Electroinductive waves role in left-handed stacked complementary split rings resonators.

In this letter it is presented a Left-Handed Metamaterial design route based upon stacked arrays of screens made of complementary split rings resonators under normal incidence in the microwave regime. Computation of the dispersion diagram highlights the possibility to obtain backward waves provided the longitudinal lattice is small enough. The experimental results are in good agreement with the computed ones. The physics underlying the Left-Handed behavior is found to rely on electroinductive waves, playing the mutual capacitive coupling the major role to explain the phenomenon. Our route to Left-Handed metamaterial introduced in this paper based on stacking CSRRs screens can be scaled to millimeter and terahertz for future applications.

Polypropylene-substrate-based SRR- and CSRR- metasurfaces for submillimeter waves.

In this paper it is presented the fabrication of low loss millimeter wave metamaterials based on patterning on polypropylene substrates by conventional contact photolitography. We study numerically and experimentally the transmission and reflection properties of two dimensional arrays of split ring resonators (SRRs), or metasurfaces, and their complementary structure (CSRRs) for co- and cross-polarization excitations up to submillimeter frequencies under normal incidence conditions. The obtained results suggest the possibility of scaling them at terahertz frequencies based on this substrate where other lossy substrates degrade the resonators quality. Left-handed metamaterials derived from these SRRs and CSRRs metasurfaces could be feasible.

Influence of gender and behavioural lateralisation on two exploratory models of anxiety in C3H mice.

Behavioural lateralisation, which has been postulated to be an individual personality trait, is related to the activity of various physiological systems including the immune system. As lateralisation has been related to anxiety, which is known to influence immune reactivity, it can be hypothesized that the relation between lateralisation and immune reactivity involves individual behavioural patterns as they appear in exploratory-based anxiety models. In order to answer this question, a behavioural investigation focussing on exploratory activity was undertaken in male and female C3H mice previously selected for their paw preference. The observations were performed using two generic paradigms: elevated plus-maze and open field. Exploratory behaviour in the open field, but not in the plus-maze, was influenced by the interactive effect of gender and behavioural lateralisation. A significant difference between male and female mice was found in left-pawed but not in right-pawed nor ambidextrous animals, left-pawed female mice displaying the less exploratory behaviours. These results provide a first evidence of inter-individual variations in exploratory behaviours involving interaction between gender and lateralisation.

Locomotor bias produced by intra-accumbens injection of dopamine agonists and antagonists.

Several experiments have shown that the dopamine (DA) receptors in the nucleus accumbens control the intensity of locomotor activity; however, there are several contradictory results concerning the role of the accumbens in the regulation of the direction of locomotion. To further evaluate the contribution of dopaminergic function in the accumbens to the direction of locomotion, we first compared the effect on the direction of locomotor activity of unilateral intra-accumbens injections of the nonspecific DA antagonist haloperidol, the specific D-1 antagonist SCH-23390, the specific D-2 antagonist metoclopramide. In the second part of the experiment, we examined the effect on the direction of locomotor activity of unilateral intra-accumbens injections of the non-specific DA agonist apomorphine, the specific D-1 agonist SKF-38393, the specific D-2 agonist LY-171555, and the combination of SKF-38393 and LY-171555. Haloperidol, metoclopramide and to a lesser extent, SCH-23393 together with peripheral amphetamine injections produced a locomotor bias that resulted in ipsilateral turning. Apomorphine, LY-171555 or the combination of SKF-38393 and LY-171555 (but not SKF-38393 alone) produced a locomotor bias that resulted in contralateral turning. No significant locomotor bias was produced by intra-accumbens injection of the various vehicles. These results suggest that the bilateral DA organization thought to exist in the nigro-striatal pathway for the control of locomotion may also be true for the mesolimbic dopamine system.

Locomotor bias produced by intra-accumbens and intracaudate injection of polyclonal dopamine anti-idiotypic antibodies.

