Drugs online research references
J Neurosci. 1989 Mar;9(3):923-42.
Cholinergic regulation of arterial pressure by the C1 area of the rostral ventrolateral medulla.
Giuliano R, Ruggiero DA, Morrison S, Ernsberger P, Reis DJ.
Division of Neurobiology, Cornell University Medical College, New York, New York 10021.
In anesthetized, paralyzed rats intravenous administration of the acetylcholinesterase inhibitor physostigmine (PHY) (100 micrograms/kg) evoked a dose-related rise in arterial pressure (AP) and heart rate (HR) and an associated increase in sympathetic nerve activity (SNA). The responses to PHY were blocked by electrolytic lesions of, or microinjection of kainic acid into, a specific site in the rostral ventrolateral medulla containing a cluster of neurons immunoreactive for the adrenaline-synthesizing enzyme phenylethanolamine N-methyltransferase and corresponding to the C1 area of the nucleus reticularis rostroventrolateralis (RVL). The C1 area and its surround contain a heretofore unrecognized network of varicose neuronal processes and perikarya labeled immunocytochemically with a monoclonal antibody to the ACh-synthesizing enzyme, choline acetyltransferase (CAT). PHY increased, by over 3-fold, the spontaneous activity of reticulospinal cardiovascular neurons in the C1 area which excite preganglionic sympathetic neurons in the intermediolateral spinal column. The effects of PHY on AP, SNA, and the discharge of reticulospinal neurons were blocked by systemic administration of the muscarinic antagonist scopolamine. Microinjections within the C1 area of the RVL of scopolamine, the M2-selective muscarinic receptor antagonist AF-DX 116, or the high-affinity choline uptake inhibitor hemicholinium-3 blocked the pressor effects of PHY. The nicotinic antagonist hexamethonium and the M1-selective muscarinic receptor antagonist pirenzepine were without effect. We conclude that (1) the increases in AP, HR, and SNA elicited by the systemic administration of PHY result from the augmented action of ACh released from cholinergic terminals within the C1 area of the RVL; (2) the locally released ACh acts through muscarinic receptors of the M2 subtype within the C1 area to produce excitation of intrinsic reticulospinal sympathoexcitatory neurons, thereby increasing the activity of sympathetic preganglionic neurons and consequently elevating AP and HR; and (3) while the specific function of the cholinergic innervation of the C1 area in cardiovascular regulation is unknown, it may contribute to the tonic regulation of AP.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=2926485&dopt=Abstract
J Neurosci. 1985 Sep;5(9):2407-14.
Quantitative in vivo receptor binding. II. Autoradiographic imaging of muscarinic cholinergic receptors.
Frey KA, Ehrenkaufer RL, Agranoff BW.
The in vivo distribution of [3H]scopolamine in rat brain following establishment of constant, saturating arterial tracer concentrations was examined with the use of quantitative autoradiography. The equilibrium drug distribution, studied 240 min after initiation of tracer infusion, was highly correlated with the regional density of muscarinic receptor sites determined in vitro in the same animals by autoradiographic analysis of [3H]quinuclidinyl benzilate binding. Brain regions of highest receptor density were generally correlated with known terminal fields of cholinergic neurons, and they demonstrated a protracted time course of in vivo labeling. An exception was noted in the basal pons, where a receptor population of high density without documented cholinergic innervation was rapidly labeled. It is suggested that synaptic muscarinic receptors are labeled slowly, as a consequence of either restricted tracer accessibility or competition between tracer and endogenous acetylcholine for available binding sites, and that the pontine receptors may be functionally distinct from those in other brain regions. The in vivo equilibrium binding technique used in the present study results in regional tissue radioligand concentrations directly proportional to receptor density and may, thus, provide a basis for receptor imaging in the human brain by means of positron emission tomography.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=4032003&dopt=Abstract
Eur J Pharmacol. 1993 Feb 16;231(3):347-54.
Activation of 5-HT2 receptors facilitates depolarization of neocortical neurons by N-methyl-D-aspartate.
Rahman S, Neuman RS.
Faculty of Medicine, Memorial University, St. John's Newfoundland, Canada.
The interaction between serotonin and excitatory amino acid agonists at rat neocortical neurons was investigated using the grease-gap recording method. Depolarization evoked by 50 microM N-methyl-D-aspartate was dose dependently facilitated by serotonin (5-HT) (1 to 100 microM) giving a bell-shaped dose-response curve with maximum enhancement at 30 microM. In contrast, quisqualate and kainate depolarizations were not enhanced. Subnanomolar concentrations of methysergide, ritanserin and spiperone, but not ICS 205-930, attenuated the 5-HT enhancement, compatible with 5-HT2, but not 5-HT1 or 5-HT3 receptor subtype involvement. Enhancement was observed with 5-HT2 receptor agonists, whereas 5-HT1 receptor subtype agonists had either no effect (1B and 1C) or reduced (1A) the N-methyl-D-aspartate depolarization. Scopolamine and prazosin reduced the N-methyl-D-aspartate depolarization and blocked facilitation induced by carbachol and phenylephrine, but not that due to 5-HT. Tetrodotoxin reduced the N-methyl-D-aspartate depolarization, but the facilitation by 5-HT persisted. Activators of protein kinase C (phorbol diacetate and 1-oleoyl-2-acetyl-sn-glycerol) did not mimic the serotonin facilitation. We conclude that serotonin enhances N-methyl-D-aspartate depolarization of rat cortical neurons through activation of 5-HT2 receptors, however the cellular mechanism underlying the facilitation remains to be established.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8449227&dopt=Abstract
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