Drugs online research references
J Neuroendocrinol. 1998 Feb;10(2):85-91.
Catecholaminergic control of intracellular free calcium and beta-endorphin secretion of rat pituitary intermediate lobe cells.
Nemethy Z, Horvath G, Makara GB, Acs Z, Barna I.
Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest.
Individual melanotropes and intermediate lobes were tested to elucidate the role of alpha- and beta-adrenergic and D-2 dopamine receptors in the regulation of concentration of intracellular free calcium ([Ca2+]i) and release of beta-endorphin. Hormone secretion was studied in a superfusion system, while [Ca2+]i was measured microspectrofluorimetrically. Noradrenaline (1 microM) resulted in a slight decrease, then a marked increase in [Ca2+]i and secretion of beta-endorphin. The nonselective beta-adrenergic agonist isoproterenol (1 microM) increased [Ca2+]i and secretion of beta-endorphin; this effect was blocked by the beta-antagonist propranolol (10 microM). The alpha-adrenergic agonist phenylephrine (1 microM) increased [Ca2+]i and beta-endorphin secretion, but this effect was not blocked by terazosin or prazosin (alpha1-adrenergic antagonists, 1 microM). Administration of the alpha2-adrenergic agonist xylazine (1 microM) increased [Ca2+]i but did not affect secretion of the hormone. Biphasic effect of noradrenaline was tested in presence of adrenergic and dopaminergic antagonists. The noradrenaline-induced rise in [Ca2+]i and beta-endorphin secretion was decreased by propranolol, but this drug did not modify the inhibition. In the presence of 1 microM sulpiride (selective D-2 dopaminergic antagonist), the inhibitory phase of the curve was abolished, and the subsequent increase was reduced. This suggests that activation of dopamine D-2 receptors is involved not only in the inhibition, but also in the subsequent increase, which may originate from a rebound after the termination of the activation of these inhibitory receptors. Our data suggest the presence of several distinct types of catecholamine receptors in the rat intermediate lobe, and the dominant involvement of D-2 and beta-adrenergic receptors in the noradrenaline-induced regulation of melanotropes.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9535054&dopt=Abstract
Br J Pharmacol. 1998 Apr;123(7):1359-66.
Alpha1L-adrenoceptor mediation of smooth muscle contraction in rabbit bladder neck: a model for lower urinary tract tissues of man.
Kava MS, Blue DR Jr, Vimont RL, Clarke DE, Ford AP.
Roche Bioscience, Palo Alto, CA 94304, USA.
1. The alpha1-adrenoceptor population mediating contractile responses to noradrenaline (NA) in smooth muscles of the bladder neck from rabbit (RBN) has been characterized by use of quantitative receptor pharmacology. 2. Experiments with several 'key' alpha1-adrenoceptor antagonists of varying subtype selectivities (RS-17053, BMY 7378, indoramin, 5-methylurapidil, prazosin, REC 15/2739, SNAP 5089, terazosin, WB 4101, tamsulosin, (+)-cyclazosin and RS-100329) were conducted. Schild regression analyses yielded affinity (mean pKb) estimates of 7.1, 6.2, 8.6, 8.6, 8.4, 9.3, 7.0, 7.4, 8.9, 10.0, 7.1 and 9.3, respectively, although deviations from unit Schild regression slope question the robustness of data for RS-17053 and SNAP 5089. 3. The nature of antagonism by these agents and the profile of affinity determinations generated together suggest that a single alpha1-adrenoceptor subtype mediates contractile responses of RBN to NA. Additional studies with phenylephrine indicated also an agonist-independence of this profile. Pharmacologically, this profile was reminiscent of that described as 'alpha1L'-adrenoceptor, which has been shown to mediate contractions of several tissues including lower urinary tract (LUT) tissues of man. Furthermore, a similarity was noticed between the 'alpha1L'-adrenoceptor described here in RBN and the rabbit and human cloned alpha1a-adrenoceptor (based on data from both whole cell radioligand binding at 37 degrees C and [3H]-inositol phosphates accumulation assays), characterizations of which have been published elsewhere. 4. In conclusion, the RBN appears to provide a predictive pharmacological assay for the study of NA-induced smooth muscle contraction in LUT tissues of man.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9579731&dopt=Abstract
J Pharmacol Exp Ther. 1998 May;285(2):628-42.
Actions of A-131701, a novel, selective antagonist for alpha-1A compared with alpha-1B adrenoceptors on intraurethral and blood pressure responses in conscious dogs and a pharmacodynamic assessment of in vivo prostatic selectivity.
Hancock AA, Brune ME, Witte DG, Marsh KC, Katwala S, Milicic I, Ireland LM, Crowell D, Meyer MD, Kerwin JF Jr.
Abbott Laboratories, Pharmaceutical Products Division, Abbott Park, Illinois, USA.
A-131701 (3-[2-((3aR,9bR)-cis-6-methoxy-2,3,3a,4,5,9b, hexahydro-[1H]-benz[e]isoindol-2-yl)ethyl]pyrido [3',4': 4,5]thieno[3,2-d]pyrimidine-2,4(1H,3H)-dione) is a novel compound previously shown to be selective for alpha-1a sites compared with alpha-1b adrenoceptors in radioligand binding studies and isolated tissue bioassays and to block canine urethral pressure (IUP) responses to exogenous alpha-1 adrenergic agonists to a greater extent than blood pressure responses. In conscious dogs in which IUP and mean arterial blood pressure (MABP) responses were measured periodically up to 24 hr, A-131701 blocked phenylephrine (PHE)-induced increases in IUP to a greater extent than MABP responses, and the blockade of the IUP effects of PHE was significantly different from control for up to 12 hr after doses greater than 0.3 mg/kg p.o., whereas blood pressure effects were of a lesser extent and duration. In addition to the weak antagonism of PHE-induced blood pressure responses, A-131701 also exhibited minimal effects on basal blood pressure in the dog, unlike terazosin, doxazosin or tamsulosin. Pharmacokinetic analysis of plasma samples from dogs indicated that A-131701 had a half-life of 0.4 to 0.8 hr and a bioavailability of 30 to 50% in dogs. Somewhat longer half-lives were observed in rat and monkey, with bioavailability values in the 25 to 30% range. Evidence of nonlinearity of pharmacokinetics was obtained in dogs and monkeys. Pharmacodynamic analysis revealed differences between A-131701 and nonselective alpha-1 adrenoceptor antagonists in selectivity for prostatic versus vascular alpha-1 adrenoceptors based on either extent or duration of blockade, which were either similar to or superior to compounds such as tamsulosin or REC 15/2739. These data demonstrate that A-131701 selectively blocks canine prostatic alpha-1 adrenoceptors for prolonged periods compared with MABP responses in vivo. Therefore, A-131701 should have clinical utility in the pharmacotherapy of benign prostatic hyperplasia.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9580607&dopt=Abstract
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