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Clonidine, an antihypertensive drug, binds to alpha 2-adrenergic and imidazoline receptors. The endogenous ligand for imidazoline receptors may be a clonidine-displacing substance, a small molecule isolated from bovine brain. This clonidine-displacing substance was purified and determined by mass spectroscopy to be agmatine (decarboxylated arginine),(More)
Agmatine, decarboxylated arginine, is a metabolic product of mammalian cells. Considering the close structural similarity between L-arginine and agmatine, we investigated the interaction of agmatine and nitric oxide synthases (NOSs), which use L-arginine to generate nitric oxide (NO) and citrulline. Brain, macrophages and endothelial cells were respectively(More)
Recent evidence suggests that agmatine, which is an intermediate in polyamine biosynthesis, might be an important neurotransmitter in mammals. Agmatine is synthesized in the brain, stored in synaptic vesicles in regionally selective neurons, accumulated by uptake, released by depolarization, and inactivated by agmatinase. Agmatine binds to(More)
We compared the properties of mammalian arginine decarboxylase (ADC) and ornithine decarboxylase (ODC) in rat liver and brain. Mammalian ADC is thermally unstable and associated with mitochondrial membranes. ADC decarboxylates both arginine (Km = 0.75 mM) and ornithine (Km = 0.25 mM), a reaction not inhibited by the specific ODC inhibitor,(More)
Agmatine (decarboxylated arginine), an endogenous ligand for imidazoline receptors, has been identified in brain where it is synthesized from arginine by arginine decarboxylase. Here we report a mechanism for the transport of agmatine into rat brain synaptosomes. The uptake of agmatine was energy- and temperature-dependent and saturable with a Km of 18.83(More)
The distribution of agmatine (decarboxylated arginine) was mapped in the central nervous system (CNS) in the rat. Agmatine-like immunoreactivity was identified by light microscopy, exclusively in the cytoplasm of neuronal perikarya. Immunoreactive neurons were present in the cerebral cortex, predominantly within laminae VI and V and, to a lesser extent, III(More)
Imidazoline (I) receptors constitute a family of nonadrenergic high-affinity binding sites for clonidine, idazoxan, and allied drugs. One major subclass, the I1 receptors, whose subcellular distribution and signal transduction mechanisms are uncertain, partly mediates the central hypotensive actions of clonidine-like drugs. The I2 receptors, another(More)
We sought to determine whether agmatine (decarboxylated arginine), a bacterial product recently discovered for the first time in mammalian brain, was contained in other organs. A method was developed for isolation of agmatine from tissue and detection by RP-HPLC following solid-liquid extraction and derivatization with o-phthalaldehyde and mercaptoethanol.(More)
Neuropeptide Y (NPY) and peptide YY (PYY) are homologous 36 amino acid amidated peptides that often, but not always, exert similar actions and binding profiles. The present study of cultured cells confirms that both peptides as well as radioiodinated analogs, i.e. 125I-Bolton-Hunter-NPY (125I-BH-NPY) and 125I-peptide YY (125I-PYY), show high affinity to(More)