Magnetic properties and the crystal field problem for tetragonal HoBa(2)Cu(3)O(x).

Magnetic susceptibilities of the first and third orders as well as the magnetization of the singlet paramagnet HoBa(2)Cu(3)O(x) (x≈6.0) at low temperatures are studied experimentally using a SQUID magnetometer and compared with theoretical calculations. The magnetic behaviour of single-crystal HoBa(2)Cu(3)O(x) at low temperature is found not to follow the one calculated on the basis of the known crystal field parameters. Different effects which may change the magnetic properties are analysed and discussed: low symmetry components of the crystal field due to some disorder in the oxygen subsystem, a noncompensated effective field from the ordered Cu subsystem acting on the Ho(3+) ions, and others.

5-HT-moduline controls serotonergic activity: implication in neuroimmune reciprocal regulation mechanisms.

The serotonergic neurotransmission is known as a neuromodulatory system exerting its activity in the central nervous system (CNS) as well as at the periphery. The anatomical and morphological organization of the system based on a marked centralization of the cellular bodies and the large, almost ubiquitary, presence of axonal projections of the neurons is in good agreement with this modulatory role. Furthermore, a very high number of varicosities located along the axonal branches are capable of releasing serotonin (5-HT). The amine stimulates a number of different specific receptor types which allows 5-HT to exert different activities on its various cellular targets. Among these receptors, the 5-HT1B subtypes play a particular role as they are autoreceptors located on 5-HT neurons terminals and heteroreceptors located on non-serotonergic terminals where they control the release of the neurotransmitter. 5-HT-moduline, an endogenous tetrapeptide, regulates the efficacy of these 5-HT1B receptors, hence, is able to control the serotonergic activity in a synchronous manner for the various varicosities from a single neuron and thus may favour the differential effect of that neuron on distinct cerebral functions. Accordingly, the peptide allows the 'fine tuning' of the cerebral activity by the serotonergic system to elaborate the response given by the brain to a particular stimulus, that is, stress situations. At the periphery, the serotonergic system also appears to possess a regulatory activity via 5-HT1B receptors. In particular, the receptors located on immunocompetent cells control their activity and are themselves regulated by 5-HT-moduline likely originating from adrenal medulla and released after acute stress. The serotonergic system appears to play a major role in the reciprocal signalling existing between the neuronal and the immune system. The participation of 5-HT-moduline is likely in physiological functions as well as in pathological disorders affecting central and peripheral activities.

High field magnetic transitions in the mixed holmium-yttrium iron garnet Ho(0.43)Y(2.57)Fe(5)O(12).

High static magnetic field magnetization measurements have been performed up to 23 T on Ho(0.43)Y(2.57)Fe(5)O(12) single crystals at helium temperature (T = 4.2 K) with fields applied along the three main cubic axes: [Formula: see text], [Formula: see text] and [Formula: see text]. The change from the spontaneous ferrimagnetic structure in zero magnetic field to the fully ferromagnetic one in high field takes place through several intermediate phases separated by transitions with step-like magnetization behaviour, but without any observed hysteresis. Using the effective spin Hamiltonian approximation, we show that the general features of these transitions can be accounted for by a large magnetocristalline anisotropy of the Ho(3+) moments of the uniaxial type along the local z axis of each rare-earth site. The model is in better agreement with the experiments than its Ising limit, widely used before, but is still unsuccessful in predicting the 'umbrella' magnetic structures found by previous neutron and NMR experiments.

5-HT1B receptors: a novel target for lithium. Possible involvement in mood disorders.

Lithium ion is widely used to treat depressive patients, often as an initial helper for antidepressant drugs or as a mood stabilizer; however, the toxicity of the drug raises serious problems, because the toxic doses of lithium are quite close to the therapeutic ones. Thus, precise characterization of the target(s) involved in the therapeutic activity of lithium is of importance. The present work, carried out at molecular, cellular, and in vivo levels, demonstrates that 5-HT1B receptor constitutes a molecular target for lithium. Several reasons suggest that this interaction is more likely related to the therapeutic properties of lithium than to its undesirable effects. First, the observed biochemical and functional interaction occurs at concentrations that precisely correspond to effective therapeutic doses of lithium. Second, 5-HT1B receptors are well characterized as controlling the activity of the serotonergic system, which is known to be involved in affective disorders and the mechanism of action of various antidepressants. These findings represent progress in our knowledge of the mechanism of action of lithium that may facilitate clinical use of the ion and also open new directions in the research of antidepressant therapies.

