Frequent administration of levodopa/carbidopa microtablets vs levodopa/carbidopa/entacapone in healthy volunteers.

OBJECTIVES: An oral dispersible microtablet formulation of levodopa/carbidopa 5/1.25 mg (LC-5) was developed for individualized repeated dosing. The aim was to compare pharmacokinetic profiles of LC-5 and levodopa/carbidopa/entacapone (LCE). MATERIALS AND METHODS: A randomized, crossover study was carried out in 11 healthy subjects. Plasma concentrations of levodopa, carbidopa and 3-O-methyldopa were determined after intake of 300 mg levodopa during the day, either as three intakes of 100/25/200 mg LCE or as a morning dose of 75/18.25 mg followed by five repeated doses of 45/11.25 mg LC-5. RESULTS: Repeated dosing (2.4-hourly) with LC-5 microtablets compared to LCE (6-hourly) avoided long periods with low plasma levodopa levels. Time to maximum plasma concentrations was significantly shorter for LC-5. LC-5 showed lower fluctuation index (FI) in plasma compared to LCE (ANOVA P = 0.0028). FI for dose 2-5 was on average 1.26 for levodopa in LC-5, and 2.23 for dose 1-2 of LCE. The ratio between the two mean FI:s is 0.565; that is, LC-5 gave nearly half the FI as compared to LCE. CONCLUSIONS: Fractionation of levodopa with LC-5 into small, frequent administrations as compared to standard administrations of LCE decreased the FI in plasma for both levodopa and carbidopa by nearly half.

Monitoring of reactive oxygen species production after traumatic brain injury in rats with microdialysis and the 4-hydroxybenzoic acid trapping method.

The detection of reactive oxygen species (ROS) after traumatic brain injury (TBI) is based on indirect methods due to the high reactivity and short half-life of ROS in biological tissue. The commonly used salicylate trapping method has several disadvantages making it unsuitable for human use. We have evaluated 4-hydroxybenzoic acid (4-HBA) together with microdialysis (MD) in the rat as an alternative method. 4-HBA forms one stable adduct, 3,4-dihydroxybenzoic acid (3,4-DHBA), when reacting with ROS and has not previously been used together with MD after TBI. Twenty-seven rats were used for the assessment of 3,4-DHBA production as an indicator of ROS formation in a controlled contusion injury model using intracerebral MD with 3 mM 4-HBA in the perfusate. For comparison, salicylate trapping was used in eight rats. TBI caused a 250% increase of 3,4-DHBA that peaked at 30 min after injury in severely injured rats and remained significantly elevated as compared to baseline for 90 min after trauma. The mild injury level caused a 100% increase in 3,4-DHBA formation at 30 min after the injury. When the MD probe was placed in the perimeter of the injury site, no significant increase in ROS formation occurred. Salicylate trapping showed a similar increase in adduct formation after severe injury. In addition, high cortical concentrations of 4-HBA and salicylate were found. It is concluded that microdialysis with 4-HBA as a trapping agent appears to be a useful method for ROS detection in the rat with a potential clinical utility.

Effects of the nitrone radical scavengers PBN and S-PBN on in vivo trapping of reactive oxygen species after traumatic brain injury in rats.

