Cutaneous malignant melanoma and exposure to sunlamps or sunbeds: an EORTC multicenter case-control study in Belgium, France and Germany. EORTC Melanoma Cooperative Group

The study objective was to assess whether exposure to sunlamps and sunbeds represents a risk factor for cutaneous malignant melanoma (CMM). A 1-to-1 unmatched case-control study was conducted among subjects 20 years old or more with naturally non-pigmented skin in Germany, France and Belgium. A total of 420 consecutive patients with CMM diagnosed from 1 January 1991 onward were derived from hospital registers; 447 controls with no history of skin cancer were chosen at random in the same municipality as the cases. Exposure to sunlamps or sunbeds starting before 1980 is associated with a crude estimated risk of CMM of 2.71 (95% CI: 1.06-7.78) for at least 10 hr of accumulated exposure. This risk is of 2.12 (95% CI: 0.84-5.37) after adjustment for age, sex, hair colour and average number of holiday weeks each year in sunny resorts. Subjects who experienced skin-burn due to sunlamps or sunbeds, and who had accumulated at least 10 hr of exposure, displayed a crude estimated CMM risk of 4.47 (95% CI: 1.45-13.7), which rose to 8.97 (95% CI: 2.10-38.6) for those who exposed their skin for tanning purposes. The risk associated with skin-burn is only marginally modified after multiple adjustments for host characteristics and recreational exposure to sunlight. Apparently, sunlamps and sunbeds share the increased risk of CMM, which seems to concentrate in subjects exhibiting hazardous behaviour towards ultraviolet radiation sources. However, although it is reasonable to believe that high doses of pure ultraviolet A radiation can be dangerous, this is not firmly established by this study. Most exposures to ultraviolet A tanning devices began after 1980; therefore, epidemiologic studies have difficulty in revealing any increase in risk of CMM starting after 1980 because of the latent period between exposure and occurrence of melanoma. Public health authorities should have a cautious approach towards the rapidly developing fashion of tanning under sunlamps or sunbeds.

Blockade of transmission at NMDA receptors facilitates the electrical and synthetic activity of ascending serotoninergic neurones

This study examined the influence of N-methyl-D-aspartate (NMDA) receptors upon the activity of serotoninergic neurones projecting from the rat dorsal raphe nucleus (DRN) to the striatum of rats. The channel blocker (+)-MK 801 (0.04-0.63 mg/kg, s.c.) augmented striatal accumulation of the serotonin (5-HT) precursor, 5-hydroxytryptophan (5-HTP), in rats treated with the inhibitor of decarboxylase, NSD 1015: the maximal effect of (+)-MK 801 was 164% relative to vehicle values (= 100%). In analogy, (+)-MK 801 (0.01-0.5 mg/kg, i.v.) increased the firing rate of DRN neurones with a maximal effect of 204%. This action was stereospecific in that (-)-MK 801, which shows lower affinity at NMDA receptors, enhanced firing only at higher doses. The selective, competitive antagonist at the NMDA recognition site, CPP (0.5-8.0 mg/kg, i.v.), also facilitated the firing rate of DRN neurones, though with a maximal effect (137%) less than that of (+)-MK 801. Further, CPP (40.0 mg/kg, s.c.) did not significantly modify striatal 5-HT synthesis. While NMDA did not significantly modify DRN firing alone, it abolished the facilitatory action of CPP, consistent with a competitive interaction at the NMDA recognition site. In conclusion, blockade of NMDA receptors specifically facilitates the activity of ascending serotoninergic neurones.

Rationale for using TNF alpha and chemotherapy in regional therapy of melanoma

Recombinant tumor necrosis factor-alpha (rTNF alpha) has potent antitumor activity in experimental studies on human tumor xenografts. However, in humans, the administration of rTNF alpha is hampered by severe systemic side-effects. The maximum tolerated dose ranges from 350 to 500 mg/m2, which is at least 10-fold less than the efficient dose in animals. Isolation perfusion of the limbs (ILP) allows the delivery of high dose rTNF alpha in a closed system with acceptable side-effects. A protocol with triple-drug regimen was based on the reported synergism of rTNF alpha with chemotherapy, with interferon-gamma, and with hyperthermia. In melanoma-in-transit metastases (stage IIIA or AB) we obtained a 91% complete response, compared with 52% after ILP with melphalan alone. Release of nanograms levels of TNF alpha in the systemic circulation was evident but control of this leakage and appropriate intensive care resulted in acceptable toxicity. Angiographic, immunohistological, and immunological studies suggest that the efficacy of this protocol is due to a dual targeting: rTNF alpha activates and electively lyses the tumor endothelial cells while melphalan is mainly cytotoxic to the tumor cells. ILP with rTNF alpha appears to be a useful model for studying the biochemotherapy of cancer in man.

