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García-Barrado MJ, Pastor MF, Iglesias-Osma MC, Carpéné C, Moratinos J. Comparative effects of idazoxan, efaroxan, and BU 224 on insulin secretion in the rabbit: Not only interaction with pancreatic imidazoline I2 binding sites. Health (London) 2010. [DOI: 10.4236/health.2010.22018] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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2
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Haller J, Makara GB, Kruk MR. Catecholaminergic involvement in the control of aggression: hormones, the peripheral sympathetic, and central noradrenergic systems. Neurosci Biobehav Rev 1998; 22:85-97. [PMID: 9491941 DOI: 10.1016/s0149-7634(97)00023-7] [Citation(s) in RCA: 87] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Noradrenaline is involved in many different functions, which all are known to affect behaviour profoundly. In the present review we argue that noradrenaline affects aggression on three different levels: the hormonal level, the sympathetic autonomous nervous system, and the central nervous system (CNS), in different, but functionally synergistic ways. Part of these effects may arise in indirect ways that are by no means specific to aggressive behaviour, however, they are functionally relevant to it. Other effects may affect brain mechanisms specifically involved in aggression. Hormonal catecholamines (adrenaline and noradrenaline) appear to be involved in metabolic preparations for the prospective fight; the sympathetic system ensures appropriate cardiovascular reaction, while the CNS noradrenergic system prepares the animal for the prospective fight. Indirect CNS effects include: the shift of attention towards socially relevant stimuli; the enhancement of olfaction (a major source of information in rodents); the decrease in pain sensitivity; and the enhancement of memory (an aggressive encounter is very relevant for the future of the animal). Concerning more aggression-specific effects one may notice that a slight activation of the central noradrenergic system stimulates aggression, while a strong activation decreases fight readiness. This biphasic effect may allow the animal to engage or to avoid the conflict, depending on the strength of social challenge. A hypothesis is presented regarding the relevance of different adrenoceptors in controlling aggression. It appears that neurons bearing postsynaptic alpha2-adrenoceptors are responsible for the start and maintenance of aggression, while a situation-dependent fine-tuning is realised through neurons equipped with beta-adrenoceptors. The latter phenomenon may be dependent on a noradrenaline-induced corticosterone secretion. It appears that by activating very different mechanisms the systems working with adrenaline and/or noradrenaline prepare the animal in a very complex way to answer the demands imposed by, and to endure the effects caused by, fights. It is a challenge for future research to elucidate how precisely these mechanisms interact to contribute to functionally relevant and adaptive aggressive behaviour.
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Affiliation(s)
- J Haller
- Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest
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Avellar MC, Markus RP. Are imidazoline receptors involved in sympathetic neurotransmission in rat vas deferens? GENERAL PHARMACOLOGY 1996; 27:1273-8. [PMID: 8981080 DOI: 10.1016/s0306-3623(96)00038-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
1. An involvement of imidazoline receptors in the modulation of neurotransmitter release was investigated in the prostatic portion of the rat vas deferens stimulated transmurally at 0.2 Hz or by single pulses. 2. Idaxozan and yohimbine induced a concentration-dependent potentiation of the contractile response to 0.2-Hz transmural stimulation in the epididymal and prostatic portion of the vas. 3. After reserpine treatment, idazoxan, but not yohimbine, still potentiated the contractile response, suggesting a possible involvement of imidazoline receptors. 4. Clonidine and rilmenidine, agonists with different affinities to alpha 2-adrenoceptors and imidazoline receptors, inhibited with the same potency the contractile responses to a single pulse transmural stimulation. 5. Yohimbine (a selective alpha 2-adrenoceptor antagonist) antagonized the inhibitory concentration effect curve to rilmenidine in a competitive manner. pA2 values for idaxozan (an antagonist to alpha 2-adrenoceptors and imidazoline receptors) were not different when noradrenaline or rilmenidine were used as agonists. Phenoxybenzamine blocked the effect of both agonists. 6. Thus, the potency relationship of agonists, as well as the effect of the antagonists, did not favor the hypothesis that imidazoline receptors are involved in the idazoxan-potentiating effect in the rat vas deferens.