In previous studies, the authors showed that the nitrone radical scavenger alpha-phenyl-N- tert -butyl nitrone (PBN) and its sulfo-derivative, 2-sulfo-phenyl-N- tert -butyl nitrone (S-PBN), attenuated cognitive disturbance and reduced tissue damage after traumatic brain injury (TBI) in rats. In the current study, the production of reactive oxygen species (ROS) after TBI was monitored with microdialysis and the 4-hydroxybenzoic acid (4-HBA) trapping method. A single dose of PBN (30 mg/kg) or an equimolar dose of S-PBN (47 mg/kg) was administered intravenously 30 minutes before a controlled cortical contusion injury in rats. Plasma and brain tissue drug concentrations were analyzed at the end of the microdialysis experiment (3 hours after injury) and, in a separate experiment with S-PBN, at 30 and 60 minutes after injury. Traumatic brain injury caused a significant increase in ROS formation that lasted for 60 minutes after the injury as evidenced by increased 3,4-dihydroxybenzoic acid (3,4-DHBA) concentrations in the dialysate. PBN and S-PBN equally and significantly attenuated the posttraumatic increase in 3,4-DHBA formation. High PBN concentrations were found bilaterally in brain tissue up to 3 hours after injury. In contrast, S-PBN was rapidly cleared from the circulation and was not detectable in brain at 30 minutes after injury or at any later time point. The results suggest that scavenging of ROS after TBI may contribute to the neuroprotective properties observed with nitrone spin-trapping agents. S-PBN, which remained undetectable even in traumatized brain tissue, reduced ROS production to the same extent as PBN that readily crossed the blood-brain barrier. This finding supports an important role for ROS production at the blood-endothelial interface in TBI.

Patient-rated versus clinician-rated side effects of drug treatment in schizophrenia. Clinical validation of a self-rating version of the UKU Side Effect Rating Scale (UKU-SERS-Pat).

A self-rating version of the UKU Side Effect Rating Scale has been developed. The present study examines the agreement between patients' self-assessment of side effects and the attending clinicians' ratings. The patient sample consisted of 63 patients with schizophrenia under maintenance treatment with risperidone, clozapine or classical antipsychotics. Approximately two thirds of the patients used concomitant medication with e.g. benzodiazepines, SSRIs, anticholinergics. Most inter-correlations between scores for single, corresponding items, subscores of Psychic, Neurological, Autonomic and Other side effects, as well as the Total Score from the patient version of the UKU Side Effect Self Rating Scale (UKU-SERS-Pat) and the clinician version (UKU-SERS-Clin) were found to be statistically significant. Patients reported side effects more frequently and or rated symptoms more severe than the clinicians. The results support the validity of the SERS-Pat and suggest that patient rated side effects may provide important clinical information not detected by clinician rated interviews. Such information can be utilised both in clinical investigations, in development of treatment programs and for individual patients in clinical practice.

Assessment of patient satisfaction with psychiatric care. Development and clinical evaluation of a brief consumer satisfaction rating scale (UKU-ConSat).

Quality management and quality control of health services has become increasingly important. Central to the concept of quality of care is the patient's (the health care consumer's) own view of the care provided and the treatment outcome. UKU (Udvalg for Kliniske Undersøgelser; that is, Committee for Clinical Trials), a working group within the Scandinavian Society for Psychopharmacology (SSP), has designed a brief consumer satisfaction rating scale, the UKU-ConSat. Based on an extensive literature review, a number of principles related to content, assessment, interview techniques, documentation and standardisation steered the design of the rating scale. UKU-ConSat consists of six items related to the structure and process of treatment care, and two items related to outcome and well-being. A manual accompanies the rating scale with guidelines for how to solicit information from the patient and how to rate each item. A first field trial of the rating scale in 135 inpatients at multiple clinical sites in Finland and Sweden showed that it could be applied to several relevant patient categories (psychotic, affective, neurotic, organic and alcohol and substance abuse disorders). According to both patients and staff the rating scale promises to become useful both for research and for improvement of routine psychiatric services.

Consumer satisfaction in schizophrenia. A 2-year randomized controlled study of two community-based treatment programs.

