Topological Phases of Polaritons in a Cavity Waveguide.

We study the unconventional topological phases of polaritons inside a cavity waveguide, demonstrating how strong light-matter coupling leads to a breakdown of the bulk-edge correspondence. We observe an ostensibly topologically nontrivial phase, which unexpectedly does not exhibit edge states. Our findings are in direct contrast to topological tight-binding models with electrons, such as the celebrated Su-Schrieffer-Heeger (SSH) model. We present a theory of collective polaritonic excitations in a dimerized chain of oscillating dipoles embedded inside a photonic cavity. The added degree of freedom from the cavity photons upgrades the system from a typical SSH SU(2) model into a largely unexplored SU(3) model. Tuning the light-matter coupling strength by changing the cavity size reveals three critical points in parameter space: when the polariton band gap closes, when the Zak phase changes from being trivial to nontrivial, and when the edge state is lost. These three critical points do not coincide, and thus the Zak phase is no longer an indicator of the presence of edge states. Our discoveries demonstrate some remarkable properties of topological matter when strongly coupled to light, and could be important for the growing field of topological nanophotonics.

Effects of inhibitors of GABA-transaminase on hole-board exploration and on temperature. Relation with effects on quasi-morphine abstinence behaviour induced by sodium dipropylacetate.

Four inhibitors of gamma-aminobutyric acid transaminase (GABA-T) were investigated together with respect to their effects on hole-board exploration and temperature and the relation with effects on quasi-morphine-abstinence behaviour induced by dipropylacetate (DPA) in rats. Amino-oxyacetic acid (AOAA), gamma-acetylenic-GABA (GAG), gamma-vinyl-GABA (GVC) and ethanolamine-O-sulfate (EOS) were found to reduce hole-board exploration especially in the higher doses used, although the time-course of the effect was different for the compounds. For EOS and GVG the decrease in hole-board exploration paralleled a strong hypothermic effect. The compounds AOAA and GAG exerted a less and more transient hypothermic effect. However, the decrease in hole-board exploration did not fall in with this decrease in temperature. AOAA and GAG were found to decrease DPA-induced body shakes and locomotor activity, while GVG and EOS had no effect on body shakes and transient effects but opposite to each other, on locomotor activity. The efficacy of the GABA-T-inhibitors was measured biochemically, and the influence on the activity of glutamate decarboxylase (GAD) was also determined. AOAA and GAG were found to be strong inhibitors of GABA-T whereas the other two compounds were less efficient in the used doses. In addition AOAA and GAG influenced the activity of GAD strongly, while using GVG only a small decrease was found. The results suggest that the anti-quasi-withdrawal, the sedative and the hypothermic effects are not related to each other nor related to an effect on GABA-T. The suppressive effects on quasi-withdrawal body shakes, however, could be related to the inhibition of GAD and a hypothesis involving a compartmentalized action of DPA on GABA-metabolism has been proposed.

Dipropylacetate-induced quasi-morphine abstinence behaviour in the rat: suppression by alpha 2-adrenoceptor stimulation.

The anti-withdrawal effect of clonidine was studied using quasi-morphine abstinence behaviour induced by dipropylacetate (DPA) in naive rats. Clonidine potently suppressed body shakes and locomotor activity (ID50 30 and 40 micrograms/kg IP respectively). Phenoxybenzamine and prazosine did not antagonize the anti-withdrawal effect of clonidine, whereas piperoxane and yohimbine were effective with respect to locomotor activity and a total abstinence score. Piperoxane also reversed the suppressive action of clonidine on body shakes. Other alpha 2-agonists (guanfacine, azepexole and BHT 920) also suppressed DPA-induced behaviour, whereas the lipophilic alpha 1-agonist ST-587 had such an effect only at high doses. The relative potencies of the alpha 2-agonists correlated well with their potency to exert other alpha 2-adrenoceptor mediated actions such as blood pressure lowering and sedation.

The effects of centrally acting adrenergic agonists on temperature and on explorative and motor behaviour. Relation with effects on quasi-morphine withdrawal behaviour.

Seven structurally unrelated adrenergic agonists were compared in three models to measure sedation viz. hole-board exploration, open-field activity and rotarod performance. It appeared that all compounds exerted the same order of potency in these models except for BHT-920 which was more active in the open-field. The other compounds were clonidine, azepexole, guanfacine, lofexidine, UK-14.304 and ST-587. The sedative effect appeared to be not causally related with the hypothermic activity since much higher doses were necessary for the latter effect. There was a relation between the sedative effects and the suppression of body shakes and enhanced locomotor activity induced by dipropylacetate, a potent model for morphine-withdrawal behaviour. The body shakes appeared to be more sensitive than locomotor activity suggesting that the antiwithdrawal action of alpha 2-agonists might be intrinsically higher than their sedative action. The data support earlier findings indicating that the antiwithdrawal action of clonidine is mediated by alpha 2-adrenoceptors.