Hypercalcaemia in B cell chronic lymphocytic leukaemia

Hypercalcaemia is common in some lymphoproliferative disorders such as myeloma or T-cell leukaemia-lymphoma, but is rarely described in B cell chronic lymphocytic leukaemia (BCLL). We report the case of a patient with BCLL, hypercalcaemia and osteolytic bone lesions. Parathyroid hormone-related protein (PTHrP) mRNA was identified by Northern blot analysis of liver, spleen and lymph node tumour samples. Serum levels of tumour necrosis factor alpha (TNF alpha) were increased.

Clinical experience with high-dose tumor necrosis factor alpha in regional therapy of advanced melanoma

Isolated perfusion of the limbs (ILP) allows the delivery of high dose rTNF alpha in a closed system with acceptable side-effects. A protocol with a triple-drug regimen was based on the reported synergism of rTNF alpha with chemotherapy, with interferon-gamma, and with hyperthermia. In melanoma-in-transit metastases (stage IIIA or AB) we obtained a 91% complete response compared with 52% after ILP with melphalan alone. Leakage and release of nanograms levels of TNF alpha in the systemic circulation can be abrogated in most patients by low pump flow, continuous leak monitoring, extensive washout, and limb massage. In case of unavoidable leakage, appropriate intensive care results in minimal toxicity. The ILP with rTNF alpha appears to be a useful model for studying the biochemotherapy of cancer in humans.

Clozapine inhibits serotoninergic transmission by an action at alpha 1-adrenoceptors not at 5-HT1A receptors

This study examined the mechanism underlying the influence of clozapine upon serotoninergic transmission in the rat. In vitro, clozapine manifested weak affinity at 5-HT1A receptors (pKi = 6.5) as compared to the agonist, 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) (9.0), but high affinity at alpha 1-adrenoceptors (8.2) as compared to the alpha 1-adrenoceptor antagonist, prazosin (9.7). Ex vivo, clozapine (inhibitory dose (ID)50 = 0.7 mg/kg s.c.) mimicked prazosin (0.5) in potently occupying central alpha 1-adrenoceptors whereas, as compared to 8-OH-DPAT (0.2), it failed to occupy 5-HT1A receptors (> 10.0). The firing of serotoninergic neurones in the dorsal raphe nucleus was abolished by 8-OH-DPAT, clozapine and prazosin with ID50 values of 0.006, 0.09 and 0.07 mg/kg i.v., respectively. At comparable doses, they reduced striatal turnover of 5-HT. While the 5-HT1A receptors antagonists, (-)-tertatolol (2.0 mg/kg i.v.) and spiperone (0.63 mg/kg i.v.), blocked the action of 8-OH-DPAT upon dorsal raphe nucleus firing, they failed to modify the effect of clozapine and prazosin. In contrast, the alpha 1-adrenoceptor agonist, cirazoline (0.005 mg/kg i.v.) prevented the actions of clozapine and prazosin, but not that of 8-OH-DPAT. It is concluded that clozapine only weakly interacts with 5-HT1A receptors and that its potent alpha 1-adrenoceptor antagonist properties underlie inhibition of serotoninergic transmission.

Early endothelium activation and polymorphonuclear cell invasion precede specific necrosis of human melanoma and sarcoma treated by intravascular high-dose tumour necrosis factor alpha (rTNF alpha)

Twenty-seven patients treated with high-dose rTNF alpha, IFN gamma and melphalan by isolated limb perfusion were histologically documented. There were 20 cases of melanoma-in-transit metastases and 7 cases of high-grade soft-tissue sarcoma. Biopsies were taken before IFN gamma, after IFN gamma, before TNF alpha and between 2 hr and 60 days after the TNF alpha perfusion. Immunohistochemistry was performed for adhesion molecules ICAM-I, ELAM-I (E selectin), VCAM-I and PECAM. During the first hours after beginning perfusion, the endothelial cells of the tumour capillaries appeared swollen. Significant tumour necrosis was already observed 3 hours after the perfusion in melanoma cases. The overall predominant feature was coagulative necrosis associated or not with haemorrhagic necrosis. TNF alpha induced increased expression of ELAM-I and VCAM-I adhesion molecules on intratumoral endothelial cells. The activated tumour vessels were progressively destroyed. Significant intravascular recruitment of polymorphonuclear cells (PMNs) was observed 3 hr after starting TNF alpha; it was followed by diapedesis and tumour colonization 3 days later. T lymphocytes and macrophages were detected during the first 7 days and B lymphocytes during the second week. Melanoma in transit metastases treated with alkylating agent alone did not show significant necrosis and did not express high levels of adhesion molecules (ELAM-I, VCAM-I) nor infiltration by PMN.