Quality management and quality control of health services have become increasingly important. Central to the concept of quality of care is the consumer's (the patient's) own view of the care provided. UKU (Udvalg for Kliniske Undersøgelser), a task force within the Scandinavian Society for Psychopharmacology, has designed a brief consumer satisfaction rating scale, the UKU-ConSat. The UKU-ConSat rating scale was applied in a randomised comparative two-year study of two community-based treatment programs. The study included 84 patients with schizophrenic disorders according to DSM-IV. The major finding was a significantly increased consumer satisfaction with the new community-based program "Integrated Care" in comparison with best-established practice, called "Rational Rehabilitation." Thus, the new UKU-ConSat rating scale can detect differences, not only for in-patients as has previously been shown, but also between programs in community care settings. By per item analysis it was possible to discriminate between various elements of consumer satisfaction. There were significant correlations between the UKU-ConSat total scores and other clinical outcome domains, viz. symptoms, social function, and patient as well as carer's distress. To conclude, the UKU-ConSat rating scale is suitable for quality management and monitoring of treatment programs in mental health services.

Pharmacogenomics to predict drug response.

From theory to proof-of-concept, pharmacogenomics promises to improve future general healthcare in a number of ways. By identifying individuals who will respond to a particular drug treatment compared to those who have a low probability of response, pharmacogenomic test development hopes to aid the physician in prescribing the optimal medication for each patient. This approach promises faster relief from symptoms, a lowering of side effect risks and a reduction in healthcare costs. Pharmacogenomic tests used by the pharmaceutical companies themselves can be used to help identify suitable subjects for clinical trials, aid in interpretation of clinical trial results, find new markets for current products and speed up the development of new treatments and therapies. This type of approach should also see fewer compounds failing during later phases of development. The questions we are faced with as we enter the new millennium, however, are if and when the promises of pharmacogenomnics in improving healthcare will be fulfilled. Currently, there are only a handful of pharmacogenomic tests and associated products which are commercially available and it remains to be seen what impact these will have on the market and on healthcare in general.

Differential tissue distribution of the enantiomers of racemic pindolol in the rat.

Racemic pindolol, a beta-adrenoceptor and a 5-HT1A/1B receptor antagonist, has been reported to augment and accelerate the clinical efficacy of antidepressants. The (S)-enantiomer is more potent than the (R)-enantiomer both at the beta-adrenergic and at the 5-HT1A/1B receptors. A chiral HPLC column was used for determination of tissue concentrations of the enantiomers of pindolol at 90 min after 8 mg/kg s.c. of the racemate. The (S)/(R) ratio was found to vary between tissues from 1.74 in brain to 0.82 in plasma. The present findings may be important for understanding the pharmacodynamic actions of racemic pindolol.

Pharmacokinetic and pharmacodynamic studies of (R)-8-hydroxy-2-(di-n-propylamino)tetralin in the rat.

Racemic 8-OH-DPAT, (R,S)-8-hydroxy-2-(di-n-propylamino)tetralin, has become the prototype 5-HT1A receptor agonist. The enantiomers of 8-OH-DPAT have similar affinities to the 5-HT1A receptor, but the (R)-enantiomer is a full agonist, whereas the (S)-enantiomer is a partial agonist. This communication describes the dose- and time-response relationships of behavioural (5-HT behavioural syndrome, cage-leaving response), physiological (body temperature) and biochemical (5-HT turnover, 5-hydroxytryptophan accumulation) effects of (R)-8-OH-DPAT in rats. A high-performance liquid chromatography (HPLC)-UV method for determination of plasma and brain concentrations of (R)-8-OH-DPAT was developed, permitting studies of the pharmacokinetics of the drug. The concentrations of 8-OH-DPAT in brain were several fold higher than in plasma, and there were large variations in (R)-8-OH-DPAT concentrations between brain regions (highest in the hippocampus). (R)-8-OH-DPAT peaked in plasma at 5 min and in brain at 15 min after subcutaneous administration. The 5-HT1A behavioural syndrome peaked within 5 min after administration and disappeared after 30 min, when brain concentrations were still high. The hypothermic and biochemical responses developed gradually and were maximal at 45-60 min post injection, when both plasma and brain concentrations were declining. Thus, there was not a simple relationship between the kinetics and the dynamics of (R)-8-OH-DPAT. These results prompt further studies on the pharmacokinetics of 8-OH-DPAT within the central nervous system.

