Local administration of sarizotan into the subthalamic nucleus attenuates levodopa-induced dyskinesias in 6-OHDA-lesioned rats.

RATIONALE: Dyskinesia affects the majority of levodopa-treated parkinsonian patients within 5-10 years of treatment with levodopa. Clinical and preclinical observations suggest that an increase in serotoninergic transmission can contribute to the appearance of dyskinesias. It is thus conceivable that a modulation of synaptic dopamine (DA) levels induced by the inhibition of serotonin (5-HT) release, as a consequence of 5-HT(1A) agonists administration, might alleviate dyskinesias. OBJECTIVE: Since 5-HT(1A) receptors are expressed in the subthalamic nucleus (STN), the aim of the present study was to assess the effect of the intrasubthalamic administration of sarizotan, a compound with full 5-HT(1A) agonist properties, on levodopa-induced dyskinesias in the 6-hydroxydopamine (6-OHDA) model of parkinsonism. MATERIALS AND METHODS: Male Sprague-Dawley rats received a unilateral 6-OHDA administration in the nigrostriatal pathway. A test of apomorphine was performed to evaluate dopamine depletion. One week later, a cannula was implanted in the STN. Animals were treated with levodopa (6 mg/kg, i.p., twice at day) for 22 consecutive days. On day 23, several doses (1 ng, 10 ng, or 1 microg) of sarizotan were administered through the cannula to the STN. The higher doses of sarizotan effectively attenuated all levodopa-induced dyskinesias including axial, limb, and orolingual subtypes. CONCLUSIONS: These results suggest that the STN is a target structure for the antidyskinetic action of sarizotan and indicate that drug-mediated modulation of STN activity may be an alternative option for the treatment of levodopa-induced dyskinesias in Parkinson's disease.

Dynorphin A, kappa opioid receptors and the antinociceptive efficacy of asimadoline in streptozotocin-induced diabetic rats.

AIMS/HYPOTHESIS: We investigated spinal and peripheral kappa opioid systems in diabetic rats. MATERIALS AND METHODS: Dynorphin A, N-methyl-D-aspartate (NMDA) and kappa opioid receptor (KOR) were measured in spinal cord, dorsal root ganglia, peripheral nerves and foot skin of control and streptozotocin-induced diabetic rats by immunoassay and Western blotting. Behavioural assessments of paw tactile sensitivity and formalin-evoked hyperalgesia were performed in normal and diabetic rats before and after treatment with asimadoline. RESULTS: Dynorphin A protein levels were significantly increased in peripheral nerves and footpad skin of diabetic rats. Dynorphin A exhibits both anti- and pro-nociceptive properties depending on activation of either KOR or NMDA receptors. Spinal protein levels of these receptors were not changed by diabetes, while KOR levels in the sciatic and peroneal nerves were significantly increased. Exploiting the presence and elevated levels of KOR in the periphery, we investigated the effect of the peripheral KOR agonist asimadoline on formalin-evoked hyperalgesia and tactile allodynia in diabetic rats. Both formalin-evoked hyperalgesia and tactile allodynia in diabetic rats were acutely ameliorated by asimadoline. To confirm that the effect of asimadoline was related to its property as KOR agonist, diabetic rats were pretreated with the selective KOR antagonist nor-binaltorphimine. Intraplantar nor-binaltorphimine abolished the ability of asimadoline to alleviate tactile allodynia in diabetic rats. Systemic and intrathecal nor-binaltorphimine partially inhibited the effect of asimadoline against formalin-evoked hyperalgesia in diabetic rats. CONCLUSIONS/INTERPRETATION: Using selective peripheral KOR agonists to take advantage of elevated peripheral KOR expression may provide a novel therapeutic approach for painful diabetic neuropathy.

Sarizotan, a serotonin 5-HT1A receptor agonist and dopamine receptor ligand. 1. Neurochemical profile.

Sarizotan exhibited high affinities only to serotonin 5-HT1A receptors and dopamine DA D4>D3>D2 receptors with the profile of a 5-HT1A agonist and DA antagonist demonstrated by the inhibition of cAMP-stimulation and guinea pig ileum contraction, decreased accumulation of the 5-HT precursor 5-hydroxytryptophan and increased levels of 5-HT metabolites, increased accumulation of DA precursor dihydroxyphenylalanine (DOPA) and the reduced levels of DA metabolites in intact rats. However, sarizotan at higher doses decreased DA precursor accumulation in reserpinized rats and induced contralateral rotational behavior in unilaterally substantia nigra lesioned rats, indicating some intrinsic dopaminergic activity; at D2 receptors sarizotan may act as a partial agonist, depending on the dopaminergic impulse flow. Sarizotan represents a new approach for the treatment of extrapyramidal motor complications such as l-DOPA-induced dyskinesia in Parkinson's disease.

