The effect of citalopram hydrobromide on 5-HT2A receptors in the impulsive-aggressive dog, as measured with 123I-5-I-R91150 SPECT

Purpose: Involvement of the serotonergic system in impulsive aggression has been demonstrated in both human and animal studies. The purpose of the present study was to investigate the effect of citalopram hydrobromide (a selective serotonin re-uptake inhibitor) on the 5-HT2A receptor and brain perfusion in impulsive-aggressive dogs by means of single-photon emission computed tomography. Methods: The binding index of the radioligand I-123-5-I-R91150 was measured before and after treatment with citalopram hydrobromide in nine impulsive-aggressive dogs. Regional perfusion was measured with Tc-99m-ethyl cysteinate dimer (ECD). Behaviour was assessed before treatment and again after 6 weeks of treatment. Results: A correlation was found between decreased binding and behavioural improvement in eight out of nine dogs. The 5-HT2A receptor binding index was significantly reduced after citalopram hydrobromide treatment in all cortical regions but not in the subcortical area. None of the dogs displayed alterations in perfusion on the post-treatment scans. Conclusion: This study supports previous findings regarding the involvement of the serotonergic system in impulsive aggression in dogs in general. More specifically, the effect of treatment on the 5-HT2A receptor binding index could be demonstrated and the decreased binding index correlated with behavioural improvement.