Pharmacodynamic and pharmacokinetic studies in rats of S-8-(2-Furyl)- and R-8-phenyl-2-(di-n-propylamino) tetralin, two novel 5-HT1A receptor agonists in-vitro with different properties in-vivo.

R- and S-8-(2-Furyl)- and R- and S-8-phenyl-2-(di-n-propylamino)tetralins (R- and S-LY-55 and R- and S-LY-49, respectively), novel enantiopure dipropylaminotetralins, have been screened as 5-HT1A receptor ligands. All had nanomolar affinities for 5-HT1A receptors and fully inhibited forskolin-stimulated adenylyl cyclase in-vitro (i.e. the four compounds appeared to be 5-HT1A agonists). It was also found that the enantiomers of LY-55 behaved as typical 5-HT1A receptor agonists in rats in-vivo by inducing a typical behavioural 5-HT syndrome, hypothermia and a decrease in 5-HT synthesis and turnover, indicating effects both on postsynaptic 5-HT1A receptors and somatodendritic 5-HT1A autoreceptors. In contrast, R- and S-LY-49 did not cause any 5-HT1A receptor-related effects in-vivo except for a partial inhibition of 5-HT synthesis after high doses. The 5-HT1A receptor antagonist WAY-100635 was shown to attenuate the R-LY-49-induced inhibition of 5-HT synthesis, indicating the compound to be a weak agonist at somatodendritic 5-HT1A autoreceptors. R-LY-49 at a high dose and with a long pre-treatment time interval inhibited the hypothermic and behavioural effects, but not the inhibition of 5-HT synthesis induced by the 5-HT1A receptor agonist R-8-hydroxy-(dipropylamino)tetralin (R-8-OH-DPAT). Taken together, these findings seem to indicate, that R-LY-49 is a weak partial agonist at 5-HT1A receptors. A comparative pharmacokinetic study showed that the enantiomers of LY-55 entered the brain rapidly after subcutaneous administration and reached peak brain tissue/plasma concentration ratios within 15-30 min of injection, whereas the brain concentrations of R-LY-49 increased slowly, reaching a relatively low peak brain tissue/plasma concentration ratio 90 min after injection despite their similar lipophilicity. The differences between the pharmacological activity of the two compounds in-vivo seem to be explained by their different abilities to cross the blood-brain barrier, and a weak agonistic activity of R-LY-49 on 5-HT1A receptors, both pre- and postsynaptically, compared with S-LY-55. Further studies are, however, needed for a deeper understanding of these differences.

Differential serotoninergic and dopaminergic activities of the (R)- and the (S)-enantiomers of 2-(di-n-propylamino)tetralin.