Effect of chronic antidepressant treatment on 5-HT1B presynaptic heteroreceptors inhibiting acetylcholine release.

The effect of long term treatment with two tricyclic antidepressants on the sensitivity of 5-HT1B presynaptic heteroreceptors inhibiting acetylcholine (ACh) release was investigated. Groups of male rats received during 14 days either saline, citalopram (20 mg/kg), a serotonin (5-HT) uptake blocker, or tianeptine (2 x 10 mg/kg), an antidepressant that enhances 5-HT uptake. The efficacy of the 5-HT1B selective agonist 7-trifluoromethyl-4-(4-1-piperazinyl)-pyrrolo[1,2-a]quinoxaline (CGS 12066B) in reducing K(+)-evoked [3H]acetylcholine release from hippocampal synaptosomes was determined 24 hr after the last administration. The chronic treatment with citalopram or tianeptine modified neither the basal nor the K(+)-evoked release of [3H]acetylcholine. In contrast, these treatments significantly reduced the efficacy of CGS 12066B to inhibit the release of [3H]acetylcholine induced by K+ depolarization. These data suggest that chronic antidepressant treatment desensitizes 5-HT1B presynaptic heteroreceptors through a mechanism which seems to be independent of the synaptic availability of 5-HT.

Immunocytochemical localization of neurons expressing 5-HT-moduline in the mouse brain.

The localization of 5-HT-moduline, an endogenous cerebral tetrapeptide (LSAL) which specifically interacts with 5-HT1B receptors (Rousselle et al., 1996; Massot et al., 1996) was examined in mouse brain using an immunocytochemistry technique with a polyclonal anti-peptide antibody highly specific for this tetrapeptide. Highest levels of 5-HT-moduline immunoreactivity were observed in the cerebral cortex including cingulate, retrosplenial, parietal and pyriform cortical areas and in the basal ganglia. Intense immunoreactivity also occurred in the hippocampus, subiculum, various hypothalamic and thalamic nuclei and in some midbrain regions such as the substantia nigra and the superior colliculi. Immunoreactive neurons generally showed intense and extensive labelling of the perikarya and dendritic arborizations with moderate to heavy characteristic deposits of reaction product along plasma membranes and within cytoplasm while the nuclei were devoid of reaction product. The results obtained indicated that 5-HT-moduline immunoreactivity was heterogenously distributed in neuronal structures of mouse brain. The distribution of 5-HT-moduline immunoreactivity closely correlated with that of 5-HT-moduline specific binding sites as visualized by autoradiography (Massot et al., 1996). Moreover, it seems to overlap with the distribution of serotonergic innervation and also with that of 5-HT1B receptors in mouse brain (Boschert et al., 1994; Bruinvels et al., 1994; Chopin et al., 1994; Langlois et al., 1995). These data provide evidence that 5-HT-moduline immunoreactivity is located in cells with the morphological appearance of neurones. Its localization in brain areas which also contain 5-HT1B receptors, is in good agreement with previous demonstrations that this peptide specifically interacts with 5-HT1B receptors to regulate their functional activity and accordingly controls the modulatory activity of the serotoninergic system on various CNS functions.

Improved brain delivery of AZT using a glycosyl phosphotriester prodrug.

The concentration of AZT in mice plasma and brain was measured using HPLC after an ingestion of 20 mg/kg of AZT or the molar equivalent of hexadecyl 2-(alpha-D-mannopyranosidyl)ethyl 3'-azido-3'-deoxy-5'-thymidinyl phosphate 3. The results demonstrated the promising qualities of the prodrug 3 which gave AZT-5'-phosphate as the main metabolite: the total concentration of AZT derivatives detected in brain presented a peak of 156 nmol/g (5 nmol/g for AZT) at 1 h; the half-life was about 24 h (1 h for AZT) with an AUC of 4366 nmol h/g as compared to 4 nmol h/g for AZT. The lipophilic properties of 3 were confirmed by its in vitro transport of inside synaptosomes. The derivative 2-(alpha-D-mannopyranosidyl)ethyl 3'-azido-3'-deoxy-5'-thymidinyl phosphate (2) provided also a good delivery of AZT to the central nervous system, with values intermediate between those of AZT and 3.

Interleukin-1 receptors type I and type II in the mouse brain: kinetics of mRNA expressions after peripheral administration of bacterial lipopolysaccharide.

