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1.
The effects of MDL 73005EF (8-[2-(2,3-dihydro-1,4-benzodioxin-2-yl)methylamino]-8- azaspiro[4,5]decan-7,9-dione methyl sulphonate), a novel selective 5-HT1A receptor ligand with putative anxiolytic properties, were explored using models of central pre- and postsynaptic 5-HT1A receptor function in the male rat. MDL 73005EF dose dependently decreased the hippocampal 5-HT output measured by in vivo microdialysis in chloral hydrate-anaesthetised rats and this response was antagonised by the 5-HT1A/B receptor antagonist, pindolol. Local administration of MDL 73005EF had no effect on the hippocampal 5-HT output. MDL 73005EF failed to alter basal plasma adrenocorticotropin (ACTH) levels but, in common with pindolol, attenuated the ACTH response to the 5-HT1A receptor agonist, 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT). In contrast to 8-OH-DPAT, MDL 73005EF significantly increased plasma prolactin but apparently not through a 5-HT receptor-mediated mechanism. The results indicate that MDL 73005EF possesses mixed 5-HT1A receptor agonist/antagonist properties, acting as an agonist at presynaptic 5-HT1A receptors controlling 5-HT release and as an antagonist at postsynaptic 5-HT1A receptors mediating ACTH release.  相似文献   

2.
The effect of a novel ligand for the 5-HT1A receptor subtype, MDL 73005EF, on the firing rate of serotonergic dorsal raphe neurons was assessed in rat midbrain slices maintained in vitro. Superfusion with MDL 73005EF inhibited neuronal firing in a concentration-dependent manner. Based upon IC50 values, MDL 73005EF was equipotent with buspirone (129 +/- 34 vs. 97 +/- 8 nM, respectively) but significantly less potent than 8-OH-DPAT (8-hydroxy-2(di-n-propylamino)tetralin; 7 +/- 2 nM). Pretreatment with (-)-propranolol (1 microM), a mixed 5-HT1A/B receptor antagonist, blocked by 50% the inhibition of unit activity elicited by MDL 73005EF. Taken together, these data suggest that MDL 73005EF is an agonist at the somatodendritic autoreceptor on dorsal raphe neurons, a 5-HT1A receptor which regulates in part the pacemaker activity of these cells. The results are discussed in the context of receptor reserve, recently proposed to explain apparent discrepancies in the actions of agonists at pre- and postsynaptic 5-HT1A sites.  相似文献   

3.
1. With radioligand binding techniques, MDL 73005 EF (8-[2-(2,3-dihydro-1,4-benzodioxin-2-yl-methylamino)ethyl]-8-az aspiro[4, 5]decane-7,9-dione methyl sulphonate) shows high affinity (pIC50 8.6) and selectivity (greater than 100 fold compared to other monoamine and benzodiazepine receptor sites) for the 5-hydroxytryptamine (5-HT)1A recognition site; it was both more potent and more selective than buspirone in this respect. 2. In rats pretreated with reserpine, 8-hydroxy-2-(di-n-propyl-amino) tetralin (8-OH-DPAT) induced forepaw treading and flat body posture; in the same model, MDL 73005EF and buspirone showed minimal agonist activity and at high doses MDL 73005EF inhibited responses to 8-OH-DPAT. 3. In rats trained to discriminate 8-OH-DPAT from saline in a drug discrimination paradigm, both MDL 73005EF and buspirone generalized dose-dependently and completely to the 8-OH-DPAT cue. 4. To define the anxiolytic potential of MDL 73005EF, it was examined in the elevated plus-maze test and in the water-lick conflict test in comparison with diazepam and buspirone. In both tests MDL 73005EF induced effects similar to those seen following diazepam. Buspirone had similar effects to both MDL 73005EF and diazepam in the water-lick conflict test but opposite effects in the elevated plus-maze. 8-OH-DPAT also had opposite effects in the elevated plus-maze test to MDL 73005EF and diazepam. 5. The anti-conflict effects of MDL 73005EF were reversed by low doses of the 5-HT1A receptor agonist, 8-OH-DPAT; those of buspirone were neither antagonised nor mimicked by 8-OH-DPAT.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

