Emotional disorders induced by Hemopressin and RVD-hemopressin(?) administration in rats

Background The endocannabinoid (eCB) system plays an important role in regulating emotional disorders, and is involved, directly or indirectly, in psychiatric diseases, such as anxiety and depression. Hemopressin, a hemoglobin ? chain-derived peptide, and RVD-hemopressin(?), a N-terminally extended form of hemopressin, act as antagonist/inverse agonist and negative allosteric modulator of the cannabinoid 1 (CB1) receptor, respectively. Methods Considering the possible involvement of these peptides on emotional behaviour, the aim of our study was to investigate the behavioural effects of a single intraperitoneal (ip) injection of hemopressin (0.05 mg/kg) and RVD-hemopressin(?) (0.05 mg/kg), using a series of validated behavioural tests (locomotor activity/open field test, light-dark exploration test, forced swim test) in rats. Prefrontal cortex levels of norepinephrine (NE), dopamine (DA) and serotonin (5-hydroxytryptamine, 5-HT) and the gene expression of monoamine oxidase (MAO-B) and catechol-O-methyltransferase (COMT) were measured by high performance liquid chromatography (HPLC) analysis and real-time reverse transcription polymerase chain reaction (RT-PCR), respectively. Results Hemopressin administration induced anxiogenic and depressive behaviour, decreased monoamine steady state levels in prefrontal cortex, and increased the gene expression of the enzymes involved in their catabolism. By contrast, RVD- hemopressin(?) induced anxiolytic and antidepressive effects, increased monoamines and decreased the enzymes in prefrontal cortex. Conclusion In conclusion, in the present study we demonstrated behavioral effects induced by peripheral hemopressin and RVD-hemopressin(?) injections, that could involve modulatory effects on monoaminergic signaling, in the prefrontal cortex.