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Affiliation(s)
- M C Avellar
- Departamento de Farmacologia, Universidade de São Paulo, Brazil
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4
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Haller J, Makara GB, Kovács JL. The effect of alpha 2 adrenoceptor blockers on aggressive behavior in mice: implications for the actions of adrenoceptor agents. Psychopharmacology (Berl) 1996; 126:345-50. [PMID: 8878351 DOI: 10.1007/bf02247386] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The effects of three alpha 2 adrenoceptor blockers (idazoxan, yohimbine and CH-38083) on isolation-induced aggressive behavior was studied in male mice. The three drugs produced different behavioral profiles. Idazoxan reduced aggressiveness dose-dependently by decreasing the duration of offensive/aggressive interactions and increasing the duration of defensive behaviors. The other two drugs produced only parts of the dual action of idazoxan: yohimbine affected mainly defensive behaviors, while CH-38083 affected only the time spent with fighting. Saline injections per se also influenced behavior and, in contrast to alpha 2 adrenoceptor blockers, induced an increase in aggressiveness. These results are different from those previously obtained in rats, which show bell-shaped dose-response curves in response to alpha 2 adrenoceptor blockers (small doses increased, while large doses decreased aggression). It is postulated that the strong behavioral reaction of mice to the injection per se may mask the aggression-heightening effects of small doses of alpha 2 adrenoceptor blockers in this species. A theory is also presented regarding the complexity of adrenoceptor interactions when both pre-, and postsynaptic alpha 2 adrenoceptors are blocked.
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Affiliation(s)
- J Haller
- Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary
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Montastruc JL, Llau ME, Senard JM, Tran MA, Rascol O, Montastruc P. A study of tolerance to apomorphine. Br J Pharmacol 1996; 117:781-6. [PMID: 8851490 PMCID: PMC1909420 DOI: 10.1111/j.1476-5381.1996.tb15260.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
1. The present study was designed to investigate tolerance to several pharmacological effects of apomorphine. 2. Changes in blood pressure, heart rate, plasma noradrenaline levels, rectal temperature, respiratory rate and retching plus vomiting were compared after administration of apomorphine (200 micrograms kg-1, i.v. as a bolus) or saline at different time intervals (30, 120 and 720 min) in four groups of chloralose-anaesthetized dogs. 3. The first administration of apomorphine induced a significant decrease in blood pressure and rectal temperature, a marked rise in heart rate with no change in noradrenaline plasma levels or respiratory rate. Emesis occurred in 71% of the animals. 4. A second administration of apomorphine 30 min later failed to modify blood pressure or heart rate. In contrast, the magnitude of apomorphine-induced changes in blood pressure and heart rate was similar to that observed after the first administration when apomorphine was given 120 or 720 min later. 5. The apomorphine-induced decrease in rectal temperature evoked by a second dose of apomorphine was less marked when given 30 and 120 min after the first dose and unchanged when given 720 min later. 6. The number of animals exhibiting retching and vomiting was lower when apomorphine was reinjected after 30 min than when the time between two successive injections of apomorphine was 120 or 720 min. 7. These results show that tolerance to apomorphine involves its cardiovascular, hypothermic and emetic effects. The time course of tolerance to repeated injections of apomorphine is longer for its hypothermic than for its hypotensive or emetic effects. This suggests a tissue-specific regulation of D2 dopamine receptors to repeated injections of apomorphine.
