Drugs online research references
Br J Pharmacol. 1994 Oct;113(2):479-84.
Modulation by neuropeptide Y of parasympathetic nerve-evoked nasal vasodilatation via Y2 prejunctional receptor.
Lacroix JS, Ulman LG, Potter EK.
Prince of Wales Medical Research Institute, Prince of Wales Hospital, Randwick, Sydney, NSW, Australia.
1. In pentobarbitone anaesthetized dogs, preganglionic stimulation of the superior cervical sympathetic nerve (15V, 1 ms, 10 Hz) induced marked reduction of nasal arterial blood flow, whereas parasympathetic nerve stimulation (5 V, 1 ms, 10-30 Hz) evoked frequency-dependent vasodilatation. 2. Sympathetic nerve stimulation for 3 min at 10 Hz evoked significant (P < 0.05) and prolonged attenuation of the vasodilator response to subsequent parasympathetic stimulation. Pretreatment with phentolamine (0.5 mg kg-1 h-1), propranolol (1 mg kg-1) and atropine (0.5 mg kg-1) reduced the vasoconstrictor effect of sympathetic stimulation by 35 +/- 4% whereas the parasympathetic nerve-evoked vasodilatation was not significantly modified. Atropine-resistant parasympathetic vasodilatation remained significantly attenuated for more than 30 min after non-adrenergic sympathetic nerve-evoked vasoconstriction. 3. Vasodilator effects of exogenous vasoactive intestinal polypeptide and peptide histidine isoleucine and vasoconstrictor effects of exogenous neuropeptide Y (NPY) and the NPY analogue [Leu31, Pro34] NPY (Y1-receptor agonist, 8 nmol kg-1), were not altered by adrenoceptor antagonists and atropine f1p4eas the effects of exogenous noradrenaline and acetylcholine were virtually abolished. Attenuation of parasympathetic-evoked vasodilatation could be mimicked by exogenous NPY (8 nmol kg-1) and the NPY analogue, N-acetyl [Leu28, Leu31] NPY 24-36 (Y2-receptor agonist, 20 nmol kg-1) but not by exogenous Y1-receptor agonist. The Y2-receptor agonist did not show significant vasoconstrictor action. 4. It is concluded that sympathetic nerve stimulation attenuates parasympathetic vasodilatation via NPY release acting on prejunctional Y2 receptors.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7834199&dopt=Abstract
Pharm Res. 1994 Nov;11(11):1646-51.
Kinetic analysis of the drug permeation process across the intestinal epithelium.
Yamashita S, Yoshida M, Taki Y, Sakane T, Nadai T.
Faculty of Pharmaceutical Sciences, Setsunan University, Osaka, Japan.
The rat intestinal lumen and the blood vessel were simultaneously perfused to study drug permeation across the intestinal epithelium. On the basis of drug disappearance from the intestinal lumen and its appearance into the vascular outflow, the mean time required for permeation across the intestinal membrane (MPT) and the permeation clearance (CLp) were calculated. MPT values of water, antipyrine, propranolol, imipramine and mannitol, varied from 0.45 min to 9.91 min depending on their physicochemical property. From both MPT and CLp, five drugs were classified as being (i) highly and rapidly absorbed (water, antipyrine), (ii) highly but slowly absorbed (propranolol, imipramine) and (iii) low and slowly absorbed (mannitol). Permeation profiles of these drugs were analyzed based on the diffusion model which defined the parameter for each permeation process, i.e. partitioning to and diffusion through the epithelium and clearance into the blood flow. Propranolol and imipramine partitioned into the membrane at a higher level than the other drugs. However, the clearance of both drugs from the epithelium was extremely slow, suggesting that this process is the rate-limiting step in their permeation. On the other hand, the rate-limiting step in the permeation of water and antipyrine was found to be the diffusion process in the epithelial layer.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7870684&dopt=Abstract
Analyst. 1994 Dec;119(12):2553-6.
In vitro and in vivo studies of drug residue accumulation in pigmented tissues.
Sauer MJ, Anderson SP.
Biochemistry Department, Central Veterinary Laboratory, Addlestone, Surrey, UK.
A procedure was developed to enable ready isolation of melanin granules from pigmented tissues of the bovine eye. The granules were used in a simple in vitro test to model the potential for a range of veterinary drugs to accumulate in melanin-containing tissues such as hair and the choroid/pigmented retinal epithelium (choroid/PRE) of the eye. The beta-agonists clenbuterol and salmeterol, but not salbutamol, showed appreciable binding, as did the beta-blockers propranolol and carazolol and the tranquillizers azaperone and xylazine. All of the natural and synthetic growth promoters tested gave rise to significant binding (17 beta-estradiol, testosterone, alpha-zeranol, diethylstilbestrol and 19-nortestosterone) but progesterone and 17 alpha-trenbolone bound to a lesser extent. To provide a preliminary indication of the validity of the model, animals were treated with clenbuterol for 21 d, to enable the assessment of accumulation in vivo. Clenbuterol was detected in choroid/PRE and hair at high concentrations from the last day of treatment (1779 ng g-1 and 424 ng g-1, respectively) until the end of the study period, 63 d later (512 ng g-1 and 483 ng g-1, respectively). These studies clearly indicate the wider potential for pigmented tissue analysis in monitoring for the use of veterinary drugs (particularly unlicensed substances) in food producing animals. Hair analysis may offer particular advantages for on-farm monitoring and in providing historic information.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7879853&dopt=Abstract
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