4.
The actions of 5-hydroxytryptamine (5-HT) and the 5-HT1A receptor ligand MDL 73005EF on neuronal activity in the CA1 region of rat hippocampal slices in vitro were recorded using intra- and extracellular recording techniques. 5-HT (1-30 microM) hyperpolarised the pyramidal neurones in a concentration-dependent manner and reduced membrane resistance and action potential after-hyperpolarisations (AHPs). MDL 73005EF (1-30 microM) had no clear effects on membrane potential, membrane resistance or AHPs. However, prior application of 3 microM MDL 73005EF to the slices for 10-60 min antagonised the hyperpolarisation induced by 30 microM 5-HT but not the reduction in spike AHP or the hyperpolarisation induced by the GABAB receptor agonist baclofen. MDL 73005EF and the 5-HT1A/2 receptor antagonist spiperone (both 3 microM) reduced the frequency and amplitude of spontaneous inhibitory (bicuculline-sensitive) postsynaptic potentials. Extracellular recordings of population action potentials revealed that MDL 73005EF did not prevent the induction or maintenance of hippocampal long-term potentiation or exhibit local anaesthetic properties. It is concluded that MDL 73005EF is an antagonist at 5-HT1A receptors on hippocampal CA1 pyramidal neurones.  相似文献   

5.
Recent studies indicate that 5-HT1A receptor agonists stimulate noradrenaline release in the brain. Here we investigate the mechanism underlying the increase in extracellular noradrenaline induced by (+/-)-MDL 73005EF, a weak 5-HT1A receptor agonist. Extracellular noradrenaline was measured in the hippocampus of the awake rat using microdialysis. (+/-)-MDL 73005EF (0.1, 1 and 5 mg/kg s.c.) caused a dose-related increase in noradrenaline. The active S(-)- enantiomer of MDL 73005EF (1 mg/kg s.c.) also increased noradrenaline whereas the inactive R(+)- enantiomer (1 mg/kg s.c.) did not. Measurements of extracellular 5-HT in hippocampus of anaesthetised rats confirmed that the 5-HT1A receptor agonist action of (+/-)-MDL 73005EF resides in the S(-)- enantiomer. Thus, S(-)-MDL 73005EF (0.3 and 1 mg/kg s.c.) markedly decreased 5-HT, whereas R(+)-MDL 73005EF (1 mg/kg s.c.) did not. The noradrenaline response to (+/-)-MDL 73005EF (1 mg/kg s.c.) was significantly blocked by the selective 5-T1A receptor antagonist, WAY 100635 (1 but not 0.3 mg/kg s.c). The noradrenaline response to (+/-)-MDL 73005EF (1 mg/kg s.c.) was not modified by pretreatment with the 5-HT synthesis inhibitor p-chlorophenylalanine. Intra-hippocampal application of (+/-)-MDL 73005EF (10 microM in perfusion medium) did not increase noradrenaline. Although (+/-)-MDL 73005EF has moderate affinity for dopamine D2 binding sites, the dopamine D2 receptor antagonist, remoxipride (1 mg/kg s.c.) did not increase noradrenaline. In conclusion, our data suggest that (+/-)-MDL 73005EF increases noradrenaline release in rat hippocampus through activation of 5HT1A receptors that appear to be located postsynaptically. These data are discussed in relation to the antidepressant/anxiolytic effects of 5-HT1A agonists.  相似文献   

