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.

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.

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.

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.

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.

(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.

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.

Effects of (R)-8-OH-DPAT and the enantiomers of UH-301 on motor activities in the rat: antagonism of (R)-8-OH-DPAT-induced effects

The effects of the enantiomers of 5-fluoro-8-hydroxy-2-(dipropylamino)tetralin, UH-301 and the potent 5-HT1A-receptor agonist (R)-8-hydroxy-2-(dipropylamino)tetralin, (R)-8-OH-DPAT, on locomotion, rearing and total activity were studied in rats. The experiments were performed as tests either of exploratory activity in non-habituated rats or of motor activity of rats habituated to the environment for 2 h before drug injection. (R)-8-OH-DPAT increased locomotion and total activity and decreased rearing in both conditions. (R)-UH-301 increased locomotion and slightly also total activity in habituated rats and decreased rearing in both conditions. (S)-UH-301 decreased locomotion and rearing in both conditions but only in doses of 10 mumol/kg and above. Lower doses of (S)-UH-301 (10 mumol/kg) antagonized (R)-8-OH-DPAT-induced increases of locomotion and total activity. As (S)-UH-301 decreased rearing, per se, it was not able to antagonize the (R)-8-OH-DPAT induced decrease. These results further support previous data that (S)-UH-301 is a 5-HT1A antagonist while (R)-UH-301 is a 5-HT1A agonist.

(S)-UH-301 antagonizes (R)-8-OH-DPAT-induced cardiovascular effects in the rat

The 5-HT1A-receptor antagonist (S)-UH-301 (S)-5-fluoro-8-hydroxy-2- (dipropylamino)tetralin) completely antagonized the hypotension and bradycardia induced by (R) = 8-OH DPAT [R)-8-hydroxy-2- (dipropylamino)tetralin) in conscious rats. (S)-UH-301 alone induced a weak hypertension, which might be due to its 5-HT1A-receptor antagonistic properties. (R)-UH-301 induced effects similar to those of (R)-8-OH DPAT, i.e., a short initial phase of hypertension followed by a long-lasting hypotension and bradycardia. Thus, (R)-UH-301 behaves as a 5-HT1A-receptor agonist and (S)-UH-301 as a 5-HT1A-receptor antagonist, abolishing the effects induced by (R)-8-OH DPAT.

Pharmacology of the novel 5-hydroxytryptamine1A receptor antagonist (S)-5-fluoro-8-hydroxy-2-(dipropylamino)tetralin: inhibition of (R)-8-hydroxy-2-(dipropylamino)tetralin-induced effects

The selective 5-hydroxytryptamine (5-HT1A) receptor agonist 8-hydroxy-2-(dipropylamino)tetralin (8-OH-DPAT) induces a large number of pharmacological effects. In the present study we demonstrate that a novel 8-OH-DPAT analog, (S)-5-fluoro-8-hydroxy-2-(dipropylamino)tetralin [(S)-UH-301], is able to antagonize completely the following (R)-8-OH-DPAT-induced effects in the rat: 1) reduction in brain 5-HT biosynthesis, measured as a decreased 5-hydroxytryptophan-accumulation after decarboxylase inhibition; 2) induction of the 5-HT1A behavior (flat body posture, forepaw treading and hindlimb abduction) in reserpine-pretreated animals; 3) reduction of body temperature; 4) inhibition of the cage-leaving response; and 5) reduction of 5-hydroxytryptophan- and quipazine-induced wet dog shakes. In addition, (S)-UH-301 reverses the 5-HT-induced inhibition of the forskolin stimulated cyclic AMP production in rat hippocampus without producing any effects per se in this assay. It is shown that high doses of (S)-UH-301 decrease rat brain biosynthesis of dopamine. These and previous data indicate that (S)-UH-301 also is a weakly potent dopamine-receptor agonist, but with a lower affinity for D2 as compared to 5-HT1A receptors. Thus, the data suggest that (S)-UH-301 is a 5-HT1A-receptor antagonist without intrinsic activity. Therefore, it is likely that (S)-UH-301 will become a valuable pharmacological tool in future 5-HT research.