Contribution of the serotonin 5-HT1A receptor agonism of 8-OH-DPAT and EMD 128130 to the regulation of haloperidol-induced muscle rigidity in rats.

The aim of the present study was to find out whether (+/-)-8-hydroxy-2(di-n-propylamino)tetralin (8-OH-DPAT), a prototypical 5-HT1A agonist, and (R)-(-)-2-[5-(4-fluorophenyl)-3-pyridylmethylaminomethyl]-chromane HCl (EMD 128130), a compound with serotonin 5-HT1A-agonist and dopamine D2-like antagonist properties, are able to attenuate the haloperidol-induced (1 mg/kg) muscle rigidity in rats. Muscle tone was examined using a combined mechano- and electromyographic (EMG) method that simultaneously measured the mechanical muscle resistance (MMG) of the rat's hind foot to passive movements in the ankle joint, and the EMG activity of two antagonist muscles. Both 8-OH-DPAT (0.125-0.5 mg/kg i.p.) and EMD 128130 (1-10 mg/kg i.p.) dose-dependently decreased the haloperidol-enhanced MMG to passive movements, as well as the tonic and the long-latency reflex EMG activities. Provided these results can be extrapolated to humans, the efficacy of EMD 128130 in relieving the haloperidol-induced muscle rigidity supports the concept that novel antipsychotics with 5-HT1A agonist and dopamine D2 antagonist activities should have a favourable extrapyramidal side-effect profile.

Systemic EMD 68843 injections reduce anxiety in the shock-probe, but not the plus-maze test.

Selective serotonin (5-hydroxytryptamine; 5-HT) reuptake inhibitors and 5-HT(1A) receptor agonists are believed to reduce anxiety. In the present study we examined the effects of injections of 5-(4-[4-(5-cyano-3-indolyl)-butyl]-1-piperazinyl)-benzofuran-2-carboxamide hydrochloride salt (EMD 68843), a 5-HT(1A) receptor agonist and selective 5-HT reuptake inhibitor, in two animal models of anxiety, plus-maze and shock-probe. Rats received intraperitoneal injections of vehicle, diazepam (2.5 mg/kg), or EMD 68843 (10, 20, or 40 mg/kg) 1 h prior to testing. Diazepam at the single dose tested and EMD 68843 dose-dependently (significantly at 20 and 40 mg/kg) reduced burying in shock-probe. However, only diazepam significantly increased open arm exploration in the plus-maze. Therefore, EMD 68843 has task specific anxiolytic properties.

Synthesis and in vitro and in vivo functional studies of ortho-substituted phenylpiperazine and N-substituted 4-N-(o-methoxyphenyl)aminopiperidine analogues of WAY100635.

WAY100635 (2), N-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-N-(2-pyridinyl)cyclohe xanecarboxamide, is a silent serotonin 5-HT(1A) antagonist, which is now widely used to study the 5-HT(1A) receptor both in vivo and in vitro. In this paper, we describe the synthesis and in vitro (5-HT(1A) affinity and pA(2) values at guinea pig ileum strips) and in vivo (hypothermia and ultrasonic vocalization) pharmacology at the serotonin 5-HT(1A) receptor of several closely related analogues of 2. Test compounds 12 and 14, in which the arylpiperazine moiety of 2 has been replaced by an arylaminopiperidine moiety, showed no affinity or antagonistic activity at the 5-HT(1A) receptor. Substitution of the o-methoxy group of 2 by larger fluoroalkoxy or sulfonyloxy substituents did not alter the in vitro or in vivo pharmacology to any great extent; in vivo both the fluoropropyl analogue 5 and the triflate analogue 7 are equipotent to WAY100635 itself. The O-desmethyl analogue 3 proved to be the most potent antagonist at the serotonin 5-HT(1A) postsynaptic receptor sites in this series.

New (sulfonyloxy)piperazinyldibenzazepines as potential atypical antipsychotics: chemistry and pharmacological evaluation.