6.
1. The actions of 5-hydroxytryptamine (5-HT) and some 5-HT1A receptor ligands on neurones in the rat dorso-lateral septal nucleus were recorded in vitro by intracellular recording techniques. 2. In the presence of tetrodotoxin (1 microM) to block any indirect effects, bath application of 5-HT (0.3-30 microM) hyperpolarized the neurones in a concentration-dependent manner and reduced membrane resistance. The hyperpolarization did not exhibit desensitization and was sometimes followed by a small depolarization. 3. The 5-HT1A receptor ligands, 8-hydroxy-2-(di-n-propylamino) tetralin (8-OH-DPAT), N,N-dipropyl-5-carboxamidotryptamine (DP-5-CT) and buspirone but not the non-selective 5-HT1 receptor agonist, 1-m-trifluoromethylphenylpiperazine (TFMPP), also hyperpolarized the neurones. 4. 5-HT, 8-OH-DPAT and DP-5-CT appeared to act as full agonists whereas buspirone behaved as a partial agonist. The estimated EC50S were: DP-5-CT 15 nM, 8-OH-DPAT 110 nM, 5-HT 3 microM and buspirone 110 nM. 5. At a concentration of 3 microM, the putative 5-HT1A receptor antagonists, spiperone, methiothepin, NAN-190 (1-(2-methoxyphenyl)-4-[4-(2-pthalimido)butyl]piperazine) and MDL 73005EF (8-[2-(2,3-dihydro-1,4-benzodioxin-2-yl-methylamino)ethyl]-8- azaspiro[4,5]decane-7,9-dione methyl sulphonate), produced a parallel rightward shift in the concentration-response curve to 5-HT with no significant reduction in the maximum response. The estimated pA2 values were: NAN-190 6.79, MDL 73005EF 6.59, spiperone 6.54 and methiothepin 6.17.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

7.
The stimulation of 5-HT1A receptors in the raphe or their blockade in the hippocampus can reduce cognitive deficits induced by blockade of muscarinic receptors in the hippocampus. We investigated the effects of MDL 73005 (8-[2-(2,3-dihydro-1,4-benzodioxin-2-ylmethylamino) ethyl]-8-azaspiro[4,5] decane-7,9-dione methyl sulphonate), an agonist at 5-HT1A somatodendritic autoreceptors and an antagonist at postsynaptic 5-HT1A receptors in rats treated systemically with scopolamine. Spatial memory was assessed in a water maze using protocols testing reference and working memory. Home cage locomotor activity was also determined. Working memory and locomotor activity were evaluated before and after para-chlorophenylalanine (pCPA) treatment. Scopolamine produced a weak impairment of reference memory at 0.5 mg/kg, and a more pronounced impairment of working memory at 0.25 and 0.5 mg/kg. MDL 73005 alone (2 mg/kg, i.p.) had no effect, but prevented the memory impairments induced by 0.25 mg/kg of scopolamine. Scopolamine induced hyperlocomotion. MDL 73005 alone did not affect locomotor activity, but exacerbated the hyperlocomotion induced by 0.5 mg/kg of scopolamine. pCPA did not abolish the effects of MDL 73005, suggesting that these effects were not due to an action at presynaptic receptors, or even that they involved receptors other than serotonergic ones (e.g., D2). In conclusion, MDL 73005 is able to antagonise moderate spatial memory dysfunctions induced by systemic muscarinic blockade.  相似文献   

8.
The antagonistic effects of MDL73005EF and tamsulosin and partial agonists clonidine and tizanidine at rat thoracic aorta and rabbit iliac artery alpha1-adrenoceptors were investigated in this study. Selective alpha1-adrenoceptor antagonists MDL73005EF and tamsulosin dose-dependently shifted the concentration-response curves for noradrenaline to the right. Schild plots of the results obtained from the inhibition by MDL73005EF (pA2 8.30 +/- 0.04) and tamsulosin (pA2 10.51 +/- 0.06) of noradrenaline yielded a straight line with a slope of unity in rat thoracic aorta. The slopes of Schild plots obtained from the inhibition by MDL73005EF and tamsulosin of noradrenaline were significantly different from unity in rabbit iliac artery. Schild plots of the results obtained from the inhibition by clonidine and tizanidine of noradrenaline yielded a straight line with a slope of unity in rat thoracic aorta (pA2 7.08 +/- 0.04 and 7.32 +/- 0.04, respectively). These results suggest that alpha1D-adrenoceptors play a significant role in the alpha1-adrenoceptor-agonist-induced contraction of rat thoracic aorta and rabbit iliac artery, and that clonidine and tizanidine interact with the alpha1D-adrenoceptor subtype as competitive antagonists in rat thoracic aorta.  相似文献   