Biochemical pharmacology of the atypical neuroleptic remoxipride

In vitro receptor ligand binding studies in the rat showed that remoxipride displaced different radioligands at the dopamine D2, but not the D1 receptor. Remoxipride did not block dopamine-stimulated adenylate cyclase activity in vitro suggesting that it did not directly interact with the dopamine D1 receptor. Like other antipsychotic compounds, it increased dopamine turnover in the dopamine-rich areas of the brain. It showed no affinity for a wide range of neurotransmitter receptors, with the exception of the opiate sigma receptor. The affinity of remoxipride for the D2 receptor was low in vitro, while in vivo, the affinity was relatively high. Remoxipride was far more potent in preventing [3H]raclopride-binding than [3H]spiperone-binding to the D2 receptor in vivo. When the D2 receptor was labelled with [3H]spiperone, remoxipride was shown to exert a preferential blockade of this binding in extrastriatal areas of the brain (for example, olfactory tubercle, septum, substantia nigra) in vivo. After the injection of high doses of remoxipride most if not all drug in the brain was identified as authentic remoxipride. After injection of [3H]remoxipride in smaller and larger doses, radioactivity was detected in all areas of brain examined, including cerebellum and neocortex. Most of the remoxipride-derived radioactivity was found in the choroid plexus and circumventricular organs, while smaller amounts were recovered in the striatum, olfactory tubercle, and substantia nigra. Taken together, these findings suggest that remoxipride acts at both the central D2 and sigma receptors and that its affinity for the D2 receptor is relatively low in vitro. A regional preference for D2 receptors can be observed in vivo depending upon the radioligand used.

Clinical profile of remoxipride--a combined analysis of a comparative double-blind multicentre trial programme

Nine double-blind studies comparing remoxipride to haloperidol in the treatment of acute schizophrenia formed the basis of this analysis. All studies followed a basic protocol with the main assessments performed regularly during the 4-6 week trial period according to the same methodology, thus allowing the data to be pooled. The results showed that remoxipride in a daily dose of 150-600 mg had a therapeutic effect comparable to that of haloperidol (5-45 mg/day), both on positive and negative symptoms. There was a clear advantage for remoxipride over haloperidol with regard to adverse events/symptoms, particularly extrapyramidal symptoms, but also drowsiness/somnolence and tiredness/fatigue. Anticholinergic drugs were used consistently less frequently as concomitant medication to alleviate extrapyramidal symptoms in the remoxipride group: the use of sedatives/hypnotics was approximately the same in both groups. Based on these and supportive clinical data, remoxipride seems to have a clinical profile characterized by antipsychotic efficacy in acute schizophrenia, apparently equal to that of haloperidol, and good tolerability in being non-sedative (in terms of drowsiness/somnolence) and with low incidences of extrapyramidal, autonomic, and endocrine symptoms.

Safety evaluation in both short- and long-term treatment of schizophrenia with remoxipride

Results for laboratory and cardiovascular variables in both short-term (4-6 weeks) and long-term (greater than 6 weeks) double-blind studies in schizophrenic patients consistently showed comparably low incidences of both transient treatment-emergent changes and changes present at last rating for both remoxipride and haloperidol. The total incidence of serious adverse events in the short-term double-blind programme was approximately 2% for both remoxipride and haloperidol. The corresponding figure for remoxipride (n = 434) in long-term treatment was approximately 6%. Compared to those on haloperidol, fewer patients on remoxipride had trough plasma prolactin levels above the normal range in short-term treatment. The results with long-term treatment with remoxipride were similar. Breast swelling and galactorrhoea were infrequent treatment-emergent side effects with either drug. It was impossible to evaluate menstrual disturbance in short-term studies but in long-term use the incidence of treatment-emergent menstrual disorder was low in remoxipride patients. Too few patients continued treatment with haloperidol for a comparative long-term evaluation. Overall, based on the information available at present, remoxipride appears to offer a high degree of safety in both short-term and long-term treatment of schizophrenia.

