piperidines and nisoxetine

We have previously reported that endothelin-1 and -3 modulate different steps of noradrenergic transmission in the hypothalamus. We showed that endothelins modify neuronal norepinephrine transport activity through the regulation of the kinetic constant and internalization. In the present work we sought to define the endothelin receptors and intracellular mechanisms involved in the down-regulation of neuronal norepinephrine uptake induced by endothelin-1 and -3 in the rat posterior hypothalamic region. Results showed that endothelin-1 reduced norepinephrine uptake through ET(B) receptors, whereas endothelin-3 through a non-conventional or atypical endothelin receptor. In both cases, the effect on norepinephrine uptake was coupled to protein kinase A and C as well as nitric oxide pathways. However, neither protein kinase G nor intracellular or extracellular calcium and calcium/calmodulin-dependent protein kinase II were involved. In addition, the same intracellular mechanisms participated in the reduction of nisoxetine binding (norepinephrine transporter internalization index) induced by both endothelins. Present findings reveal the underlying mechanisms involved in the regulation of the neuronal norepinephrine transporter by endothelins and further support the role of these peptides in the modulation of noradrenergic transmission at the presynaptic nerve endings in the posterior hypothalamus.

Topics: Adenylyl Cyclases; Animals; Cyclic AMP-Dependent Protein Kinases; Endothelin-1; Endothelin-3; Enzyme Activation; Fluoxetine; Hypothalamus, Posterior; Male; Neurons; Nitric Oxide; Norepinephrine; Norepinephrine Plasma Membrane Transport Proteins; Oligopeptides; Piperidines; Protein Kinase C; Rats; Rats, Sprague-Dawley; Receptor, Endothelin A; Receptor, Endothelin B; Signal Transduction

In a wide search program toward new, efficient, and fast-acting antidepressant drugs, we have prepared series of new compounds having an (aryl)(aryloxy)methyl moiety linked directly or through a methylene chain to different substituted and unsubstituted cycles (isoquinoline, piperazine, piperidine, tetrahydropyran, or cyclopentane). These compounds have been evaluated for their affinities for serotonin (5-HT) transporter (SERT) and 5-HT(1A) and 5-HT(2A) receptors. Racemic mixtures of 4-[(aryl)(aryloxy)methyl]piperidine derivatives showed much higher affinity values for SERT than fluoxetine and resulted in lack of affinity for 5-HT(1A) and 5-HT(2A) receptors. Some of these racemic mixtures were resolved to their enantiomers and tested for binding to norepinephrine (NE) transporter (NET), dopamine (DA) transporter (DAT), and alpha(2) receptor. Several of these enantiomers [(-)-15b, (-)-15j, (-)-15t, (+)-15u] displayed a dual binding profile with affinities for SERT and NET with K(i) < 25 nM and a NET/SERT ratio <10. Compound (-)-15j (coded as F-98214-TA for development studies) showed a dual binding profile with very high affinity values for SERT and NET (K(i) = 1.9 and 13.5 nM, respectively), and further pharmacological characterization is in progress for its evaluation as a antidepressant.

Topics: Adrenergic Uptake Inhibitors; Animals; Antidepressive Agents; Brain; Carrier Proteins; Fluoxetine; In Vitro Techniques; Male; Membrane Glycoproteins; Membrane Transport Proteins; Morpholines; Nerve Tissue Proteins; Norepinephrine; Norepinephrine Plasma Membrane Transport Proteins; Piperidines; Radioligand Assay; Rats; Rats, Wistar; Reboxetine; Receptor, Serotonin, 5-HT1A; Receptor, Serotonin, 5-HT2A; Selective Serotonin Reuptake Inhibitors; Serotonin; Serotonin Plasma Membrane Transport Proteins; Stereoisomerism; Structure-Activity Relationship; Symporters