Astrocytes and neurons are inseparable partners in the brain. Neurotransmitters released from neurons activate corresponding G protein-coupled receptors (GPCR) expressed in astrocytes, resulting in release of gliotransmitters such as glutamate, D-serine, and ATP. These gliotransmitters in turn influence neuronal excitability and synaptic activities. Among these gliotransmitters, ATP regulates the level of network excitability and is critically involved in sleep homeostasis and astrocytic Ca2+ oscillations. ATP is known to be released from astrocytes by Ca2+-dependent manner. However, the precise source of Ca2+, whether it is Ca2+ entry from outside of cell or from the intracellular store, is still not clear yet. Here, we performed sniffer patch to detect ATP release from astrocyte by using various stimulation. We found that ATP was not released from astrocyte when Ca2+ was released from intracellular stores by activation of Galpha(q)-coupled GPCR including PAR1, P2YR, and B2R. More importantly, mechanical stimulation (MS)-induced ATP release from astrocyte was eliminated when external Ca2+ was omitted. Our results suggest that Ca2+ entry, but not release from intracellular Ca2+ store, is critical for MS-induced ATP release from astrocyte.
Adenosine Triphosphate* ; Astrocytes* ; Brain ; Glutamic Acid ; Homeostasis ; Neurons ; Neurotransmitter Agents

BACKGROUND AND OBJECTIVES: Patients with isolated vertigo could have central or peripheral vestibular disorders. Although some differential points exist between the two conditions, sometimes it is not easy to differentiate central vertigo from that of peripheral vestibular origin, especially in patients with isolated vertigo. We performed this study to determine the frequency of acute infarction and predictors of vertigo associated with stroke in isolated spontaneous vertigo. MATERIALS AND METHODS: We prospectively evaluated 185 consecutive patients who were admitted to neurology department with acute isolated vertigo, after excluding the patients with benign paroxysmal positioning vertigo. Diffusion-weighted MRI (DWI) was obtained in 161 (87.0%) patients. Demographics, stroke risk factors, associated symptoms and signs were reviewed. Also, the locations and vascular territories of the lesions on DWI were investigated. RESULTS: Twenty three (14.3%) patients had acute infarction on DWI. Old age and male sex were the predictors of stroke using multivariate analysis (p=0.03 and 0.02). The lesions were located in the cerebellum in 17 patients, medulla in four, and pons in another four. Cerebellar lesions were in the territory of the posterior inferior cerebellar artery in all patients. CONCLUSION: Isolated spontaneous vertigo may develop in posterior circulation stroke, especially in men of old age. The possibility of central origin should be considered in patients with isolated vertigo and DWI might be a good diagnostic tool.
Arteries ; Cerebellum ; Cerebral Infarction ; Demography ; Diffusion Magnetic Resonance Imaging ; Humans ; Infarction ; Male ; Multivariate Analysis ; Neurology ; Pons ; Prospective Studies ; Risk Factors ; Stroke ; Vertigo