F15599 (0.06 or 0.12 mg/kg) significantly reduces l-DOPA-induced dyskinesia (LID), without affecting motor performance of rats. Rats treated with F15599 manifest less LID and mild 5-HT syndrome with the high dose of 30 μg/μL. F15599 (0.0625, 0.125, 0.25, 0.5 and 1.0 mg/kg, i,p,) results in a significant and dose-dependent (MED = 0.125 mg/kg) delay in the latency to attack, and a potent reduction (ID50 = 0.095 mg/kg) in the amount of aggressive behaviour directed towards the intruder rat. Starting from the 0.25 mg/kg dose, F15599 induces clear signs of the so-called serotonin syndrome characterized by flat body posture, head-waving, lower lip retraction and hindlimb abduction, leading to increased behavioural inactivity scores and social disengagement. F15599 increases the discharge rate of pyramidal neurones in medial prefrontal cortex (mPFC) from 0.2 µg/kg i.v and reduces that of dorsal raphe 5-hydroxytryptaminergic neurones at doses >10-fold higher (minimal effective dose 8.2 µg/kg i.v.). F15599 increases dopamine output in mPFC (an effect dependent on the activation of postsynaptic 5-HT1A receptors) with an ED50 of 30 µg/kg i.p., whereas it reduces hippocampal 5-HT release (an effect dependent exclusively on 5-HT1A autoreceptor activation) with an ED50 of 240 µg/kg i.p.