9.
The affinity for functional alpha1-adrenoceptor subtypes of buspirone in comparison with its close structural analogs and selective alpha1D-adrenoceptor antagonists, BMY 7378 (8-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-8-azaspiro[4.5]dec ane-7,9-dione) and MDL 73005EF (8-[2-(1,4-benzodioxan-2-ylmethylamino)ethyl]-8-azaspiro+ ++[4.5]decane-7,9-dione), was determined, namely at subtype A in rat vas deferens and perfused kidney, at subtype B in guinea-pig and mouse spleen, at subtype L in rabbit spleen, and at subtype D in rat aorta and pulmonary artery against noradrenaline-evoked contractions. BMY 7378 and MDL 73005EF were confirmed as 30- and 20-fold selective antagonists, respectively, for alpha1D- over both alpha1A- and alpha1B-adrenoceptors. Buspirone was a weak antagonist without intrinsic activity at alpha1A-adrenoceptors in rat vas deferens (pA2 = 6.12), at alpha1B-adrenoceptors in guinea-pig and mouse spleen (pA2 = 5.54 and 5.59) and at alpha1L-adrenoceptors in rabbit spleen (pA2 = 4.99), but caused partial vasoconstriction in rat kidney that was attenuable by the subtype D-selective adrenoceptor antagonist BMY 7378, but hardly by the subtype A-selective adrenoceptor antagonist B8805-033 ((+/-)-1,3,5-trimethyl-6-[[3-[4-((2,3-dihydro-2-hydroxymethyl)-1,4-be nzodioxin-5-yl)-1-piperazinyl]propyl]amino]-2,4(1H,3H)-pyrimidinedion e), confirming the additional presence of alpha1D-adrenoceptors mediating rat renal vasoconstriction. Buspirone behaved as a partial agonist at alpha1D-adrenoceptors in rat aorta (pD2 = 6.77, intrinsic activity (i.a.)= 0.40) and pulmonary artery (pD2 = 7.16, i.a. = 0.59). With buspirone as agonist in these tissues, the pA2 values of subtype-discriminating antagonists were consistent with their alpha1D-adrenoceptor affinity determined in rat aorta against noradrenaline and with published binding data on cloned alpha1d-adrenoceptors. The results provide pharmacological evidence that (1) in functional preparations for the A subtype, like rat vas deferens and perfused kidney, for the B subtype, like guinea-pig and mouse spleen, and for the L subtype, like rabbit spleen, buspirone is a weak antagonist without intrinsic activity, but (2) behaves as a partial agonist in rat aorta and pulmonary artery as models for the D subtype and (3) detects an additional vasoconstrictor alpha1D-adrenoceptor in rat kidney. Buspirone, like its close analogs BMY 7378 and MDL 73005EF, thus might also be a useful tool for functionally discriminating alpha1D- from alpha1A-, alpha1B- and alpha1L-adrenoceptors in various tissues.  相似文献   

10.
MDL 73,147EF (1H-indole-3-carboxylic acid-trans-octahydro-3-oxo-2,6- methano-2H-quinolizin-8-yl-ester methanesulphonate) is a potent and selective 5-HT3 receptor antagonist (pA2 9.8, rabbit heart; pIC50 less than 5, D-2 receptor). The effects of acutely and chronically administered haloperidol and MDL 73,147EF were compared in an electrophysiologic model for antipsychotic activity. Haloperidol, but not MDL 73,147EF, given acutely increased the number of active dopamine neurons in the substantia nigra (A9). Both haloperidol and MDL 73,147EF, given chronically, decreased the number of active ventral tegmental dopamine neurons and the number of active A9 dopamine neurons. The results indicate that MDL 73,147EF may prove useful as an antipsychotic with a unique mechanism of action.  相似文献   

