ABSTRACT
<p><b>OBJECTIVE</b>To establish an ex vivo model of myocardial ischemia reperfusion in tree shrews.</p><p><b>METHODS</b>The Langendorff ex vivo heart perfusion system was used to establish the myocardial ischemia reperfusion model in tree shrews with different irrigation and reperfusion time settings. Alanine aminotransferase (ALT), aspartate transaminase (AST) and lactic dehydrogenase (LDH) levels were measured by enzyme-labeled immunosorbent assay, creatine kinase MB (CK-MB) was detected using immunosuppression method, and malondialdehyde was measured with thiobarbital staining method; the infarct size was measured using 2, 3, 5-triphenyltrazoliumchloride (TTC) method.</p><p><b>RESULTS</b>Ischemia for 30 min and reperfusion for 30 and 60 min caused more significant increase in CK-MB and LDH levels in the perfusion fluid and also in the levels of ALT, CK-MB and AST in the myocardial tissue compared with other experimental settings (P<0.05), but these parameters were comparable between the former two settings (P>0.05). The mean heart rate in 30-min ischemia with 60-min reperfusion group was obviously lower than that in continuous reperfusion group, 15-min ischemia with 30-min reperfusion group and 30-min ischemia with 30-min reperfusion group (P<0.05), and the heart rate was similar between the latter 3 groups (P>0.05). ECG analysis showed that the mean heart rate in 30-min ischemia with 30-min reperfusion group was closer to the physiological heart rate of tree shrews.</p><p><b>CONCLUSION</b>We successfully established an ex vivo myocardial ischemia reperfusion model using tree shrews, and ischemia for 30 min followed by reperfusion for 30 min is the optimal experimental setting.</p>
ABSTRACT
Parkinson's disease is a progressive neurodegenerative disorder characterized clinically by rigidity, akinesia, resting tremor and postural instability. It has recently been suggested that low frequency stimulation of the pedunculopontine nucleus (PPN) has a role in the therapy for Parkinsonism, particularly in gait disorder and postural instability. However, there is limited information about the mechanism of low frequency stimulation of the PPN on Parkinson's disease. The present study was to investigate the effect and mechanism of low frequency stimulation of the PPN on the firing rate of the ventrolateral thalamic nucleus (VL) in a rat model with unilateral 6-hydroxydopamine lesioning of the substantia nigra pars compacta. In vivo extracellular recording and microiontophoresis were adopted. The results showed that the firing rate of 60.71% VL neurons in normal rats and 59.57% VL neurons in 6-hydroxydopamine lesioned rats increased with low frequency stimulation of the PPN. Using microiontophoresis to VL neurons, we found the firing rate in VL neurons responded with either an increase or decrease in application of acetylcholine (ACh) in normal rats, whereas with a predominant decrease in M receptor antagonist atropine. Furthermore, the VL neurons were mainly inhibited by application of γ-aminobutyric acid (GABA) and excited by GABA(A) receptor antagonist bicuculline. Importantly, the VL neurons responding to ACh were also inhibited by application of GABA. We also found that the excitatory response of the VL neurons to the low frequency stimulation of the PPN was significantly reversed by microiontophoresis of atropine. These results demonstrate that cholinergic and GABAergic afferent nerve fibers may converge on the same VL neurons and they are involved in the effects of low frequency stimulation of the PPN, with ACh combining M(2) receptors on the presynaptic membrane of GABAergic afferents, which will inhibit the release of GABA in the VL and then improve the symptoms of Parkinson's disease.