Lack of Effect of the 5-HT4 Receptor Ligands RS 67333 and RS 39604 on Murine Agonistic Behaviour

In comparison to studies investigating the roles of 5-HT1, 5-HT2 and 5-HT3 receptors in aggressive behaviour there is a dearth of material examining the function of 5-HT4 receptors in this behaviour. In view of this, the current study examined the effects of the 5-HT4 receptor partial agonist RS 67333 and antagonist RS 39604 in murine agonistic behaviour. RS 67333 failed to produce any significant changes in the offensive. Significant variation in the frequency of evade behaviour was detected but this occurred between treatment groups rather than with controls. Interestingly, both the frequency and duration of stretched attend behaviour were increased by RS 67333 0.1 mg/kg, a result indicative of increased risk assessment. The administration of RS 39604 (0.01 1 mg/kg) produced significant variation in the frequency and duration of following, and aggressive grooming. Frozen crouch behaviour was also increased significantly at 0.1 mg/kg. It is concluded that since the 5-HT4 receptor ligands employed in this study produced very few significant behavioural effects across the treatment groups, 5-HT4 receptors do not play a role in the modulation of murine aggressive behaviour.