The interaction between the cholinergic and dopaminergic system in learning and memory process in rats.

In normal rats, muscarinic acetylcholine receptors (mAChRs) have a facilitating role on both short-term and long-term memory tested by Y-maze task and multi-trial passive avoidance test, respectively, since scopolamine, a specific mAChRs antagonist, impairs both types of memory. A low dose of nicotine (0.3 mg/kg b.

The modulator role of the hypothalamic paraventricular nucleus on immune responsiveness.

Role of the paraventricular nucleus of the hypothalamus (PVH) upon immune modulation was studied by either mechanically destroying the PVH (PVHL) or by isolating the PVH (PVHI) with a knife-cut. PVHL or PVHI manipulations induced significant leukopenia characterized by a decrease in the number of neutrophils and lymphocytes two weeks post surgery. The numbers of circulating monocytes and eosinophils were not affected by PVH interventions.

Role of the mesotelencephalic dopamine system in learning and memory processes in the rat.

The effects of lesioning the ventral tegmental area or substantia nigra pars reticulata by means of bilateral microinjections of two doses of kainic acid (50 ng/250 nl and 100 ng/500 nl) or 6-hydroxydopamine (8 microg/4 microl) were investigated to clarify the role of the mesotelencephalic dopamine system in learning and memory processes. Our findings suggest that ventral tegmental area and substantia nigra dopaminergic neurons play an important role in retention of both short-term memory, tested in the Y-maze task and long-term memory evaluated with the multi-trial passive avoidance test, without affecting memory acquisition. As compared to short-term memory, long-term memory is more susceptible to the decreased dopamine level in nervous structures involved in processing and storage of information.

Effects of nicotine on memory impairment induced by blockade of muscarinic, nicotinic and dopamine D2 receptors in rats.

Scopolamine dose-dependently inhibits passive avoidance latency and decreases spontaneous alternation in the Y-maze, suggesting effects on long-term and short-term memory, respectively. Chlorisondamine (10 mg/kg), a compound which produces a long-lasting central nicotinic receptor blockade, did not affect short-term and long-term memory performance. In normal rats, nicotine at the doses of 0.

Memory impairment induced by chronic intracerebroventricular infusion of beta-amyloid (1-40) involves downregulation of protein kinase C.

Signaling pathways underlying the cognitive deficit of the Alzheimer's disease (AD) are not completely understood. Protein kinase C (PKC), a major neuronal protein plays a critical role in cellular signal transduction and it is known to be subjected to modulation in AD. We showed previously that, chronic infusion of beta-amyloid (1-40) into rat cerebroventricle leads to deficit in spatial and non-spatial memory formation.

Memory deficits and increased emotionality induced by beta-amyloid (25-35) are correlated with the reduced acetylcholine release and altered phorbol dibutyrate binding in the hippocampus.

In the present study we found that chronic infusion of beta-amyloid fragment (25-35) at nanomolar concentration into rat cerebral ventricle impairs learning and memory. At a concentration of 3 nmol/day but not 0.3 nmol/day, beta-amyloid significantly reduced the spontaneous alternation behavior and the memory performance in the water maze and multiple passive avoidance tests.

Polyurethanes based on dihydroxamic acids. Synthesis, chemical characterization, and biological activity.

A series of segmented polyurethanes based on polyethylene oxide/polycaprolactone diol, isophorone diisocyanate, and dihydroxamic acids were synthesized and characterized. Biocompatibility and antitumoral activity were in vivo tested on Wistar male rats and Wistar rats affected with Walker 256 carcinosarcoma, respectively. The effect of dihydroxamic acid structure on the biological properties was determined.

[Ginkgo biloba extract (EGb 761) as an antioxidant factor of exogenous origin].

Extracted from Ginkgo biloba leaves, the EGb 761 has a great number of therapeutical properties and anti-stress effects, for example the antioxidant one. We estimated in our experiment the influence of a chronic treatment with EGb 761 on the concentration of the main product of lipidic degradation--malondialdehyde (MDA), in cerebral cortex, in diencephalon, thymus and gastric mucosa. The experiment was performed on Wistar rats, male, young.