[Remoxipride, a selective antagonist of dopamine D2 receptors, in the treatment of delusional psychoses]

Remoxipride, a substituted benzamide, is a new antipsychotic agent which differs from classical neuroleptics in several ways. It has a selective action on the dopamine D2 receptors in the brain and little effect on a variety of other receptor types including serotonin, noradrenaline, acetylcholine and histamine receptors. This implies advantages over classical neuroleptics which have less selective modes of action and subsequently increased propensities to cause side effects. The pharmacokinetics of remoxipride are uncomplicated. The drug is rapidly absorbed, plasma levels increase with dose, and elimination is via urinary excretion. No clinically significant drug interactions have been found. Remoxipride has been shown to be as effective in the treatment of schizophrenic patients as haloperidol in both short and long term double-blind trials. Both positive and negative symptoms are improved. However, remoxipride shows advantages over haloperidol in that the incidences of extrapyramidal symptoms and increased plasma prolactin concentrations are lower in remoxipride recipients. There are no clinically relevant adverse effects on chemistry, haematology or cardiovascular variables.

Rhythmic jaw movements induced by ethanol in rats

Intraperitoneal administration of an anaesthetic dose of ethanol, 3.0 mg/kg, produced rapid rhythmic jaw movements (RJM) in rats. The peak effect (90 RJM/min.) occurred after 5 min., and all movements ceased after about 15 min. Clozapine, (4.4 mg/kg intraperitoneally) completely abolished this RJM phenomenon, whereas halopridol (0.5 mg/kg intraperitoneally), apomorphine (1.0 mg/kg subcutaneously) and atropine (10 mg/kg intraperitoneally) reduced it. It is suggested that the postulated brain stem masticatory pattern generator is activated or released from inhibition during induction of ethanol anaesthesia. Apparently this masticatory movement pacemaker is amenable to pharmacological manipulation, as shown by the present experiments.

Effects of d-amphetamine and methylphenidate on hyperactivity produced by neonatal 6-hydroxydopamine treatment

Neonatal intracisternal administration of 6-hydroxydopamine (6-OHDA, 50 micrograms on day 1 after birth) caused a marked hyperactivity when the rats were tested as adults. These rats also showed severe DA depletions in striatum and nucleus accumbens. Pretreatment with the noradrenaline (NA) uptake inhibitor desipramine provided protection against NA depletion in frontal cortex and nucleus accumbens. Pretreatment with DA uptake inhibitors, amfolenic acid or GBR 12909, before 6-OHDA, provided full protection against DA depletion but produced marked NA depletion in frontal cortex. These rats did not demonstrate any degree of hyperactivity. Low doses of d-amphetamine (0.25 mg/kg SC) or methylphenidate (1 mg/kg SC) reversed the hyperactivity in DA-depleted rats but increased motor activity in vehicle-treated and NA-depleted rats. Higher doses of d-amphetamine (1 mg/kg) or methylphenidate (4 mg/kg) produced potentiated levels of locomotion but attenuated levels of rearing in DA-depleted animals. The results further suggest the utility of the neonatal DA lesion in rats as a potential animal model for derivation of therapeutic agents that may be efficacious in the treatment of the hyperkinetic syndrome.

Prenatal methylazoxymethanol treatment potentiates d-amphetamine- and methylphenidate-induced motor activity in male and female rats

The effects of the stimulant drugs, d-amphetamine and methylphenidate, upon the motor activity of male and female off-spring of pregnant rats, treated on gestation day 15 with the antimitotic agent methylazoxymethanol (MAM, 25 mg/kg) were studied in four experiments. Cortical and striatal hypoplasia induced by prenatal administration of MAM resulted in increased concentrations of catecholamines in those regions. Administration of d-amphetamine and methylphenidate caused significant increases in motor activity; this effect was markedly potentiated in the MAM-treated rats, both the male and female off-spring. Thus, the locomotion and total activity parameters showed similar, but not identical, drastic increases in behaviour induced by the stimulant drugs as a result of the prenatal MAM treatment whereas for the rearing parameter a lesser potentiation by the MAM treatment was observed. This potentiation of the excitatory effects of the stimulant compounds upon the behavioural parameters is interpreted in terms of a relative increase in the density of catecholaminergic terminals in the forebrain regions of the central nervous system. The present results are discussed with regard to the utility of prenatal MAM treatment as a possible animal model for certain neurological disorders.

