No abstract

[125I]RTI-55 is a newly synthesized cocaine congener that may offer advantages over other ligands previously used to examine cocaine binding sites. However, the in vitro pharmacological and anatomical characterization of [125I]RTI-55 binding sites has not been previously performed in human brain. To determine the specificity, stability, and feasibility of [125I]RTI-55 for use in radioligand binding assays in postmortem human tissue, a series of experiments were performed characterizing [125I]RTI-55 binding sites in human brain using homogenized membrane preparations and quantitative autoradiography. Analysis of the association, dissociation, and saturation data favored two-phase processes. A curve-fitting analysis of the data derived in saturation experiments found a high-affinity site with KD = 66 +/- 35 pM and Bmax = 13.2 +/- 10.1 pmol/g of tissue and a low-affinity site with KD = 1.52 +/- 0.55 nM and Bmax of 47.5 +/- 11.2 pmol/g of tissue. Competition by ligands known to bind to the dopamine transporter showed a rank order of RTI-55 > GBR-12909 > maxindol > WIN 35428 > = methylphenidate > (-)-cocaine > buproprion > (+)-amphetamine. Binding to serotonergic sites was evaluated in the midbrain. Results of the saturation experiment performed autoradiographically in the midbrain showed a single site with KD = 370 +/- 84 pM. It appears that [125I]RTI-55 should be useful in further studies of the regulation of cocaine binding sites using postmortem human specimens.

No abstract

The secretion of melatonin by the pineal has been promoted as a direct monitor of adrenergic function in depressive illness. However, discrepant findings have been reported, possibly reflecting a complex adrenergic regulation of pineal output. In order to clarify the anatomical localization and relative density of beta-adrenergic receptors and their subtypes in human pineal, quantitative autoradiographic analysis was conducted of beta-adrenergic receptors in postmortem specimens using the high affinity radioligand 125I-pindolol. Dense specific binding was found throughout the gland. beta 1 -adrenergic receptors were more numerous, but beta 2-receptors were present in an overlapping anatomical distribution with beta 1-receptors.