11.
1. The effect of acute and repeated treatment with 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT), a 5-HT1A receptor ligand, on excitatory amino acid-mediated synaptic transmission was examined in the stratum radiatum CA1 region of the dorsal hippocampus of alert, gently restrained, rats. 2. Acute administration of 8-OH-DPAT transiently reduced the amplitude of the field excitatory postsynaptic potential (e.p.s.p.) in a dose-dependent (25-75 micrograms kg-1, i.p.) manner. This effect was blocked by the postsynaptic 5-HT1A receptor antagonist, MDL 73005EF (2 and 4 mg kg-1, i.p.). 3. 8-OH-DPAT (25 micrograms kg-1, i.p.) administered daily for 7 days produced a gradual reduction in the 24 h pre-injection baseline field e.p.s.p. amplitude. The reduction reached its lowest level after 7-8 days and was transiently reversed by acute injection of MDL 73005EF (2 mg kg-1, i.p.) on day 8. The field e.p.s.p. baseline amplitude recovered fully 5-8 days after cessation of drug treatment. 4. 8-OH-DPAT (25 micrograms kg-1, i.p.) administered daily for 7 days produced a marked reduction in acute response to 8-OH-DPAT (25 and 50 micrograms kg-1, i.p.) which did not recover until between day 36 and day 80 of the study. 5. It was concluded that repeated treatment with 8-OH-DPAT produced adaptive changes which resulted in a reduction in the dynamic range of 5-HT1A receptor-mediated transmission in the hippocampus.  相似文献   

12.
Twenty agonists and nine antagonists were evaluated for their ability to compete for [3H]-8-hydroxy-2-(di-n-propylamino)tetralin ([3H]-8-OH-DPAT) binding to the cloned human serotonin-1A (ch-5-HT1A) receptor expressed in Chinese hamster ovary cells and for their ability to alter adenylyl cyclase activity in the same cells. The most potent full agonists of high affinity included N,N-dipropyl-5-carboxamidotryptamine (pEC50=9.6 +/- 0.1), MDL 73005EF (pEC50=9.3 +/- 0.2), 5-methyl-urapidil (pEC50=9.2 +/- 0.1), 5-carboxamidotryptamine (pEC50=9.1 +/- 0.2), R(+)-8-OH-DPAT (pEC50=8.6 +/- 0.1) and BMY-7378 (pEC50=8.6 +/- 0.1). WB-4101 (pEC50=8.3 +/- 0.2; IA=79%), clozapine (pEC50=8.1 +/- 0.3; IA=29%), (buspirone (pEC50=7.6 +/- 0.2; IA=79%), quipazine (pEC50 <5; IA=45%) and R-DOI (pEC50 < 5; IA=31%) were weaker agonists with partial agonist properties. The most potent antagonists were WAY-100,635 (pKi=10.2 +/- 0.1), methiothepin (pKi=8.8 +/- 0.2), spiperone (pKi=8.7 +/- 0.2) and NAN-190 (pKi=8.5 +/- 0.2). The receptor affinities and functional potencies were well correlated (r=0.88; P <0.0001). Our binding data correlated well with the pharmacology of endogenous 5-HT1A receptors in the rabbit iris-ciliary body (r=0.91; P <0.001) and rat hippocampus (r=0.93, P <0.0001). Our functional cAMP data correlated well with other cAMP accumulation data (r=0.8, P <0.01 vs calf hippocampus) but less so with [35S]-GTPgammaS binding to the ch-5-HT(1A) receptor as a functional activity read-out (r=0.58, P <0.05). The present study provides a detailed pharmacological characterization of the ch-5-HT1A receptor using binding and functional assays.  相似文献   