Recreational exposure to sunlight and lack of information as risk factors for cutaneous malignant melanoma. Results of an European Organization for Research and Treatment of Cancer (EORTC) case-control study in Belgium, France and Germany. The EORTC Malignant Melanoma Cooperative Group

This study addressed the impact of exposure to ultraviolet radiation on the risk of cutaneous malignant melanoma (CMM), as well as the behavioral components at stake in its occurrence. We performed a one-to-one unmatched case-control study among subjects aged 20 years or more with naturally non-pigmented skin in Germany, France and Belgium. Four-hundred and twenty consecutive patients with CMM diagnosed from 1 January 1991 on were derived from hospital registries; 447 controls were chosen randomly in the same municipality as cases. Subjects unaware of the dangers of exaggerated exposure to sunlight display an estimated CMM risk of 3.72% (95% confidence interval 2.63-5.26). The number of holiday weeks spent annually in sunny resorts and sunbathing during the hot hours of the day are strong risk factors in the three countries, but not the number of years spent outdoors, as farmers or building workers. Multiple logistic adjustments on the host characteristics increases the CMM risk associated with recreational exposure to sunlight, as well as the adjustment on the unawareness of the dangers of exaggerated exposure to sunlight. Recreational exposure to sunlight and sunburn early in life seem capable of fostering the proliferation of pigmented lesions of the skin. Our data support the hypothesis that most CMM develop from pigmented lesions of the skin containing initiated melanocytes, and that the cell proliferation due to brutal, intermittent exposures to solar radiation amplifies the likelihood of a melanocyte entering into a malignant process.(ABSTRACT TRUNCATED AT 250 WORDS)

Novel benzodioxopiperazines acting as antagonists at postsynaptic 5-HT1A receptors and as agonists at 5-HT1A autoreceptors: a comparative pharmacological characterization with proposed 5-HT1A antagonists

The novel benzodioxopiperazines [4-(benzodioxan-5-yl)1-[2- (benzocyclobutane-1-yl)ethyl]piperazine] (S 14489), [4-(benzodioxan-5-yl)1-(indan-2-yl)piperazine)] (S 15535) and [4-(benzodioxan-5-yl)1-[2(indan-1-yl)ethyl]piperazine (S15931) competitively displaced the binding of [3H]-8-OH-DPAT at serotonin (5-HT)1A receptors with affinities (pKis) of 9.2, 8.8 and 8.9, respectively. These values compared favorably with those of the structurally related eltoprazine (8.0) and the proposed 5-HT1A antagonists NAN-190 (9.2), MDL 73005 EF (8.9), SDZ 216-525 (8.8), BMY 7378 (8.7), (-)-tertatolol (8.1), (-)-alprenolol (7.7), WAY 100,135 (7.5) and spiperone (6.9). The affinities of S 14489, S 15535 and S 15931 for other 5-HT receptor types (5-HT1B, 5-HT1C, 5-HT1D, 5-HT2 and 5-HT3) were about 50 to 1000-fold lower. The spontaneous tail-flicks, flat-body posture and hypothermia mediated by an action of the 5-HT1A agonist 8-OH-DPAT at postsynaptic 5-HT1A receptors were dose-dependently and completely antagonized by S 14489, S 15535 and S15931 at doses of 0.63 to 10.0 and 2.5 to 40.0 mg/kg for s.c. and oral administration, respectively. They did not induce these responses alone, and in their presence, dose-response curves for 8-OH-DPAT were shifted in parallel to the right without loss of maximal effect. By contrast, eltoprazine, MDL 73005 EF, BMY 7378 and NAN-190 behaved as "partial" agonists and only incompletely antagonized the actions of 8-OH-DPAT in these tests. At 5-HT1A autoreceptors, S 14489, S 15535 and S 15931 acted as agonists in inhibiting striatal 5-hydroxytryptophan accumulation (0.16-2.5 mg/kg, s.c.) and in abolishing the electrical activity of the dorsal raphe nucleus (0.005-0.100 mg/kg, i.v.). Eltoprazine, BMY 7378, NAN-190 and MDL 73005 EF also behaved as agonists at these 5-HT1A autoreceptors, whereas WAY 100,135, spiperone, (-)-tertatolol, (-)-alprenolol and SDZ 216-525 inhibited neither accumulation nor firing. WAY 100,135 and spiperone antagonized the inhibition of DRN firing induced by S 14489, S 15535 and S 15931. The affinity of 15535 for dopamine D1 and D2 receptors, as well as for beta-, alpha 1- and alpha 2-adrenoceptors, was > 100-fold lower than its affinity for 5-HT1A receptors. Further, in vivo, at doses of 10.0 to 40.0 mg/kg, s.c., it showed minimal activity in tests of dopamine D2 (and D1) receptor-mediated activity. Similarly, in vivo, S 15535 was weakly active in a test of alpha 1-adrenoceptor-mediated activity.(ABSTRACT TRUNCATED AT 400 WORDS)

