Central kappa opioid receptors modulate salt appetite in rats.

The role of the central opioid system in the control of water and salt intake is complex, with both stimulatory and inhibitory effects having been observed. The aim of the present study was to investigate the participation of the central κ-opioid receptors in the control of salt appetite. Male Wistar rats were submitted to two different experimental protocols: sodium deficit produced by the diuretic, furosemide, and brain angiotensinergic stimulation in rats under normal sodium balance. Lateral ventricle (LV) injections of Nor-binaltorphimine (Nor-BNI) at different doses (5, 10 and 20 nmol) inhibited hypertonic saline solution (1.5%) intake in sodium-depleted rats. The salt appetite induced by an LV injection of angiotensin II (Ang II) (10 ng) was also blocked by Nor-BNI injections into the LV, while no significant change was observed in water intake. Furthermore, the decrease in salt intake seems not to have been due to a general inhibition of locomotor activity or to any change in palatability, since central administration of Nor-BNI failed to modify the intake of a 0.1% saccharin solution when the animals were submitted to a "dessert test" or to induce any significant locomotor deficit in the open-field test. Also the central administration of Nor-BNI was unable to modify blood pressure in sodium-depleted animals. The present results suggest that activation of endogenous κ-opioid receptors modulates salt appetite induced by sodium depletion and by central angiotensinergic stimulation in rats.

Phytochemical prospection and modulation of aminoglycoside antibiotic activity by Croton campestris A.

BACKGROUND: Escherichia coli is known to produce enterotoxins whose properties and role in diarrheal disease have been extensively investigated; besides, this bacterium is related to several extra-intestinal problems in the intensive care unit and in surgical wound infections. Some species of Staphylococcus are recognized as etiological agents of opportunistic infections in animals and humans. This study is the first test on the modulation of antibiotic activity by Croton campestris A. against multiresistant strains of E. coli and Staphylococcus aureus. METHODS: In this study, the hexane and methanol extract of C. campestris A. was tested for antibacterial activity alone and in combination with aminoglycosides against bacterial strains. The synergy of the methanol and hexane extract was verified by microdilution method. RESULTS: A synergistic effect of both extracts combined with the aminoglycosides was demonstrated. CONCLUSIONS: It is suggested that the extracts from C. campestris A. could be used as a source of natural product derived from this plant with resistance-modifying antibacterial activity, providing a new weapon against the problem of bacterial resistance to antibiotics.

Ab initio approach to the electronic properties of sodium-ammonia clusters: comparison with ammonia clusters.

Ab initio results for the electronic properties of sodium-ammonia [Na(NH(3))(n);n=1-8] and the corresponding ionized structures [Na(+)(NH(3))(n)] are reported and compared with those for neutral ammonia clusters [(NH(3))(n)]. Emphasis was placed on the analysis of polarization effects and calculation of vertical and adiabatic ionization potentials. The theoretical discussion is based on second order Møller-Plesset perturbation theory and Green's function or electron propagator theory calculations. Our results for the ionization energies (IEs) of Na(NH(3))(n) clusters are in very good agreement with experimental information. The relationship between the dependence of the IEs on the number of ammonia molecules (n), polarization effects, and hydrogen bond formation is investigated. The presence of a hydrogen bond acceptor-only ammonia molecule that binds a delocalized excess electron in Na(NH(3))(6-7) clusters is discussed.