A series of 2- or 8-trifluoromethylsulfonyloxy (TfO) and 2- or 8-methylsulfonyloxy (MsO) 11-piperazinyldibenzodiazepines, -oxazepines, and -thiazepines were synthesized and evaluated in pharmacological models for their potential clozapine-like properties. In receptor binding assays, the 2-TfO analogues (18a, GMC2-83; 24, GMC3-06; and previously reported GMC1-169, 9a) of the dibenzazepines have profiles comparable to that of clozapine, acting on a variety of CNS receptors except they lack M1 receptor affinity. Introduction of 2-TfO to clozapine leads to compound 9e (GMC61-39) which has a similar binding profile as that of clozapine including having M1 receptor affinity. Interestingly, the MsO analogues, as well as the 8-TfO analogues, have no or weak dopaminergic and serotonergic affinities, but all 8-sulfonyloxy analogues do have M1 affinities. In behavioral studies performed to indicate the potential antipsychotic efficacy and the propensity to induce EPS, 2-TfO analogues blocked effectively the apomorphine-induced climbing in mice in a dose-dependent manner with ED50 values (mg/kg) of 2.1 sc for 9a, 1.3 po for 18a, 2.6 sc for 24, and 8.2 sc for 9e. On the other hand, they showed a clear dose separation with regard to their ED50 values (mg/kg) for indicating catalepsy in rats (>44 sc for 9a, 28 po for 18a, 30 sc for 24, and >50 sc for 9e, respectively), thus implicating a more favorable therapeutic ratio (K/A, ED50 climbing/ED50 catalepsy) in comparison with typical neuroleptics such as haloperidol and isoclozapine. Furthermore, compound 18a was also demonstrated to be an orally potent DA antagonist with an ED50 value of 0.7 mg/kg po in the ex vivo L-DOPA accumulation model. The present study contributes to the SAR of 11-piperazinyldibenzazepines, and the 2-TfO analogues of 11-piperazinyldibenzazepines are promising candidates as clozapine-like atypical antipsychotics with low propensity to induce EPS.

Anxiolytic effects of dopamine receptor ligands: I. Involvement of dopamine autoreceptors.

The anxiolytic-like properties of dopamine agonists and antagonists with different receptor profiles were investigated in the ultrasonic vocalization test in rats after subcutaneous administration. Only dopamine D2 receptor agonists inhibited ultrasonic vocalization with the following ED50 values: apomorphine (0.07 mg/kg), quinelorane (0.01 mg/kg), quinpirole (0.04 mg/kg), pramipexole (0.09 mg/kg), roxindole (0.04 mg/kg), talipexole (0.04 mg/kg), (+/-)-7-OH-DPAT (0.05 mg/kg), (+/-)-PPHT (0.03 mg/kg), (-)-TNPA (0.06 mg/kg), PD128907 (0.13 mg/kg). The D2 antagonists haloperidol, mazapertine, raclopride, remoxipride, L745870, U99194A, U101958 and S(-)-DS121, the partial agonists PD143188 and preclamol, the selective D1 agonist R(+)-SKF38393 and the D1 antagonist SCH23390, and the uptake inhibitors GBR12909, GBR12935 and indatraline lacked significant inhibitory effects on ultrasonic vocalization. Because at least some of the D2 receptor agonists investigated have selectivity for dopamine autoreceptors, it is speculated that the dopamine autoreceptor may be a target for the development of new antianxiety drugs.

SAR of novel biarylmethylamine dopamine D4 receptor ligands.

SAR for a novel series of dopamine D4 receptor ligands is shown. Very selective, highly potent compounds like 1-(2-pyrimidinyl)-4-(3-(3-thienyl)-benzyl)-piperazine (5f) and 2-(4-(1-fluorenylmethyl)-1-piperazinyl)-pyrimidine (8c) were obtained.

EMD 68843, a serotonin reuptake inhibitor with selective presynaptic 5-HT1A receptor agonistic properties.