Electrospray mass spectrometric analysis of new alpha-MSH analogues carrying nitrogen mustard at their amino terminus

Two different chlorinated drugs, chlorambucil and melphalan, have been linked to the carrier alpha-melanocyte-stimulating hormone at the end of the solid-phase peptide synthesis of the hormone. The [Nle4, D-Phe7] and the [Nle4, L-Phe7] derivatives of the hormone have both been used. It was found by electrospray mass spectrometric analysis that the products undergo hydrolysis of the chlorinated moiety of the drugs, most likely due to the acidic conditions necessary for cleavage of the peptide from the resin. Only the melphalan-O(ethyl)-N(succinyl)-derivative of alpha-melanocyte-stimulating hormone [Nle4, L-Phe7] did not show a bis-hydroxylated form. It was proven by blank experiments with commercially available melphalan that this mustard occurs for some 45%-50% in the mono-hydroxylated form, which is known to be pharmacologically poorly active.

Glutathione depletion increases tyrosinase activity in human melanoma cells

The aim of the present work was to estimate the effect of intracellular glutathione depletion on melanogenesis in human melanoma cells. We determined tyrosine hydroxylation activity, the rate-limiting step of the pathway, and 14C-melanin formation, an assay reflecting the global eumelanogenic pathway. Intracellular glutathione was depleted by treatment with buthionine-S-sulfoximine, a well-known inhibitor of gamma-glutamylcysteine synthetase. The intracellular depletion of glutathione was substantial after 20 h of incubation with 50 microM buthionine-S-sulfoximine, although a significant effect could be observed after 6 h. Tyrosine hydroxylase activity increased in parallel with glutathione depletion, to reach 160% with respect to the control values during 24 h of buthionine-S-sulfoximine treatment. We have found the response to buthionine-S-sulfoximine to be dose dependent and the two different human cell lines HBL and LND1 to have similar, if not identical, responses. 14C-melanin formation assay revealed even greater activation, up to 400% of the control values. This indicates that glutathione depletion may have two distinct effects: first, a direct one on tyrosinase activity and, second, an effect on the promotion of eumelanogenesis. The stimulation of tyrosine hydroxylase can be explained by a possible inactivation of the enzyme by endogenous thiol compounds rather than by a direct effect of buthionine-S-sulfoximine itself on tyrosinase. The data suggest that thiol compounds may play a role for stimulation of melanogenesis by ultraviolet radiation.

Early prediction of response to recombinant human erythropoietin in patients with the anemia of renal failure by serum transferrin receptor and fibrinogen

