Intracellular pathways of calcitonin gene-related peptide-induced relaxation of human coronary arteries: A key role for Gβγ subunit instead of cAMP

BACKGROUND AND PURPOSE

Calcitonin gene-related peptide (CGRP) is a potent vasodilator. While its signalling is assumed to be mediated via increases in cAMP, this study focused on elucidating the actual intracellular signalling pathways involved in CGRP-induced relaxation of human isolated coronary arteries (HCA).

EXPERIMENTAL APPROACH

HCA were obtained from heart valve donors (27 M, 25 F, age 54 ± 2 years). Concentration-response curves to human α-CGRP or forskolin were constructed in HCA segments, incubated with different inhibitors of intracellular signalling pathways, and intracellular cAMP levels were measured with and without stimulation.

RESULTS

Adenylyl cyclase (AC) inhibitors SQ22536 + DDA and MDL-12330A, and PKA inhibitors Rp-8-Br-cAMPs and H89, did not inhibit CGRP-induced relaxation of HCA, nor did the guanylyl cyclase inhibitor ODQ, PKG inhibitor KT5823, EPAC1/2 inhibitor ESI09, potassium channel blockers TRAM-34 + apamin, iberiotoxin or glibenclamide, or the Gαq inhibitor YM-254890. Phosphodiesterase inhibitors induced a concentration-dependent decrease in the response to KCl but did not potentiate relaxation to CGRP. Relaxation to forskolin was not blocked by PKA or AC inhibitors, although AC inhibitors significantly inhibited the increase in cAMP. Inhibition of Gβγ subunits using gallein significantly inhibited the relaxation to CGRP in human coronary arteries.

CONCLUSION

While CGRP signalling is generally assumed to act via cAMP, the CGRP-induced vasodilation in HCA was not inhibited by targeting this intracellular signalling pathway at different levels. Instead, inhibition of Gβγ subunits did inhibit the relaxation to CGRP, suggesting a different mechanism of CGRP-induced relaxation than generally believed.

Invasive Motor Cortex Stimulation Influences Intracerebral Structures in Patients With Neuropathic Pain: An Activation Likelihood Estimation Meta-Analysis of Imaging Data

Objective

Invasive motor cortex stimulation (iMCS) has been proposed as a treatment for intractable neuropathic pain syndromes. Although the mechanisms underlying the analgesic effect of iMCS remain largely elusive, several studies found iMCS‐related changes in regional cerebral blood flow (rCBF) in neuropathic pain patients. The aim of this study was to meta‐analyze the findings of neuroimaging studies on rCBF changes to iMCS.

Methods

PubMed, Embase, MEDLINE, Google Scholar, and the Cochrane Library were systematically searched for retrieval of relevant scientific papers. After initial assessment of relevancy by screening title and abstract by two investigators, independently, predefined inclusion and exclusion criteria were used for final inclusion of papers. Descriptive results were statistically assessed, whereas coordinates were pooled and meta‐analyzed in accordance with the activation likelihood estimation (ALE) methodology.

Results

Six studies were included in the systematic narrative analysis, suggesting rCBF increases in the cingulate gyrus, thalamus, insula, and putamen after switching the MCS device “ON” as compared to the “OFF” situation. Decreases in rCBF were found in for example the precentral gyrus and different occipital regions. Two studies did not report stereotactic coordinates and were excluded from further analysis. ALE meta‐analysis showed that, after switching the iMCS electrode “ON,” increased rCBF occurred in the (1) anterior cingulate gyrus; (2) putamen; (3) cerebral peduncle; (4) precentral gyrus; (5) superior frontal gyrus; (6) red nucleus; (7) internal part of the globus pallidus; (8) ventral lateral nucleus of the thalamus; (9) medial frontal gyrus; (10) inferior frontal gyrus; and (11) claustrum, as compared to the “OFF” situation. Reductions in rCBF were found in the posterior cingulate gyrus when the iMCS electrode was turned “OFF.”

Conclusions

These findings suggested that iMCS induces changes in principal components of the default mode‐, the salience‐, and sensorimotor network.

Facial mimicry in 6-7 year old children with disruptive behavior disorder and ADHD

Background

Impairments in facial mimicry are considered a proxy for deficits in affective empathy and have been demonstrated in 10 year old children and in adolescents with disruptive behavior disorder (DBD). However, it is not known whether these impairments are already present at an earlier age. Emotional deficits have also been shown in children with attention-deficit/hyperactivity disorder (ADHD).

Aims

To examine facial mimicry in younger, 6–7 year old children with DBD and with ADHD.

Methods

Electromyographic (EMG) activity in response to emotional facial expressions was recorded in 47 children with DBD, 18 children with ADHD and 35 healthy developing children.

Results

All groups displayed significant facial mimicry to the emotional expressions of other children. No group differences between children with DBD, children with ADHD and healthy developing children were found. In addition, no differences in facial mimicry were found between the clinical group (i.e., all children with a diagnosis) and the typically developing group in an analysis with ADHD symptoms as a covariate, and no differences were found between the clinical children and the typically developing children with DBD symptoms as a covariate.

Conclusion

Facial mimicry in children with DBD and ADHD throughout the first primary school years was unimpaired, in line with studies on empathy using other paradigms.