Agmatine ameliorates lipopolysaccharide induced depressive-like behaviour in mice by targeting the underlying inflammatory and oxido-nitrosative mediators

• Agmatine attenuated the LPS-induced depressive-like behavioural abnormalities in mice.
• Treatment of agmatine alleviated LPS evoked oxidative stress in mouse brain.
• LPS-induced elevated brain IL-1β and TNF-α level were reversed by agmatine in the hippocampus.
• Agmatine up-regulated the BDNF level in hippocampus of LPS-treated mice.
• Agmatine may be effective for the treatment of depression associated with inflammation.

Experimental and clinical evidence indicates that pro-inflammatory cytokines, oxidative stress and brain-derived neurotrophic factor (BDNF) signalling mechanisms play a role in the pathophysiology of depression. Agmatine is a neurotransmitter and/or neuromodulator that has emerged as a potential agent to manage diverse central nervous system disorders. Agmatine has been shown to exert antidepressant-like effect. The present study investigated ability of agmatine to abolish the depressive-like behaviour induced by the administration of the lipopolysaccharide (LPS) in mice. Agmatine (20 and 40 mg/kg) was administered daily for 7 days, then the mice were challenged with saline or LPS (0.83 mg/kg; i.p.) on the 7th day. After 24 h of LPS administration we tested mice for depressive-like behaviour. LPS treated animals presented an increase in immobility time in the forced-swim test (FST), tail suspension test (TST) which was reversed by agmatine pre-treatment (20 and 40 mg/kg). Oxidative/nitrosative stress evoked by LPS was ameliorated by both doses of agmatine in hippocampus (HC) and prefrontal cortex (PFC). Administration of LPS caused an increase in interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α), whereas BDNF was down regulated in the HC. Agmatine pre-treatment at 40 mg/kg ameliorated LPS-induced neuroinflammation by attenuating brain IL-1β and TNF-α level. In addition, agmatine pre-treatment also up-regulated the BDNF level in the HC. The present study shows that pre-treatment of agmatine is able to abolish the behavioural responses in the FST and TST elicited by the LPS-induced model of depression that may depend on the inhibition of pro-inflammatory mediators, reduction of oxidative stress as well as activation neuroplasticity-related signalling in mice, suggesting that agmatine may constitute an monotherapy/adjuvant for the management of depression associated with inflammation.