Larissa Resende Oliveira

Induction of chronic non-inflammatory widespread pain increases cardiac sympathetic modulation in rats.

Fibromyalgia (FM) is characterized by chronic non-inflammatory widespread pain (CWP) and changes in sympathetic function. In attempt to elucidate the pathophysiological mechanisms of FM we used a well-established CWP animal model. We aimed to evaluate changes in cardiac autonomic balance and baroreflex function in response to CWP induction in rats. CWP was induced by two injections of acidic saline (pH 4.0, n=8) five days apart into the left gastrocnemius muscle. Control animals were injected twice with normal saline (pH 7.2, n=6). One day after the second injection of acidic saline or normal saline, the animals had pulse interval (PI) and systolic arterial pressure (SAP) variability, and spontaneous baroreflex sensitivity (BRS) evaluated. After induction of CWP, there was an increase of power in the low frequency (LF) band of PI spectrum (12.75 ± 1.04 nu), a decrease in the high frequency (HF) band (87.25 ± 1.04 nu) and an increase of LF/HF ratio (0.16 ± 0.01), when compared to control animals (7.83 ± 1.13 nu LF; 92.16 ± 1.13 nu HF; 0.08 ± 0.01 LF/HF). In addition, there was an increase of power in the LF band of SAP spectrum (7.93 ± 1.39 mmHg(2)) when compared to control animals (2.97 ± 0.61 mmHg(2)). BRS was lower in acidic saline injected rats (0.59 ± 0.06 ms/mmHg) when compared to control animals (0.71 ± 0.03 ms/mmHg). Our results showed that induction of CWP in rats shifts cardiac sympathovagal balance towards sympathetic predominance and decreases BRS. These data corroborate findings in humans with FM.

Increased Nitric Oxide Bioavailability and Decreased Sympathetic Modulation Are Involved in Vascular Adjustments Induced by Low-Intensity Resistance Training

Resistance training is one of the most common kind of exercise used nowadays. Long-term high-intensity resistance training are associated with deleterious effects on vascular adjustments. On the other hand, is unclear whether low-intensity resistance training (LI-RT) is able to induce systemic changes in vascular tone. Thus, we aimed to evaluate the effects of chronic LI-RT on endothelial nitric oxide (NO) bioavailability of mesenteric artery and cardiovascular autonomic modulation in healthy rats. Wistar animals were divided into two groups: exercised (Ex) and sedentary (SED) rats submitted to the resistance (40% of 1RM) or fictitious training for 8 weeks, respectively. After LI-RT, hemodynamic measurements and cardiovascular autonomic modulation by spectral analysis were evaluated. Vascular reactivity, NO production and protein expression of endothelial and neuronal nitric oxide synthase isoforms (eNOS and nNOS, respectively) were evaluated in mesenteric artery. In addition, cardiac superoxide anion production and ventricle morphological changes were also assessed. In vivo measurements revealed a reduction in mean arterial pressure and heart rate after 8 weeks of LI-RT. In vitro studies showed an increased acetylcholine (ACh)-induced vasorelaxation and greater NOS dependence in Ex than SED rats. Hence, decreased phenylephrine-induced vasoconstriction was found in Ex rats. Accordingly, LI-RT increased the NO bioavailability under basal and ACh stimulation conditions, associated with upregulation of eNOS and nNOS protein expression in mesenteric artery. Regarding autonomic control, LI-RT increased spontaneous baroreflex sensitivity, which was associated to reduction in both, cardiac and vascular sympathetic modulation. No changes in cardiac superoxide anion or left ventricle morphometric parameters after LI-RT were observed. In summary, these results suggest that RT promotes beneficial vascular adjustments favoring augmented endothelial NO bioavailability and reduction of sympathetic vascular modulation, without evidence of cardiac overload.

Correlations between brain changes and pain management after cognitive and meditative therapies: A systematic review of neuroimaging studies

BACKGROUND There are different ways of dealing with pain and cognitive and meditative therapies (CMT) are alternative ways to regulate the emotions associated with pain. Current studies apply neuroimaging techniques trying to elucidate the neural mechanisms of cognitive strategies for pain. This systematic review aimed to summarize the evidence on brain activity changes after CMT, which include cognitive behavioral therapy, mindfulness and/or meditation, for pain management as well as to evaluate clinical pain outcomes. METHODS Electronic databases - Pubmed, EMBASE, PsycINFO, Science Direct, Scopus - were searched to find randomized controlled trials (RCTs) examining neuroimaging data of CMT for chronic pain patients or healthy individuals with experimental pain. Two reviewers independently selected the relevant trials, rated for quality assessment and extracted all data using a standardized form. Primary outcome was brain activity changes (activation, deactivation or functional connectivity). Secondary outcomes were pain intensity, self-management, pain coping, quality of life, anxiety and depression. RESULTS Nine RCTs were included involving 280 adults (18-59 years), 139 chronic pain patients vs. 148 healthy subjects. Three main kinds of intervention were identified: cognitive-behavioral therapy (n = 4), mindfulness meditation (n = 4) and transcendental meditation technique (n = 1). Neuroimaging results revealed distinct patterns of activity, but the main findings were related to increased activation of prefrontal cortex (PFC), specially dorsolateral prefrontal cortex (dlPFC) and ventrolateral prefrontal cortex (vlPFC), orbitofrontal cortex (OBF), somatosensory cortices (SSC) and limbic system in chronic pain population; and increased activation of anterior cingulate cortex (ACC), anterior insular cortex (AI) and decreased activation of thalamus in healthy individuals following CMT. CONCLUSION This result means that regulation of pain by CMT can alter functioning of brain regions in an extensive network including non-nociceptive regions. CMT reduced the affective experience of pain, while reductions of pain intensity ratings were less consistent. Brain changes have been demonstrated as a result of the application of psychological measures and may represent the clinical implications of changes in brain activity or morphology.