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  • 1
    Electronic Resource
    Electronic Resource
    SDZ GLC 756, a novel octahydrobenzo[g]quinoline derivative exerts opposing effects on dopamine D1 and D2 receptors (1996)
    Springer
    Journal of neural transmission 103 (1996), S. 17-30 
    Details
    ISSN: 1435-1463
    Keywords: SDZ GLC 756 ; octahydrobenzo[g]quinoline ; dopamine D1 receptor ; dopamine D2 receptor ; prolactin ; circling (rats) rearing (mice)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary SDZ GLC-756, a novel octahydrobenzo[g]quinoline derivative, is equipotent in displacing [3H]SCH23390 from dopamine D1 receptors and [3H]205–501 from dopamine D2 receptor binding sites. It blocks dopamine sensitive adenylate cyclase with the same potency as SCH23390, indicating antagonist properties at dopamine D1 receptors. On the other hand, SDZ GLC 756 inhibits electrically evoked acetylcholine release from rat striatal slices with the same potency as the selective dopamine D2 receptor agonist bromocriptine. This effect is blocked by spiperone suggesting that it is mediated by dopamine D2 receptor activation. The opposing action of SDZ GLC 756 on dopamine D1 and D2 receptors is also evident in vivo. SDZ GLC 756, like SCH23390, blocks apomorphine-induced rearing in mice. On the other hand, it inhibits prolactin secretion and produces circling in unilateral 6-OHDA-lesioned rats, which is compatible with stimulant properties at dopamine D2 receptors. This drug might be a new tool to study linkage between dopamine D1 and D2 receptors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01292613
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  • 2
    Electronic Resource
    Electronic Resource
    Differential effect of calcium entry blockers on α 1-adrenoceptor-mediated vasoconstriction in vivo (1983)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 324 (1983), S. 239-245 
    Details
    ISSN: 1432-1912
    Keywords: α1-Adrenoceptor agonists ; Postjunctional vascular α1-adrenoceptor ; Vasoconstriction ; Pithed normotensive rat ; Calcium entry blockade
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The effects of the calcium entry blockers nifedipine, (−)-verapamil and the dihydropyridine derivative PY 108-068 were evaluated on the increase in diastolic pressure of pithed normotensive rats caused by the selective α1-adrenoceptor agonists cirazoline, (−)-phenylephrine, (±)-erythro-methoxamine, (−)-amidephrine and St 587 [(2-chloro-5-trifluoromethylphenylimino)-2-imidazolidine] as well as by the mixed α1/α2-adrenoceptor agonists clonidine and DPI [(3,4-dihydroxyphenylimino)-2-imidazolidine]. The calcium entry inhibitors (up to 3 mg/kg) caused 3- to 5-fold, parallel rightward shifts of the log dose-pressor effect curves to cirazoline, (−)-phenylephrine, (±)-erythro-methoxamine and (−)-amidephrine accompanied by only a slight depression of the maximal pressor response. In contrast, the calcium entry inhibitors produced a dose-dependent profound depression of both maximum and slope of the log dose-pressor response curves to St 587 and clonidine. For DPI about 10-and 100-fold parallel displacements to the right without reduction of the maximum were found following treatment with 1 and 3 mg/kg of nifedipine, respectively. Infusion of vasopressin to counteract the vasodilatory action produced by the calcium entry inhibitors did not significantly change the pattern of interference observed under the conditions of decreased baseline diastolic pressure. The results indicate that α1-adrenoceptor-mediated vasoconstriction in the pithed normotensive rat, which is characterized by its sensitivity to blockade by prazosin and its relative insensitivity to antagonism by yohimbine or rauwolscine, can be subdivided into two distinct processes which are differentially influenced by blockade of calcium entry. It is suggested that cirazoline, (−)-phenylephrine, (±)-erythro-methoxamine and (−)-amidephrine initiate vasoconstriction predominantly by a mechanism independent of extracellular calcium influx. On the other hand, St 587 and clonidine increase arterial pressure via a mechanism which seems to be mainly governed by an entry of extracellular calcium ions. DPI probably triggers both processes of vasoconstriction in the intact circulatory system of the pithed normotensive rat.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00502618
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  • 3
    Electronic Resource
    Electronic Resource
    Effect of converting enzyme inhibition and angiotensin receptor blockade on the vasoconstriction mediated by α1 and α2 stimulation in pithed normotensive rats (1982)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 321 (1982), S. 309-313 
    Details
    ISSN: 1432-1912
    Keywords: Angiotensin converting enzyme inhibition ; Saralasin ; Vasoconstriction ; Pithed normotensive rat ; Vascular α1- and α2-adrenoceptors ; Endogenous angiotensin II
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The effect of functional impairment of the renin-angiotensin system on the vasoconstriction mediated by postsynaptic α1 and α2-adrenoceptors in pithed normotensive rats was studied. Selective α1-adrenoceptor stimulation was induced by intravenously administered cirazoline, whereas B-HT 920 was used as a selective agonists at α2-adrenoceptors. The angiotensin converting enzyme was inhibited by intravenous treatment of the pithed rats with captopril, teprotide or enalapril. Blockade of angiotensin receptors was produced by intravenously applied [Sar1 Ala8]angiotensin II (saralasin). Pretreatment with angiotensin converting enzyme inhibitors or with saralasin in doses which produced a maximal reduction in basal diastolic blood pressure, only slightly attenuated the hypertensive response to cirazoline. In contrast, these drugs provoked a most significant reduction of the α2-adrenoceptor mediated vasoconstriction. Restoration of the