Racemic 2-(di-n-propylamino)tetralin ((R,S)-DPAT), which lacks phenolic or other aromatic substituents, induces both dopaminergic (sniffing, licking and gnawing) and serotoninergic (forepaw treading and flat body posture) behavioural responses. The present study shows that s.c. administration of (R)-DPAT induces typical 5-HT1A receptor agonist behaviours. These effects are blocked by the 5-HT1A receptor antagonist (S)-5-fluoro-8-hydroxy-2-(di-n-propylamino)tetralin ((S)-UH-301). Administration of (S)-DPAT induces dopaminergic behaviours, which are fully antagonised by raclopride, a dopamine D2 receptor antagonist. Both enantiomers induce hypothermia, (R)-DPAT being antagonised by (S)-UH-301, whereas (S)-DPAT is antagonised by raclopride. The accumulation of 5-hydroxytryptophan and DOPA (3,4-dihydroxyphenylalanine) after decarboxylase inhibition that reflects presynaptic actions on 5-HT (5-hydroxytryptamine, serotonin) and dopamine neurons, respectively, are inhibited by both enantiomers of DPAT. (R)-DPAT is more potent than (S)-DPAT as an inhibitor of 5-hydroxytryptophan accumulation whereas (S)-DPAT is more potent than (R)-DPAT as an inhibitor of DOPA accumulation. Thus, in functional tests of postsynaptic actions (R)-DPAT behaves as a 5-HT1A receptor agonist and (S)-DPAT as a dopamine D2 receptor agonist. Presynaptically, (R)-DPAT shows selectivity for 5-HT1A receptors and (S)-DPAT for dopamine D2 receptors. Receptor binding studies, utilizing [3H]8-hydroxy-2-(di-n-propylamino)tetralin and [3H]quinpirole as radioligands for 5-HT1A and dopamine D2 receptors, respectively, showed (R)-DPAT to have a 3-fold higher affinity than (S)-DPAT for 5-HT1A receptors, whereas (S)-DPAT had a 6-fold higher affinity than (R)-DPAT for dopamine D2 receptors. Thus, the results from receptor binding studies support the conclusion that (R)- and (S)-DPAT are agonists showing selectivity for 5-HT1A and dopamine D2 receptors, respectively. Taken together, these findings may explain previous controversies with regard to the pharmacology of racemic DPAT and re-emphasise the necessity to study pure enantiomers of chiral compounds.

Oral cavity absorption of (R)-8-hydroxy-2-(di-n-propylamino)tetralin and (S)-8-acetyl-2-(di-n-propylamino)tetralin in the rat.

The present communication reports on the efficacy of (R)-8-OH-DPAT ((R)-8-hydroxy-2-(di-n-propylamino)tetralin) and (S)-LY-41 ((S)-8-acetyl-2-(di-n-propylamino)tetralin) in displaying the 5-HT1A syndrome and decreasing body temperature after administration of the compound subcutaneously into the gastric ventricle or into the oral cavity in the rat. The dose range eliciting a clear-cut HT1A syndrome and hypothermia after oral cavity administration was 1/10-1/30 that of the gastric ventricle dose range, but 10-30 times higher than the dose range used for subcutaneous administration of both (R)-8-OH-DPAT and (S)-LY-41. Determination of the concentrations of (R)-8-OH-DPAT in plasma and brain tissue confirmed a higher bioavailability after oral cavity than after gastric ventricle administration; plasma and brain tissue concentrations of the drug were found to be approximately 3 times those after 10 mumol/kg-1 orally than after 100 mumol/kg-1 gastroventrically at 15-60 min after administration of (R)-8-OH-DPAT. These findings suggest that the oral cavity may be an important site for drug delivery of 8-OH-DPAT, LY-41 and other compounds with a low gastrointestinal bioavailability.

Synthesis and pharmacology of the enantiomers of UH301: opposing interactions with 5-HT1A receptors.

The (S)-enantiomer of 5-fluoro-8-hydroxy-2-(dipropylamino) tetralin [(S)-2a; (S)-UH301] was the first reported 5-HT1A receptor antagonist. We now give a full account on the synthetic effort leading to the preparation of the racemate and the enantiomers of 2a. The crystal and molecular structure of 2a. HBr has been determined by X-ray diffraction and the absolute configuration has been deduced using statistical tests of the crystallographic R values. The unit cell is tetragonal (P4(1)2(1)2) with a = b = 13.2235(2), c = 39.560(1) A and contains two crystallographically independent molecules in each asymmetric unit. The two solid state conformers differ in the conformation of the N-propyl groups. The pharmacological characterization of the enantiomers was done by use of in vivo biochemical and behavioural assays in rats. The (R)-enantiomer of 2a is a 5-HT1A receptor agonist of low potency while (S)-2a does not exhibit any agonist properties at 5-HT1A receptors. As a consequence of the opposing effects of the enantiomers, the racemate, rac-2a, does not produce any clear-cut effects in rats. The reduced efficacy of (S)-2a as compared to the well known 5-HT1A receptor agonist 8-hydroxy-2-(dipropylamino) tetralin (1;8-OH-DPAT) may be due to the fluoro-substituent induced negative potential of the aromatic ring.

