The P2 Receptor Antagonist PPADS Supports Recovery from Experimental Stroke In Vivo

BACKGROUND: After ischemia of the CNS, extracellular adenosine 5'-triphosphate (ATP) can reach high concentrations due to cell damage and subsequent increase of membrane permeability. ATP may cause cellular degeneration and death, mediated by P2X and P2Y receptors. METHODOLOGY/PRINCIPAL FINDINGS: The effects of inhibition of P2 receptors by pyridoxalphosphate-6-azophenyl-2',4'-disulphonic acid (PPADS) on electrophysiological, functional and morphological alterations in an ischemia model with permanent middle cerebral artery occlusion (MCAO) were investigated up to day 28. Spontaneously hypertensive rats received PPADS or vehicle intracerebroventricularly 15 minutes prior MCAO for up to 7 days. The functional recovery monitored by qEEG was improved by PPADS indicated by an accelerated recovery of ischemia-induced qEEG changes in the delta and alpha frequency bands along with a faster and sustained recovery of motor impairments. Whereas the functional improvements by PPADS were persistent at day 28, the infarct volume measured by magnetic resonance imaging and the amount of TUNEL-positive cells were significantly reduced by PPADS only until day 7. Further, by immunohistochemistry and confocal laser scanning microscopy, we identified both neurons and astrocytes as TUNEL-positive after MCAO. CONCLUSION: The persistent beneficial effect of PPADS on the functional parameters without differences in the late (day 28) infarct size and apoptosis suggests that the early inhibition of P2 receptors might be favourable for the maintenance or early reconstruction of neuronal connectivity in the periinfarct area after ischemic incidents

Ultrasound in Dual Nerve Impairment after Proximal Radial Nerve Lesion

Introduction Sonography in classical nerve entrapment syndromes is an established and validated method. In contrast, few publications highlight lesions of the radial nerve, particularly of the posterior interosseus nerve (PIN). Method Five patients with a radial nerve lesion were investigated by electromyography, nerve conduction velocity and ultrasound. Further normative values of 26 healthy subjects were evaluated. Results Four patients presented a clinical and electrophysiological proximal axonal radial nerve lesion and one patient showed a typical posterior interosseous nerve syndrome (PINS). The patient with PINS presented an enlargement of the PIN anterior to the supinator muscle. However four patients with proximal lesions showed an unexpected significant enlargement of the PIN within the supinator muscle. Conclusion High-resolution sonography is a feasible method to demonstrate the radial nerve including its distal branches. At least in axonal radial nerve lesions, sonography might reveal abnormalities far distant from a primary proximal lesion site clearly distinct from the appearance in classical PINS

Normative values.

<p>Cross sectional area (CSA) and antero-posterior diameter (APD) of the radial nerve and the posterior interosseus nerve (PIN) of 26 healthy volunteers (= 52 nerves) presented as mean ± standard deviation.</p><p>Normative values.</p

Antero-posterior diameter (APD) of posterior interosseous nerve (PIN).

<p>Antero-posterior diameter (APD) of PIN in four patients shows a significant swelling of the PIN in comparison to controls. ** <i>p</i><0.001</p

Patient data.

<p>Detailed clinical, electrodiagnostic and sonographic findings of all patients. (AD—active denervation, APD—anterior-posterior diameter, BR—brachioradialis muscle, ECR—extensor carpi radialis muscle, ECU—extensor carpi ulnaris muscle, EDC—extensor digitorum communis muscle, MRC—medical researche council, SNAP—sensory nerve action potential, SCV—sensory conduction velocity, T—triceps brachii muscle, WFE—wrist/finger extension, + mild, ++ moderate, +++ severe)</p><p>Patient data.</p

Sonographic studies of a patient with a proximal radial nerve lesion.

<p>(A, B) Transversal study of the posterior interosseous nerve (PIN; arrow) within the supinator muscle (asterisk) on the healthy side (A) in comparison to the affected side (B) with a significant swelling of the PIN within the muscle. (C) Longitudinal study of the PIN with a swelling before entering the Arcade of Frohse (thin arrows) and within the supinator muscle (asterisk). (D) Longitudinal study of the radial nerve in the distal upper arm with impression of the nerve (arrow) by a screw (thin arrow). p—proximal, d—distal</p

Sonographic studies of the patient with a posterior interosseous nerve (PIN) syndrome.

<p>(A, B) Longitudinal study of healthy PIN (A) and the affected side (B) with significant swelling (thick arrow) before entering the supinator muscle (asterisk). (C) Transversal study with a significant swelling of the PIN (arrow) anterior to the supinator muscle. p—proximal, d—distal</p

Time schedule of the treatments and investigations in the three types of experiments performed.

<p>OP, operation; MCAO, medial cerebral artery occlusion.</p

Effect of PPADS on the time course of EEG changes in the delta- and alpha-frequency bands caused by permanent MCAO of rats in four cortical regions up to day 28 after permanent MCAO.

<p>The delta-frequency band is shown in the left panel (<b>A</b>, <b>C</b>, <b>E</b>, <b>G</b>) and the alpha-frequency band in the right panel (<b>B</b>, <b>D</b>, <b>F</b>, <b>H</b>). The inset shows the placement of the four cortical electrodes and the reference electrode. The electrode P2 is located above the expected ischemic area indicated by grey shading, whereas the other electrodes are located above the contralateral parietal cortex (P1) and the respective frontal cortices (F2 and F1). Data are calculated as percental changes of the relative power from baseline measurements and expressed as means ± SEM. (ACSF: n = 7; PPADS: n = 8), * <i>P</i><0.05, ** <i>P</i><0.001 <i>vs.</i> MCAO/ACSF; + <i>P</i><0.05 <i>vs.</i> day 1, # <i>P</i><0.01 <i>vs.</i> basal.</p

Effect of PPADS on the infarct volume calculated at days one, seven and 28 after MCAO from volumetric image analysis of T2W MRI.

<p>Examples for the extension of the infarct area at day 7 after MCAO with ACSF and PPADS by T2W MRI (<b>A</b>). Volumes are expressed as means ± SEM (n = 8); * <i>P</i><0.05 <i>vs.</i> MCAO/ACSF (<b>B</b>). The infarct volumes are expressed as means ± SEM (n = 8 each), * <i>P</i><0.05 <i>vs.</i> MCAO/ACSF treated animals, + <i>P</i><0.05 <i>vs.</i> day 1.</p