Differential subcellular distribution of rat brain dopamine receptors and subtype-specific redistribution induced by cocaine

Abstract

We investigated the subcellular distribution of dopamine D 1 , D 2 and D 5 receptor subtypes in rat frontal cortex, and examined whether psychostimulant-induced elevation of synaptic dopamine could alter the receptor distribution. Differential detergent solubilization and density gradient centrifugation were used to separate various subcellular fractions, followed by semi-quantitative determination of the relative abundance of specific receptor proteins in each fraction. D 1 receptors were predominantly localized to detergent-resistant membranes, and a portion of these receptors also floated on sucrose gradients. These properties are characteristic of proteins found in lipid rafts and caveolae. D 2 receptors exhibited variable distribution between cytoplasmic, detergent-soluble and detergent-resistant membrane fractions, yet were not present in buoyant membranes. Most D 5 receptor immunoreactivity was distributed into the cytoplasmic fraction, failing to sediment at forces up to 300,000g, while the remainder was localized to detergent-soluble membranes in cortex. D 5 receptors were undetectable in detergent-resistant fractions or raft-like subdomains. Following daily cocaine administration for seven days, a significant portion of D 1 receptors translocated from detergent-resistant membranes to detergent-soluble membranes and the cytoplasmic fraction. The distributions of D 5 and D 2 receptor subtypes were not significantly altered by cocaine treatment. These data imply that D 5 receptors are predominantly cytoplasmic, D 2 receptors are diffusely distributed within the cell, whereas D 1 receptors are mostly localized to lipid rafts within the rat frontal cortex. Dopamine receptor subtype localization is susceptible to modulation by pharmacological manipulations that elevate synaptic dopamine, however the functional implications of such drug-induced receptor warrant further investigation.

Psychostimulants, Brain Membrane Lipids and Dopamine Transmission

“…For instance, repeated cocaine administration (20 mg/kg, i.p.) for seven days induces translocation of dopamine receptors in rat frontal cortex [37]. Moreover, dopamine D1 receptors (D1R) translocate from lipid raft to non-lipid raft and the cytoplasmic fractions of the frontal cortex following cocaine treatment whereas the localization of dopamine D5 receptors (D5R) and dopamine D2 receptors (D2R) were not significantly altered.…”

Lipid rafts, synaptic transmission and plasticity: Impact in age-related neurodegenerative diseases

“…Dopamine D 1 Rs were found to interact with caveolin-1 in both COS-7 and in the rat brain (Kong et al, 2007;Voulalas et al, 2011). In COS-7 cells, upon D 1 R agonist binding, there is an increased partition of the receptor to lipid rafts and internalization through caveolae (Kong et al, 2007).…”

“…In COS-7 cells, upon D 1 R agonist binding, there is an increased partition of the receptor to lipid rafts and internalization through caveolae (Kong et al, 2007). Interestingly, cocaine administration for several days, which presumably leads to sustained changes in the degree of activation of dopaminergic receptors, causes a shift of D 1 R to non-raft fractions in the rat frontal cortex (Voulalas et al, 2011). In clear contrast with the D 1 R, which within the rat frontal cortex is mostly localized to lipid rafts, the dopamine D 2 R or D 5 R are predominantly outside the rafts, in spite of their different distribution among cytoplasmic, detergent-soluble and detergentresistant membrane fractions (Voulalas et al, 2011).…”

Potential neurochemical links between cholesterol and suicidal behavior

“…It has been suggested that serotonin depletion could be mediated by serotonindopamine interactions, in which a deficient inhibitory effect of serotonin on dopaminergic neurons would result in a higher dopamine activity (Harrison et al, 1997). It may be noted that D 1 R dopamine receptors, in contrast to D 2 R, are localized in lipid rafts and interact with Caveolin-1 (at least in the rat frontal cortex) (Voulalas et al, 2011), and that cholesterol changes could affect dopaminergic activity. Interestingly, cocaine leads to the migration of D 1 R from lipid to non-raft fractions in rats (Voulalas et al, 2011), possibly explaining why cocaine use is associated with suicidal behavior (Vijayakumar et al, 2011).…”