Drugs online research references
Br J Pharmacol. 1995 Feb;114(4):745-50.
Mediation of noradrenaline-induced contractions of rat aorta by the alpha 1B-adrenoceptor subtype.
Testa R, Guarneri L, Poggesi E, Simonazzi I, Taddei C, Leonardi A.
Research and Development Division, Recordati S.p.A., Milan, Italy.
1. The subtypes of alpha 1-adrenoceptor mediating contractions to exogenous noradrenaline (NA) in rat aorta have been examined in both biochemical and functional studies. 2. Incubation of rat aortic membranes with the irreversible alpha 1B-adrenoceptor antagonist, chloroethylclonidine (CEC: 10 microM) did not change the KD of [3H]-prazosin binding in comparison to untreated membranes, but reduced by 88% the total number of binding sites (Bmax). 3. Contractions of rat aortic strips to NA after CEC (50 microM for 30 min) incubation followed by repetitive washing, showed a marked shift in the potency of NA and a partial reduction in the maximum response. The residual contractions to NA after CEC incubation were not affected by prazosin (10 nM). 4. The competitive antagonists prazosin, terazosin, (R)-YM-12617, phentolamine, 5-methylurapidil and spiperone inhibited contractions to NA with estimated pA2 values of 9.85, 8.54, 9.34, 7.71, 7.64 and 8.41, respectively. 5. The affinity of the same antagonists for the alpha 1A- and alpha 1B- adrenoceptors was evaluated by utilizing membranes from rat hippocampus pretreated with CEC, and rat liver, respectively. 5-Methylurapidil and phentolamine were confirmed as selective for the alpha 1A-adrenoceptors, whereas spiperone was alpha 1B-selective. 6. A significant correlation was found between the pA2 values of the alpha 1-adrenoceptor antagonists tested and their affinity for the alpha 1B-adrenoceptor subtype, but not for the alpha 1A-subtype. 7. In conclusion, these findings indicate that in rat aorta most of the contraction is mediated by alpha 1B-adrenoceptors, and that the potency (pA2) of an antagonist in this tissue should be related to its antagonistic effect on this subtype of the alpha 1-adrenoceptor population.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7773533&dopt=Abstract
Neurourol Urodyn. 1995;14(2):141-52.
Autonomic dysreflexia in a rat model spinal cord injury and the effect of pharmacologic agents.
Rivas DA, Chancellor MB, Huang B, Salzman SK.
Department of Urology, Jefferson Medical College, Thomas Jefferson University, Philadelphia, PA 19107, USA.
The object of this study was to develop a spinal cord injury (SCI) rat model for autonomic dysreflexia (AD), assessing the effect of alpha-adrenergic and calcium channel blockade and to determine the relationship of detrusor-external sphincter dyssynergia (DESD) to the development of AD. A laminectomy was performed in male rats at the T4 or T10 level and a controlled 50 g cm blunt SCI was induced using an impounder. Four weeks after injury, changes in arterial blood pressure and heart rate were monitored while simultaneous cystometry (CMG) and pelvic floor electromography (EMG) were performed in vivo in sham (control) and spinal cord injured rats. The effects of terazosin (0.1 mg/kg), diltiazem (0.5 mg/kg), and oxybutynin chloride (0.1 mg/kg) on hemodynamic changes were assessed independently. Both T4 and T10 SCI rat displayed evidence of DESD (enhanced pelvic floor EMG activity at cystometric capacity) while control rats did not. Only T4 injured rats exhibited evidence of AD, with mean blood pressure elevations from 82.9 +/- 13.6 to 93.9 +/- 11.3 mm Hg (P < 0.01) and a mean heart rate decrease from 332.2 +/- 56.5 to 311.1 +/- 54.5 beats/min (P = 0.02) at cystometric capacity. The intravenous administration of terazosin or diltiazem abolished the AD response during CMG. The administration of oxybutynin exhibited the ability to increase bladder capacity and improve compliance in all 3 groups but did not blunt AD. The rat model of SCI effectively reproduced hemodynamic changes consistent with the AD complex in T4 level SCI but not T10 level SCI animals, despite incomplete lesions. Blockade with either an alpha-1 or a calcium channel antagonist effectively ablated the AD response to bladder distention. Anticholinergic agents had no effect on AD. DESD frequently accompanies autonomic dysreflexia, although the development of AD is not a prerequisite for DESD.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7780441&dopt=Abstract
Biol Pharm Bull. 1994 Aug;17(8):1126-9.
Comparison of displacemental potencies of terazosin enantiomers for alpha 1-adrenoceptor subtypes.
Maruyama K, Ohkura N, Yagi Y, Nagatomo T.
Department of Pharmacology, Niigata College of Pharmacy, Japan.
The present study was designed to assess displacemental potencies of terazosin and its isomers for alpha 1 High and alpha 1 Low adrenoceptor subtypes in rat brain, heart, bovine prostate and canine aorta using a radioligand binding assay method. Although no significant difference in pKi values of each terazosin isomer for alpha 1 High in canine aorta and rat brain were observed, the displacemental potency of (S-)terazosin for those in rat heart and bovine prostate was stronger than that of (R+)isomer (p < 0.01). On the other hand, only in alpha 1 Low subtypes of bovine prostate was stronger displacemental potency of (S-)terazosin than (R+)isomer (p < 0.05) observed. Thus, these results imply that there is a different affinity between (S-)terazosin and (R+)isomer on the alpha 1 High in bovine prostate and rat heart and alpha 1 Low in bovine prostate.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7820122&dopt=Abstract
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