13.
Pre-weaning rat pups emit ultrasonic vocalizations when removed from the litter. These 'separation-induced vocalizations' (SIV) are suppressed by classical benzodiazepine anxiolytics and by non-benzodiazepine anxiolytics which lack muscle relaxant and sedative properties. The present study used the SIV model to assess potential anxiolytic properties of compounds which target different sites associated with the NMDA receptor complex. Comparison was made to drugs which affect benzodiazepine or serotonin (5-HT) receptors. Muscle relaxant potential was assessed using 'TIP' (time on an inclined plane), the amount of time a pup was able to retain its position on a steeply inclined surface. Mephenesin, a centrally acting muscle relaxant, significantly suppressed TIP but not SIV. The benzodiazepine agonist diazepam suppressed both SIV and TIP, whereas the 5-HT1A partial agonists, buspirone and MDL 73,005EF, suppressed SIV without affecting TIP. The 5-HT2 antagonist MDL 11,939 suppressed TIP but not SIV, whereas neither measure was affected by the 5-HT3 antagonist MDL 73,147EF. SIV was suppressed by NMDA antagonists including those acting at the glutamate recognition site (D,L-amino-phosphonovaleric acid (AP5) and MDL 100,453) or at the ion channel (MK-801), or by the strychnine-insensitive glycine antagonist 5,7-dichlorokynurenic acid (5,7-DCKA). TIP was suppressed even more potently by AP5, MDL 100,453 and MK-801, whereas 5,7-DCKA was inactive on this measure. Thus, antagonists acting at different sites present on the glutamate recognition site exhibit potential anxiolytic activity, but the glycine antagonist was unusual in its lack of prominent muscle relaxant side effects.  相似文献   

14.
J.R. Fozard 《Neuropharmacology》1984,23(12):1473-1486
5-Hydroxytryptamine (5-HT) induces responses in neurones from all branches of the mammalian peripheral nervous system. Responses may be excitatory or inhibitory and are mediated through at least four distinct receptor sites.One receptor mediates excitation in motoneurones and preganglionic sympathetic neurones and can be designated a D (or possibly 5-HT2) receptor since “classical” antagonists such as methysergide, metergoline or cinanserin are potent and selective antagonists at this site. A second receptor mediating neuronal excitation can be positively identified on the basis of susceptibility to blockade by small concentrations of 1αH,3α,5αH-tropan-3-yl-3,5-dichlorobenzoate (MDL 72222) and the weak or negligible affinity, relative to 5-HT, of certain agonists such as 5-methoxytryptamine. Such sites mediate depolarization of sympathetic and parasympathetic neurones and excitation of both the cell bodies and terminals of primary afferent fibres. A third receptor, mediating neuronal excitation, is the classical M-receptor of Gaddum and Picarelli, at this stage clearly identified only on postganglionic parasympathetic neurones of the guinea-pig myenteric plexus. These sites can be differentiated from other excitatory 5-HT receptors since MDL 72222 is neither potent nor selective as an antagonist and 5-methoxytryptamine approaches the potency of 5-HT as an agonist. (3α-Homotropanyl)-1-methyl-5-fluoro-indole-3-carboxylic acid is a potent, surmountable antagonist of 5-HT at the M-receptor of the ileum, but is non-selective.Neuronal inhibitory responses have been observed using electrophysiological techniques or by monitoring the decrease in depolarization-evoked release of transmitter in enteric, parasympathetic and sympathetic neurones. Largely negative results, using selective agonists and antagonists, allow the receptor(s) mediating inhibition to be clearly differentiated from the three neuronal excitatory receptors for 5-HT. Comparison of relative potencies of agonists suggests similarities with the 5-HT1 recognition site of the central nervous system; no selective antagonist has yet emerged to permit their positive identification.  相似文献   

