1. TRPV1 and Osmoregulation
Sorana Ciura and Charles W. Bourque
Central control of systemic osmoregulation is the job of the organum vasculosum lamina terminalis (OVLT), located at the rostral ventral edge of the third ventricle. In this week's Journal, Ciura and Bourque demonstrate that OVLT neurons are intrinsically osmosensitive because they express transient receptor potential vanilloid 1 (TRPV1) channels. The authors compared the neuronal activity of hypothalamic explants from wild-type and TRPV1-deficient mice. OVLT neurons in wild-type mice responded to increased osmolality with an increased firing rate, whereas TRPV1−/−neurons did not. OVLT neurons responded directly to the change in osmolality with membrane depolarization. Ruthenium red, a blocker of nonselective cation channels, prevented hypertonic solution-induced depolarization, pointing to TRPV1 as the transducer. In vivo, TRPV1−/− mice drank less water after an osmotic challenge than did their WT counterparts, placing TRPV1 in the pathway that triggers thirst.
2. Astrocyte Processes and Dendritic Spines in Motion
Michael Haber, Lei Zhou, and Keith K. Murai
Glial cells sure aren't what they were thought to be. They have calcium signals, release transmitters, and receive "synaptic" input. Now Haber et al. provide evidence that they can even move faster than neurons. The authors used time-lapse confocal imaging of organotypic hippocampal explants to monitor the movements of dendritic spines and their associated glial processes. Two Semliki Forest viral vectors were used to selectively infect glia and neurons with membrane-tethered enhanced green fluorescent protein and red fluorescent protein. The membrane-tethered probes facilitated imaging of fine glial processes. In the hippocampal CA1 area, astrocytes and dendrites showed complex interactions, including astrocytic processes tha
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Society for Neuroscience