The 5-HT1A receptor agonist 8-hydroxy-(di-n-propylamino)tetralin (8-OH-DPAT; 0.55 mg/kg s.c.) and the 5-HT (5-hydroxytryptamine, serotonin) reuptake inhibitor/5-HT1A receptor ligand 5-[4-[4-(5-cyano-3-indolyl)-butyl]-1-piperazinyl]-benzofuran-2-carbox ami de (EMD 68843; 55 mg/kg p.o.) inhibited ultrasonic vocalization in rats, an effect which was antagonized by the 5-HT1A receptor antagonist N-[2-[4-(2-methoxyphenyl)-1-piperazinyl]-ethyl]-N-(2-pyridyl)- cyclohexancarboxamide (WAY 100635; 1.0 mg/kg s.c.). 8-OH-DPAT decreased body temperature in rats, an effect which was also antagonized by WAY 100635, whereas EMD 68843 neither affected body temperature by itself nor interacted with 8-OH-DPAT or WAY 100635. The selective 5-HT reuptake inhibitor fluoxetine (100 mg/kg p.o.) had no effect on ultrasonic vocalization or body temperature. Therefore EMD 68843 is suggested to be a 5-HT1A receptor agonist selective for presynaptic 5-HT1A receptors.

Induction of c-fos gene expression by the selective sigma receptor ligand EMD 57445 in rat brain.

Based on animal studies it has been reasoned that ligands to sigma binding sites might be effective in the treatment of schizophrenic disorders and may also be used to investigate this largely elusive disorder on a molecular level. Expression patterns of c-fos in rat brain were studied following treatment with single doses of the sigma ligand EMD 57445 (0.3, 1, 3, 30 mg/kg s.c.). Specific c-fos gene expression was detected at all concentrations tested in various cortical areas. The signals observed were dose-dependent with the highest intensities in the piriform cortex. Strong signals were also detected in hippocampal areas CA 1,2,3 and the gyrus dentatus, as well as in the medial habenula nuclei. In the caudate putamen, nucleus accumbens and lateral septal nucleus signals were detectable after administration of doses > or = 1 mg/kg. Furthermore, c-fos hybridization was visible in the amygdala, in the mammillary bodies, the islands of Calleja and in the olfactory tubercle. In the hypothalamus, c-fos expression was seen in the median eminence area after 30 mg/kg EMD 57445. No hybridization signals were obtained in brainstem or cerebellum. Since c-fos expression induced by EMD 57445 resembled the pattern obtained with atypical neuroleptics and studies on animal behavior point to antipsychotic activity, it is concluded that the drug might be suitable in the treatment of schizophrenia.

5-HT1A receptors are not involved in clozapine's lack of cataleptogenic potential.

Clozapine and 8-OH-DPAT antagonized haloperidol-induced catalepsy in rats (ED50 10 and 0.1 mg/kg s.c., respectively). Whereas the selective 5-HT1A receptor antagonist WAY 100635 (0.1 mg/kg s.c.) completely antagonized the inhibitory effect of 8-OH-DPAT, clozapine's effect was not affected. On the other hand, clozapine and 8-OH-DPAT inhibited ultrasonic vocalization in rats (ED50 0.7 and 0.03 mg/kg s.c., respectively), which effects were antagonized by WAY 100635. The lack of catalepsy of clozapine, therefore, cannot be addressed primarily to clozapine's agonistic activity at 5-HT1A receptors.

Roxindole: psychopharmacological profile of a dopamine D2 autoreceptor agonist.

The putative, selective dopamine (DA) dopamine-2 autoreceptor agonist roxindole, which also exhibits serotonin-1A-agonistic and 5-hydroxytryptamine reuptake-inhibiting properties, was examined for its behavioral effects in rats and mice. Roxindole inhibited apomorphine-induced climbing in mice and stereotyped behavior in rats with ED50 values of 1.4 mg/kg s.c. and 0.65 mg/kg s.c., respectively, and inhibited conditioned avoidance response in rats (ED50 = 1.5 mg/kg s.c.). Thus roxindole showed a profile resembling those of the classical antipsychotic haloperidol and the atypical neuroleptic clozapine but differing from that of the DA autoreceptor agonist talipexole, which did not prevent apomorphine-induced behaviors. Unlike haloperidol, roxindole did not induce catalepsy in rats and mice. Investigations directed to the DA autoreceptor properties revealed that spontaneous motility of rats with normosensitive postsynaptic DA receptors was monophasically decreased by roxindole and talipexole, with a threshold dose of 0.0625 mg/kg s.c. for both compounds. In reserpinized rats with presumably hypersensitive postsynaptic DA receptors, roxindole only partially reversed reserpine-induced hypomotility (threshold dose: 0.25 mg/kg); talipexole re-established the activity level to that of normal rats. In contrast to apomorphine, roxindole did not induce and talipexole only marginally induced stereotyped behavior in normal rats. After administration of the DA dopamine-1 agonist SKF 38393, talipexole induced stereotyped behavior in rats, which indicated its activity at postsynaptic dopamine-2 receptors. In contrast, roxindole did not induce stereotyped behavior in rats when co-administered with SKF 38393. These results indicate that, compared with talipexole, roxindole possesses a greater selectivity for DA autoreceptors.

