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  • 1
    ISSN: 1432-2072
    Keywords: Key words Cocaine ; Dopamine ; D1 agonists ; D1 partial agonists ; D1 antagonists ; Efficacy ; Schedule-controlled behavior ; Cocaine discrimination ; SKF 38393 ; SKF 75670 ; SKF 81297 ; SKF 82958 ; SKF 83189 ; SCH 39166 ; Squirrel monkeys
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Dopamine D1 agonists differing in efficacy with respect to stimulation of adenylate cyclase activity and other in vitro and in vivo criteria were evaluated for their capacity to modulate the behavioral effects of cocaine in squirrel monkeys. Monkeys were trained either to respond on a fixed-ratio schedule in which lever pressing terminated a stimulus associated with electric shock or to discriminate cocaine from vehicle using a two-lever drug-discrimination procedure. When administered in combination with cocaine, D1 agonists displaying relatively low efficacy (SKF 38393, SKF 75670) attenuated both the rate-altering effects of cocaine on fixed-ratio responding and the discriminative-stimulus effects of cocaine, resulting in overall rightward shifts of the cocaine dose-response functions. Maximal attenuation of the behavioral effects of cocaine by the D1 partial agonists was comparable to that produced by the D1 antagonist SCH 39166. In contrast, D1 agonists displaying relatively high efficacy (SKF 81297, SKF 82958, SKF 83189) either had little effect on or accentuated the rate-altering and discriminative-stimulus effects of cocaine. The results show that D1 partial agonists can act as functional cocaine antagonists and may be viable candidate medications for the management of cocaine addiction.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Psychopharmacology 101 (1990), S. 132-134 
    ISSN: 1432-2072
    Keywords: Chlorpheniramine ; d-Chlorpheniramine ; l-Chlorpheniramine ; H1 antagonists ; Psychomotor stimulants ; Schedule-controlled behavior
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The behavioral effects of the histamine H1 antagonistsd- andl-chlorpheniramine and of the H2 antagonist zolantidine were determined in squirrel monkeys responding under a fixed-interval (FI) 3-min schedule of stimulus-shock termination. Althoughd-chlorpheniramine is known to be much more potent thanl-chlorpheniramine for antagonizing H1 receptor-mediated effects of histamine or displacing [3H]-mepyramine from histamine H1 receptors, similar doses of racemic chlorpheniramine and thed- andl-isomers (3.0–10.0 mg/kg) produced comparable increases in rates of responding. Zolantidine (1.0–17.0 mg/kg) did not alter or, at the highest dose, markedly decreased responding. These findings suggest that the psychomotor stimulant effects of chlorpheniramine involve actions other than the blockade of histamine H1 or H2 receptors. Selected H1 antagonists and cocaine are known to have comparable rateincreasing, reinforcing, and discriminative stimulus effects and, recently, the enantiomers of chlorpheniramine have been shown to displace [3H]-cocaine from binding sites in CNS with approximately equal potency. Possibly, such actions mediate behavioral effects common to H1 antagonists and cocaine.
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  • 3
    ISSN: 1432-2072
    Keywords: Rhesus monkey ; Morphine dependence ; Naloxone ; Nalorphine ; Postdependent sensitization ; Abstinence ; Schedule-controlled responding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effects of morphine, naloxone, and nalorphine on responding maintained under a variable-interval schedule of food presentation were assessed in rhesus monkeys before and after successive periods of daily morphine maintenance (15.0 mg/kg/day SC). Withdrawal from morphine dependence was accomplished gradually following the first two maintenance periods and abruptly following the third period. Schedule-controlled responding was disrupted when morphine maintenance was abruptly discontinued but not when the maintenance dosage was gradually reduced to zero. Tolerance to the acute effects of IV morphine on responding developed during morphine maintenance and dissipated after daily injections were discontinued. The effects of IV naloxone and IV nalorphine following each period of morphine maintenance were generally similar to their effects in initial determinations. These data indicate that tolerance-producing regimens of repeated daily injections with morphine do not necessarily produce enduring changes in the effects of opiate antagonists on schedule-controlled behavior. Additionally, gradual withdrawal from morphine maintenance can minimize the behavioral disruptions that attend abrupt abstinence.
