Complex Inhibition of [<sup>3</sup>H]Imipramine Binding by Serotonin and Nontricyclic Serotonin Uptake Blockers

Sette, Mario; Briley, Mike; Langer, Salomón Z.

doi:10.1111/j.1471-4159.1983.tb08026.x

Cited by 142 publications

(59 citation statements)

References 18 publications

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“…3). In addition, these data support the possibility that the sites where [3H]imipramine binds are physiological regulatory sites for the uptake of 5HT (17,30). Hence one might infer that the 5HT uptake functions as a supramolecular organization in which various subunits are involved in the fine tuning of the uptake, which therefore can be viewed as an energy-dependent, receptor-modulated process.…”

Section: Characterizationsupporting

confidence: 60%

“…Although DMI is less selective-than imipramine as an inhibitor of the 5HT uptake, it can displace the [3H]imipramine specifically bound to crude synaptic membranes (8,15,30). At the present level of knowledge the down-Tegulation of brain A-adrenergic receptors elicited by DMI could be explained by its binding to 5HT axons and could be considered to be unrelated to the specific 3H-DMI binding to noradrenergic axons.…”

Section: Characterizationmentioning

confidence: 86%

See 1 more Smart Citation

Modulation of neuronal serotonin uptake by a putative endogenous ligand of imipramine recognition sites.

Barbaccia¹,

Gandolfi²,

Chuang³

et al. 1983

Proc. Natl. Acad. Sci. U.S.A.

121

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Imipramine inhibits the serotonin uptake by binding with high affinity to regulatory sites of this uptake located on axons that release serotonin. The number of imipramine recognition sites located on crude synaptic membrane preparations is reduced by two daily injections of imipramine or desmethylimipramine for 3 weeks. When the binding sites for [3H]imipramine are down-regulated the Vma of the neuronal uptake of serotonin is increased. Moreover, in minces prepared from the brain hippocampus of rats receiving imipramine in a dose regimen that reduces the number of [3H]imipramine recognition sites, the efficiency of imipramine as a blocker of the serotonin uptake is diminished. Hence the high-affinity binding sites for [3H]imipramine may have a physiological role in modulation of serotonin reuptake. Probably this is mediated by an endogenous effector of these regulatory sites. A nonpeptidic constituent of rat brain capable of displacing [3H]imipramine from its high-affinity binding site and of inhibiting the serotonin uptake in a dose-related manner has been extracted and its partial purification is described.Imipramine and desmethylimipramine (DMI) have been used for longer than two decades to relieve the symptoms of depression (1, 2). Their capacity to block norepinephrine (NE) and serotonin (5-hydroxytryptamine; 5HT) uptake has been considered to be important for their therapeutic action, but when it was noted that imipramine and DMI block amine uptake almost instantaneously, whereas their antidepressant action occurs with a latency time of 1-2 weeks (1), the importance of the uptake inhibition in explaining their therapeutic action was deemphasized. Upon repeated daily administration to rats imipramine and a number of its congeners down-regulate the function of NE recognition sites in several brain structures (3-6); because the onset of this down-regulation and that of the antidepressant action are delayed with respect to the beginning of the treatment, it has been suggested that the NE response downregulation and the antidepressant action may be related (6). An additional tool to study the mechanism of the down-regulation of /3-adrenergic receptors became available when Langer and his colleagues reported that specific Na+-dependent and highaffinity binding sites for [3H]imipramine are located in crude synaptic membranes prepared from various structures of mammalian brains (7,8). The maximal number, Bmax, of [3H]imipramine binding sites is down-regulated by repeated injections of imipramine or DMI (9-11). These recognition sites are located on 5HT axon terminals (12)(13)(14) and appear to be anatomically and functionally associated with the 5HT uptake mechanism (15)(16)(17).In 1981 at a symposium on the mode of action of antidepressants we reported that the selective destruction of 5HT axons by 5,7-dihydroxytryptamine (5,7-DHT), which eliminates[3H]imipramine recognition sites, prevented the down-regulation of f3-adrenergic recognition sites elicited by two daily injections of DMI repeated for 3 wee...

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Section: Characterizationsupporting

confidence: 60%

Section: Characterizationmentioning

confidence: 86%

Modulation of neuronal serotonin uptake by a putative endogenous ligand of imipramine recognition sites.

Barbaccia¹,

Gandolfi²,

Chuang³

et al. 1983

Proc. Natl. Acad. Sci. U.S.A.