The peripherally acting kappa-opiate agonist EMD 61753 and analogues: opioid activity versus peripheral selectivity.

EMD 61753 (N-methyl-N-[(1S)-1-phenyl-2-((3S)-3-hydroxypyrrolidin-1-yl) -ethyl ]- 2,2-diphenyl-acetamide hydrochloride) is a peripherally selective kappa-opiate agonist. It exhibits antihyperalgesic activity in animal models of inflammatory pain at doses which do not cause signs of central action. The structure of this compound was varied in different ways and the resulting derivatives were tested for affinity to the kappa-receptor. Furthermore, those compounds with binding values comparable to that of EMD 61753 were tested for central activity. This was done by measuring the extent to which the haloperidol-induced L-DOPA accumulation in the nucleus accumbens of the rat could be reversed after application of 10 mg/kg s.c. of the test compound. Structure-activity relationships revealed that none of the analogues or reference compounds tested is superior to the parent compound with regard to its favourable ratio between kappa-receptor affinity and peripheral selectivity.

A pharmacological profile of the novel, peripherally-selective kappa-opioid receptor agonist, EMD 61753.

1. The pharmacological properties of the novel diarylacetamide kappa-opioid receptor agonist, EMD 61753, have been compared with those of ICI 197067 (a centrally-acting kappa agonist) and ICI 204448 (a peripherally-selective kappa agonist). 2. EMD 61753 binds with high affinity (IC50 5.6 nM) and selectivity (kappa:mu:delta:sigma binding ratio 1:536:125: > 1,786) to kappa-opioid receptors and is a full and potent (IC50 54.5 nM) agonist in an in vitro assay for kappa-opioid receptors (rabbit vas deferens preparation). 3. Systemically-applied [14C]-EMD 61753 is found in high concentrations in the lungs, liver, adrenal glands and kidneys. Considerably less radioactivity is detected in the whole brain, and this radioactivity is concentrated in the region of the cerebral ventricles in the choroid plexuses. EMD 61753 penetrates only poorly into the CNS. 4. EMD 61753 was weakly effective in pharmacological tests of central activity. This compound reversed haloperidolol-induced DOPA accumulation in the nucleus accumbens of the rat only at a dose of 30 mg kg-1, s.c., (doses of 0.1, 1.0 and 10 mg kg-1, s.c., and 1.0, 10 and 100 mg kg-1, p.o., were inactive). Hexobarbitone-induced sleeping in mice was prolonged by EMD 61753 at threshold doses of 10 mg kg-1, s.c., and 100 mg kg-1, p.o., whereas the motor performance of rats in the rotarod test was impaired by EMD 61753 with an ID50 value of 453 mg kg-1, s.c. 5. EMD 61753 produced dose-dependent, naloxone-reversible antinociception in the mouse formalin test (1st phase ID50 1.9 mg kg-1, s.c., and 10.4 mg kg-1, p.o.; 2nd phase ID50 0.26 mg kg-1, s.c., and 3.5 mg kg-1, p.o.) and rodent abdominal constriction test (ID50 mouse 1.75 mg kg-1, s.c., and 8.4 mg kg-1, p.o.; ID50 rat 3.2 mg kg-1, s.c., and 250 mg kg-1, p.o.). EMD 61753 was inactive, or only weakly effective, in the rat pressure test under normalgesic conditions. After the induction of hyperalgesia with carrageenin, however, this compound elicited potent, dose-dependent (ID50 0.08 mg kg-1, s.c., and 6.9 mg kg-1, p.o., after remedial application, and 0.2 mg kg-1, s.c., and 3.1 mg kg-1, p.o., after prophylactic application) and naloxone-reversible antinociception. The antinociceptive action of systemically-applied (50 mg kg-1, p.o.) EMD 61753 in the hyperalgesic pressure test was completely inhibited by injection of the K-opioid antagonist norbinaltorphimine (100 Lg) into the inflamed tissue, a result which indicates that this opioid effect is mediated peripherally.6. Cutaneous plasma protein extravasation produced by antidromic electrical stimulation of the rat saphenous nerve was dose-dependently inhibited by systemically-applied EMD 61753 (ID13 values 3.7 mg kg-1, s.c., and 35.8 mg kg-1, p.o.), and this effect was completely antagonized by intraplantar application of norbinaltorphimine (50 microg). Extravasation elicited by the intraplantar application of substance P (10 microg) was not influenced by the administration of EMD 61753.7. EMD 61753 produced dose-dependent diuresis in non-hydrated rats at doses of and above 1.0 mg kg-1, s.c., and 10 mg kg-1, p.o., and in saline-loaded rats at doses of and above 10 mg kg-1, s.c.,and 30mgkg-1, p.o.8. The prostaglandin-mediated fall in mean arterial blood pressure elicited in anaesthetized rats by i.v.application of arachidonic acid was not inhibited by prior treatment with EMD 61753 (10mg kg-1,p.o.). Thus, a blockade of prostaglandin synthesis via inhibition of cyclo-oxygenase activity does not contribute to the in vivo effects of EMD 61753 and its metabolites.9 The present experiments therefore indicate that EMD 61753 is a potent, selective and orally-effective full ic-opioid receptor agonist which has a limited ability to penetrate the blood-brain barrier and elicit centrally-mediated sedation, putative aversion, diuresis, and antinociception. The inhibitory actions of systemically-applied EMD 61753 against hyperalgesic pressure nociception and neurogenic inflammation are mediated peripherally, probably by opioid receptors on the endings of sensory nerve fibres.