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  • 4
    ISSN: 1432-2072
    Keywords: Lu 19-005 ; Stereoselectivity ; Monoamine uptake inhibitor ; Cocaine ; GBR 12909 ; Cocaine recognition site ; Operant behavior ; Radioreceptor assay ; Temperature dependence ; Indatraline
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effects of the monoamine uptake inhibitor Lu 19-005 ((±)-trans-3-(3,4-dichlorophenyl)-N-methyl-1-indanamine) and its (+) and (−) enantiomers, Lu 20-042 and Lu 20-043, were compared with those of cocaine and the selective dopamine uptake inhibitor GBR 12909 (1-{2-[bis-(4-fluorophenyl)methoxyl]ethyl}-4-(3-phenylpropyl)piperazin e) in behavioral and radioligand binding experiments. Behavioral experiments were conducted in groups of squirrel monkeys trained under fixed-interval schedules of reinforcement in which responding was maintained either by presentation of food or by termination of a visual stimulus associated with mild electric shock. Radioligand binding studies were conducted using [3H]CFT and [3H]GBR 12935 to label elements of the dopamine uptake system in caudate-putamen membranes of cynomolgus monkeys. All drugs produced dose-related increases in response rate under the fixed-interval schedules. Lu 19-005, Lu 20-042, and Lu 20-043 had relatively slow onsets (approximately 2 h) and relatively long durations of action, with effects persisting for two or more days following administration. Stereoselectivity was evident in the behavioral effects of the enantiomers of Lu 19-005, with Lu 20-042 being approximately 14 times more potent than Lu 20-043. In radioligand binding experiments, Lu 19-005 and its enantiomers were potent inhibitors of specifically bound [3H]CFT and [3H]GBR 12935. As in behavioral experiments, Lu 20-042 was more potent than Lu 20-043. The degree of stereoselectivity, however, varied with the temperature of the assay medium. At 37° C, Lu 20-043 was approximately 36 times more potent than Lu 20-043 in inhibiting the binding of [3H]CFT, whereas at 0–4° C, the difference in potency was only about 2-fold. The increased stereoselectivity at 37° C was due to a reduced potency for Lu 20-043. The results support the view that the behavioral effects of Lu 19-005 and its enantiomers are mediated at cocaine recognition sites associated with the dopamine uptake system. The results also show that incubation temperature can be a relevant factor in determining the relative potencies of drugs at [3H]CFT binding sites in vitro.
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  • 5
    ISSN: 1432-2072
    Keywords: SKF 81297 ; SKF 82958 ; R(+)-6-Br-APB ; R-SKF 38393 ; SKF 75670 ; SCH 39166 ; (+)-PHNO ; Quinpirole ; Bromocriptine ; Cocaine ; d-Amphetamine ; GBR 12909 ; Observable behavior ; Partial agonist ; Efficacy ; Squirrel monkeys
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The behavioral effects of selective D1 and D2, nonselective, and indirectly acting dopamine agonists were compared in squirrel monkeys using continuous observation procedures. D1 agonists including SKF 81297, SKF 82958, andR(+)-6-Br-APB produced dose-dependent increases in the frequencies of stationary postures and head movements and had little or no effect on either huddling or scratching. In contrast, SKF 75670 andR-SKF 38393, which are considered to be D1 partial agonists, had effects comparable to those of the D1 antagonist SCH 39166. That is, the D1 partial agonists increased the duration of huddling without greatly altering the frequencies of stationary postures, head movements, or scratching. Unlike the D1 agonists, the D2 agonists (+)-PHNO, quinpirole, and bromocriptine increased the frequency of scratching, but did not consistently alter other observable behaviors. The indirect dopamine agonists cocaine, GBR 12909, andd-amphetamine and the nonselective D1/D2 agonist CY 208–243, but not (−)apomorphine, had effects comparable to those of D1 agonists such as SKF 81297. That is, each of these drugs increased the frequencies of stationary postures and head movements with little or no effect on scratching or huddling. Additionally, effects of the D1 agonist SKF 82958 and the indirect dopamine agonist cocaine were surmountably antagonized by the D1 antagonist SCH 39166. The present results show that: 1) behavioral effects of D1 and D2 agonists in monkeys are qualitatively different; 2) D1 agonists presumed to differ in intrinsic activity have dissimilar effects; and 3) effects of indirect dopamine agonists are comparable to those of D1 agonists with presumably high intrinsic activity.
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  • 6
    ISSN: 1432-2072
    Keywords: Diazepam ; Pentobarbital ; Cocaine ; Substitution procedure ; Reinforcing properties ; Dependence potential ; Fixed-ratio schedules ; Rhesus monkeys
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Diazepam self-administration was studied in rhesus monkeys under several conditions of availability. Leverpress responding was maintained in twelve monkeys under a fixed-ratio 10 (FR 10) schedule of IV cocaine or pentobarbital delivery in daily sessions of 1–3 h duration. Each of several doses of diazepam (0.012–0.4 mg/kg/infusion) or vehicle was periodically substituted for 5–14 consecutive sessions. Between each substitution, responding was maintained by the baseline drug (cocaine or pentobarbital). Another procedure was to decrease the response requirement for drug delivery to a fixed-ratio one (FR 1). In three of eleven monkeys studied under conditions of a cocaine baseline and the FR 10 schedule, responding was maintained by diazepam and was inversely related to dose. In each of five monkeys tested in a similar manner but with a pentobarbital baseline, at least one dose of diazepam maintained responding above vehicle levels. Three of these monkeys had previously failed to self-administer diazepam under the cocaine baseline condition. Subsequently when two of these monkeys were returned to the cocaine baseline, diazepam was not self-administered above vehicle levels. Under FR 1 conditions of substitution, vehicle and pentobarbital intake increased in each monkey tested and cocaine intake increased in two of four monkeys. Diazepam self-administration also increased but did not exceed vehicle levels under the FR 1 schedule. However, in two monkeys the number of diazepam infusions was increased compared to the FR 10 substitution condition. These results emphasize the importance of testing drugs under several conditions to determine their relative dependence potential.
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