The preceding article described anti-idiotypic antibodies to conjugated dopamine (AIDA); results were consistent with the hypothesis that these antibodies contained the internal image of conjugated dopamine (DA-G-BSA) and binded to dopamine (DA) receptors. We further tested these anti-idiotypic antibodies to conjugated dopamine by examining the functional changes produced by unilateral injection of AIDA (or DA-G-BSA) into the nucleus accumbens or into the medio-dorsal caudate in mice. Our results showed that unilateral injection of AIDA (or DA-G-BSA) into the nucleus accumbens or into the medio-dorsal caudate produced an ipsilateral locomotor asymmetry in amphetamine-treated animals which was similar to the one produced by unilateral intra-caudate injection of haloperidol (a non-specific DA antagonist). The asymmetry was site specific: injection of AIDA around the nucleus accumbens or into the anterior caudate was not effective. The asymmetry was also shown not to depend on the peripheral injection of amphetamine. Taken together, the present results and those in the preceding article suggest that the AIDA contains the internal image of DA-G-BSA and that these two substances bind to DA receptors to produce behavioral changes.

Bidirectional potentiation between D1 and D2 dopamine agonists: effects of unilateral intra-accumbens injections on locomotor activity in mice.

We tested the effect of a single unilateral injection of a specific D1 agonist into the nucleus accumbens on the behavioral response to a subsequent unilateral intra-accumbens injection of a selective D2 agonist ten days later. The effect of the inverse order of presentation (D2 agonist followed ten days later by a D1 agonist) was also tested. No significant differences between the locomotor effects of the intra-accumbens injection of either SKF-38393 (3.5 micrograms) or LY-171555 (10 micrograms) were observed during the first test. Ten days later, during the second test, intra-accumbens injection of either the LY-171555 and SKF-38393 increased the percentage of contralateral rotations relative to the first test while LY-171555 also increased the total number of rotations. Control injections showed that these effects of LY-171555 and SKF-38393 were not due to a conditioning process. Rather, the results suggested that the locomotor changes observed during the second test were the result of behavioral sensitization due to the initial acute injection of the agonists.

Memory-improving action of glucose: indirect evidence for a facilitation of hippocampal acetylcholine synthesis.

The effect of a 3 g/kg glucose injection on the velocity of the sodium-dependent high-affinity choline uptake mechanism in the hippocampus was both measured in quiet control mice and in mice immediately after training in an operant bar pressing task. Glucose did not significantly change high-affinity choline uptake in resting animals. High-affinity choline uptake in the hippocampus was increased by training in the operant bar pressing task. Glucose significantly reduced the amplitude of the increase in high-affinity choline uptake observed in the trained animals. Similarly, a 3 g/kg glucose injection also attenuated the increase in high-affinity choline uptake observed in animals injected with 1 mg/kg scopolamine. Finally, a 3 g/kg glucose injection significantly attenuated the amnesia produced by a post-training 1 mg/kg scopolamine injection in mice trained for an operant bar pressing task. These results provide additional evidence for an action of glucose on hippocampal cholinergic activity under conditions of high acetylcholine demand. This action may be mediated via an increase in acetyl coenzyme A availability, one of the precursors of acetylcholine. This facilitative effect of glucose on hippocampal acetylcholine synthesis may constitute the physiological basis for its facilitative action on memory and its attenuation of scopolamine amnesia.

[Circling behavior produced by the unilateral intra-accumbens injection of dopaminergic agonist and two dopaminergic antagonists in mice]. / Comportement de rotation produit par l'injection unilatérale intra-accumbens d'un agoniste et de deux antagonistes dopaminergiques chez la souris.

Unilateral intra-accumbens injection of apomorphine, a dopaminergic agonist, produced circling contralateral to the site of injection in Balb/c mice. Unilateral intra-accumbens injection of haloperidol and metoclopramide, two dopaminergic antagonists, produced ipsilateral circling. These results support the hypothesis that the dopaminergic receptors in the nucleus accumbens also contribute to the direction of locomotor activity.