; Sexual behaviour; Sildenafil; Sildenafil Citrate; Social subordination; Stress; Sulfones - pharmacology; Tadalafil; Vardenafil
• ISSN: 0166-4328; 1872-7549
• DOI: 10.1016/j.bbr.2010.07.036

▶ Subordination was associated with low sexual motivation in male mice. ▶ Chronic Sildenafil normalized sexual motivation in subordinate male mice. ▶ Chronic Sildenafil increased aggressive motivation in subordinate male mice. ▶ Chronic Sildenafil counteracted subordination-induced weight gain. The effects of chronic intra-peritoneal administration of 10 mg/kg (t.i.w., for 5 weeks) of sildenafil on competitive aggression, sexual behaviour and body weight gain was tested in CD1 subordinate male mice in two experimental contexts: 1) “low levels of aggression”, i.e. housing in dyads of siblings 2) “high levels of aggression”, i.e. exposure to a model of chronic psychosocial stress with an unfamiliar mice. Subordinate mice in both experimental contexts were injected with sildenafil or saline. After 2 weeks of sildenafil administration, a subgroup of subordinates exposed to “high levels of aggression” began to counterattack their dominant counterparts at higher rates than saline-injected subordinates. This effect was essentially similar but faster in subordinates subjected to “low levels of aggression”. As far as sexual behaviour is concerned, in both experimental contexts, sildenafil-injected subordinated mice showed significant lower latencies to mount a proceptive female when compared to saline-injected subjects. Furthermore, in the “high levels of aggression” context, Sildenafil reduced stress-induced body weight gain. Sildenafil showed no effects in individually housed males serving as controls. In conclusion, chronic Sildenafil treatment counteracts the inhibitory effects of social subordination on male competitive aggression, sexual behaviour and body weight gain. Overall our data suggests that sildenafil could be acting in the central nervous system to modulate sexual and agonistic motivation.