The expression of transcripts for Interleukin-1 (IL-1) type I and type II receptors (IL-1R1, IL-1R2) was investigated in the mouse brain and spleen using reverse transcription-polymerase chain reaction techniques under basal conditions and following injection of endotoxin (LPS, i.p., 4 mg/kg). Under basal conditions, mRNAs for both receptor types were found in various parts of the brain, in pituitary as well as in spleen. Following LPS stimulation, mRNA expressions were increased in all studied tissues. IL-1R1 mRNAs were predominant in the brain and pituitary while, IL-1R2 mRNAs were more abundant in the spleen. The maximal quantity of transcripts (IL-1R1, IL-1R2) was obtained 6 h after LPS injection in all studied tissues. The decrease to basal level was observed within 48 h in the brain. In the spleen, IL-1R1 mRNAs remained elevated 48 h after LPS while IL-1R2 mRNAs had already reached basal level. These results indicate a LPS-induced stimulation of IL-1 receptors mRNAs in the brain and a differential expression of IL-1R1 and IL-1R2 transcripts in brain and immune tissues.

Receptors for interleukin-1 (alpha and beta) in mouse brain: mapping and neuronal localization in hippocampus.

Interleukin-I receptors were mapped and characterized in mouse brain by quantitative autoradiography using human recombinant [125I]interleukin-I alpha and [125I]interleukin-1 beta as ligands. Both ligands provide identical receptor mapping. In terms of specificity, interleukin-1 alpha and interleukin-1 beta were equally potent in binding competitions assays with either [125I]interleukin-1 alpha or [125I]interleukin-1 beta (EC50 11 pM). These receptors were shown to be highly concentrated in the dentate gyrus, in the choroid plexus at various levels of the brain, in the pituitary and in the meninges. They were also present at low concentrations in the cortex but undetectable in other brain structures. In the dentate gyrus, interleukin-1 receptors were localized on the granular and molecular layers (granule cells) when visualized on slides dipped in nuclear emulsion. Cellular localization of interleukin-1 receptors was assessed using selective lesion by colchicine. The complete loss of [125I]interleukin-1 binding in hippocampal areas where neurons were destroyed by colchicine demonstrates that interleukin-1 receptors are located on granule cells. Following lesion, sparse undestroyed cells, with glial cell morphology, also showed significant labelling. In conclusion, interleukin-1 receptors are located on the granule cells in the mouse dentate gyrus. These neurons may therefore be targets for neuromodulation by interleukin-1 and they may play a key role in the central effect of interleukin-1 as well as in the control of the immune response by the brain.

5-Hydroxytryptamine-moduline: a novel endogenous peptide involved in the control of anxiety.

The serotonergic system is considered as a neuromodulatory system interacting with other neurotransmissions in the brain and participating in the elaboration of an adapted response of the central nervous system to external stimuli. Indeed, serotonin is involved in a large number of physiological events, such as temperature regulation, sleep, learning and memory, behaviour, sexual function, hormonal secretions and immune activity, and in parallel, it is also implicated in pathological disorders particularly in stress, anxiety, aggressivity and depression. At least 14 different types of serotonin receptors mediate serotonergic activity and among them, serotonin-1B receptors play an important role in the control of the serotonergic function. Serotonin-1B receptors are autoreceptors localized on serotonergic neuron terminals (varicosities) where they inhibit the evoked release of serotonin and its biosynthesis; they are also heteroreceptors located on non-serotonergic terminals, where they inhibit the release of the corresponding neurotransmitters (acetylcholine, GABA, noradrenaline, etc.). 5-Hydroxytryptamine-moduline, an endogenous tetrapeptide (Leu-Ser-Ala-Leu) recently isolated and characterized from rat and bovine brain extracts, was shown to specifically interact with serotonin1B receptors as an allosteric modulator having antagonistic properties in vitro and in vivo. Immuncytochemical studies using specific polyclonal anti-peptide antibodies have shown that this peptide is distributed heterogeneously in mouse brain and located in areas which also contain serotonin-1B receptors. Moreover, the content of these cerebral tissues in 5-hydroxytryptamine-moduline is affected by stress. In the present work, polyclonal anti-5-hydroxytryptamine-moduline antibodies were administered to mice via intracerebroventricular injections to study the in vivo effects of a lowering (or suppression) of this neuropeptide in the central nervous system. The inactivation of the peptide by the specific antibodies significantly modified the behaviour of the animals in two behavioural tests, the open-field and elevated plus-maze, known to be animal models related to anxiety behaviour. Treated mice displayed behaviour consistent with an anxiolytic effect of the antibody, suggesting a potential role of 5-hydroxytryptamine-moduline in the control of anxiety.

