## 2 Results
### Results of Individual Studies
#### 2.2.2 Botulinum Toxin Key Effect  
Table 3 illustrates the summary of the findings regarding BoNT key effects on each biomarker reported in more than one of the included studies. Supplementary File S6, Table S5 shows the information for the biomarkers evaluated in only one study, and Supplementary File S7, Table S6 provides a synopsis of the methodological details and outcomes of the included studies. Overall, regardless of methodological and characteristic variations, all the six studies evaluating IL-1\(\beta\), in the context of peripheral- and neuro-inflammation, reported a significant decrease of the mRNA and/or protein expression of the biomarker after BoNT administration, when compared to vehicle administration and/or control disease models. Similar settings and results were observed for TNF-\(\alpha\), with only one out of five studies showing that BoNT had no effect in the peripheral release of this cytokine from the TMJ periarticular tissues and TG in a model of persistent inflammatory hypernociception (PIH) induced by rheumatoid arthritis [15]. For SNAP25 expression, mostly evaluating the toxin central effects and transport extended beyond the peripheral administration site, there were mixed results after BoNT exposure in the investigated conditions; one study reported no alterations in the hippocampus of an induced model of depression (experimental or control groups) [21], which differed from another study in trigeminal neuropathy settings, revealing a significant increase in brainstem Vc region (caudal subnucleus of the spinal trigeminal nucleus) when compared to control [23]; two studies observed cleaved SNAP25 (clSNAP25) only in the ipsilateral treated side of cranial dura and TNC, while the contralateral nontreated side was devoid of this major part of the N-ethylmaleimide-sensitive-factor attachment receptor (SNARE) complex [20; 22]. A fifth study in MDD induced by chronic restrain stress showed a maximum and persistent expression of clSNAP25 in hindbrain sections, ipsilaterally to injected areas, with higher BoNT dosages [24]. The four studies evaluating neuronal activation after BoNT injection and potential central pathways involved in sensory processing, through expression of marker c-Fos in models of PIH, MDD, and trigeminal neuralgy [induced by either infraorbital nerve constriction (IoNC) or N-methyl-D-aspartate receptor (NMDA)], all reported a significant decrease in both ipsilateral and contralateral of ventrolateral periaqueductal gray, medullary dorsal horn, and TNC. Two studies observed that the upregulation of the neuropeptide CGRP levels induced by TMD inflammatory pain and migraine models were significantly suppressed in jugular plasma and medulla oblongata containing TNC, as well as cranial dura, respectively [19; 20]. In addition, another experiment reported that BoNT significantly inhibited the peripheral release of CGRP in TG and periarticular TMJ tissues induced by PIH in arthritis [15]. In contrast, the same author observed that neither the PIH model nor BoNT injection influenced the CGRP expression in TNC [22], while another experiment showed a significant increase of the biomarker in TNC evoked by a TMD inflammatory pain model, which was not altered following BoNT administration [20]. This study also revealed that the disease model, before or after BoNT, showed no significant changes in the concentration of CGRP in TG and cerebrospinal fluid sampling. Two of the studies evaluating CGRP after BoNT administration also reported on another neuropeptide (SP), having showed a significant reduction in the levels of upregulated SP in both PNS and CNS [15; 19]. \begin{table}
\begin{tabular}{l l l l l l l} \hline \hline
**Bionuclear CIS** & \ \begin{tabular}{c} **Author** \\ **Year** \\ \end{tabular}  & **Unit Measure** & \multicolumn{2}{c}{**BaNT Key Effect (Outcome)**} & **Summary** & \begin{tabular}{c} **Overall** \\ **GRADE** \\ \end{tabular}