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Ricci D, Taira CA. Brain alpha 1-adrenoceptor in the cardiovascular responses to BHT-920 and phenylephrine. GENERAL PHARMACOLOGY 1996; 27:299-304. [PMID: 8919646 DOI: 10.1016/0306-3623(95)02006-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
1. It is well known that alpha 1A-adrenoceptors have binding sites for imidazolic and for phenylethylaminic drugs. A study was made relating alpha 1A-adrenoceptor involvement in cardiovascular responses to intracerebroventricular (ICV) injection of BHT-920, an imidazoliclike drug, and phenylephrine, a phenylethylaminic drug, in conscious sham-operated and sinoaortically-denervated rats. 2. In sham-operated rats, cardiovascular responses to BHT-920 (30 micrograms, ICV) were increase of blood pressure and bradycardia but in sinoaortically denervated rats, after the pressor response, a decrease of blood pressure was also seen. The pressor and bradycardic responses to agonist were greater in sinoaortically denervated rats than in sham-operated rats. Phenylephrine (90 micrograms, ICV) showed a biphasic effect on blood pressure: an increase followed by a decrease, and bradycardia. The cardiovascular responses to phenylephrine in sinoaortic-denervated rats were greater than in sham-operated rats. 3. In sinoaortically denervated and sham-operated rats subchronically treated with the alpha 1-adrenoceptor antagonist prazosin (0.5 mg kg-1, intraperitoneally twice daily, for 6 days), an increase of cardiovascular responses to ICV administration of BHT-920 and phenylephrine was seen. 4. Baroreceptor deafferentation by sinoaortic denervation enhances the cardiovascular responses to BHT-920 and phenylephrine. The effects of BHT-920 could be mediated by brain alpha 1A adrenoceptors because this agonist has an imidazoliclike structure; phenylephrine could also be activating central alpha 1A-adrenoceptors. The enhanced cardiovascular responses after prazosin treatment could also be due to a supersensitivity of brain alpha 1A-adrenoceptors.
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Affiliation(s)
- D Ricci
- Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Argentina
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Abstract
Opioids have been used for centuries as antidiarrhoeal drugs. In recent years, their mechanism and sites of action in exerting their antidiarrhoeal effect have been studied intensely. Attempts have been made to propose their general mode of action. Whilst there are numerous similarities in their general effects on motility, fluid secretion, and neuroeffector transmission, the differences between species, in some cases, can be remarkable. We highlight and contrast the similarities and differences in the commonly examined species and compare them to humans. Insights into mechanisms of opioid antidiarrhoeal action now also provide some new perspectives of opioid action in the intestine.
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Affiliation(s)
- A De Luca
- Department of Medical Laboratory Science, Royal Melbourne, Institute of Technology University, Victoria, Australia
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Abstract
Previous research has shown that resident rats treated with alpha 2 adrenoceptor blockers display a modified aggressive response towards intruding animals. In the present study we report data on the behavioral changes induced by alpha 2 adrenoceptor blockers in intruder animals. In experiments 1 and 2 intruders smaller in body weight than the residents were treated with 0.0, 0.5, and 1.0 mg/kg CH-38083 and idazoxan, respectively; in experiment 3 weight matched intruders were injected with 1 mg/kg CH-38083 or idazoxan. The treatment of smaller intruders did not change the behavior of residents. In contrast, weight-matched intruders injected with alpha 2 adrenoceptor blockers elicited increased aggression in residents. Social behaviors, exploration and offensive aggression showed insignificant variation in intruders. Defensive behaviors, in contrast, showed major changes: in experiments 1 and 2 a dose-dependent decrease in immobility and a dose-dependent increase in defensive upright was noticed. In experiment 3, high scores of defensive upright were apparent, precluding detection of drug-induced changes. However, when the last 5 min of the encounter were analysed separately, results similar to the first two experiments were observed. Significant negative correlations were found between immobility and defensive upright scores. The results suggest that alpha 2 adrenoceptor blockers induce a shift from a passive (immobility) towards a more active (defensive upright) coping style. These and previous data show that alpha 2 adrenoceptor blockers, other than yohimbine, seem to exert a behavior-activating effect in rats.
