raclopride and Pituitary-Neoplasms

Positron emission tomography (PET) is a well-recognized technique used in research, especially for intracranial studies, as well as for clinical practice, and has contributed to the fast development in neuroscience during the last decades.. We have used PET in pituitary tumors for in vivo characterization with respect to metabolism, 11C-L-methionine and 18F-fluorodeoxyglucose, receptor properties, 11C-N-methylspiperone and 11C-raclopride, and monoamine oxidase B enzyme content, 11C-L-deprenyl; further, for diagnosing and outlining the tumors in differential diagnostic perspectives and in the follow-up of treatment.. 11C-raclopride, a specific dopamine antagonist, demonstrated high amounts of dopamine D2 binding in prolactinomas and some growth hormone-secreting adenomas. There was a significant correlation between high amounts of D2 receptors and the positive treatment effect of dopamine agonist therapy. When 11C-L-methionine and 18F-fluorodeoxyglucose were used for metabolic mapping, the highest metabolic activity was found in the prolactinomas, which correlated well with the serum prolactin levels. The growth hormone adenomas also showed high metabolic rates. At treatment follow-up, a considerable decrease in 11C-L-methionine uptake was observed in all tumors that responded positively to the treatment and thus foretold that the medical treatment, both concerning dopamine agonist and somatostatin analogue, was effective. In this respect, PET was valuable to monitor treatment. PET was also shown valuable in differential diagnosing between pituitary adenomas, meningiomas and skull base neuromas.. We have found PET to be highly valuable in the research and clinical handling of patients with a pituitary adenoma for in vivo tumor characterization.

Topics: Acromegaly; Adenoma; Brain Mapping; Dopamine Antagonists; Humans; Pituitary Neoplasms; Positron-Emission Tomography; Raclopride; Radiopharmaceuticals; Receptors, Dopamine D2

In humans, behavioral dopamine supersensitivity occurs in schizophrenia and in Parkinson's disease. In animals, behavioral dopamine supersensitivity is consistently associated with increased dopamine D2(High) receptors in homogenized striata in vitro. Because D2(High) receptors have not yet been detected in intact cells, we used [(3)H]domperidone to detect D2(High) sites in intact rat anterior pituitary adenoma culture cells. Although [(3)H]raclopride and [(3)H]spiperone did not detect D2(High) receptors in intact cells or in rat fresh striatal slices, [(3)H]domperidone readily detected D2(High) receptors, warranting an in vivo search for D2(High) variations in human diseases.

Topics: Adenoma; Animals; Binding, Competitive; Corpus Striatum; Domperidone; Dopamine Antagonists; Pituitary Neoplasms; Raclopride; Rats; Rats, Sprague-Dawley; Receptors, Dopamine D2; Spiperone

The dopamine D2 receptor antagonist remoxipride (30 microM) stimulated prolactin release from the prolactin-producing rat pituitary tumour cell strains GH3 and GH4C1 as well as from transfected GH4C1 cells expressing the short isoform of the rat D2 receptor (GH4ZR7). The effect of remoxipride on prolactin release is probably not due to an interaction with D2 receptors since GH4C1 cells, in contrast to GH3 and GH4ZR7 cells, are completely devoid of D2 receptors; in contrast, we have previously shown that the D2 antagonist haloperidol causes prolactin release from D2 receptor-expressing cells, only. Exposure of GH3 cells to the inhibitor of intracellular Ca2+ mobilization, 8-(diethylamino)-octyl 3,4,5-trimethoxybenzoate hydrochloride (TMB-8) prevented the prolactin-releasing effect of remoxipride whereas pretreatment with the membrane Ca2+ channel antagonist nimodipine did not influence the response. The D2 receptor antagonist raclopride counteracted the reduction of VIP-stimulated prolactin release induced by the D2 agonist quinpirole but caused no prolactin release per se.

Topics: Animals; Calcium Channel Blockers; Clone Cells; Dopamine Agonists; Dopamine Antagonists; Ergolines; Gallic Acid; Nimodipine; Pituitary Neoplasms; Prolactin; Quinpirole; Raclopride; Rats; Remoxipride; Salicylamides; Tumor Cells, Cultured

Positron emission tomography (PET) was used in over 400 examinations in patients with pituitary adenoma. It was demonstrated that PET with carbon-11-methionine can give valuable complementary information in the diagnosis of this tumor due to PET's ability to adequately depict viable tumor tissue in contrast to fibrosis, cysts and necrosis. Furthermore, PET with dopamine D2 receptor ligands can characterize the degree of receptor binding and thus give information as to the prerequisites for dopamine agonist treatment. Most important is the very high sensitivity given by PET with carbon-11-methionine in the evaluation of treatment effects. It is concluded that when properly used PET can be fully justified in the clinical handling of patients with pituitary adenomas and other intracranial tumors.

Topics: Adenoma; Carbon Radioisotopes; Diagnosis, Differential; Dopamine Antagonists; Humans; Methionine; Pituitary Neoplasms; Prolactinoma; Raclopride; Salicylamides; Tomography, Emission-Computed