RESUMO
@#Objective: Cervical dystonia (CD) is a clinically under-recognized symptom occurring at the later- to end-stages of Parkinson’s disease (PD). The frequency of CD and its influence on prognosis have not been well studied. Here, we conducted an in-depth examination of CD incidence and impact on disease progression in later-stage PD. Methods: We retrospectively reviewed the clinical features of 22 deceased patients with sporadic PD treated at a hospital in Japan from 1983 to 2008. Results: The most common cause of death in PD was pneumonia. CD, in particular retrocollis, was frequent in the later stages of the disease in elderly patients (9/22, 40.9%). Pneumonia incidence increased sharply in the later period with CD. There was a positive trend between CD duration and duration of pergolide use. Conclusion: Analysis revealed that CD increases markedly in late- to end-stage PD, which may be associated with aspiration pneumonia due to dysphagia. Pathological mechanisms underlying CD might be influenced by treatments including dopamine agonists. Prevention of CD may increase quality of life and prolong survival of PD patients.
RESUMO
A variety of G protein coupled receptors (GPCRs) are expressed in the presynaptic terminals of central and peripheral synapses and play regulatory roles in transmitter release. The patch-clamp whole-cell recording technique, applied to the calyx of Held presynaptic terminal in brainstem slices of rodents, has made it possible to directly examine intracellular mechanisms underlying the GPCR-mediated presynaptic inhibition. At the calyx of Held, bath-application of agonists for GPCRs such as GABAB receptors, group III metabotropic glutamate receptors (mGluRs), adenosine A1 receptors, or adrenaline alpha2 receptors, attenuate evoked transmitter release via inhibiting voltage-activated Ca2+ currents without affecting voltage-activated K+ currents or inwardly rectifying K+ currents. Furthermore, inhibition of voltage-activated Ca2+ currents fully explains the magnitude of GPCR-mediated presynaptic inhibition, indicating no essential involvement of exocytotic mechanisms in the downstream of Ca2+ influx. Direct loadings of G protein beta gamma subunit (G beta gamma) into the calyceal terminal mimic and occlude the inhibitory effect of a GPCR agonist on presynaptic Ca2+ currents (IpCa), suggesting that G beta gammamediates presynaptic inhibition by GPCRs. Among presynaptic GPCRs glutamate and adenosine autoreceptors play regulatory roles in transmitter release during early postnatal period when the release probability (p) is high, but these functions are lost concomitantly with a decrease in p during postnatal development.