GnRH receptors in rat brain, pituitary and testis; modulation following surgical and gonadotropin-releasing hormone agonist-induced castration.

The regulation of rat gonadotropin-releasing hormone (GnRH) receptors in male rat pituitary, hippocampus and testis was studied, in vivo, under steady-state conditions during treatment with D-Trp6 GnRH (triptorelin, slow-release form, at 300 micrograms/kg/month). GnRH receptors were characterized on tissue sections by quantitative autoradiography using 125I-GnRHa as a tracer. Castrating doses of triptorelin strongly down-regulated pituitary GnRH receptors (50% of reduction after 8 h, 80% on days 1-30); in contrast, only a transient decrease (20% at 8 h) was observed in the hippocampus with a rapid return to control levels. Triptorelin induced a marked (2-fold) increase in GnRH receptors in testicular interstitial tissue during 5 days with a return to control value by day 20. Administration of a GnRH antagonist (BIM 21009, 1 mg/kg/24 h) induced a rapid reduction of pituitary and testicular receptors to undetectable levels at 24 h, while hippocampal receptors were strongly reduced only. This indicates that GnRH receptors with similar pharmacology are differently controlled in various tissues and that brain receptors are likely to be also regulated by GnRH agonists and antagonists.

Potential of 5-HT-moduline as a drug target for affective disorders.

The serotonergic system is one of the aminergic neurotransmitter systems participating in the maintenance of homeostasis of the organism in mammals; accordingly, it regulates the activity of various cerebral functions to organize adapted responses of the brain to environmental stimuli. The regulatory activity of the serotonergic system itself is modulated by an endogenous mechanism based on an allosteric interaction involving a newly discovered peptide, 5-HT-moduline, and the 5-HT1B receptor which, as an autoreceptor, controls the release of 5-HT from serotonergic neuron terminals. 5-HT-moduline specifically interacts with 5-HT1B receptors at nanomolar concentrations resulting in the desensitization of the receptor. As 5-HT1B autoreceptors have an inhibitory effect on the release of 5-HT, 5-HT-moduline ultimately increases its release. The peptide is characterized by several criteria which correspond to those of a neurotransmitter, strongly suggesting that 5-HT-moduline is a novel neuropeptide locally controlling serotonergic activity. 5-HT-moduline is released in various parts of the brain, particularly under conditions of stress; moreover, its deactivation by specific antibodies in mice induces changes in the behavior of the animal. These results strongly suggest that the peptide may play a role in the physiopathology of central nervous system disorders in mammals, particularly in conditions related to stress and anxiety. Furthermore, the fact that 5-HT-moduline increases the release of 5-HT suggests that synthetic drugs which recognize the 5-HT-moduline binding site on 5-HT1B receptors and mimic the effect of the peptide, may have antidepressant properties by increasing the release of 5-HT.

Expression of interleukin 1 alpha, interleukin 1 beta and interleukin 1 receptor antagonist mRNA in mouse brain: regulation by bacterial lipopolysaccharide (LPS) treatment.

Lipopolysaccharide (LPS) stimulation is known to induce interleukin-1 (IL-1) mRNA expression in various immune cell types. Since IL-1 synthesis has been suggested to occur locally in brain tissue, we investigated the expression of IL-1 (alpha and beta) and IL-1 receptor antagonist (IL-1ra) mRNAs in various structures of the central nervous system, as well as in the spleen, following intraperitoneal injection of LPS (100 micrograms/mouse). After RNA extraction and amplification by the reverse transcription-polymerase chain reaction (RT-PCR), the PCR products were separated on an agarose gel, transferred and hybridized with digoxigenin-labeled probes synthetized by nested PCR. Glyceraldehyde phosphate deshydrogenase mRNA was used as an internal control. Under basal conditions the expression of IL-1 alpha, IL-1 beta and IL-1ra mRNAs in the brain was extremely low for the three cytokines; in the spleen these mRNAs were clearly detectable. Following LPS stimulation, mRNAs were strongly increased in all the tested tissues (cortex, hippocampus, hypothalamus, cerebellum, pituitary and spleen). The kinetics of mRNAs expressions in the brain were similar for all the tested regions, with a maximum at 6 h and a decrease up to 24 h after LPS administration. In the spleen the maximum was observed as soon as 1 h following stimulation. In conclusion, peripheral LPS stimulation induces a strong and transient expression of IL-1 alpha and IL-1 beta mRNAs in the brain. IL-1ra mRNA is also stimulated by LPS in various regions of the brain.(ABSTRACT TRUNCATED AT 250 WORDS)

Cellular localization of 5-HT1B receptor mRNA in the rat olfactory tubercle: do GABAergic neurons express the 5-HT1B gene?