Ethanol-induced hypothermia and biogenic amine metabolites

Ethanol is known to cause hypothermia. The rectal temperature of rats receiving ethanol, 4 g/kg i.p., at an ambient temperature of 23 degrees C decreased by 2 degrees C. This body temperature decrease could be prevented by keeping the animals at an ambient temperature of 34 degrees C. Irrespective of the body temperature it was found that the concentration of the major metabolites of dopamine and serotonin in brain tissue was significantly increased. Thus, the change in brain monoamine metabolite levels in rats after administration of ethanol are not due to ethanol-induced hypothermia.

The effect of ethanol on the brain catecholamine systems in female mice, rats, and guinea pigs

The effect of acute ethanol administration on the concentrations of dopamine (DA), norepinephrine (NE) and their metabolites (3,4-dihydroxyphenylacetic acid [DOPAC], homovanillic acid [HVA], 3,4-dihydroxyphenylglycol [DHPG] and 4-hydroxy-3-methoxyphenylglycol [HMPG]) in brains of female mice, rats, and guinea pigs were investigated. A subhypnotic dose (2 g/kg) or a hypnotic dose (4 g/kg) of ethanol was administered intraperitoneally and the animals were killed 45 min later. In the rat the DA levels were unchanged, while the NE concentrations were decreased after both doses of ethanol. The DA levels did not change in the mouse and guinea pig, while the concentrations of NE showed a minor decrease in the mouse but were unaffected in the guinea pig. After 4 g/kg of ethanol the DOPAC and HVA concentrations were elevated significantly in all three species, and after 2 g/kg the DOPAC levels were increased in the rat and guinea pig brains and the HVA levels in the mouse and guinea pig brains. In the mouse and rat brain the DOPAC + HVA concentrations indicated a dose response relationship: 4 g/kg was significantly more effective than 2 g/kg. The DHPG concentration increased in the rat brain after both 2 and 4 g/kg, while the HMPG concentrations increased significantly only after 2 g/kg. In the mouse and guinea pig the brain DHPG concentrations remained unchanged, while the HMPG concentrations increased after both 2 and 4 g/kg ethanol. These data suggest, that the turnover of both DA and NE was increased 45 min after a subhypnotic as well as after a hypnotic dose of ethanol in all three species studied.(ABSTRACT TRUNCATED AT 250 WORDS)

Central noradrenaline depletion antagonizes aspects of d-amphetamine-induced hyperactivity in the rat

The effects of noradrenaline (NA) depletion upon amphetamine-induced hyperactivity were examined in five experiments. Central NA depletion via either systemic DSP4 or neonatal 6-OHDA antagonised the amphetamine-induced (2 mg/kg SC) increase in rearing behaviour, whereas lesions of the dorsal noradrenergic bundle using 6-hydroxydopamine antagonised the increase in locomotor activity. Peripheral NA depletion following systemic 6-hydroxydopamine to adult rats did not cause any changes in motor activity after acute amphetamine administration. Desipramine, the selective NA uptake inhibitor, blocked the effects of DSP4 upon amphetamine-induced rearing. NA depletion antagonised hyperactivity produced by the 2 mg/kg dose of amphetamine, but not the hyperactivity (rearing or locomotion) effects of amphetamine at 1, 4 or 8 mg/kg.

Increased total activity in the rat after L-tryptophan plus the monoamine oxidase-A inhibitor amiflamine but not after L-tryptophan plus clorgyline