Recombinant human erythropoietin (rHuEpo) has been shown to be effective in correcting the anemia of chronic renal failure, but the dose needed may be variable. The reason for this variation is not known, but several factors could be involved, such as iron deficiency, inflammation, aluminum intoxication, hyperparathyroidism, blood losses, or marrow dysfunction. Treatment with rHuEpo was given intravenously thrice weekly after hemodialysis to 64 consecutive unselected patients with the anemia of chronic renal failure. The starting dose was 50 U/kg/dose, which was increased to 75 and 100 U/kg/dose if no response was observed after 1 and 2 months of treatment. After a minimum follow-up of 6 months, response was evaluated as early (hematocrit [Hct] > or = 30% before 3 months) or late (Hct > or = 30% after 3 months) response, or failure (target Hct not attained). We examined the value of various laboratory parameters (baseline values and early changes) as predictors of response to rHuEpo. The best prediction by pretreatment parameters only was obtained with baseline serum transferrin receptor (TfR) (< or > or = 3,500 ng/mL) and fibrinogen (< or > or = 4 g/L): 100% response rate when both parameters were low, versus only 29% when they were both high, and versus 67% when one was low and the other high. When the 2-week TfR increment was greater than 20%, the response rate was 96%. When TfR increment was less than 20%, the response rate was 100% when baseline TfR and fibrinogen were low, 12% when fibrinogen was elevated, and 62% when fibrinogen was low but baseline TfR high. The predictive value of baseline TfR and fibrinogen and of the 2-week increment of TfR was confirmed by life table analysis and stepwise discriminant analysis. Major reasons for failure or late response were identified and included subclinical inflammation, iron deficiency, functional iron deficiency, marrow disorders, hemolysis, bleeding, and low Epo dose. We conclude that response to rHuEpo can be predicted early by pretreatment fibrinogen and TfR, together with early changes of TfR levels. These prognostic factors illustrate the importance of the early erythropoietic response, subclinical inflammation, and functional iron deficiency. Early recognition of a low probability of response in a given patient could help identify and correct specific causes of treatment failure to hasten clinical improvement and avoid prolonged ineffective use of an expensive medication.

Labelled polycyanoacrylate nanoparticles for human in vivo use

Isobutyl and isohexyl cyanoacrylate nanoparticles are used as drug carriers, particularly for some anti-cancer drugs. Body distribution as well as pharmacokinetics have been well studied in animal and partially in man. Labelling of the monomer itself or of the carried drug with beta-emitters allowed such studies. In man, however, organ distribution and uptake could easily be done and followed by means of scintigraphy (imaging) techniques if one could achieve nanoparticle labelling with gamma-emitting isotopes. We have developed labelling methods able to supply such carriers using gamma-emitters like radioactive iodine (125I or 131I), indium or technetium. We used DTPA as a spacer in order to fix the last two isotopes. This would mean that any other gamma-emitting cation can theoretically be tried pending on its ability to be chelated by DTPA. The preparations were obtained with high labelling yields, usually > 80% and were relatively stable in human plasma over the whole period of investigation. 111In and 99mTc labelled forms have been administered to rabbit and then to man with 60-75% accumulation in the reticulo-endothelial system.

WAY 100,135 and (-)-tertatolol act as antagonists at both 5-HT1A autoreceptors and postsynaptic 5-HT1A receptors in vivo

In binding studies, WAY 100,135 (N-tertiobutyl-3-[4-(2-methoxyphenyl)-piperazinyl]-2-phenylpropana mide) and (-)-tertatolol showed affinities (Ki) of 29 nM and 10 nM, respectively, at 5-HT1A receptors. In vivo, they both dose dependently blocked the flat-body posture and corticosterone secretion provoked by an action of the 5-HT1A receptor agonist, S 14671 (1-[2-(2-thenoyl-amino)ethyl]-4-[1-(7- methoxynaphtyl)]piperazine), at postsynaptic 5-HT1A receptors. Alone, they exerted little effect. The firing rate of dorsal raphe neurones, which bear inhibitory 5-HT1A autoreceptors, was reduced by S 14671 whereas it was not affected by WAY 100,135 and was increased by (-)-tertatolol. Both WAY 100,135 and (-)-tertatolol blocked the ability of S 14671 to inhibit raphe firing. In conclusion, these data demonstrate that WAY 100,135 and (-)-tertatolol behave as antagonists at both 5-HT1A autoreceptors and postsynaptic 5-HT1A receptors in vivo.

Plasma cell leukaemia mimicking acute monocytic leukaemia in the course of multiple myeloma

We report a case of acute leukaemia occurring early in the course of IgA multiple myeloma. Ultrastructural studies, immunophenotyping and karyotyping were required to identify the origin and clonality of the leukaemic cells. Although ultrastructural examination of the blast cells revealed both monocytoid and plasma cell features, all cells expressed the CD 38 antigen and intracytoplasmic kappa light chains, while karyotyping revealed a clone with numerous abnormalities, leading to the diagnosis of clonal plasma cell disease. The occurrence of leukaemia in multiple myeloma is discussed.

