Down-regulation of neurotensin receptors after ligand-induced internalization in rat primary cultured neurons.

When rat cultured neurons were incubated with unlabelled neurotensin (3 nM) for 1 or 24 h at 37 degrees C, the [3H]-neurotensin specific binding measured in cell homogenates was decreased to about 35 and 65% of control values, respectively. In these experiments, the decreases in binding corresponded to reductions of Bmax values without changes in the affinity. The slow neurotensin-induced receptor down-regulation is thought to result from receptor degradation since it was reduced by the lysosomotropic drugs chloroquine and methylamine and because no change in neurotensin mRNA level could be measured after the neurotensin stimulation.

Fractionation of human brain by differential and isopycnic equilibration techniques.

Fractionation of brain tissue by either differential or isopycnic centrifugation is a useful cytological and biochemical tool to study the intracellular localization of neuronal elements involved in neurotransmission. Several neuroreceptors and uptake sites were found to display a subcellular bimodal distribution in rat brain. However, in the human brain, little is known about the subcellular distribution of neurotransmitter receptors and amine uptake sites.

Subcellular distribution of receptor sites in human brain: differentiation between heavy and light structures of high and low density.

Studies of the subcellular localization of neuroreceptors in the rat brain have shown that most of them are associated with light and low density subcellular fractions. In two human brain areas, quite different subcellular distributions were observed. After fractionation by differential centrifugation of frontal cortex homogenates, benzodiazepine and serotonin 5-HT2 receptors were mainly found in the heavy mitochondrial (M) fraction, whereas mu-opiate and muscarinic cholinergic receptors were mainly concentrated in the microsomal (P) fraction.

Rapid agonist-induced decrease of neurotensin receptors from the cell surface in rat cultured neurons.

The regulation of neurotensin receptors was studied in vitro in primary cultures of neuronal cells. High affinity receptors for [3H]neurotensin were found in homogenates and at the cell surface of intact neurons cultured from the brain of rat embryos. When intact cells were incubated with 3 nM neurotensin (1-13), a rapid decrease in [3H]neurotensin binding was observed; about 60% of neurotensin receptors disappeared from the cell surface in less than 15 min.

[3H]GBR 12935 binding to dopamine uptake sites: subcellular localization and reduction in Parkinson's disease and progressive supranuclear palsy.

[3H]GBR 12935 bound with high affinity to dopamine uptake sites in rat striatum where a close parallelism was observed between the subcellular localization profiles for [3H]dopamine uptake and [3H]GBR 12935 specific binding. Using the same ligand, we characterized the dopamine uptake sites in human striatum: the mean KD value was 3.2 nM and the specific binding was inhibited by several dopamine uptake blockers but with slightly lower affinities than those observed in the rat.

Regional and subcellular localization in human brain of [3H]paroxetine binding, a marker of serotonin uptake sites.

The characteristics of the binding of [3H]paroxetine, a selective serotonin (5-HT) uptake blocker, were investigated in human brain. The Kd value was 0.23 +/- 0.

Benzodiazepine receptors in normal human brain, in Parkinson's disease and in progressive supranuclear palsy.

Benzodiazepine receptors have been characterized in human brain. They have been localized mainly in the cerebral cortex and a synaptosomal enrichment was observed after brain fractionation by differential centrifugation. Benzodiazepine receptors were studied in Parkinson's disease and in progressive supranuclear palsy (PSP).

Benzodiazepine receptors in human brain: characterization, subcellular localization and solubilization.

1. Benzodiazepine receptors have been characterized in human brain mainly using [3H]-Ro 15-1788 and [3H]-flunitrazepam. Both ligands present a very high affinity for the receptor sites (Kd values of 0.