Drugs online research references
Neurosci Behav Physiol. 1998 Jul-Aug;28(4):386-91.
Role of the cholinergic systems of the dorsal and ventral striatum of the rat brain in controlling learned movements.
Dubrovskaya NM, Zhuravin IA.
I. M. Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, St. Petersburg, Russia.
Comparative studies were performed of the effects of injections of a cholinergic agonist (carbachol) and antagonist (scopolamine) into the ventral and dorsal striatum on the performance of a learned movement involving prolonged maintenance of extension of the forelimb in rats. Doses of carbachol (0.03-3.00 micrograms) into the ventral striatum were accompanied by increases in the numbers of movements with prolonged maintenance of extension with application of pressure against an obstacle, with a simultaneous decrease in the percentage of rapid nonreinforced movements (by an average of 18.8%). Injections into the dorsal striatum disrupted slow movements which were not reinforced during training, on a background of stable performance of the learned reflex. Doses of scopolamine (0.3-3.0 micrograms) into both the dorsal and ventral parts of the striatum produced increases (by 22.7 +/- 8.2% and 68.9 +/- 14.3%) in the numbers of rapid nonreinforced movements typical of the repertoire of untrained animals. These data led to the suggestion that the cholinergic system of the ventral striatum is involved in the maintenance of forelimb muscle tone in rats during the performance of movements in which pressure is applied to an obstacle. The cholinergic system of the dorsal striatum does not have this property, but plays a significant role in the process of learning new sensory-controlled movements.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9762709&dopt=Abstract
Life Sci. 1998;63(13):1169-82.
Heterologous regulation of muscarinic and beta-adrenergic receptors in rat cardiomyocytes in culture.
Myslivecek J, Lisa V, Trojan S, Tucek S.
Institute of Physiology, Academy of Sciences of the Czech Republic, Prague.
Previous work indicated that hyperstimulation of muscarinic receptors brings about profound changes not only in the density of the muscarinic receptors, but also of the beta-adrenoceptors in rat heart atria in vivo. We have now investigated whether a similar receptor cross-regulation occurs in cardiomyocytes in vitro. Cardiomyocytes from 3-4 day old rats were exposed to chemical agents on days 5-6 in culture. Densities of muscarinic and beta-adrenergic receptors were measured according to the binding of N-[3H]methylscopolamine and [ H]CGP 12177, respectively, to cell surface membranes and cell homogenates. Exposure of cells to the muscarinic agonist carbachol (1 mmol/l) brought about a profound decrease in the number of muscarinic receptors. The number of beta-adrenoceptors displayed biphasic changes, being augmented after 24 h (by 20-45% on the cell surface and by 29% in the homogenate) and diminished after 48 h and 72 h (after 48 h, decrease by 44-75% on the cell surface and by 36% in the homogenate). These effects of carbachol were not prevented by dimethylaminopropyl-bis-indolylmaleimide, the inhibitor of protein kinase C. Exposure of cells to the beta-adrenoceptor agonist isoprenaline (0.1 mmol/l) strongly diminished the number of beta-adrenoceptors on the cell surface and in the homogenate. The density of muscarinic receptors on the cell surface was diminished by 24-43% after 24 h exposure to isoprenaline and unchanged after 48 h, whereas the concentration of muscarinic receptors in the homogenate was unchanged after 24 h and increased by 20% after 48 h. The isoprenaline-induced decrease in the density of cell surface muscarinic receptors could not be simulated by forskolin and was not abolished by the protein kinase A inhibitors Rp-cAMPS and HA-1004. Dibutyryl cyclic AMP diminished the density of cell surface muscarinic receptors more than that of the beta-adrenergic receptors. Our data reveal a novel phenomenon of a biphasic change (an increase followed by a loss) in the density of beta-adrenoceptors during exposure of cardiocytes to carbachol. Activation of beta-adrenoceptors brings about less conspicuous changes in the density of muscarinic receptors. The observed phenomena of receptor cross-regulation cannot be explained by simple activations of protein kinases A and C.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9763212&dopt=Abstract
Proc Natl Acad Sci U S A. 1998 Oct 13;95(21):12683-8.
Memory-enhancing effects of secreted forms of the beta-amyloid precursor protein in normal and amnestic mice.
Meziane H, Dodart JC, Mathis C, Little S, Clemens J, Paul SM, Ungerer A.
Laboratoire Ethologie et Neurobiologie, Universite Louis Pasteur, Unite de Recherche Associee-Centre National de la Recherche Scientifique 1295, 7 rue de l'Universite, 67000 Strasbourg, France.
When administered intracerebroventricularly to mice performing various learning tasks involving either short-term or long-term memory, secreted forms of the beta-amyloid precursor protein (APPs751 and APPs695) have potent memory-enhancing effects and block learning deficits induced by scopolamine. The memory-enhancing effects of APPs were observed over a wide range of extremely low doses (0.05-5,000 pg intracerebroventricularly), blocked by anti-APPs antisera, and observed when APPs was administered either after the first training session in a visual discrimination or a lever-press learning task or before the acquisition trial in an object recognition task. APPs had no effect on motor performance or exploratory activity. APPs695 and APPs751 were equally effective in the object recognition task, suggesting that the memory-enhancing effect of APPs does not require the Kunitz protease inhibitor domain. These data suggest an important role for APPss on memory processes.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9770546&dopt=Abstract
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