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  • 1
    Electronic Resource
    Electronic Resource
    Mu-Selective Opioid Peptides Stimulate Prolactin Release in Lactating Rats (1990)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neuroendocrinology 2 (1990), S. 0 
    Details
    ISSN: 1365-2826
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The fact that opiates elicit prolactin secretion is well known. However, we have recently discovered that morphine does not stimulate prolactin release in lactating rats. The physiological basis for this alteration in opiate sensitivity during lactation is not known. Since morphine-induced prolactin secretion in male rats is mediated via the mu opioid receptor subtype, one possible explanation is that mu receptors are down-regulated during lactation. To address this possibility, the effects of mu opioid peptides on prolactin secretion were examined in lactating rats. The presumed mu-selective peptides DAGO ([D-Ala2, Me-Phe4, Gly-ol5]-enkephalin) and PLO-17 ([NMe-Phe3, D-Pro4]-morphiceptin) were administered to primiparous lactating rats and the resulting hormone responses measured. Both DAGO and PLO-17 caused a rapid and significant rise in plasma prolactin during lactation. The prolactin-releasing effects of both peptides were naloxone reversible, suggesting involvement of opioid receptors. Moreover, the DAGO-induced secretion of prolactin could be completely abolished by pretreatment with the irreversible mu antagonist β-funaltrexamine. In lactating rats, DAGO and PLO-17 were poor growth hormone-releasing agents, providing further evidence for the mu specificity of these peptides. These results imply that during lactation, as in other reproductive states, mu opioid receptor sites are positively coupled to the prolactin secretory mechanism. Thus, the previously observed inability of morphine to elicit prolactin release in lactating rats cannot be explained on the basis of down-regulation of mu opioid receptors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2826.1990.tb00404.x
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  • 2
    Electronic Resource
    Electronic Resource
    Inhibition of Tuberoinfundibular Dopaminergic Neural Activity During Suckling: Involvement of μ and κ Opiate Receptor Subtypes (1996)
    Oxford : Blackwell Science Ltd.
    Journal of neuroendocrinology 8 (1996), S. 0 
    Details
    ISSN: 1365-2826
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Previous studies have shown that mu (μ) and kappa (κ) opioid antagonists inhibit suckling-induced prolactin release. Prolactin responses elicited by pup suckling or opioid administration are mediated, at least in part, by suppression of dopamine (DA) release from tuberoinfundibular dopaminergic (TIDA) neurons in the hypothalamus. We examined the effects of the μ opiate receptor antagonist, β-funaltrexamine (β-FNA), and the κ opiate receptor antagonist, nor-binaltorphimine (nor-BNI) on the activity of TIDA neurons in lactating rats. TIDA neuronal activity was determined by measuring DOPA accumulation in the caudate putamen (CP) and median eminence (ME). The effects of opioid antagonist treatment were determined in pup-deprived (low circulating prolactin levels) or pup-suckled rats (high circulating prolactin levels). The accumulation of 5-hydroxytryptophan (5-HTP) in the medial preoptic area (MPOA), the anterior hypothalamus (AH) and the median eminence (ME) was quantified as an index of serotonergic activity in the same animals for comparative purposes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2826.1996.05207.x
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  • 3
    Electronic Resource
    Electronic Resource
    Effects of dopamine and serotonin-releasing agents on methamphetamine discrimination and self-administration in rats (1999)
    Springer
    Psychopharmacology 141 (1999), S. 287-296 
    Details
    ISSN: 1432-2072
    Keywords: Key words Methamphetamine ; Dopamine ; Serotonin ; Phentermine ; Fenfluramine ; Drug-discrimination ; Self-administration ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  To analyze the involvement of dopamine (DA) and serotonin (5-HT) release in the stimulus properties of methamphetamine, two amphetamine analogs that selectively release either brain DA (phentermine) or 5-HT (fenfluramine) were tested for their ability to substitute for methamphetamine in rats discriminating methamphetamine (1.0 mg/kg) from saline. They were subsequently tested for their ability to alter IV methamphetamine (0.06 mg/kg per injection) self-administration in the same species when given as a pretreatment. The DA releaser phentermine, like methamphetamine itself, decreased methamphetamine self-administration (to 70% of baseline responding), but only at a dose of 3.0 mg/kg that fully generalized to the methamphetamine stimulus in the discrimination study. The 5-HT releaser fenfluramine attenuated methamphetamine self-administration to a much larger extent than phentermine (to 37% of baseline responding) at a dose of 1.8 mg/kg that did not generalize to methamphetamine and did not decrease rate of responding in the discrimination study. Tolerance developed to the inhibitory effect of 1.8 mg/kg fenfluramine on methamphetamine self-administration when it was given repeatedly over four consecutive daily sessions. The fenfluramine-induced decrease in methamphetamine self-administration was also attenuated when it was given together with the small 1.0 mg/kg dose of phentermine. These results suggest that DA release plays a dominant role in the discriminative stimulus effects of methamphetamine. However, stimulation of 5-HT release can strongly modify methamphetamine self-administration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002130050836
