The Impact of Sildenafil Citrate on Neurotransmitter Amino Acid Levels in Brain Tissue of Albino Rats
Abstract
Background and Aim: Sildenafil citrate is an active cyclic guanosine monophosphate‑specific phosphodiesterase type 5 inhibitor that is successful in the therapy of male erectile dysfunction. Previous studies have seen the behavioral changes associated with sildenafil, but they have not studied the chronic effect of sildenafil or its possibly related neurochemical changes. Therefore, in the present work, brain neurochemical alterations (excitatory and inhibitory neurotransmitter amino acids) associated with chronic administration of sildenafil citrate using male albino rats were investigated. Methods: Rats were categorized into two groups (n = 8): Group 1 received saline (0.5 ml/kg) and Group 2 received single dose of sildenafil citrate (Viagra®, Pfizer Inc.) dissolved in saline and administered at a dose of 10 mg/kg intraperitoneal (i.p) (0.5 ml) to rats in the treated group once in 3 days for a total of 8 weeks. All rats were sacrificed 24 h after the last injection. Brain area homogenate for neurotransmitter evaluation was done by high‑performance liquid chromatography. Results: It has been found that the chronic i.p. injection of sildenafil citrate caused a pronounced increase in the levels of both excitatory and inhibitory amino acids in most of the brain regions studied. The maximal increase in the concentration of excitatory (glutamate and aspartate) and inhibitory (γ‑aminobutyric acid and glycine) amino acids was obtained in the cerebellum. Glutamine and alanine concentration recorded the maximal increase in cerebral hemisphere of the rat brain. While the maximal increase in the levels of asparagine was recorded in the olfactory lobe, the maximal decrease in the excitatory (glutamine and asparagine) and the inhibitory (glycine and alanine) amino acids was obtained in the pons medulla, while taurine concentration showed a significant increase in pons medulla. Conclusion: Our results explained the effect of sildenafil on central neural pathways that are related to the control of sexual arousal (erection).