The ways through which the hypothalamic paraventricular nucleus (PVH) and the medial hypothalamus affect the organism's defence function.

In the rats, mechanical lesion or isolation of the PVH either alone or together with the medial hypothalamic sympathetic area, which includes hypophyseotropic area, too, induces a long lasting decrease of the total number of leukocytes and of the most components of the leukocytary formula, which are attributed mainly to the decreased sympathetic tonus, induced by medial hypothalamus disconnection.

The role of the hypothalamic paraventricular nucleus upon the activity of thyroid and adrenal glands and their relation with body defense function.

Lesion of the PVH or its isolation--either alone or together with the medial hypothalamus, at fronto-lateral or complete level, induces a significant decrease in plasma thyroxine and a negligible modification of triiodothyronine. Variations recorded with various groups, having the medial hypothalamus deconnected, suggest that the main thyroliberin secreting (TRH) region is located at the level of PVH. Immunization of animals restores the thyroid function in the animals with damaged PVH, under the action of thyrotropin (TSH) of lymphocyte origin.

The effect of partial or total medial hypothalamic isolations on lipid metabolism in rats.

Medial hypothalamic isolation in the rat occurring under free food acces or after 24 hours starvation determines a significant increase in serum lipemia, serum esterified fatty acids and carcass fat. A significant rise in carcass fat was evident in rats made hyperphagic by medial hypothalamus isolation and maintained on limited food intake. It has been concluded that the VMH nuclei are involved in the control of the lipid metabolism primarily through the inhibitory effect exerted on the lateral hypothalamic parasympathetic area.

Feeding behaviour in rats with isolated medial hypothalamus as a function of ambient temperature.

The experiments of mechanical isolation of medial hypothalamus from the lateral hypothalamus and the preoptic anterior hypothalamic (POAH) region in rats showed that: 1. The interruption of neural connections between POAH area and medial hypothalamus do not prevent the decrease of food intake which normally occur in a hot environment. 2.

Lipid metabolism in rats with isolated medial hypothalamus.

Based on determinations of the serum total cholesterolemia, triglyceridemia, free fatty acids and obesity Lee index, performed in rats with isolated medial hypothalamus--VMH included--which had either free food access, or after 24 hours of starvation, or maintained on limited food intake, it has been concluded that the VMH nucleus is involved in the control of lipid metabolism especially through its inhibitory action on the lateral hypothalamic parasympathetic area.

The hypothalamus and protein metabolism in rats.

Using the technique of mechanical isolation of the medial hypothalamus from the rest of the CNS, it has been concluded--based on total serum protein content, protein fractions as well as total serum amino acids--that under resting conditions the hypothalamic influence upon protein metabolism is achieved through the control exerted upon endocrine system rather than by a direct neural mechanism. The authors' results show that aminoacidemia is not a determining factor in feeding behaviour.

Carbohydrate metabolism in rats after partial or total isolation of the medial hypothalamus.

After medial hypothalamic deafferentation at complete (CD), frontal (FD), or frontolateral (FL) levels, at the same time with adrenocortical hormone determination, sensitivity to insulin and insulinemia were determined at a postoperative time, when adenohypophyseal hormonogenetic process concerned to ACTH and growth hormone, is reverted to the normal. The glucose assimilation coefficient (K) was followed weekly for a month postoperatively. Insulin sensitivity decreased after CD and increased after FD.

Feeding behavior in the rat with isolated medial hypothalamus.

After complete, unilateral, frontolateral, dorsal isolation of the medial hypothalamus, VMH included, or fornix section above the hypothalamus, total food consumption and diurnal pattern of food intake were followed 85 days postoperatively. It is suggested that the saftety signals are generated not only in VMH nucleus, but in a VMH-retrochiasmatic region located anteriorly to the VMH.