Dopamine/adenosine interaction in effort-related processes in rodents: Studies using T-Maze paradigm in mice

Catorzenes Jornades de Foment de la Investigació de la FCHS (Any 2008-2009)Humans and animals realize cost/benefits analysis of our responses with the goal of use the lowest energy possible to obtain the major benefit. Mesolimbic dopamine (DA) is a critic component in the cerebral circuitry regulating decision making based on the effort that the response requires, because it regulates behavioral activation. Research with rodents show that DA antagonists displace the behavior from the response that supposes more effort, though it has more reinforcement, to other behavior with less effort required. Interaction between A2A adenosine receptors and D2 receptors play an essential paper in these processes. In the T-Maze paradigm the animal is exposed to an option of choose one arm with two food pellets, to which it accedes after climbing a 14 cm barrier, or to choose the arm without barrier and with only one food pellet. Control animals choose to do the effort of climbing the barrier to obtain the high reinforcement. Haloperidol, D2 antagonist, produces change behavior towards the less density arm, been this effect partially reverted with theophylline, unspecific adenosine antagonist, and with MSX-3, selective A2A antagonist. These drugs could have applications for the treatment of amotivational syndromes

Effects of dietary inclusion of Opuntia ficus-indica on the glycemia and productive performance in lactating sows

Sows with increased blood glucose during late gestation may have decreased feed intake in lactation. Supplying dietary fibre to the sow reportedly modulates blood glucose and improves feed intake. The objective of this study was to evaluate the effects of dietary inclusion of cactus (Opuntia ficus-indica) on the regulation of blood glucose and productive performance in lactating sows. Data from 52 hybrid sows were analysed. The sows were divided into two groups, namely a control group (CG), that is, sows fed conventionally; and an experimental group (EG), that is, sows fed commercial feed plus cacti. Blood glucose in late gestation, and feed intake, milk production and milk quality, development of the piglet, energy balance, post-weaning body weight balance and the interval from weaning to oestrus were recorded. Preprandial blood glucose was 55.9 mg per dL in EG and 71.4 in CG. Sows on EG had greater daily feed intake and lower negative energy balance (5.4 kg/day and -2.8 MJ/day) than those on CG (4.5 kg/day and -9.4 MJ/day). Sows fed EG produced more milk (8.6 L/day) than those on CG (8.1 L/day). The quality of milk produced and the weaning weight of piglets were similar for the two groups. Body weight balance after weaning was greater for sows fed EG, 3.5% versus -1.5% in those fed CG. The weaning to oestrus interval was 0.6 days less for sows fed EG than those fed CG. Feeding cactus to lactating sows regulated blood glucose, which improved most of their productive indicators.Keywords: cactus, dietary fibre, energy balance, hypophagia, pigle

A Numerical Study of the Hierarchical Ising Model: High Temperature Versus Epsilon Expansion

We study numerically the magnetic susceptibility of the hierarchical model with Ising spins ($\sigma =\pm 1$) above the critical temperature and for two values of the epsilon parameter. The integrations are performed exactly, using recursive methods which exploit the symmetries of the model. Lattices with up to $2^18$ sites have been used. Surprisingly, the numerical data can be fitted very well with a simple power law of the form $(1- \beta /\beta _c )^{- \gamma}$for the {\it whole} temperature range. The numerical values for $\gamma$ agree within a few percent with the values calculated with a high-temperature expansion but show significant discrepancies with the epsilon-expansion. We would appreciate comments about these results.Comment: 15 Pages, 12 Figures not included (hard copies available on request), uses phyzzx.te

The Oscillatory Behavior of the High-Temperature Expansion of Dyson's Hierarchical Model: A Renormalization Group Analysis

We calculate 800 coefficients of the high-temperature expansion of the magnetic susceptibility of Dyson's hierarchical model with a Landau-Ginzburg measure. Log-periodic corrections to the scaling laws appear as in the case of a Ising measure. The period of oscillation appears to be a universal quantity given in good approximation by the logarithm of the largest eigenvalue of the linearized RG transformation, in agreement with a possibility suggested by K. Wilson and developed by Niemeijer and van Leeuwen. We estimate $\gamma$ to be 1.300 (with a systematic error of the order of 0.002) in good agreement with the results obtained with other methods such as the $\epsilon$-expansion. We briefly discuss the relationship between the oscillations and the zeros of the partition function near the critical point in the complex temperature plane.Comment: 21 pages, 10 Postcript figures, latex file, uses revte

On the recurrence and robust properties of Lorenz'63 model

Lie-Poisson structure of the Lorenz'63 system gives a physical insight on its dynamical and statistical behavior considering the evolution of the associated Casimir functions. We study the invariant density and other recurrence features of a Markov expanding Lorenz-like map of the interval arising in the analysis of the predictability of the extreme values reached by particular physical observables evolving in time under the Lorenz'63 dynamics with the classical set of parameters. Moreover, we prove the statistical stability of such an invariant measure. This will allow us to further characterize the SRB measure of the system.Comment: 44 pages, 7 figures, revised version accepted for pubblicatio

A Two-Parameter Recursion Formula For Scalar Field Theory

We present a two-parameter family of recursion formulas for scalar field theory. The first parameter is the dimension $(D)$. The second parameter ($\zeta$) allows one to continuously extrapolate between Wilson's approximate recursion formula and the recursion formula of Dyson's hierarchical model. We show numerically that at fixed $D$, the critical exponent $\gamma$ depends continuously on $\zeta$. We suggest the use of the $\zeta -$independence as a guide to construct improved recursion formulas.Comment: 7 pages, uses Revtex, one Postcript figur

Evidence for Complex Subleading Exponents from the High-Temperature Expansion of the Hierarchical Ising Model

Using a renormalization group method, we calculate 800 high-temperature coefficients of the magnetic susceptibility of the hierarchical Ising model. The conventional quantities obtained from differences of ratios of coefficients show unexpected smooth oscillations with a period growing logarithmically and can be fitted assuming corrections to the scaling laws with complex exponents.Comment: 10 pages, Latex , uses revtex. 2 figures not included (hard copies available on request