Tumor-necrosis factor can enhance radio-antibody uptake in human colon carcinoma xenografts by increasing vascular permeability

Marked differences in the tumor uptake of a 125I-labeled monoclonal antibody (MAb) directed against carcinoembryonic antigen (CEA) were observed in 4 serially transplanted human colorectal carcinomas in nude mice. A comparative study showed that elevated values of measurable tumor vascular parameters, such as permeability, blood flow and blood volume, correlated better with high MAb tumor uptake than the concentration of target antigen in the tumor. In an attempt to modify the vascular parameters and to determine if this could increase antibody uptake by the tumor, rhTNF alpha (TNF) was injected i.t. or i.v. and antibody localization experiments were performed immediately thereafter. Results showed that the permeability of the tumor vessels increased 8 to 10 fold 1 hr after i.t. injection of TNF as compared to control tumors injected with saline. Tumor uptake of 125I-labeled anti-CEA MAb, was 3 times higher 2 hr after i.v. injection and still 27% higher 22 hr later, as compared to results from controls. Intravenous injection of TNF simultaneously with the 125I-labeled anti-CEA MAb also resulted in a 2-fold increase in tumor uptake 4 hr after injection, but the increase was no longer significant 24 hr after injection. Interestingly after i.v. injection of TNF, the MAb concentration in the blood and other normal tissues, such as liver, kidneys, lungs and heart was decreased, resulting in significantly higher ratios of tumor to normal tissue. Taken together the results demonstrate that injection of TNF can increase tumor vascular permeability and improve radio-antibody uptake. This raises the possibility of increasing the radiation dose delivered by antibody to the tumor in the course of radioimmunotherapy.

Disseminated melanoma, preclinical therapeutic studies, clinical trials, and patient treatment

Disseminated malignant melanoma is a very resistant tumor to therapy. Mechanisms of resistance to chemotherapy may be due to glutathione reductase and O6 alkyltransferase, two enzymes especially able to detoxify from alkylation. An interesting model is represented by dacarbazine in the treatment of melanoma with nitrosourea derivatives. Cytokines may come to play an increasing role in the combination with chemotherapy; interferon-alpha and interleukin-2, for example, seem to potentiate the action of chemotherapy in well-designed clinical protocols. Moreover, tumor necrosis factor-alpha was shown to be active in combination therapy with interferon-gamma and chemotherapy when administered by isolation perfusion. Targeting with monoclonal antibodies or melanocyte-stimulating hormone-alpha conjugated to cytotoxic agents represents a promising area. The discovery of a gene, designated MAGE1, coding for a peptide presented by HLA-A1 and able to specifically activate cytotoxic T lymphocytes may represent a unique approach to specific active immunotherapy for melanoma. The interference with integrins and adhesion molecules may play a role in the prevention of metastases. Some preclinical models seem to validate this approach. Current treatment of disseminated malignant melanoma involves chemotherapy often associated with other cytotoxic agents or cytokines, which may potentiate the antitumor effect. Other therapeutic issues reviewed concern targeting and immunotherapy. This review ends with a survey of biologic factors that may constitute new approaches to melanoma therapy.

S 15535: a highly selective benzodioxopiperazine 5-HT1A receptor ligand which acts as an agonist and an antagonist at presynaptic and postsynaptic sites respectively

The novel benzodioxopiperazine, S 15535 (4-(benzodioxan-5-yl)1-(indan-2- yl)piperazine), displayed high affinity for 5-HT1A binding sites (1.8 nM) whereas its affinity was 100-fold lower at other 5-HT receptor types, at alpha 1, alpha 2- and beta-adrenoceptors and at dopamine D1 and D2 receptors. In vivo, S 15535 (0.16-10 mg/kg s.c.) acted as an antagonist at postsynaptic 5-HT1A receptors in completely blocking the flat-body posture and hypothermia elicited by the 5-HT1A receptor agonist, 8-OH-DPAT. It had no effect when applied alone. At presynaptic 5-HT1A receptors, S 15535 acted as an agonist in inhibiting striatal accumulation of 5-hydroxytryptophan (0.04-0.63 mg/kg s.c.) and in spiperone reversibly reducing electrical activity of the dorsal raphe nucleus (0.004-0.031 mg/kg i.v.). At doses up to 40.0 mg/kg s.c., S 15535 neither inhibited methylphenidate-induced gnawing nor elicited ptosis suggesting a lack of antagonist properties at, respectively, dopamine D2 receptors and alpha 1-adrenoceptors. In conclusion, S 15535 is a potent 5-HT1A ligand which acts, in vivo, as a highly selective agonist and antagonist at presynaptic and postsynaptic 5-HT1A receptors, respectively.