In situ hybridization with a 5-HT1B receptor probe and immunocytochemistry with gamma-aminobutyric acid (GABA) antibody performed on adjacent sections of rat brains reveal that GABAergic cell bodies, which represent 10-15% of the cellular population, do not express the 5-HT1B gene in rat olfactory tubercle. Most of the cells expressing the 5-HT1B gene were of small to medium size; large neurons expressing RNA transcripts may correspond to cholinergic neurons. It cannot be excluded that the absence of detectable 5-HT1B mRNA in GABAergic neurons was due to limited sensitivity of the in situ hybridization and immunocytochemistry procedures. Our data suggest that GABAergic neurons originating from olfactory tubercle are not directly controlled by serotonin through 5-HT1B receptors.

Expression of serotonin receptors in human fetal astrocytes and glioma cell lines: a possible role in glioma cell proliferation and migration.

Expression of seven serotonin or 5-hydroxytryptamine (5-HT) receptors (5-HT1D alpha, 5-HT1E, 5-HT2, 5-HT1A, 5-HT1C, 5-HT1D beta, and 5-HT6) was investigated in human normal fetal astrocytes and eight glioma cell lines by reverse transcription and polymerase chain reaction (RT-PCR). No expression of 5-HT1D beta and 5-HT6 was observed in any of the cell lines studied. The 5-HT1D alpha receptor was found to be expressed in two human glioma cell lines but not in normal astrocytes. In addition, only three glioma cell lines expressed the 5-HT1E receptor. The 5-HT1C receptor was expressed in six glioma cell lines but not in normal astrocytes while the 5-HT1A was found to be expressed in normal astrocytes from the left hemisphere and in six glioma cell lines but not in normal astrocytes from the cerebellum. Interestingly, the 5-HT2 receptor was expressed in all cells studied but very weakly in normal astrocytes. The effect of 5-HT on glioma cell proliferation, migration, and invasion was also investigated. Serotonin was found to positively modulate these three processes in vitro. These results suggest that 5-HT may play an important role in the control of the biological properties of human glioma cells.

Molecular, cellular and physiological characteristics of 5-HT-moduline, a novel endogenous modulator of 5-HT1B receptor subtype.

The serotonergic transmission is considered as a neuromodulatory system in the Central Nervous System. 5-HT1B receptors play an important role in this modulatory activity. We have purified from mammalian brain an endogenous peptide, LSAL, we called 5-HT-moduline, interacting specifically with 5-HT1B receptors. This interaction is characterized by a high affinity (Ki = 10(-10) M) and a non-competitive mechanism. Direct [3H]5-HT-moduline binding revealed a single population of sites having an apparent affinity constant close to 10(-10) M. Autoradiographic studies showed a brain distribution of [3H]5-HT-moduline binding sites closely related to the 5-HT1B receptors. In functional studies, the peptide is able to reverse the activity of a 5-HT1B agonist in the nanomolar range. Furthermore, this antagonist effect is also observed in vivo on mice behavior. Immunocytochemistry revealed an heterogeneous distribution of 5-HT-moduline in mouse brain. The labeled structures correspond to cellular profiles with axon-like prolongations. Moreover, in vitro, LSAL is released in a Ca++, K(+)-dependent manner. Therefore, 5-HT-moduline behaves as a neurotransmitter. The fact that 5-HT-moduline induces the desensitization of 5-HT1B receptors reflects the existence of a novel and efficient mechanism able to rapidly modulate the serotonergic activity.

The endogenous cerebral tetrapeptide 5-HT-moduline reduces in vivo the functional activity of central 5-HT1B receptors in the rat.

