Drugs online research references
J Pharmacol Exp Ther. 1992 Mar;260(3):1180-4.
Functional innervation of pig tracheal smooth muscle: neural and non-neural mechanisms of relaxation.
Kannan MS, Johnson DE.
Department of Veterinary Biology, College of Veterinary Medicine, University of Minnesota, St. Paul.
In pig tracheal smooth muscle (TSM), the isometric tension responses to electrical field stimulation (EFS) were compared to exogenous peptides, vasoactive intestinal polypeptide (VIP) and calcitonin gene-related peptide (CGRP), as well as to the nicotinic agonist dimethylphenyl piperazinium chloride (DMPP). The objectives of this study were to understand the mechanisms of nonadrenergic, noncholinergic relaxations of pig TSM and identify some putative candidate substances mediating the neural inhibitory response. In strips of TSM obtained from 6- to 12-week-old pigs set up in vitro in organ baths in Kreb's solution, EFS resulted in frequency-dependent contractions that were abolished by 1 microM atropine or 0.1 microM tetrodotoxin (TTX). Addition of DMPP (20-100 microM) resulted in a transient, atropine-sensitive contraction, which quickly desensitized. EFS failed to elicit any further contractions, but the tissues responded to carbachol. In tissues exposed to DMPP and contracted with carbachol, EFS elicited frequency-dependent relaxations that were unaffected by 1 microM propranolol, abolished by TTX and partially inhibited by omega-conotoxin. At the peak of carbachol-induced contraction, addition of DMPP resulted in rapid relaxation reversing spontaneously to base line, with no significant relaxation to further addition of DMPP. DMPP-induced relaxations were unaffected by TTX or omega-conotoxin. These tissues readily relaxed to 10(-8) M VIP. In carbachol precontracted tissues, VIP elicited concentration-dependent relaxations that quickly desensitized. However, these tissues readily relaxed to DMPP. CGRP produced only weak relaxations.(ABSTRACT TRUNCATED AT 250 WORDS)
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J Invest Dermatol. 1978 Mar;70(3):119-22.
Epinephrine activation of pig skin adenylate cyclase in vivo and subsequent refractoriness to activation.
Iizuka H, Adachi K, Halprin KM, Levine V.
Epinephrine injected intradermally activated pig skin adenylate cyclase and increased the epidermal cyclic AMP level in vivo. This biphasic response reached a maximum in 5 min and gradually decreased thereafter. The simultaneous injection of a cyclic AMP phosphodiesterase inhibitor, isobutyl methyl xanthin (IBMX) potentiated the increase. The simultaneous injection of a specific beta-adrenergic receptor inhibitor, propranolol, inhibited this accumulation of cyclic AMP. After the first activation by epinephrine in vivo, there was a marked refractoriness of the skin (epidermal) adenylate cyclase to subsequent epinephrine stimulation vivo and in vitro. This refractoriness was specific for catecholamine stimulation as responses to histamine were normal. Recovery from refractoriness started at 48 hr and was completed at 1 week after the injection of epinephrine.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=204708&dopt=Abstract
J Ethnopharmacol. 2001 Jan;74(1):83-8.
Relaxant effect of Pimpinella anisum on isolated guinea pig tracheal chains and its possible mechanism(s).
Boskabady MH, Ramazani-Assari M.
Department of Physiology, Ghaem Medical Centre, Mashhad University of Medical Sciences, 91735, Mashhad, Iran.
We have studied the relaxant effect of Pimpinella anisum on isolated guinea pig tracheal chains and its possible mechanism(s). The bronchodilatory effects of aqueous and ethanol extracts and essential oil were examined on precontracted isolated tracheal chains of the guinea pig by 10 microM methacholine in two different conditions including: non-incubated tissues (group 1) and incubated tissues with 1 microM propranolol and 1 microM chlorpheniramine (group 2). In addition, the anticholinergic effects of essential oil and 10 nM atropine were tested by comparing the cumulative log concentration-response curves of methacholine induced contraction of tracheal chains and the effective concentration of methacholine, causing 50% of maximum response (EC(50)) in the presence of essential oil or atropine. Aqueous and ethanol extracts, essential oil and theophylline (1 mM) showed significant relaxant effects compared to those of controls. Although relaxant effect of essential oil was lower than theophylline, there was no significant difference between the effect of aqueous and ethanol extracts and that of theophylline. There was also no significant difference between the relaxant effects obtained in group 1 and 2 experiments. The results also showed parallel rightward shifts of methacholine-response curves and significant increase in EC(50) with the presence of atropine or essential oil. These results indicated bronchodilatory effects of essential oil, aqueous, and ethanol extracts from P. anisum. The results also showed that the relaxant effect of this plant is not due to an inhibitory effect of histamine (H(1)) or stimulatory effect of beta(2)-adrenergic receptors, but due to inhibitory effects on muscarinic receptors.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11137352&dopt=Abstract
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