15.
Activity at the 5-HT2A receptor versus that of the 5-HT2C receptor was studied in three behavioural paradigms. In pigeons trained to discriminate 0.32 mg/kg of 1-(2,5-diemethoxy-4-iodophenyl)-2-aminopropane (DOI) (a mixed 5-HT2A/C receptor agonist) from vehicle, quipazine (0.1-1 mg/kg) and m-chlorophenylpiperazine (mCPP) (1-3 mg/kg) substituted for DOI in a dose-related manner, and this generalization was blocked by MDL100907 (0.0001-0.01 mg/kg), a selective 5-HT2A receptor antagonist. RO60-0175 (a relatively selective 5-HT2C agonist) induced partial substitution at 3 mg/kg that was antagonized by both MDL100907 and by 3 mg/kg of SB242084, a relatively selective 5-HT2C antagonist. MK212 (a mixed 5-HT2C/A agonist) induced partial substitution that was antagonized by SB242084, but not by MDL100907. On a progressive ratio 5 operant schedule (PR5) for food reinforcement, DOI, quipazine, mCPP, MK212 and R060-0175 decreased the break point; mCPP, DOI, MK212 and quipazine also induced vomiting. Although MDL100907 antagonized both the reductions of break point and vomiting, SB242084 only partially attenuated the decrease in break point observed with MK212 and DOI, and was unable to eliminate vomiting. Thus pharmacological activity at the 5-HT2A receptor can be behaviourally distinguished from pharmacological activity at the 5-HT2C receptor in the pigeon. Furthermore, the decrease in the break point of a PR5 schedule induced by 5-HT2C receptor agonists may be related to decreased appetite, whereas that induced by 5-HT2A receptor agonists may be due to unrelated factors, such as emesis.  相似文献   

16.
In receptor binding assays (+/-)MDL 72832, 8-[4-(1,4-benzodioxan-2-ylmethylamino)butyl]-8-azaspiro++ +[4,5] decane-7,9-dione, was a potent (pIC50 9.1), selective and stereospecific ligand for central 5-HT1A recognition sites. In functional tests, (+/-)MDL 72832 and its S(-) and R(+) enantiomers blocked stereoselectively the 8-OH-DPAT-induced neuronal inhibition of the transmurally stimulated guinea-pig ileum and the cardiovascular effects of 8-OH-DPAT in anaesthetized rats. In contrast, (+/-)MDL 72832 and its enantiomers were exclusively '8-OH-DPAT-like' in their ability to fully and stereoselectively generalize to the 8-OH-DPAT discriminative stimulus and, in reserpinised rats, to induce forepaw treading and flat body posture. These results characterize (+/-)MDL 72832 as a potent, stereoselective ligand with mixed agonist and antagonist properties at central and peripheral 5-HT1A receptors. The similar stereoselective requirements for the recognition site and functional effects provides compelling evidence that the 5-HT1A recognition site is indeed a functional receptor.  相似文献   

17.
Aripiprazole has made a significant contribution to the treatment of schizophrenia and related disorders. It has improved its safety and tolerability profiles, and these effects have been attributed to its pharmacological profile at the serotonin 5-HT and dopamine D(2) receptors. To discover compounds that have a similar pharmacological profile, we introduced a generic single-cell-based calcium imaging assay that standardizes the readouts from various assays used in previous studies on aripiprazole. In the present assay, the efficacy and potency of known ligands of serotonin 5-HT(1A), 5-HT(2A), 5-HT(2C), 5-HT(7) and dopamine D(2L) receptors were comparable to those found in previous studies using a variety of readouts. The developed assay was also able to reproduce the partial agonist activity, the low intrinsic activity and the selective activation of aripiprazole at the dopamine D(2L) receptors. Under identical experimental conditions, geissoschizine methyl ether (GM), a plant indole alkaloid, behaved as a partial agonist at the serotonin 5-HT(1A) receptor, a partial agonist/antagonist at the dopamine D(2L) receptor and an antagonist at the serotonin 5-HT(2A), 5-HT(2C) and 5-HT(7) receptors. Interestingly, GM showed a relatively low intrinsic activity and evoked a partial activation response in a subset of cells expressing the dopamine D(2L) receptor; both of these effects were similarly observed for aripiprazole. Although GM is far less potent at the dopamine receptor than aripiprazole at dopamine D(2L) receptors (EC(50)=4.4 μM for GM vs. EC(50)=56 nM for aripiprazole), GM and GM derivatives may comprise a new set of candidates for atypical antipsychotics.  相似文献   