Long-term studies of antipsychotic drugs in schizophrenia.

Studies on long-term efficacy and safety should be a main concern in the evaluation of novel antipsychotics. The present paper is a review of important issues related to the design and performance of such trials. The variability of the natural course of schizophrenia, the variability in treatment response, and the variability of actions of different neuroleptics need to be considered. Long-term studies need to address maintenance of efficacy, prevention of relapse and recurrence, health economics, quality of life and a large number of safety issues in order to get approval for new drug applications and reimbursement on expensive new medicines. Assessment instruments for efficacy, tolerability and safety, need to be supplemented with rating scales for various aspects of psychopathology (positive, negative, deficit symptoms), social and work functioning, drug induced mental side effects, quality of life and accounts of total treatment costs.

Derivatives of cis-2-amino-8-hydroxy-1-methyltetralin: mixed 5-HT1A-receptor agonists and dopamine D2-receptor antagonists.

(1S,2R)-8-Hydroxy-1-methyl-2-(dipropylamino)tetralin [(1S,2R)-3] has been previously characterized as a selective and potent but partial 5-HT1A-receptor agonist. In the present study, we have prepared derivatives of (1S,2R)- and (1R,2S)-3 in which various C8-substituents have been introduced. In addition, the enantiomers of the N-isopropyl-N-n-propylamino derivative of 3 were prepared. The new derivatives were tested in vivo by use of behavioral and biochemical tests in rats. In addition, the affinity of the compounds was studied by competition experiments with [3H]-8-OH-DPAT in rat brain tissue. The only new derivative which behaved like a selective 5-HT1A-receptor agonist was the C8-carboxamide derivative (1S,2R)-13. The other active derivatives, including (1S,2R)-3, have more complicated pharmacological profiles and may be best characterized as mixed 5-HT1A-receptor agonists/dopamine D2-receptor antagonists.

Overcoming the neuroleptic-induced deficit syndrome: clinical observations with remoxipride.

Remoxipride is a selective dopamine D2 antagonist with virtually no activity on other transmitter receptors. It antagonizes dopamine agonists within a wide dose range in animals when it does not cause sedation or akinesia. Clinical studies with remoxipride have demonstrated antipsychotic efficacy apparently equal to classical neuroleptics in short- and long-term treatment of schizophrenia. Remoxipride has a low extrapyramidal syndrome (EPS) profile, and it is generally well tolerated. In clinical practice remoxipride has been reported to differ from classical neuroleptics with regard to subjective side effects. On switching to remoxipride, patients report improvement in cognitive, conative, affective and emotional functions. In many cases the reports are supported by family members and/or caregivers. Although anecdotal, such reports are in line with the low EPS profile of remoxipride and its weak sedative properties. It may indicate that remoxipride does not elicit the neuroleptic-induced deficit syndrome, commonly experienced with classical neuroleptics, or that remoxipride improves the deficit syndrome (or primary negative symptoms) of schizophrenia. These and other hypotheses need to be confirmed by formal clinical studies.

Neuroleptics and the neuroleptic-induced deficit syndrome.

The first central pharmacodynamic action of chlorpromazine to be described was sedation without narcosis. The antipsychotic action and extrapyramidal symptoms were observed later. Sedation can be separated into nonspecific sedation (drowsiness, somnolence) and specific sedation (psychomotor inhibition and psychic indifference). Both types are parts of the clinical profiles of classical neuroleptics. The sedative properties of neuroleptics may contribute to the overall efficacy in the treatment of psychotic patients, depending on the clinical situation. In most patients, however, sedation is only needed for a short period, or not at all. The drug induced sedation may adversely affect the patients' well-being and functional capabilities. The term neuroleptic-induced deficit syndrome (NIDS) has been coined to focus attention on the adverse mental effects of neuroleptics. NIDS still needs to be properly defined and to be differentiated from the deficit syndrome of schizophrenia and postpsychotic depression. Assessment methods are needed to establish the incidence and prevalence of NIDS, to evaluate the importance of NIDS in the overall treatment outcome in psychoses and to facilitate development of better antipsychotic agents.

