Brain differences in newborn rats predisposed to helpless and depressive behavior.

Inborn brain differences in metabolic capacity were mapped in congenitally helpless rats, a genetically selected strain predisposed to show helpless and depressive behavior. There are a number of brain regions showing abnormal metabolism in adult congenitally helpless rats. Some of these alterations may be innate while others may be due to environmental factors, such as maternal care and postnatal stress. To identify which brain structures show innate differences, brains of newborn rats from congenitally helpless and non-helpless strains were compared using cytochrome oxidase histochemistry, an endogenous marker of regional metabolic capacity. A smaller subset of regions affected in adults showed significantly less metabolic activity in the newborn brains, including paraventricular hypothalamus, habenula, hippocampus, subiculum, lateral septal nucleus, anterior cingulate cortex, infralimbic cortex, and medial orbitofrontal cortex. A covariance analysis further revealed a striking reduction of functional connectivity in the congenitally helpless brain, including a complete decoupling of limbic forebrain regions from midbrain/diencephalic regions. This pattern of brain metabolism suggests that helplessness vulnerability is linked to altered functioning of limbic networks that are key to controlling the hypothalamic-pituitary-adrenal axis. This implies that vulnerable animals have innate deficits in brain systems that would normally allow them to cope with stress, predisposing them in this manner to more readily develop helpless and depressive behaviors.

Quantitative histochemical assessment of oxidative metabolism in the subfornical organ after partial aortic ligature in rats.

Circumventricular organs are considered to be involved in hydromineral homeostatic responses. In this study we used quantitative histochemistry of cytochrome oxidase to evaluate the oxidative metabolic activity of the subfornical organ of rats with a partial aortic occlusion. These rats showed a significant increase in water intake from the second day after the ligature, while natriophilia was already significant on the first day. Greater levels of cytochrome oxidase activity were found in subfornical organs of partial aortic ligated rats when compared with control, providing further evidence for the involvement of this circumventricular structure in fluid homeostasis at least in this hyperdipsic, hypernatriophilic, hyperreninemic and hypertensive experimental model.

[Hepatic alterations in a model of alcoholism in the rat]. / Alteraciones hepáticas en un modelo de alcoholismo en ratas.

Today, there are a great number of investigations about alcoholism. The effects of alcohol had been studied in Medicine, Psychology, Biology, Biochemistry, Physiology or Pharmacology. Many investigations are carried out with humans, however, in most experiments is necessary to use animal models. Many experimental models of alcoholism in animals are usually used in the laboratories and they present several differences among them. In our investigation we have studied the hepatic alterations in an experimental model of alcoholism in the rat because the liver is a very sensitive organ which suffers the effects of alcohol and its metabolites. We try to demonstrate that there are hepatic lesions which allows the use of this experimental in the study of the behavioral and neural parameters in the rat. The experimental model of alcoholism that we propose has been considered appropriate to study the behavioral effects of alcohol, not only because the animals show the characteristic hepatic lesions, but also because they do not suffer manipulations that could alter them and as a consequence bias the behavioral data.