Sensitivity of dopamine D2 receptors following long-term treatment with roxindole.

The selective presynaptic dopamine D2 receptor agonist roxindole was studied in specific pre- and postsynaptic models in rats to see whether it induced changes in dopamine D2 receptor sensitivity. Following treatment with 0.3 or 3 mg/kg per day i.p. for 21 days, the reversal of gamma-butyrolactone-induced striatal dihydroxyphenylalanine accumulation was unchanged as compared to that after acute treatment. The efficacy of roxindole in this model was not decreased after long-term treatment. Likewise, treatment for 19 days with up to 10 mg/kg per day i.p. failed to induce behavioral supersensitivity, i.e. potentiation of apomorphine-induced stereotypies. In a cotreatment paradigm with haloperidol (1 mg/kg per day p.o.), roxindole (10mg/kg per day i.p.) did not alter the behavioral supersensitivity measured after a drug washout phase as compared to the effect of haloperidol alone; however, stereotypies were observed after termination of haloperidol but continuation of roxindole treatment. In contrast, roxindole (10 mg/kg i.p.) induced only weak stereotypies in haloperidol-sensitized rats when given after the washout phase instead of apomorphine. The results indicate that roxindole induces neither desensitization of presynaptic nor supersensitization of postsynaptic dopamine D2 receptors. Nevertheless, in add-on clinical studies with neuroleptics, switching of treatment regimens should be performed gradually over several days until further experience is available.

Central and peripheral actions of the novel kappa-opioid receptor agonist, EMD 60400.