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  • 4
    Electronic Resource
    Electronic Resource
    Behavioural and neurochemical characteristics of phentermine and fenfluramine administered separately and as a mixture in rats (1997)
    Springer
    Psychopharmacology 131 (1997), S. 296-306 
    Details
    ISSN: 1432-2072
    Keywords: Key words Drug discrimination ; Microdialysis ; Dopamine ; Serotonin ; Phentermine ; Fenfluramine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Clinical case studies suggest that combined administration of the serotonergic agent fenfluramine (FEN) and the weak amphetamine-like anorexic agent phentermine (PHEN) may be useful in the treatment of alcohol and cocaine addictions. The present experiment examined the nature of the interaction between the two agonists using the drug discrimination paradigm. In vivo microdialysis served to examine the neurochemical profile of dopamine and serotonin release in the nucleus accumbens. In conscious rats, acute injections of FEN (1.0–2.0 mg/kg IP) or PHEN (1.0–2.0 mg/kg IP) selectively elevated levels of serotonin and dopamine in the nucleus accumbens, respectively. A mixture (1 mg/kg of each) increased levels of both amines by similar magnitudes to those observed with each individually. Three groups of Sprague-Dawley rats were trained to discriminate (1) FEN (1.0 mg/kg IP) alone, (2) PHEN (1.0 mg/kg IP) alone or a mixture (3) PHEN+FEN (1 mg/kg of each, IP) from saline under a fixed ratio (FR-10) schedule of food reinforcement. Rats acquired the mixture discrimination rapidly, while for the other groups the training dose had to be increased to 2.0 mg/kg to attain stimulus control. The individual components of the mixture at the training dose generalized partially to the mixture, and complete generalisation was observed following 3.0 mg/kg FEN or PHEN. Rats trained to discriminate the individual components showed respective cross-generalisation profiles. Generalisation to cocaine (0.3–10.0 mg/kg IP), amphetamine (0.1–3.0 mg/kg IP) and nicotine (0.1–0.8 mg/kg SC) was greatest in the MIX-trained rats, while partial or no generalisation was observed in rats trained to discriminate the individual compounds. From the present results, it may be concluded that the two drugs given as a mixture do not produce a novel cue. Rather, these aminergics appear to interact additively. Furthermore, the dual stimulation of the amines by the mixture may be the basis for the cueing effects of the FEN+PHEN drug mixture, and its effectiveness in treating drug addictions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002130050296
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  • 5
    Electronic Resource
    Electronic Resource
    Pleural macrophages differentially alter mesothelial cell growth and collagen production (1993)
    Springer
    Inflammation 17 (1993), S. 1-12 
    Details
    ISSN: 1573-2576
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Intrapleural tetracycline (TCN) results in pleural macrophage influx and pleural fibrosis; intrapleural carrageenan (CAR) induces macrophage influx without fibrosis. Because macrophage products can modulate mesothelial cell activity, we investigated the role of TCN- and CAR-induced pleural macrophages on mesothelial cell growth can collagen production. Rabbit pleural macrophages, isolated by plastic adherence 72 h after 20 mg/kg TCN or 10 mg CAR instilled intrapleurally, were cultured for 20 h. Macrophage-conditioned media (MCM) from TCN- or CAR-induce pleural macrophages (TCN MCM, CAR MCM, respectively), were added to nonconfluent or confluent rat visceral pleural mesothelial cells and compared to the effects of TCN and CAR. Ncnconfluent mesothelial cells were harvested 72 h later for hemacytometry cell counts. A 20-h pulse of [3H] proline (1μCi, 30 Ci/mM) preceded 72-h-cell harvesting of confluent cells. Collagen content was determined in the cell fraction and cell media separately after bacterial collagenase exposure. Mesothelial cells exposed to TCN MCM were found to have decreased numbers when compared to all groups (P 〈 0.05) except CAR. Cell media collagen content was increased in all macrophage-conditicned-media and chemical-exposed groups compared with control, with TCN MCM having a larger increase than TCN alone (P 〈 0.05). We conclude that stimulated pleural macrophages release a factor(s) that alters mesothelial cell growth and collagen production and that TCN- and CAR-stimulated pleural macrophages are functionally different. These in vitro mesothelial cell alterations may be important in the genesis of TCN pleurodesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00916387
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