phenylthiazolylthiourea and Nerve-Degeneration

1-Phenyl-3-(2-thiazolyl)-2-thiourea (200 mg/kg, 1 h) protected the adrenergic nerve plexus in the mouse atrium against the destructive action of i.v. 5,7-dihydroxytryptamine. Protection was also observed with ethanol (4 g/kg, 1 h) and with nialamide (50 mg/kg, 2 h).

Topics: 5,6-Dihydroxytryptamine; Animals; Drug Interactions; Ethanol; Heart Atria; Male; Mice; Nerve Degeneration; Phenylthiazolylthiourea; Phenylthiourea; Sympathetic Nervous System; Tryptamines

The uptake-accumulation and binding of radioactivity in mouse heart after administration of the catecholamine neurotoxin [3H]6-hydroxydopamine (6-OH-DA, 1 or 3 mg/kg, i.v.) has been investigated. It was confirmed that a substantial portion (8--20%) of the radioactivity taken up and retained by the heart could not be extracted with perchloric acid, in all probability representing covalently bound oxidation products of 6-OH-DA to tissue proteins. Pharmacological analysis showed that a large part of this fraction was associated with the adrenergic nerves. The time-course of the perchloric acid resistant binding to the adrenergic nerves was found to parallel that of the neurotoxic action of 6-hydroxydopamine as evaluated by monitoring the change in [3H]noradrenaline uptake. Calculation of the intranelronal 6-hydroxydopamine concentration (average) needed to induce degeneration showed it to be in the order of 50 mM. The binding ratio for tritium deriving from [3H]6-OH-DA between the intraneuronal and extraneuronal compartments was found to be 10,000 to 30,000, pointing to a very high neuronal specificity for 6-hydroxydopamine. The 'covalent' binding of oxidation products of [3H]6-OH-DA was considerably reduced after desipramine or 1-phenyl-3(2-thiazolyl)-2-thiourea administration, treatments both known to protect the adrenergic nerves from undergoing degeneration. Conversely it was found that the binding increased during conditions known to potentiate the neurotoxic action of 6-hydroxydopamine, e.g., after monoamine oxidase inhibition with nialamide. Subcellular fractionation studies indicated that the predominant site of interaction between 6-hydroxydopamine oxidation products and neuronal proteins is the cytoplasm and the axonal membrane. Analysis of the effect in vivo administration of 6-hydroxydopamine on the field-stimulated induced release of [3H]noradrenaline previously taken up in the adrenergic nerves showed a 6-hydroxydopamine indiced reduction in [3H]noradrenaline release which was approximately proportional to the reduction in the number of nerve terminals. These findings further support the view that 6-hydroxydopamine acts largely in an "all-or-none' fashion with respect to the neurodegenerative action. Administration of [3H]dopamine also resulted in a fraction which was not extractable with perchloric acid, although this fraction was very small compared to that found after an equal dose of [3H]6-hydroxydopamine. These data may indicate that oxida

Topics: Adrenergic Fibers; Animals; Axons; Cell Membrane; Cytoplasm; Desipramine; Dopamine; Humans; Hydrogen Bonding; Hydroxydopamines; Male; Mice; Myocardium; Nerve Degeneration; Nialamide; Norepinephrine; Phenylthiazolylthiourea; Receptors, Adrenergic; Thiourea