Biomaterial Database

Prejunctional alpha2-adrenoceptors and peroxide-induced potentiation of norepinephrine release from the bovine iris. 1998

C A Opere, and S E Ohia

Department of Pharmaceutical and Administrative Sciences, Creighton University Health Sciences Center, Omaha, NE 68178, USA.

Peroxides can enhance field-stimulated [3H]norepinephrine ([3H]NE) release in isolated irides from several mammalian species. In the present study, we investigated the role of prejunctional alpha2-adrenoceptors in peroxide-induced potentiation of sympathetic neurotransmission in bovine isolated irides. Isolated hemi-irides were incubated in a Krebs buffered-solution containing [3H]NE and prepared for studies of neurotransmitter release using the superfusion method. Alpha2-adrenoceptor agonists, oxymetazoline, UK-14304 and clonidine inhibited field-stimulated [3H]NE overflow without affecting basal tritium efflux. Pretreatment of tissues with H2O2 (300 microM) had no effect on inhibition of evoked [3H]NE release caused by the alpha2-adrenergic agonists. However, H2O2 (300 microM) caused significant (P < 0.01) leftward shifts of excitatory concentration-response curves to yohimbine (10 nM-1 microM). In contrast, yohimbine (1 microM) did not prevent the enhancement of evoked [3H]NE overflow induced by H2O2 (300 microM). In conclusion, excitatory effects of peroxides on sympathetic neurotransmission in bovine irides are not mediated by prejunctional alpha2-adrenoceptors.

UI	MeSH Term	Description	Entries
D007498	Iris	The most anterior portion of the uveal layer, separating the anterior chamber from the posterior. It consists of two layers - the stroma and the pigmented epithelium. Color of the iris depends on the amount of melanin in the stroma on reflection from the pigmented epithelium.
D009435	Synaptic Transmission	The communication from a NEURON to a target (neuron, muscle, or secretory cell) across a SYNAPSE. In chemical synaptic transmission, the presynaptic neuron releases a NEUROTRANSMITTER that diffuses across the synaptic cleft and binds to specific synaptic receptors, activating them. The activated receptors modulate specific ion channels and/or second-messenger systems in the postsynaptic cell. In electrical synaptic transmission, electrical signals are communicated as an ionic current flow across ELECTRICAL SYNAPSES.	Neural Transmission,Neurotransmission,Transmission, Neural,Transmission, Synaptic
D009451	Neuroeffector Junction	The synapse between a neuron (presynaptic) and an effector cell other than another neuron (postsynaptic). Neuroeffector junctions include synapses onto muscles and onto secretory cells.	Junction, Neuroeffector,Junctions, Neuroeffector,Neuroeffector Junctions
D009638	Norepinephrine	Precursor of epinephrine that is secreted by the ADRENAL MEDULLA and is a widespread central and autonomic neurotransmitter. Norepinephrine is the principal transmitter of most postganglionic sympathetic fibers, and of the diffuse projection system in the brain that arises from the LOCUS CERULEUS. It is also found in plants and is used pharmacologically as a sympathomimetic.	Levarterenol,Levonorepinephrine,Noradrenaline,Arterenol,Levonor,Levophed,Levophed Bitartrate,Noradrenaline Bitartrate,Noradrénaline tartrate renaudin,Norepinephrin d-Tartrate (1:1),Norepinephrine Bitartrate,Norepinephrine Hydrochloride,Norepinephrine Hydrochloride, (+)-Isomer,Norepinephrine Hydrochloride, (+,-)-Isomer,Norepinephrine d-Tartrate (1:1),Norepinephrine l-Tartrate (1:1),Norepinephrine l-Tartrate (1:1), (+,-)-Isomer,Norepinephrine l-Tartrate (1:1), Monohydrate,Norepinephrine l-Tartrate (1:1), Monohydrate, (+)-Isomer,Norepinephrine l-Tartrate (1:2),Norepinephrine l-Tartrate, (+)-Isomer,Norepinephrine, (+)-Isomer,Norepinephrine, (+,-)-Isomer
D010109	Oxymetazoline	A direct acting sympathomimetic used as a vasoconstrictor to relieve nasal congestion. (From Martindale, The Extra Pharmacopoeia, 30th ed, p1251)	Oxymetazoline Hydrochloride,Hydrochloride, Oxymetazoline
D010477	Perfusion	Treatment process involving the injection of fluid into an organ or tissue.	Perfusions
D011810	Quinoxalines		Quinoxaline
D002417	Cattle	Domesticated bovine animals of the genus Bos, usually kept on a farm or ranch and used for the production of meat or dairy products or for heavy labor.	Beef Cow,Bos grunniens,Bos indicus,Bos indicus Cattle,Bos taurus,Cow,Cow, Domestic,Dairy Cow,Holstein Cow,Indicine Cattle,Taurine Cattle,Taurus Cattle,Yak,Zebu,Beef Cows,Bos indicus Cattles,Cattle, Bos indicus,Cattle, Indicine,Cattle, Taurine,Cattle, Taurus,Cattles, Bos indicus,Cattles, Indicine,Cattles, Taurine,Cattles, Taurus,Cow, Beef,Cow, Dairy,Cow, Holstein,Cows,Dairy Cows,Domestic Cow,Domestic Cows,Indicine Cattles,Taurine Cattles,Taurus Cattles,Yaks,Zebus
D003000	Clonidine	An imidazoline sympatholytic agent that stimulates ALPHA-2 ADRENERGIC RECEPTORS and central IMIDAZOLINE RECEPTORS. It is commonly used in the management of HYPERTENSION.	Catapres,Catapresan,Catapressan,Chlophazolin,Clofelin,Clofenil,Clonidine Dihydrochloride,Clonidine Hydrochloride,Clonidine Monohydrobromide,Clonidine Monohydrochloride,Clopheline,Dixarit,Gemiton,Hemiton,Isoglaucon,Klofelin,Klofenil,M-5041T,ST-155,Dihydrochloride, Clonidine,Hydrochloride, Clonidine,M 5041T,M5041T,Monohydrobromide, Clonidine,Monohydrochloride, Clonidine,ST 155,ST155
D006861	Hydrogen Peroxide	A strong oxidizing agent used in aqueous solution as a ripening agent, bleach, and topical anti-infective. It is relatively unstable and solutions deteriorate over time unless stabilized by the addition of acetanilide or similar organic materials.	Hydrogen Peroxide (H2O2),Hydroperoxide,Oxydol,Perhydrol,Superoxol,Peroxide, Hydrogen