The effect of pretreatment with either saline or the monoamine oxidase-A inhibitors clorgyline and amiflamine upon the total activity, locomotion and rearing behaviour of the rat induced by various doses of the monoamine precursor L-tryptophan was studied by use of automated activity boxes. Amiflamine (2.5 and 5.0 mg kg-1, i.p.) increased in a dose-dependent manner total activity and to a lesser extent, locomotion when given 60 min before L-tryptophan (100 mg kg-1, i.p.). The increased activity was seen after amiflamine plus either 25 or 75 mg kg-1 L-tryptophan. Rearing behaviour was not affected. Analysis of 5-hydroxytryptamine (5-HT) and its deaminated metabolite 5-hydroxyindoleacetic acid (5-HIAA) by high performance liquid chromatography with electrochemical detection indicated that in both frontal cortex and hypothalamus, amiflamine (at both doses) increased 5-HT and reduced 5-HIAA concentrations. Combination of amiflamine with L-tryptophan (100 mg kg-1, i.p.) resulted in a higher 5-HT concentration being found than after amiflamine alone. L-Tryptophan treatment alone did not change 5-HT concentrations but increased 5-HIAA concentrations. Clorgyline, at a dose of either 1 or 5 mg kg-1 i.p. plus L-tryptophan (25 or 100 mg kg-1, i.p.) did not increase total activity, locomotion or behaviour. A number of possible explanations for the differences in the behavioural effects of clorgyline and amiflamine when given with L-tryptophan are discussed. It is concluded that in addition to monoamine oxidase-A inhibition, other pharmacological effects of the drugs, such as 5-HT release (amiflamine) and inhibition of tryptophan hydroxylation (clorgyline) may be of importance in determining the magnitude of the increase in activity when the compounds are given together with L-tryptophan.

The pharmacological assessment of a new, potent oxotremorine analogue in mice and rats

Some of the central and peripheral effects of oxotremorine (OT) and its azetidine analogue, N-[4-azetidinyl)-2-butynyl]-2-pyrrolidone (BM 120), were compared in mice and rats. BM 120 was found to be about twice as potent as OT and to have a somewhat longer duration of action. All its effects were antagonized by pretreatment with atropine sulphate. BM 120 acted as powerful muscarinic agonist on the isolated guinea pig ileum.

Thermic and tremorogenic effects of thyroliberin (TRH) in reserpine-treated mice--the non-involvement of GABA-ergic mechanisms

Administration of thyroliberin (TRH) to reserpinized mice causes tremor and counteracts the hypothermia in a dose-dependent fashion. The thyroliberin response is inhibited by gamma-hydroxybutyric acid (GHB) and baclofen, but not by other, more specific GABA-ergic agents, such as THIP, gamma-acetylenic GABA, and sodium valproate. Picrotoxin neither potentiates nor inhibits the thyroliberin actions. Nor are the thyroliberin effects dependent on cholinergic, monoaminergic or histaminergic mechanisms. The results repudiate a current hypothesis, that the peptide actions may be mediated by GABA-ergic pathways in the brain.

Dopamine metabolism in red blood cells in schizophrenia

A method was developed for the separation by thin-layer chromatography of 14C-labelled 3-methoxy, 4-hydroxyphenethylamine, 3-hydroxy, 4-methoxyphenethylamine and 3,4-dimethoxyphenethylamine (DMPEA) after incubation of dopamine with catechol-O-methyltransferase (COMT) in lysates of human red blood cells (RBC). 14 C-methyl-S-adenosyl-menthionine was used as the methyl donor. Total COMT activity with noradrenaline or dopamine as substrates, respectively, and the pattern of 14C-methylated metabolites of dopamine were measured in RBC of 47 schizophrenic patients and in 34 control subjects. There were no differences between patients and controls. DMPEA was not formed by RBC in schizophrenic patients (or in controls), a finding which argues against the "pnk spot"/DMPEA hypothesis of schizophrenia. The methods used seem suitable for studies of other human disorders where COMT might be involved.

Tolerance to alpha-methyl-p-tyrosine in rats: studies on the antagonism of amphetamine-induced motor activity and excitatory behaviour

Rats were treated chronically with alpha-methyl-p-tyrosine methyl-ester HCl (alpha-MT) twice daily for 0--14 days. At 1 h after the (last) alpha-MT injection, d-amphetamine sulphate was given and motor activity was measured in an ANIMEX activity meter for 4 h. Amphetamine-induced excitatory and stereotyped behaviour was scored according to a rating scale in a separate experiment. A single dose of alpha-MT markedly reduced the activity response after amphetamine. After 1--3 days of alpha-MT treatment, tolerance to its amphetamine-antagonistic affect started to develop, reaching a maximal degree after 7--14 days. The pattern of the amphetamine response, monophasic in control rats, became biphasic in the alpha-MT tolerant rats with an early (at 0--1 h) and a late (2--4 h) peak of motor activity. The late peak appeared within 3 days, while the early peak appeared after 7 days of alpha-MT treatment. The results on amphetamine-induced excitatory and stereotyped behaviour in essence agreed with the motor-activity data. It is concluded that tolerance to the amphetamine-antagonistic action of alpha-MT is not complete. Its rate of development varies in a complex pattern, indicating the presence of more than one mechanism of tolerance.

