University of Cagliari

About: University of Cagliari is a education organization based out in Cagliari, Italy. It is known for research contribution in the topics: Population & Dopamine. The organization has 11029 authors who have published 29046 publications receiving 771023 citations. The organization is also known as: Università degli Studi di Cagliari & Universita degli Studi di Cagliari.

Old and new parameter choice rules for discrete ill-posed problems

Abstract: Linear discrete ill-posed problems are difficult to solve numerically because their solution is very sensitive to perturbations, which may stem from errors in the data and from round-off errors introduced during the solution process. The computation of a meaningful approximate solution requires that the given problem be replaced by a nearby problem that is less sensitive to disturbances. This replacement is known as regularization. A regularization parameter determines how much the regularized problem differs from the original one. The proper choice of this parameter is important for the quality of the computed solution. This paper studies the performance of known and new approaches to choosing a suitable value of the regularization parameter for the truncated singular value decomposition method and for the LSQR iterative Krylov subspace method in the situation when no accurate estimate of the norm of the error in the data is available. The regularization parameter choice rules considered include several L-curve methods, Reginska's method and a modification thereof, extrapolation methods, the quasi-optimality criterion, rules designed for use with LSQR, as well as hybrid methods.

Factors affecting chemical variability of essential oils: a review of recent developments.

Abstract: This review, covering mainly papers of the last decade, focuses on recent findings on the different factors affecting the chemical composition of essential oils, such as exogenous and endogenous fa...

Stimulation of voluntary ethanol intake by cannabinoid receptor agonists in ethanol-preferring sP rats.

Abstract: Rationale: Recent studies have shown that the cannabinoid CB1 receptor antagonist, SR 141716, is capable of reducing voluntary ethanol intake in rodents, suggesting the involvement of the CB1 receptor in the neural circuitry mediating the positive reinforcing properties of ethanol. Objectives: The present study extended to the agonists the investigation on the pharmacological manipulation of ethanol intake by cannabinoid agents. Methods: Selectively bred, Sardinian alcohol-preferring (sP) rats were offered ethanol and water under the two-bottle free choice procedure with unlimited access for 24 h/day. Results: The acute administration of WIN 55,212-2 (0.5–2 mg/kg; IP) and CP 55,940 (3-30 µg/kg; IP) induced a significant, dose-dependent increase in ethanol intake. Conversely, water consumption and intake of regular food and a highly palatable sucrose solution were not affected by treatment with WIN 55,212-2 and CP 55,940. The stimulatory effect of WIN 55,212-2 and CP 55,940 on ethanol intake was completely prevented by administration of SR 141716 (0.3 mg/kg; IP) and the opioid receptor antagonist, naloxone (0.1 mg/kg; IP). Conclusions: Administration of WIN 55,212-2 and CP 55,940 promoted voluntary ethanol intake in sP rats. This effect was mediated by stimulation of the cannabinoid CB1 receptor and required the activation of the endogenous opioid system. The results of the present study add further support to the hypothesis that the cannabinoid CB1 receptor is part of the neural substrate regulating ethanol intake. These results are also discussed in terms of WIN 55,212-2 and CP 55,940 administration possibly fixing to a higher level the hedonic set-point mechanism regulating ethanol drinking behavior in sP rats.

Cannabinoid self-administration in rats: sex differences and the influence of ovarian function

Abstract: Background and purpose: We recently demonstrated the existence of strain differences in self-administration of the cannabinoid CB1 receptor agonist WIN55,212-2 (WIN) by Long Evans (LE) and Lister Hooded (LH) but not Sprague-Dawley (SD) male rats. This follow-up study is aimed at verifying whether sex and ovarian hormones might also be critical factors in the initiation, retention and extinction of WIN self-administration. Experimental approach: LE, LH and SD male and female rats, the latter either intact or bilaterally ovariectomized (OVX), were trained to self-administer WIN (12.5 μg kg−1 per infusion) under a FR1 reinforcement schedule, using lever-pressing. Key results: Data showed that contrary to the findings in SD rats, LE and LH rats developed robust cannabinoid intake, with rates of responding for WIN being constantly higher in intact females than in males (+45 and +42% for LE and LH strains, respectively). In comparison with intact females, OVX females of both strains acquired self-administration at lower rates, displaying slower acquisition, lower drug intake (−42 and −52% for LE and LH, respectively) and longer extinction. Conclusions and implications: These findings provide the first evidence of significant sex differences in cannabinoid self-administration, females acquiring stable WIN intake at higher rates and more rapidly than males. Moreover, when compared to intact females, a lower percentage of LE and LH OVX rats acquired and maintained stable drug intake, suggesting that ovarian hormones might represent a critical factor in modulating the reinforcing effect of cannabinoids. British Journal of Pharmacology (2007) 152, 795–804; doi:10.1038/sj.bjp.0707465; published online 24 September 2007