## 4 Discussion  
Through behavioral analysis and a brief neurophysiological approach, our study aims to offer nuanced insights into the intricate pharmacodynamic interactions within the CNS, expanding our comprehension of tramadol's effects beyond its recognized analgesic profile and emphasizing its wider neuropharmacological ramifications. Within the design of this study, we used only male animals for the differences between the sexes regarding the action of \(\upmu\) receptor agonist substances between the sexes [28,29]. Since one of the mechanisms of action of tramadol is the stimulation of \(\upmu\) receptors, we chose to work only with male animals as a standardized approach. We also aligned the work protocol with the current literature on the topic. Therefore, the dose of efaroxan is considered 1 mg/kg, while the doses of idazoxan used in rats are situated between 0.1 and 1 mg/kg [30,31]. The doses of tramadol used in rat experiments are between 20 and 100 mg/kg/day [32,33,34]. The working methodology was in accordance with the techniques for CPP in rats used by various authors [35,36]. Tramadol, a potent antinociceptive drug, is still of interest and debate at this moment, as it diverges significantly from morphine in its mechanism of action. As a racemic mixture, it is composed of two enantiomers, one of them acting as a weak agonist on morphine \(\upmu\)-receptors and inhibiting serotonin reuptake, while the other, the (\(-\)) enantiomer, serves as a norepinephrine uptake inhibitor [37]. Nonetheless, despite its modest impact on \(\upmu\)-opioid receptors, tramadol's primary pharmacodynamic activities involve weak receptor activation and monoamine reuptake inhibition, portraying a complex modulatory profile [38]. Beyond its antinociceptive effects, tramadol extends its influence to G protein-coupled receptors (GPCRs) and ion channels. Additionally, it acts as an inhibitor of both noradrenaline and serotonin transporters, which contributes to its antinociceptive effects by impeding norepinephrine reuptake [24]. The primary metabolite, O-desmethylramadol, further augments analgesia through norepinephrine uptake inhibition, emphasizing the multifaceted nature of its mechanism [39]. The relevance of this topic remains open to discussion, particularly because tramadol use has rapidly increased worldwide over the past few decades for conditions such as acute postoperative pain, musculoskeletal pain, epidermolysis bullosa, and Stevens-Johnson syndrome [22,40,41,42]. On the other hand, the addictive potential of tramadol is still under debate, with limited reports of abuse worldwide. Tramadol's reward-inducing effect, associated with increased dopamine levels in the nucleus accumbens, is subject to modulation by nalbuphine, a kappa-opioid agonist and \(\upmu\)-opioid partial antagonist [22]. Additionally, within the intricate reward system, neurotransmitters like dopamine, glutamate, and NMDA receptors orchestrate a complex interplay. IR, particularly the II subtype, is present in critical reward system structures such as the nucleus accumbens and locus coeruleus. These receptors stimulate locus coeruleus neuron activity and interact with NMDA receptors, contributing to the nuanced modulation of the reward system [43,44,45]. This led to conclusions that tramadol induces CPP at doses of 20 mg/kg ip or more [46]. Our study possesses certain limitations that warrant consideration. The limitations of our findings are the relatively small sample size, which may have restricted our capacity to identify minor effects; therefore, we did not focus more on biochemical or immunohistochemical analyses. The validity of the data provided is primarily based on behavioral testing in relationship with tramadol's reward implications, rather than modulation of pain, as one may have expected.