The relationship between amphetamine antagonism and depletion of brain catecholamines by alpha-methyl-p-tyrosine in rats

The time-course and the dose-response relationship for the antagonistic effect of alpha-methyl-p-tyrosine methyl ester HCl H 44/68 (alpha-MT) on d-amphetamine (10.6 mumoles/kg) induced increase in motor activity was studied. The effect of amphetamine was gradually reduced from 30--60 min to a minimum at 1--4 h after the administration of 0.407 mmoles/kg of alpha-MT. From (4--) 8 h the amphetamine response started to reappear and the original response was restored completely at 16 h after alpha-MT. The dose-response curve showed, that between 0.051--0.41 mmoles/kg of alpha-MT, given 1 h before amphetamine, there was a gradual reduction of the amphetamine response; doses above 0.41 mmoles/kg did not cause any further effect. The antiamphetamine action of alpha-MT was compared with its time- and dose-dependent effects of inhibition of synthesis and reduction of stores of brain catecholamines. It was found, that the antiamphetamine action was more closely correlated with the reduction of the levels of brain dopamine, than with the brain noradrenaline levels. Further, the inhibition of catecholamine synthesis per se did not appear to be a sufficient condition for alpha-MT induced antagonism of amphetamine. These findings support the view that amphetamine is dependent on a substantial portion of the brain pool of dopamine and possibly noradrenaline rather than on very small, newly synthesized pools of these neurotransmitters.

Inhibition of the in vivo biosynthesis and changes of catecholamine levels in rat brain after alpha-methyl-p-tyrosine; time- and dose-response relationships

Male Sprague-Dawley rats were given 0.407 mmoles/kg of D,L-alpha-methyl-p-tyrosine methylester HCl (H44/68; alpha-MT) at eleven time-points between 0--24 h, or 8 doses between 0.013--1.628 mmoles/kg of the drug at 1 h before i.v. injection of 160 micronCi tyrosine-2,6-3H. The rats were killed 15 min after tyrosine-3H and brain alpha-MT, tyrosine and catecholamines (endogenous and labelled), and plasma alpha-MT and tyrosine (--3H) were chromatographically isolated before being assayed spectrophotofluorimetrically (endogenous) or by liquid scintillation methods (labelled compounds). A delayed penetration of alpha-MT from plasma into brain, different elimination rates of alpha-MT in plasma and brain, and decreasing brain/plasma drug concentration on increasing alpha-MT dosages, indicated, that alpha-MT in brain and plasma belong to different pharmacokinetic compartments. The endogenous levels of catecholamines in the time-response experiments, declined to a minimum 4 h after alpha-MT administration, where the dopamine level was 38% and the noradrenaline level 51% of the saline controls. Kinetic data of the catecholamine elimination is given. In the dose-response experiment the decrease in the endogenous catecholamine levels was dose-related up to 0.407 mmoles/kg of alpha-MT, with no further decline on higher doses. The maximal inhibition of brain catecholamine synthesis occurred within 30 min after alpha-MT administration and the inhibition correlated better with the brain than with plasma alpha-MT content. The inhibition was dose-related with a maximal synthesis inhibition of 95% for dopamine and 80% for noradrenaline at the highest dose of alpha-MT. The duration of synthesis inhibition and storage depletion were shorter for noradrenaline (12 h) than for dopamine (16 h). Further, the ED50 for synthesis inhibition of dopamine (0.057 mmoles/kg) was half of the ED50 for synthesis inhibition of noradrenaline (0.117 mmoles/kg). This might suggest different sensitivities towards alpha-MT or different availabilities of alpha-MT in the two neuron populations. At the three highest doses of alpha-MT there were signs of interference with the uptake process for tyrosine from plasma into the brain. This was indicated by increased plasma levels and decreased brain levels of tyrosine (--3H).