1. The pharmacological characteristics of the kappa-opioid receptor agonist, EMD 60400, have been investigated, with particular reference to its central and peripheral sites of action and its ability to influence nociception. The kappa agonists ICI 197067 and ICI 204448 were tested for purposes of comparison. 2. EMD 60400 and ICI 197067 bind with high affinity (IC50 values of 2.8 and 1.5 nM, respectively) and high selectivity to kappa-opioid receptors. ICI 204448 has a lower binding affinity (IC50 13.0 nM) and selectivity for kappa-opioid receptors. 3. EMD 60400, ICI 197067, and ICI 204448 are full and potent agonists in the rabbit vas deferens in vitro assay for kappa-opioid receptors (IC50 values of 41.8, 15.7 and 15 nM, respectively). 4. Ex vivo binding experiments in mice revealed that EMD 60400 and ICI 197067 were well taken up after s.c. administration. Brain levels of EMD 60400 were lower than those of ICI 197067 at comparable doses, indicating that EMD 60400 does not penetrate into the CNS as well as ICI 197067. 5. Haloperidol-induced DOPA accumulation in the nucleus accumbens of the rat was dose-dependently reversed by s.c. application of EMD 60400 and ICI 197067 at doses of and above 3 and 0.3 mg kg-1, respectively. ICI 204448 had no effect on DOPA accumulation at 30 mg kg-1, s.c. 6. Prolongation of hexobarbitone-induced sleeping time in mice and motor impairment in the rat rotarod test were observed for EMD 60400 at doses above 3 and 2.5 mg kg-1, s.c., respectively, and for ICI 197067 at doses above 0.3 and 0.25 mg kg-1, s.c., respectively. ICI 204448 was inactive in these tests at doses of 30 and 100 mg kg-1, s.c., respectively.7. EMD 60400 applied s.c. produced dose-dependent naloxone-reversible antinociception in the mouse formalin test (1st and 2nd phase ID50 0.44 and 0.47 mg kg-1, respectively) and rodent writhing test (ID50 mouse 0.55 mg kg-1 and rat 0.3mg kg-1). Furthermore, EMD 60400 was considerably more potent in the rat pressure pain test after the induction of inflammation with carrageenin than under normalgesic conditions (ID50 values 0.1 Microg kg-1 and 4.0 mg kg-1, s.c., respectively). The action of EMD 60400 (50 microgkg-1, s.c.) in the hyperalgesic pressure pain test was completely antagonized by injection of the K-opioid antagonist, norbinaltorphimine (100 microg) into the inflamed tissue, thus demonstrating the peripheral opioid nature of this effect.8. EMD 60400 produced dose-dependent inhibition of neurogenic plasma extravasation elicited byantidromic electrical stimulation of the rat saphenous nerve (ID50 value 0.3 mg kg-1, i.v.). This inhibition was completely antagonized by intraplantar injection of norbinaltorphimine (50 microg).9. EMD 60400, ICI 197067, and ICI 204448 have diuretic effects in rats at doses of and above 0.1, 0.01,and 0.3 mg kg-1, s.c., respectively. An antidiuretic action was also observed with ICI 197067 at very low doses (3 and 6 microgkg-1, s.c.).10. Pharmacological and biochemical data therefore indicate that the three K-opioid receptor agonists tested here have different tendencies to elicit centrally-mediated sedation and putative aversion(ICI 197067 > EMD 60400 > ICI 204448) which correspond to their ability to cross the blood-brain barrier. EMD 60400 combines high affinity and selectivity for the K receptor with a degree of peripheral selectivity. The peripheral actions of systemically-applied EMD 60400 against hyperalgesic pressure pain and neurogenic inflammation are very probably mediated by opioid receptors on the endings of sensory nerve fibres.

Effects of ageing and long-term operant conditioning on behavior and presynaptic cholinergic and dopaminergic neuronal mechanisms in rats.

Presynaptic events in the brain, such as neurotransmitter synthesis and release, may change during ageing or by performance of an operant behavior. Therefore, we measured the acetylcholine synthesis and release, and the dopamine release in brain tissue from different groups of rats. Male Sprague-Dawley rats, 4-5 or 16-17 months old, were housed individually under identical conditions; one group of the older rats was maintained under an operant conflict procedure for 8 months. Striatal and cerebral cortex slices were preincubated with [3H]dopamine and [3H]choline, respectively, superfused and stimulated electrically. Different Ca++ concentrations were used and, in [3H]dopamine experiments, 0.1 mumol/l of apomorphine was added. Hippocampal slices were incubated with [3H]choline, and 3H-uptake and [3H]acetylcholine synthesis were measured. Gross behavior was not different between the groups as regards duration of exploration, defecation rate or spontaneous motility. Uptake of [3H]choline and synthesis of [3H]acetylcholine tended to be lower in the aged rats but did not differ significantly in the groups. The [3H]dopamine release was significantly reduced by 20% in aged rats as compared to young or aged, trained rats. The effect of changes in Ca++ concentrations and the response to apomorphine on the release of [3H]dopamine were similar in all groups, indicating a lack of age-related changes of the N-type Ca++ channels and presynaptic D-2 receptors. Thus, ageing coincided with an impaired striatal dopamine release which was prevented by the operant conditioning.

[The interactions of vitamins B1, B6 and B12 with non-steroidal antirheumatic and analgesic drugs: animal experiment results]. / Zur Wechselwirkung der Vitamine B1, B6 und B12 mit nichtsteroidalen Antirheumatika und Analgetika: Tierexperimentelle Befunde.

B-vitamins are therapeutically used in combination with nonsteroidal antiinflammatory drugs and weak analgesics. The animal experiments dealing with the antinociceptive and antiinflammatory activity of such combinations are reviewed with reference to the significance of the single vitamins B1, B6, and B12, the possible mechanisms of action, and the relevance of the animal data to man.