5-HT-moduline (Leu-Ser-Ala-Leu, LSAL) is a novel endogenous peptide isolated from rat brain which interacts in vitro specifically with 5-HT(1B) receptors by a non-competitive mechanism. In the present study, we demonstrate that the efficacy of the selective 5-HT(1B) receptor agonist CP 93 129 in inhibiting the forskolin-stimulated adenylyl cyclase activity in the rat substantia nigra was reduced 15 min after intracerebral injection of LSAL compared to vehicle or ALLS (scrambled peptide) injected rats. Accordingly, the concentration-response curve of the agonist is shifted to the right with a 3.5-fold increase of the half-maximal inhibitory concentration compared to vehicle injected rats. Thus, the in vivo desensitization of serotonergic autoreceptors strongly strengthens the important role of 5-HT-moduline in the rapid adaptative control of the serotonergic system, implicated in numerous pathological events as anxiety and depression.

Production and characterization of an antibody directed against the mouse 5HT1B receptor.

We have developed a polyclonal antibody directed against a peptide located in the third intracellular loop of the 5HT1B receptor. Its characterization was carried out using NIH cells stably transfected with a eukaryotic expression vector containing the mouse 5HT1B receptor cDNA. The synthetic antigenic peptide had a unique sequence to the mouse 5HT1B receptor corresponding to amino acids 273-287 localized in the third intracellular loop. In dot blot analysis, antisera detected 2 ng to 2 micrograms of synthetic peptide at dilutions of 1/200-1/20,000 and bound antibody was visualized using an immunoperoxidase procedure. Preimmune serum showed no immunoreactivity to the synthetic peptide. NIH cells stably transfected expressing mouse 5HT1B receptor displayed an intense immunoreactivity with the antiserum. In contrast no immunoreactivity was seen in any of the control experiments. In the present study, we have produced a specific antibody which is an essential tool suitable for immunocytochemical applications such as regional distribution, anatomical localization and phenotypical characterization of the cells expressing the 5HT1B receptors in brain by double immunolabelling procedure.

A new peptide, 5-HT-moduline, isolated and purified from mammalian brain specifically interacts with 5-HT1B/1D receptors.

5-HT-Moduline (Leu-Ser-Ala-Leu) is a new endogenous peptide purified from rat brain which interacts specifically with 5-HT1B/1D receptors. The binding interaction of 5-HT-Moduline with 5-HT1B/1D receptors appeared to be a non-competitive process, since the Bmax value of [125I] cyanopindolol binding on rat brain cortical membranes was decreased without modification of the Kd. This interaction was conserved on NIH 3T3 cells expressing the 5-HT1B receptor (IC50 = 10(-11)M) suggesting that the binding site for 5-HT-Moduline is localized on the 5-HT1B receptor protein. The observed interaction may lead to functional alterations of 5-HT1B/1D receptors known to play an important role in regulating the release of 5-HT from serotonergic nerve terminals (autoreceptors) as well as the release of other neurotransmitters (heteroreceptors).

Autoradiographic characterization of binding sites for [3H]milnacipran, a new antidepressant drug, and their relationship to the serotonin transporter in rat brain.

Milnacipran is a new antidepressant drug and an equipotent inhibitor of the uptake of serotonin and noradrenaline. Quantitative autoradiography and radioligand binding studies were used to characterize recognition sites of [3H]milnacipran in rat brain. [3H]Milnacipran demonstrated saturable, reversible and nanomolar affinity binding. The binding was Na(+)-dependent, potently displaced by serotonin uptake inhibitors in all structures and moderately or weakly displaced by catecholamine uptake inhibitors (order of potency: paroxetine > fluoxetine > mazindol > desipramine > nomifensine > maprotiline). High density of recognition sites were found in structures dense in serotonergic innervation (raphe, basal ganglia, colliculi, cortex). The autoradiographic pattern of [3H]milnacipran recognition sites resembled that of [3H]paroxetine, but their distribution did not correlate well in some structures. Selective lesioning of serotonergic neurons by intracerebral injection of 5,7-dihydroxytryptamine caused a large decrease of [3H]milnacipran binding in various regions (septum, caudate, hippocampus, thalamus, ventral and dorsal hypothalamus), but in other structures, the [3H]milnacipran binding was partially affected (putamen) or even unchanged (amygdala, lateral hypothalamus). In contrast, lesion of noradrenergic neurons by intraperitoneal administration of [N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine] did not affect the binding of [3H]milnacipran in any region. These results show that [3H]milnacipran mainly binds to the serotonin transporter and does not recognize the catecholamine transporters under the conditions used. In addition, [3H]milnacipran might also bind to other sites, serotonin transporter localized on non-serotonergic neurons or serotonergic neurons insensitive to 5,7-DHT neurotoxicity.