Agonists stimulate guanylyl 5'-[gamma-[35S]thio]-triphosphate (GTP[gamma-35S]) binding to receptor-coupled guanine nucleotide protein (G proteins) in cell membranes as revealed the presence of excess GDP. We now report that this reaction can be used neuroanatomically localize receptor-activated G proteins brain sections by vitro autoradiography GTP[gamma-35S] binding. Using mu opioid-selective peptide [D-Ala2,N-MePhe4,Gly5-ol]enkephalin (DAMGO) an agonist rat and isolated thalamic membranes,...

Chronic Δ 9 -tetrahydrocannabinol (Δ -THC) administration produces tolerance to cannabinoid effects, but alterations in signal transduction that mediate these changes are not yet known. The present study uses vitro autoradiography of agonist-stimulated [ 35 S]GTPγS binding localize receptor-activated G-proteins after chronic -THC treatment. Cannabinoid (WIN 55212-2)-stimulated was performed brain sections from rats treated chronically with 10 mg/kg for 21 d. Control animals received saline...

Abstract : Chronic treatment of rats with ▵ 9 ‐tetrahydrocannabinol (▵ ‐THC) results in tolerance to its acute behavioral effects. In a previous study, 21‐day ‐THC decreased cannabinoid activation G proteins brain, as measured by vitro autoradiography guanosine‐5′‐ O ‐(3‐[ 35 S]thiotriphosphate) ([ S]GTPγS) binding. The present study investigated the time course changes cannabinoid‐stimulated [ S]GTPγS binding and receptor both brain sections membranes, following daily treatments for 3, 7,...

Previous studies have shown that cannabinoid receptor analogs increase voltage-dependent potassium A-current (IA) in cultured hippocampal cells. Because receptors inhibit adenylate cyclase, the present study explored whether cAMP played a role mediating this effect on IA. The specific issue of modulation IA acts via cAMP-dependent process was investigated. analog, 8-bromo-cAMP, as well cyclase stimulant forskolin, produced concentration-dependent shifts were opposite those by ligands....

Over the past several years, our group has provided considerable evidence that expression of sigma-2 (σ2) receptors may serve as a biomarker tumour cell proliferation. In these in vitro studies, σ2receptors were expressed 8–10 times more proliferative (P) cells than quiescent (Q) cells, and extent kinetics their independent number biological, physiological environmental factors often found solid tumours. Moreover, followed both population growth when Q-cells recruited into P-cell compartment...

G protein activation by different μ-selective opioid agonists was examined in rat thalamus, SK-N-SH cells, and μ-opioid receptor-transfected mMOR-CHO cells using agonist-stimulated guanosine-5′-<i>O</i>-(γ-thio)-triphosphate ([³⁵S]GTPγS) binding to membranes the presence of excess GDP. [d-Ala²,<i>N</i>-MePhe⁴,Gly⁵-ol]Enkephalin (DAMGO) most efficacious agonist thalamus followed (in rank order) fentanyl = morphine ≫ buprenorphine. In expressing a...

Abstract: Guanine nucleotides differentiate binding of tritium‐labeled agonists and antagonists to rat brain membranes. In the absence sodium, GTP (50 μM) decreased [ 3 H]‐labeled by 20–60% 0–20%. presence 100 mM‐NaCl, had no effect on antagonist binding, but agonist 60–95%. GMP was less potent than either or GDP in decreasing binding. reduced high‐affinity H]dihydromorphine sites 52% low‐affinity 55%. Without H]‐naloxone 36%; high‐ H]naloxone sites. increased association rate twofold...

Cannabinoid receptor activation of G-proteins can be measured by WIN 55212–2-stimulated [ 35 S]GTPγS binding. Receptor/transducer amplification factors, interpreted as the number activated per occupied receptor, are ratio apparent B max net agonist-stimulated binding to The present study examined whether factors for cannabinoid receptors differ among various rat brain regions. In autoradiographic studies with 3 H]WIN 55212–2 and binding, some regions displayed different relative levels than...

Administration of naloxazone, a hydrazone derivative naloxone, to intact mice produces prolonged inhibition in vitro [3H]opiate binding lasting up 3 days. The effect is selective since naloxazone treatment no changes alpha or beta adrenergic, muscarinic benzodiazepine receptor and the effects on opiate sites are not reproduced by non-narcotic hydrazines. Scatchard analyses saturation experiments 24 hr after vivo show an absence high affinity [3H]naloxone, [3H]dihydromorphine...

The relationship between GDP and cannabinoid-stimulated [35S]guanosine-5′-O-(3-thiotriphosphate) ([35S]GTPγS) binding was investigated in rat cerebellar membranes. Kinetic analyses showed that [35S]GTPγS reached steady-state levels the association rate increased by agonist WIN 55212-2 proportional to concentration of GDP. Dissociation occurred with two rates (t½ = 7 170 min), proportion sites exhibiting faster rate. Without GDP, bound membranes high low affinity, had no effect. With 30 μm...

In previous studies from our laboratory, chronic noncontingent morphine administration decreased μ opioid receptor-activated G-proteins in specific brainstem nuclei. the present study, receptor binding and were examined after heroin self-administration. Rats trained to self-administer intravenous for up 39 d, achieving intake 366 mg · kg −1 d . opioid-stimulated [ 35 S]GTPγS 3 H]naloxone autoradiography performed adjacent brain sections. Agonist-stimulated also other G-protein-coupled...