New aspects of longitudinal instabilities in electron storage rings.

Novel features of the longitudinal instability of a single electron bunch circulating in a low-emittance electron storage ring are discussed. Measurements and numerical simulations, performed both in time and frequency domain, show a non-monotonic increase of the electron beam energy spread as a function of single bunch current, characterized by the presence of local minima and maxima, where a local minimum of the energy spread is interpreted as a higher-order microwave instability threshold. It is also shown that thresholds related to the same zero-intensity bunch length depend linearly on the accelerating radio frequency voltage. The observed intensity-dependent features of the energy spread, confirmed by measurements with two independent diagnostics methods, i.e. horizontal beam profile measurements by a synchrotron light monitor and photon energy spectrum measurements of undulator radiation, are given a theoretical interpretation by applying a novel eigenvalue analysis based on the linearized Vlasov equation.

Morphine decreases the voltage sensitivity of slow sodium channels.

Cell membrane recordings were made in conditions of voltage clamping with tight attachment of the microelectrode-patch clamping--to study the effects of morphine on tetrodotoxin-resistant (TTXr) sodium channels in rat spinal ganglion neurons in culture. The effects of a number of biologically active substances which regulate the receptor-mediated actions of morphine were studied. The effects of morphine were found to involve a chain of sequential reactions leading to decreases in the transfer of effective charge (Zeff) by the activatory gate system of TTXr sodium channels, depending on the concentration of agonist in the extracellular solution. A value of 8 nM was obtained for KD. with a Hill coefficient of X = 0.5. Non-specific antagonists of opioid receptors blocked the actions of morphine; these included ouabain at a concentration of 100 microM. An inhibitor, and activator, and a blocker of G-proteins had no effect on the effective charge. These data provide evidence that morphine decreases the voltage sensitivity of TTXr sodium channels.

Effects of meconic and comenic acids on slow sodium channels of secondary neurons.

Effects of comenic and meconic acids on cultured dorsal root ganglion cells were investigated by the whole-cell patch clamp technique. The acids, having a well-known antiinflammatory and antibacterial action, decreased effective charge transfer in the activation gating system of TTX-resistant (slow) sodium channels in a dose-dependent manner. The effects were described by Hill's equation. The dissociation constant and Hill coefficient values were K(D) = 100 nM and X = 0.5 (for comenic acid) and K(D) = 10 nM and X = 0.34 (for meconic acid). The nonspecific antagonist of opioid receptors naltrexone totally blocked the effects. We suggest that the acids studied activate a subpopulation of opioid receptors negatively coupled to TTXr sodium channels.

[Morphine decreases the voltage sensitivity of the slow sodium channels]. / Morfine umen'shaet chuvstvitel'nost' k potentsialu medlennykh natrievykh kanalov.

Morphine was shown to decrease in a dose-dependent manner the effective charge transfer in tetrodotoxin-resistant (TTXr) sodium channel activation system in short-term cultured dorsal root ganglion cells. Morphine seems to interact with opioid receptors because of total block of the binding by naloxone and naltrexone. Neither activating, nor inhibiting G-protein agents exerted any effect on this process. The morphine signal was blocked by extracellular application of 2 x 10(-4) M ouabain. The findings suggest existence of sodium signalling pathway involving receptors, Na+, K(+)-ATPase and the TTXr sodium channels.