basal diastolic blood pressure by intravenous infusion with angiotensin II or with vasopressin completely reversed the inhibitory effect of captopril on the vasopressor response to B-HT 920. One hour after bilateral nephrectomy, captopril still reduced the α2-adrenoceptor mediated vasoconstriction. However, 18–24 h after bilateral nephrectomy, captopril had no additional inhibitory effect on the vasopressor response to selective α2-adrenoceptor stimulation. It is concluded that in pithed normotensive rats the pressor response to α2-adrenoceptor stimulation is significantly potentiated by endogenous angiotensin II, even at low circulating levels of the octapeptide. The modulatory action of angiotensin II on the α-adrenoceptor mediated vasoconstriction probably represents an effect on the basal arteriolar muscular tone rather than a specific interaction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00498519
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  • 4
    Electronic Resource
    Electronic Resource
    Organic and inorganic calcium antagonists reduce vasoconstriction in vivo mediated by postsynaptic α 2-Adrenoceptors (1981)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 316 (1981), S. 288-293 
    Details
    ISSN: 1432-1912
    Keywords: Postsynaptic α 1- α 2-adrenoceptors ; Methoxamine ; B-HT 920 ; Calcium antagonists ; Divalent metal ions ; Calcium ions ; Vasoconstriction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The influence of various calcium antagonists and divalent metal cations on the pressor responses induced by the selective α 1-adrenoceptor agonist methoxamine and the selective α 2-adrenoceptor stimulating agent B-HT 920 (2-amino-6-allyl-5,6,7,8-tetrahydro-4H-thiazolo-[4,5-d]-azepine) was studied in pithed rats. 1. The calcium antagonists verapamil, D 600 and nifedipine, when given intraarterially (i.a.) in doses up to 1 mg/kg did not influence the pressor effects of methoxamine. Only higher amounts of these calcium antagonistic drugs (1–3 mg/kg i.a.) somewhat reduced this pressor response. 2. The vasoconstriction due to B-HT 920, as reflected by the increase in diastolic pressure, was markedly inhibited by verapamil, D 600 and nifedipine in a dose-dependent manner. In low doses a parallel displacement to the right was observed, whereas in higher amounts the shift was non-parallel. 3. The divalent cations Mn2+, Ni2+ and Co2+ (0.05–0.15 mmol/kg i.a.) hardly affected the pressor effect of methoxamine, whereas B-HT 920-induced vasoconstriction was highly sensitive to these metal ions. La3+ and Mg2+ were ineffective. 4. The calcium antagonists verapamil, D 600 and nifedipine displayed only minor affinities for [3H]prazosin (α 1) as well as [3H]clonidine (α 2) binding sites of rat brain membranes. 5. It is concluded that an influx of extracellular Ca2+ is necessary for the vasoconstriction in vivo initiated by stimulation of vascular postsynaptic α 2-adrenoceptors. On the other hand, vasopressor responses to α 1-adrenoceptor stimulation are not directly dependent on a transmembrane influx of calcium ions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00501359
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  • 5
    Electronic Resource
    Electronic Resource
    Clozapine inhibits catalepsy induced by olanzapine and loxapine, but prolongs catalepsy induced by SCH 23390 in rats (1997)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 355 (1997), S. 361-364 
    Details
    ISSN: 1432-1912
    Keywords: Key words Clozapine ; Olanzapine ; Loxapine ; SCH 23390 ; Catalepsy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Loxapine (0.3mg/kg s.c.), olanzapine (10 mg/ kg s.c.) and SCH 23390 (R-(+)-chloro-2, 3, 4, 5-tetrahydro-3-methyl-5-phenyl-1-H-3-benzazepine; 1mg/kg, s.c.), but not clozapine (10mg/kg, s.c.), induced catalepsy in rats. Co-administration of clozapine (1, 3 and 10mg/ kg s.c.) dose-dependently inhibited loxapine-induced catalepsy. Clozapine (10mg/kg s.c.) also prevented the induction of catalepsy by olanzapine. In addition, clozapine abolished the catalepsy induced by loxapine when it was administered after the response had fully developed. In contrast, the duration of SCH 23390-induced catalepsy was prolonged by clozapine, indicating that its anti-catalepsy effects against olanzapine and loxapine are unlikely to be caused by muscle relaxation, sedation or stimulation. Since SCH 23390-induced catalepsy is reported to be blocked by scopolamine, dizocilpine (MK-801) or 8-hydroxy-dipropylamino-tetralin, it is unlikely that muscarinic blockade, NMDA ion channel blockade and 5-HT1A receptor agonism, respectively, are involved in clozapine’s action, but the mechanism by which clozapine exerts this anti-cataleptic effect remains unknown.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00004955
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  • 6
    Electronic Resource
    Electronic Resource
    Discriminative stimulus properties of 8-OH-DPAT in rats are not altered by pretreatment with para-chlorophenylalanine (1990)
    Springer
    Psychopharmacology 101 (1990), S. 39-42 
    Details
    ISSN: 1432-2072
    Keywords: Drug discrimination test ; 5-HT1A autoreceptor ; 8-OH-DPAT ; pCPA ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The role of 5-HT1A autoreceptors in the discriminative stimulus properties of 8-OH-DPAT (0.1 mg/kg, SC) in rats, was investigated. Drug lever appropriate responding to 8-OH-DPAT (0.1 mg/kg, SC) and ipsapirone (3 mg/kg, SC) was measured before and after treatment with para-chlorophenylalanine (pCPA) at a dose (150 mg/kg IP, −3 and −2 days) which causes severe depletion of brain 5-HT stores. The recognition of the drug stimulus was not significantly altered by pCPA. These results indicate that activation of 5-HT1A autoreceptors is of minimal importance to the 8-OH-DPAT cue.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02253715
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