4,211 research outputs found
Decrease of vanillin sucrose intake by victorious and defeated mice: development of anhedonia?
Hedonic reactions to various rewards play a key role in various forms of motivated behavior. The influence of repeated experience of social victories or defeats in daily agonistic interactions between male mice on voluntary consumption of vanillin sucrose solution used as hedonic reinforcer was studied. Intake of vanillin sucrose solution was shown to decrease in the winners and losers exposed to social confrontations as compared with the controls. Three days of deprivation failed to restore the intake of vanillin sucrose solution to the control level in the losers and did so in the winners. The results obtained imply that similar reaction of animals to a hedonic non-drug reinforcer may have different motivational origin depending on positive or negative social experience
Molecular implications of prolonged aggression experience: Th, Dat1, Snca and Bdnf gene expression in the ventral tegmental area of the victorious male mice
Th, Dat1, Snca and Bdnf were the genes whose mRNA levels in the ventral tegmental area of the midbrain were measured in male mice that were victorious in 20 daily agonistic interactions and in a group of such victorious mice that had later not been allowed to fight for 14 days. This experiment demonstrated increased Th, Dat1 and Snca but not Bdnf mRNA levels in the former group as compared to the controls. In the latter group, the expression of the Th and Dat1 genes was still enhanced, while the level of Snca mRNA did not differ from that in the controls. These findings suggest that positive fighting experience enhances the expression of the genes concerned with dopaminergic systems and this enhanced expression is preserved for a long time afterwards. Significant positive correlations were found between the level of aggression and Th and Snca mRNA levels in the winners
Application of the Sensory Contact Model for Pharmacological Studies under Simulated Clinical Conditions
The sensory contact model allows forming different psycho-pathological states (anxious depression, catalepsy, social withdrawal, pathological aggression, cognition disturbances, anhedonia, addictive states etc.) produced by repeated agonistic interactions in male mice and investigating the therapeutic and preventive properties of any drug as well as its efficiency under simulated clinical conditions. This approach can be useful for a better understanding of the drugs’ action in different stages of disease development in individuals. It is suggested that this behavioral approach and pharmacological designs may be applied for the screening of novel psychotropic drugs. 

Anhedonia in the shadow of chronic social defeat stress, or When the experimental context matters
One of the core symptoms of major depression in human is anhedonia. For that reason, one of the main requirements towards experimental depression models is that they be able to demonstrate anhedonia in animals, that have been exposed to stressful events, and other behavioral changes attributable to a depression-like state. However, the results presented in the literature are contradictory: sweet solution intake, which is considered as a parameter of hedonic/anhedonic behavior in animals, responds quite differently to stressful situations in that it is either unaffected or increased or decreased. Different experimental designs used for the study of anhedonia in male mice exposed to chronic social defeat stress were tried to understand the reasons for so contradictory responses. Anhedonia appears as an abrupt reduction in sweet solution consumption in stressed animals and by failure to attain recovery after deprivation. However, it was also demonstrated that sucrose solution intake and preference strongly depend on the experimental context; that the possible critical factor may be prior acquaintance with the hedonic stimulus – or the lack whereof. Analysis of literature data and ours allowed us to conclude that the lack of a significant decrease in sweet solution intake in stressed animals is no evidence of lack of depression. This decrease is evidence of anhedonia only provided other symptoms of depression are present. Hedonic consumable intake can be decreased over various motivations, conditions or diseases, in particular, a high level of anxiety or pathological aggression
Paramagnetic-diamagnetic interplay in quantum dots for non-zero temperatures
In the usual Fock-and Darwin-formalism with parabolic potential characterized
by the confining energy \eps_o := \hbar\omega_o= 3.37 meV, but including
explicitly also the Zeeman coupling between spin and magnetic field, we study
the combined orbital and spin magnetic properties of quantum dots in a
two-dimensional electron gas with parameters for GaAs, for N =1 and N >> 1
electrons on the dot.
For N=1 the magnetization M(T,B) consists of a paramagnetic spin contribution
and a diamagnetic orbital contribution, which dominate in a non-trivial way at
low temperature and fields rsp. high temperature and fields.
For N >> 1, where orbital and spin effects are intrinsically coupled in a
subtle way and cannot be separated, we find in a simplified Hartree
approximation that at N=m^2, i.e. at a half-filled last shell, M(T,B,N) is
parallel (antiparallel) to the magnetic field, if temperatures and fields are
low enough (high enough), whereas for N\ne m^2 the magnetization oscillates
with B and N as a T-dependent periodic function of the variable
x:=\sqrt{N}eB/(2m^*c\omega_o), with T-independent period \Delta x =1 (where m^*
:= 0.067 m_o is the small effective mass of GaAs, while m_o is the electron
mass). Correspondingly, by an adiabatic demagnetization process, which should
only be fast enough with respect to the slow transient time of the magnetic
properties of the dot, the temperature of the dot diminishes rsp. increases
with decreasing magnetic field, and in some cases we obtain quite pronounced
effects.Comment: LaTeX, 28 pages; including three .eps-figures; final version accepted
by J. Phys. CM, with minimal changes w.r.to v
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