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Binding sites labeled by [3H]p-aminoclonidine ([3H]PAC) were characterized in bovine brain membranes prepared from the ventrolateral medulla, the probable site of the antihypertensive action of clonidine and analogs. Comparison was made with [3H]PAC binding to membranes prepared from frontal cortex, which has been studied extensively. Saturation binding(More)
Intraventricular injection of colchicine in rat results in the appearance within hypothalamus of numerous neurons containing the adrenaline-synthesizing enzyme, phenylethanolamine N-methyltransferase, but not the other catecholamine biosynthetic enzymes. Increased PNMT staining in hypothalamus was paralleled by an increase in PNMT activity measured in(More)
In previous experiments we implicated projections from the medial geniculate body (MG) to a subcortical field, involving portions of the posterior caudate-putamen and amygdala, in the classical conditioning of emotional responses to acoustic stimuli in the rat. In the present series of experiments we examined whether intrinsic neurons in the subcortical(More)
We sought to characterize the interactions of an endogenous clonidine-displacing substance (CDS) with the specific receptor sites to which clonidine and its analogs bind: (a) the non-adrenergic imidazole binding site, which is present in the ventrolateral medulla (VLM) but not the frontal cortex, (b) high-affinity and (c) low-affinity states of the alpha(More)
A substance has been isolated from brain which potently inhibits the binding of clonidine to brain membranes (clonidine displacing substance, CDS). We sought to determine if CDS is biologically active on smooth muscle. CDS had no effect on vascular smooth muscle. In contrast, CDS potently contracted rat gastric fundus strips in a dose dependent manner. The(More)
A substance has been isolated from bovine brain which displaces 3H-clonidine binding to rat brain membranes (clonidine-displacing substance; CDS). To determine whether CDS is similar to the antihypertensive agent clonidine, the in vitro binding properties of partially-purified CDS and its physiological action in the rostral ventrolateral medulla were(More)
We sought to isolate and partially purify proteins corresponding to the binding element of the imidazoline receptor (IR) from adrenal chromaffin cell membranes. These cells express IRs of the I-2 subclass and not alpha 2-adrenergic receptors. Proteins were solubilized in 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate-containing buffer and were(More)
Glutamic acid decarboxylase (GAD), the enzyme which synthesizes the inhibitory transmitter gamma-aminobutyric acid (GABA), was localized immunocytochemically within cells and processes distributed throughout the ventrolateral medulla. In caudal regions, GAD-stained cells were adjacent to the 'precerebellar' lateral reticular nucleus and partially overlapped(More)
Clonidine-displacing substance (CDS) from brain is biologically active in the kidney and stomach and on platelets. To determine whether CDS is contained in these and other peripheral tissues, homogenates of fresh brain, eight other organs and serum from rat were ultrafiltered (less than 10,000 mol. wt only), dried and extracted with methanol. Evaluation by(More)
Identification of nonadrenergic binding sites for clonidine and related imidazolines in brain and peripheral tissues and partial purification of an endogenous ligand for these sites have led to the postulation of a novel transmitter/receptor system. The receptors seem to be present in adrenal medulla and to regulate chromaffin cell function. The present(More)