## 4 Discussion
Moreover, evaluation of specific physical activity in terms of intensity, aerobic capacity, or anaerobic threshold was not the purpose of the study; additional research is necessary to investigate these specific physical implications concerning CPP, particularly as we align to the tendency to consider that CPP would notbe typically influenced by such factors. For all that, we placed much greater emphasis on a basic pattern of electrical activity in the brain as a direct response to substance influence, which, although simple in our protocol, reveals the influence of CNS stimulants on the cerebral effects of tramadol, particularly pronounced in the right hemisphere at the level of the thalamus. This adds to the knowledge of the modulation of the reward system in Wistar rats. Of course, dedicated EEG studies could provide much better insights towards specific EEG parameters to follow, other than signal amplitude and assessment of \(\beta\) waveforms, as in our case, but more related to spectral power or frequency bands. The results did show that efaroxan blocked the acquisition of tramadol-induced CPP, while idazoxan did not produce a significant effect. Because efaroxan is an II antagonist, while idazoxan is an I2 antagonist, and both act as \(\propto\)2 antagonists, the imidazoline II receptor may be responsible for this effect, but we cannot rule out the possible partial involvement of \(\propto\)2 antagonist activity. We consider that these findings provide enough evidence supporting the involvement of the imidazoline system in tramadol stimulation of the reward system and in cases of tramadol dependence. The conclusion that II receptors mediate the tramadol reward effect is, however, only a hypothesis. There is already available data showing that II receptors (IRAS/Nischarin receptors in mice) modulate morphine reward [47]. Morphine produces this effect by stimulating \(\mu\) receptors. Tramadol acts as an agonist of \(\mu\) receptors and an inhibitor of serotonin reuptake [48]. We also only consider as a hypothesis the II/I2 receptors having a role in the antagonism at the alpha 2 receptor level. There would be the possibility of a partial modulatory effect of II receptor antagonists (e.g., efaroxan) on the CPP-stimulating action of tramadol. The lack of positive control (CPP to morphine) and negative control is also a limitation of this study. However, there is documented data showing that morphine stimulates conditioned place preference (CPP) [48]. Additionally, in our case, the significantly longer duration spent by the tramadol + efaroxan group in preconditioning (Figure 6), approximately 150 s, which is over three times longer than other preconditioning groups, we consider can only be attributed to the complex interplay of tramadol's effects on the brain and its interaction with IR. The synergistic effect increases dopaminergic activity, which often corresponds with greater time spent in environments linked to rewarding effects, hence the observed behavior. Tramadol's antinociceptive effects are still understood as predominantly mediated via its interaction with \(\mu\)-opioid receptors (MOR) and the regulation of neurotransmitters such as serotonin and norepinephrine [49; 50]. Our study is of actuality and of interest, especially since tramadol has been demonstrated to induce seizures in animal models due to the excessive activation of opioid receptors [51; 52]. EEG investigations frequently demonstrate spike-and-wave discharges or other seizure-associated patterns during tramadol-induced convulsions, indicating a distinct neurophysiological effect that can be analyzed utilizing EEG technology [53]. By all that, our subjects did not present such patterns. IR can coexist with opioid systems in brain areas critical for pain perception [54]. The regulation of these receptors by drugs like maxonidine and tramadol may impact neuronal stability and the response to excitatory stimuli, considerably altering the EEG waveforms related to seizures [55; 56].