Inhibition of dendritic Ca2+ spikes by GABAB receptors in cortical pyramidal neurons is mediated by a direct Gi/o- -subunit interaction with Cav1 channels

Voltage-dependent calcium channels (VDCCs) serve a wide range of physiological functions and their activity is modulated by different neurotransmitter systems. GABAergic inhibition of VDCCs in neurons has an important impact in controlling transmitter release, neuronal plasticity, gene expression and neuronal excitability. We investigated the molecular signalling mechanisms by which GABAB receptors inhibit calcium-mediated electrogenesis (Ca2+ spikes) in the distal apical dendrite of cortical layer 5 pyramidal neurons. Ca2+ spikes are the basis of coincidence detection and signal amplification of distal tuft synaptic inputs characteristic for the computational function of cortical pyramidal neurons. By combining dendritic whole-cell recordings with two-photon fluorescence Ca2+ imaging we found that all subtypes of VDCCs were present in the Ca2+ spike initiation zone, but that they contribute differently to the initiation and sustaining of dendritic Ca2+ spikes. Particularly, Cav1 VDCCs are the most abundant VDCC present in this dendritic compartment and they generated the sustained plateau potential characteristic for the Ca2+ spike. Activation of GABAB receptors specifically inhibited Cav1 channels. This inhibition of L-type Ca2+ currents was transiently relieved by strong depolarization but did not depend on protein kinase activity. Therefore, our findings suggest a novel membrane-delimited interaction of the Gi/o-βγ-subunit with Cav1 channels identifying this mechanism as the general pathway of GABAB receptor-mediated inhibition of VDCCs. Furthermore, the characterization of the contribution of the different VDCCs to the generation of the Ca2+ spike provides new insights into the molecular mechanism of dendritic computation.

Dysbalance in sympathetic neurotransmitter release and action in cirrhotic rats: impact of exogenous neuropeptide Y

Splanchnic vasodilation is an essential disturbance in portal hypertension. Increased systemic sympathetic nerve activity is well known, but potential corresponding vascular desensitization is incompletely characterized. Release of splanchnic sympathetic neurotransmitters noradrenaline (NA) and co-transmitter neuropeptide Y (NPY) remains to be elucidated. Finally, the effects of exogenous NPY on these mechanisms are unexplored.

Biomimetic coating of organic polymers with a protein-functionalized layer of calcium phosphate: the surface properties of the carrier influence neither the coating characteristics nor the incorporation mechanism or release kinetics of the protein

Polymers that are used in clinical practice as bone-defect-filling materials possess many essential qualities, such as moldability, mechanical strength and biodegradability, but they are neither osteoconductive nor osteoinductive. Osteoconductivity can be conferred by coating the material with a layer of calcium phosphate, which can be rendered osteoinductive by functionalizing it with an osteogenic agent. We wished to ascertain whether the morphological and physicochemical characteristics of unfunctionalized and bovine-serum-albumin (BSA)-functionalized calcium-phosphate coatings were influenced by the surface properties of polymeric carriers. The release kinetics of the protein were also investigated. Two sponge-like materials (Helistat® and Polyactive®) and two fibrous ones (Ethisorb and poly[lactic-co-glycolic acid]) were tested. The coating characteristics were evaluated using state-of-the-art methodologies. The release kinetics of BSA were monitored spectrophotometrically. The characteristics of the amorphous and the crystalline phases of the coatings were not influenced by either the surface chemistry or the surface geometry of the underlying polymer. The mechanism whereby BSA was incorporated into the crystalline layer and the rate of release of the truly incorporated depot were likewise unaffected by the nature of the polymeric carrier. Our biomimetic coating technique could be applied to either spongy or fibrous bone-defect-filling organic polymers, with a view to rendering them osteoconductive and osteoinductive.

Long-term cell-mediated protein release from calcium phosphate ceramics

Efficient delivery of growth factors from carrier biomaterials depends critically on the release kinetics of the proteins that constitute the carrier. Immobilizing growth factors to calcium phosphate ceramics has been attempted by direct adsorption and usually resulted in a rapid and passive release of the superficially adherent proteins. The insufficient retention of growth factors limited their bioavailability and their efficacy in the treatment of bone regeneration. In this study, a coprecipitation technique of proteins and calcium phosphate was employed to modify the delivery of proteins from biphasic calcium phosphate (BCP) ceramics. To this end, tritium-labeled bovine serum albumin ([(3)H]BSA) was utilized as a model protein to analyze the coprecipitation efficacy and the release kinetics of the protein from the carrier material. Conventional adsorption of [(3)H]BSA resulted in a rapid and passive release of the protein from BCP ceramics, whereas the coprecipitation technique effectively prevented the burst release of [(3)H]BSA. Further analysis of the in vitro kinetics demonstrated a sustained, cell-mediated release of coprecipitated [(3)H]BSA from BCP ceramics induced by resorbing osteoclasts. The coprecipitation technique described herein, achieved a physiologic-like protein release, by incorporating [(3)H]BSA into its respective carriers, rendering it a promising tool in growth factor delivery for bone healing.

Long-term outcome analysis of the supraclavicular surgical release for the treatment of thoracic outlet syndrome

This is a long-term outcome analysis of patients who underwent surgical treatment with a supraclavicular release for thoracic outlet syndrome (TOS).

Pi release from myosin: a simulation analysis of possible pathways

The release of phosphate (Pi) is an important element in actomyosin function and has been shown to be accelerated by the binding of myosin to actin. To provide information about the structural elements important for Pi release, possible escape pathways from various isolated myosin II structures have been determined by molecular dynamics simulations designed for studying such slow processes. The residues forming the pathways were identified and their role was evaluated by mutant simulations. Pi release is slow in the pre-powerstroke structure, an important element in preventing the powerstroke prior to actin binding, and is much more rapid for Pi modeled into the post-rigor and rigor-like structures. The previously proposed backdoor route is dominant in the pre-powerstroke and post-rigor states, whereas a different path is most important in the rigor-like state. This finding suggests a mechanism for the actin-activated acceleration of Pi release.

Assertive community treatment as part of integrated care versus standard care: a 12-month trial in patients with first- and multiple-episode schizophrenia spectrum disorders treated with quetiapine immediate release (ACCESS trial)

The ACCESS trial examined the 12-month effectiveness of continuous therapeutic assertive community treatment (ACT) as part of integrated care compared to standard care in a catchment area comparison design in patients with schizophrenia spectrum disorders treated with quetiapine immediate release.