18.
Aripiprazole, 7-[4-[4-(2,3-dichlorophenyl)-1-piperazinyl]butyloxy]-3,4-dihydro-2(1H)-quinolinone, a novel antipsychotic with partial agonist activity at dopamine D2 receptors, bound with high affinity to recombinant human 5-HT(1A) receptors (h5-HT(1A)) in Chinese hamster ovary cell membranes and displayed potent, partial agonism at 5-HT(1A) receptors in a guanosine-5'-O-(3-[(35)S]thio)-triphosphate ([(35)S]GTP gamma S)-binding assay that was blocked completely by a selective 5-HT(1A) receptor antagonist. An interaction with 5-HT(1A) receptors may contribute to the overall efficacy of aripiprazole against symptoms of schizophrenia, including anxiety, depression, cognitive and negative symptoms, and to its favorable side-effect profile. Combined with previous studies demonstrating the potent partial agonism of aripiprazole at dopamine D2 receptors, this study suggests aripiprazole is the first dopamine-serotonin system stabilizer.  相似文献   

19.
Summary The properties of MDL 72222 (1H,3,5H-tropan-3-yl-3,5-dichlorobenzoate), a novel compound with potent and selective blocking actions at certain excitatory 5-hydroxytryptamine (5-HT) receptors on mammalian peripheral neurones, are described.On the rabbit isolated heart, MDL 72222 was a potent antagonist of responses mediated through the receptors for 5-HT present on the terminal sympathetic fibres. The threshold for antagonism was approximately 0.1 nM and the negative logarithm of the molar concentration of MDL 72222 which reduced the chronotropic response of the isolated rabbit heart to twice an ED50 of 5-HT to that of the ED50 was 9.27. MDL 72222 was also highly selective since responses to the nicotine receptor agonist, dimethylphenylpiperazinum iodine (DMPP), were inhibited only at concentrations more than 1000 times those necessary to inhibit 5-HT.In the anaesthetised rat, MDL 72222 produced marked blockade of the Bezold-Jarisch effect of 5-HT. Again, inhibition was selective since much higher doses of MDL 72222 failed to alter the response to electrical stimulation of the efferent vagus nerves. In contrast, MDL 72222 proved only a weak and essentially non-selective antagonist of responses mediated by the 5-HT M-receptor present on the cholinergic nerves of the guinea-pig ileum.MDL 72222 does not block smooth muscle contractile responses elicited by oxytocin or mediated through 5-HT D-receptors, muscarinic or nicotinic cholinoceptors or histamine H1-receptors except at relatively high concentrations. Similarly, in a number of radioligand binding assays carried out using brain tissue membranes, the displacing effects of MDL 72222 were absent or weak at sites identifying compounds with activity at 1, 2 or -adrenoceptors, 5-HT1 or 5-HT2 receptors, benzodiazepine receptors or histamine H1-receptors.MDL 72222 is the first reported selective and potent antagonist of responses mediated through the 5-HT receptors present on the terminal sympathetic neurones of the rabbit heart and on the neurones subserving the afferent limb of the Bezold-Jarisch reflex. The compound should provide a useful means by which responses mediated through such sites can be distinguished.  相似文献   

20.
Latent inhibition (LI) is a behavioral model of selective attention that has been used to study the attentional deficits seen in schizophrenia. In the present study, we examined the effect of 5-hydroxytryptamine3 (5-HT3) receptor blockade on LI using the conditioned emotional response (CER) procedure. Prior exposure to 20, 30, or 40 stimulus presentations significantly, and almost completely, inhibited the CER to that stimulus. This LI effect was much weaker when only 10 preexposures were given. 1H-indole-3-carboxylic acid, trans-octahydro-3-oxo-2,6-methano-2H-quinolizin-8-yl ester methanesulfonate (MDL 73,147EF), a selective 5-HT3 receptor antagonist, significantly facilitated the LI effect observed after 10 preexposures at 0.1 mg/kg but not at 0.01 mg/kg. The magnitude of this effect was comparable to that observed with the classical neuroleptic haloperidol (0.1 mg/kg). Neither MDL 73,147EF nor haloperidol affected the CER in animals not preexposed to the stimulus. These results strongly corroborate suggestions that 5-HT3 receptor antagonists will be of use in the treatment of schizophrenia.  相似文献   

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