Derivatives of 2-(dipropylamino)tetralin: effect of the C8-substituent on the interaction with 5-HT1A receptors.

A series of 2-(dipropylamino)tetralin derivatives in which the C8 substituent is varied has been prepared and evaluated pharmacologically to explore the importance of the C8 substituent in the interaction of 2-aminotetralin-based ligands with serotonin (5-HT1A) receptors. Enantiopure derivatives were prepared by facile palladium-catalyzed reactions of the triflates of the enantiomers of 8-hydroxy-2-(dipropylamino)tetralin (8-OH-DPAT, 1). The affinity of the compounds for the 5-HT1A receptors was evaluated by competition experiments with [3H]-8-OH-DPAT in rat hippocampal and cortical tissue. In addition, the compounds were evaluated for central 5-HT and dopamine receptor stimulating activity in vivo by use of biochemical and behavioral assays in rats. With the exception of the carboxy-substituted derivative which is devoid of 5-HT1A receptor affinity, the compounds have moderate to high affinities (K(i) values range from 0.7 to 130 nM) for 5-HT1A receptors. Surprisingly, several of the derivatives do not produce any apparent effects in vivo although they have fairly high 5-HT1A receptor affinities. However, the methoxycarbonyl- and acetyl-substituted derivatives are potent 5-HT1A receptor agonists in vivo and exhibit in vitro affinities in the same range as the enantiomers of 1.

Neuromedicinal chemistry of 5-HT1A-receptor agonists and antagonists.

Recent progress in a project aiming at developing selective 5-HT1A-receptor agonists and antagonists is reviewed. A large number of analogues of 8-OH-DPAT has been synthesized, and throughout, we have attempted to prepare enantiopure derivatives. Modifications have been concentrated to the N-alkyl substituents, and substitutions in the C1, C2 and C3-positions. The synthetic strategies and procedures are discussed. A number of interesting observations have been made. Affinity, efficacy and stereoselectivity are modified by the various substitutions. The results have been used to deduce a 3D-model for 5-HT1A-receptor agonists. Recently, Pd-catalyzed reactions have been utilized to prepare a number of pharmacologically interesting analogues of 8-OH-DPAT with various C8-substituents. We have also succeeded to convert the agonist 8-OH-DPAT into an antagonist by introduction of a C5-fluoro substituent, producing (S)-UH-301. The pharmacology of this selective 5-HT1A-receptor antagonist is discussed.

(R)- and (S)-8-acetyl-2-(dipropylamino)tetralin (LY-41): two novel 5-HT1A receptor agonists.

Interactions between central 5-HT1A receptors and the enantiomers of LY-41, a 2-aminotetralin derivative related to 8-OH-DPAT (8-hydroxy-2-(dipropylamino)tetralin), were studied. Both enantiomers of LY-41 behaved as potent 5-HT1A receptor agonists in rats, inducing the 5-HT behavioural syndrome, decreasing body temperature and inhibiting the cage-leaving response. The behavioural syndrome and the hypothermia were antagonized by the 5-HT1A receptor antagonist, (S)-UH-301. The LY-41 enantiomers also reduced brain 5-HTP accumulation in rats treated with a decarboxylase inhibitor. The pharmacology of the enantiomers of LY-41 appeared similar to that of 8-OH-DPAT. However, it is noteworthy that the stereoselective interaction of 5-HT1A receptors with LY-41 was opposite to that of 8-OH-DPAT. Thus, (R)-8-OH-DPAT was more potent than (S)-8-OH-DPAT, whereas (S)-LY-41 appeared to be more potent than (R)-LY-41.