121

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“…Based on the general good correspondences between uptake and binding potencies across multiple uptake blockers for the SERT (D'Amato et al, 1987;Koe et al, 1990;Sette et al, 1983), DAT (Janowsky et al, 1986;Javitch et al, 1984; Kennedy and Hanbauer, 1983;Schoemaker et al, 1985) and NET (Cheetham et al, 1996;Lee et al, 1982) binding assays gained wide acceptance as tools for measuring transporter affinities of newly synthesized transporter blockers. It is important to restrict this observation to blockers, because early on, it was realized that substrates were generally weaker in inhibiting ligand binding to monoamine transporters than in inhibiting monoamine uptake for the SERT (D'Amato et al, 1987;Sette et al, 1983), DAT (Dubocovich and Zahniser, 1985; Kennedy and Hanbauer, 1983;Schoemaker et al, 1985), and NET (Lee et al, 1982). In the case of the NET, the originally described [ 3 H]desipramine binding assay was later replaced with the [ 3 H]nisoxetine assay (Tejani-Butt et al, 1990), which is superior in terms of the affinity of the radioligand binding (leading to a better signal) and the membrane preparation (not requiring extensive high-salt washing).…”

Section: Introductionmentioning

confidence: 99%

Pharmacological profile of radioligand binding to the norepinephrine transporter: instances of poor indication of functional activity

Reith

Wang

Dutta

2005

Journal of Neuroscience Methods

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“…Pharmacological studies indicate the existence of distinct binding sites for tricyclic antidepressants and selective serotonin (5-hydroxytryptamine, 5-HT) re-uptake inhibitors on the SERT protein, and complex interactions between these sites as well as the substrate translocation site have been reported (5)(6)(7)(8)(9)(10)(11). The cloning of SERT from different species (12)(13)(14)(15)(16) has fostered attempts to define structure-function relationships in this protein.…”

mentioning

confidence: 99%

A single serine residue controls the cation dependence of substrate transport by the rat serotonin transporter

Sur

Betz

Schloss

1997

Proc. Natl. Acad. Sci. U.S.A.

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The serotonin transporter (SERT) is a member of the Na ؉ ͞Cl ؊ -dependent neurotransmitter transporter family and constitutes the target of several clinically important antidepressants. Here, replacement of serine-545 in the recombinant rat SERT by alanine was found to alter the cation dependence of serotonin uptake. Substrate transport was now driven as efficiently by LiCl as by NaCl without significant changes in serotonin affinity. Neurotransmitter transporters mediate the re-uptake of released neurotransmitters from the synaptic and nonsynaptic environment and play a key role in regulating synaptic transmission. Functional studies and sequence comparison of the transporters for different amino acid and monoamine transmitters have allowed their classification into two distinct families (1-3). The Na ϩ ͞Cl Ϫ -dependent transporter family includes the biogenic amine, glycine, and ␥-aminobutyric acid transporters, which share 12 putative transmembrane domains (TMDs) and a large extracellular loop between TMD3 and TMD4 that contains several potential N-glycosylation sites. The glutamate transporter family, in contrast, has a different transmembrane organization and needs K ϩ for substrate transport. All transmitter uptake systems display a stringent Na ϩ requirement for substrate translocation.The serotonin transporter (SERT) has received particular attention because it represents the target of clinically important antidepressants as well as drugs of abuse and has been implicated in neurological and psychiatric disorders (4). Pharmacological studies indicate the existence of distinct binding sites for tricyclic antidepressants and selective serotonin (5-hydroxytryptamine, 5-HT) re-uptake inhibitors on the SERT protein, and complex interactions between these sites as well as the substrate translocation site have been reported (5-11). The cloning of SERT from different species (12-16) has fostered attempts to define structure-function relationships in this protein. Notably, analysis of chimeric human and rat SERT has revealed domains important for the selective binding of tricyclic antidepressants (10). However, little is known about the amino acid side chains implicated in substrate and Na ϩ binding as well as 5-HT transport.Serine residues are known to be crucial for the binding of catecholamines to adrenergic receptors (17) and for [ 3 H]dopamine uptake mediated by the dopamine transporter (18). Here, we substituted alanine for three serine residues located in TMD11 of the rat SERT. The effects of these substitutions on 5-HT transport and antidepressant binding were then analyzed in transfected cells. Our results show that a serine residue at position 545 is important for the cation dependence of 5-HT transport. Additionally, this mutation affects the velocity of substrate translocation as well as binding of imipramine, but not citalopram.

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Complex Inhibition of [³H]Imipramine Binding by Serotonin and Nontricyclic Serotonin Uptake Blockers

Cited by 142 publications

References 18 publications

Modulation of neuronal serotonin uptake by a putative endogenous ligand of imipramine recognition sites.

Modulation of neuronal serotonin uptake by a putative endogenous ligand of imipramine recognition sites.

Pharmacological profile of radioligand binding to the norepinephrine transporter: instances of poor indication of functional activity

A single serine residue controls the cation dependence of substrate transport by the rat serotonin transporter

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Complex Inhibition of [3H]Imipramine Binding by Serotonin and Nontricyclic Serotonin Uptake Blockers

Cited by 142 publications

References 18 publications

Modulation of neuronal serotonin uptake by a putative endogenous ligand of imipramine recognition sites.

Modulation of neuronal serotonin uptake by a putative endogenous ligand of imipramine recognition sites.

Pharmacological profile of radioligand binding to the norepinephrine transporter: instances of poor indication of functional activity

A single serine residue controls the cation dependence of substrate transport by the rat serotonin transporter

Contact Info

Product

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Complex Inhibition of [³H]Imipramine Binding by Serotonin and Nontricyclic Serotonin Uptake Blockers