Optogenetic Manipulation of Cerebellar Purkinje Cell Activity In Vivo

Purkinje cells (PCs) are the sole output neurons of the cerebellar cortex. Although their anatomical connections and physiological response properties have been extensively studied, the causal role of their activity in behavioral, cognitive and autonomic functions is still unclear because PC activity cannot be selectively controlled. Here we developed a novel technique using optogenetics for selective and rapidly reversible manipulation of PC activity in vivo. We injected into rat cerebellar cortex lentiviruses expressing either the light-activated cationic channel channelrhodopsin-2 (ChR2) or light-driven chloride pump halorhodopsin (eNpHR) under the control of the PC-specific L7 promoter. Transgene expression was observed in most PCs (ChR2, 92.6%; eNpHR, 95.3%), as determined by immunohistochemical analysis. In vivo electrophysiological recordings showed that all light-responsive PCs in ChR2-transduced rats increased frequency of simple spike in response to blue laser illumination. Similarly, most light-responsive PCs (93.8%) in eNpHR-transduced rats decreased frequency of simple spike in response to orange laser illumination. We then applied these techniques to characterize the roles of rat cerebellar uvula, one of the cardiovascular regulatory regions in the cerebellum, in resting blood pressure (BP) regulation in anesthetized rats. ChR2-mediated photostimulation and eNpHR-mediated photoinhibition of the uvula had opposite effects on resting BP, inducing depressor and pressor responses, respectively. In contrast, manipulation of PC activity within the neighboring lobule VIII had no effect on BP. Blue and orange laser illumination onto PBS-injected lobule IX didn't affect BP, indicating the observed effects on BP were actually due to PC activation and inhibition. These results clearly demonstrate that the optogenetic method we developed here will provide a powerful way to elucidate a causal relationship between local PC activity and functions of the cerebellum

Varying constants, Gravitation and Cosmology

Fundamental constants are a cornerstone of our physical laws. Any constant varying in space and/or time would reflect the existence of an almost massless field that couples to matter. This will induce a violation of the universality of free fall. It is thus of utmost importance for our understanding of gravity and of the domain of validity of general relativity to test for their constancy. We thus detail the relations between the constants, the tests of the local position invariance and of the universality of free fall. We then review the main experimental and observational constraints that have been obtained from atomic clocks, the Oklo phenomenon, Solar system observations, meteorites dating, quasar absorption spectra, stellar physics, pulsar timing, the cosmic microwave background and big bang nucleosynthesis. At each step we describe the basics of each system, its dependence with respect to the constants, the known systematic effects and the most recent constraints that have been obtained. We then describe the main theoretical frameworks in which the low-energy constants may actually be varying and we focus on the unification mechanisms and the relations between the variation of different constants. To finish, we discuss the more speculative possibility of understanding their numerical values and the apparent fine-tuning that they confront us with.Comment: 145 pages, 10 figures, Review for Living Reviews in Relativit

Supraclavicular reoperation for neurogenic thoracic outlet syndrome

Thirty-nine reoperations in 38 patients with recurrent symptoms of neurogenic thoracic outlet syndrome were performed by the supraclavicular approach. Scarring around the brachial plexus was the primary cause in 59% of procedures, whereas in 41% of reoperations residual osseous and soft tissue anomalies were identified in the supraclavicular area and were responsible for recurrence of symptoms. Anterior and middle scalenectomy and neurolysis of the brachial plexus were the procedures of choice. Complications included pleural entry (62%), lymphatic leak (10%), brachial plexus and phrenic nerve injuries (5% each), and long thoracic and recurrent laryngeal nerve palsies (3% each). The initial success rate for secondary operation was 74%, and long-term success at 18 months was 45%. Patients who had demonstrable anatomic anomalies had better short- and long-term results than had patients with scarring alone. Compared with the results of primary operations for neurogenic thoracic outlet syndrome, reoperations led to a longer hospital stay and inferior long-term results. Supraclavicular decompression allows maximal exposure of the brachial plexus and identification and correction of causative soft tissue and bony anomalies. For these reasons we recommend this as the approach of choice in both primary and secondary operations for neurogenic thoracic outlet syndrome.link_to_subscribed_fulltex