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Affiliation(s)
- J Haller
- Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest
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Abstract
Male Wistar rats were injected with CH-38083, an alpha 2-adrenoceptor blocker, after which they were challenged by a size-matched Wistar or Long-Evans opponent. In residents facing low-aggression opponents, the alpha 2-adrenoceptor blockade significantly reduced aggressiveness, whereas in those facing highly aggressive opponents the treatment significantly increased aggression scores compared to saline-treated controls, irrespective of the strain of the intruder. When the animals were treated with CH-38083, the frequency of biting attacks correlated significantly with the aggressiveness of the opponent in residents fighting with Wistar and Long-Evans rats. Similar correlations were not found in control (saline-injected) rats. The results suggest that the catecholaminergic activation caused by the alpha 2 receptor antagonist elicits a more efficient adaptation to the behavioral actions of the opponent. Plasma corticosterone levels were not influenced by the treatment, but this variable seemed to be correlated with the defensive behavior performed by the intruder.
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Affiliation(s)
- J Haller
- Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest
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Haller J, Barna I, Kovács JL. Alpha 2-adrenoceptor blockade, pituitary-adrenal hormones, and agonistic interactions in rats. Psychopharmacology (Berl) 1994; 115:478-84. [PMID: 7871092 DOI: 10.1007/bf02245571] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The effects of adrenergic activation on aggressiveness and the aggression induced endocrine changes were tested in rats. Alpha 2 adrenoceptor blockers were used for enhancing activation of the adrenergic system, and changes in aggressiveness were tested in resident-intruder contests. Three experiments were conducted. In experiment 1, saline injected rats responded to the presence of an opponent by aggression and the increase in plasma ACTH and corticosterone. Intraperitoneal administration of 1 mg/kg CH-38083 (an alpha 2 adrenoceptor antagonist) produced a several fold increase in clinch fighting and mutual upright scores, and also further enhanced the plasma ACTH and corticosterone response. In experiment 2, the effect of three doses (0.5, 1 and 2 mg/kg) of three different alpha 2 adrenoceptor blockers CH-38083, idazoxan and yohimbine were tested. All the substances increased aggression at 0.5 and 1 mg/kg; at 2 mg/kg the effect of idazoxan and yohimbine disappeared, while with CH-38083 an additional increase was obtained. In yohimbine treated animals the enhancement of aggression was reduced already at 1 mg/kg. In experiment 3, indomethacin, a potent inhibitor of the catecholamine-induced ACTH release completely abolished the effects of the alpha 2 adrenoceptor antagonist CH-38083: the intensity of agonistic interactions, as well as ACTH and corticosterone plasma concentrations, returned to control levels. The possible role of catecholamines and the stress hormones in the activation of aggression is discussed.
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Affiliation(s)
- J Haller
- Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest
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Evans RG, Haynes JM. Characterization of binding sites for [3H]-idazoxan, [3H]-P-aminoclonidine and [3H]-rauwolscine in the kidney of the dog. Clin Exp Pharmacol Physiol 1994; 21:649-58. [PMID: 7813124 DOI: 10.1111/j.1440-1681.1994.tb02566.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
1. We characterized the binding of [3H]-rauwolscine, [3H]-p-aminoclonidine and [3H]-idazoxan in a dog kidney membrane preparation. Our aim was to determine the pharmacological nature of the alpha 2-adrenoceptor- and imidazoline-preferring binding sites in this organ. 2. [3H]-Rauwolscine bound to an apparent single site with an affinity (KD) of 2.2 nmol/L and a maximum density (Bmax) of 58.5 fmol/mg protein, when 10 mumol/L idazoxan defined non-specific binding. However displacement studies demonstrated that a number of compounds, including prazosin, inhibited [3H]-rauwolscine binding in a complex manner consistent with displacement from two distinct binding sites. The majority (69%) of the [3H]-rauwolscine binding sites had a relatively low affinity for prazosin (KI = 398 nmol/L), while the remainder had a relatively high affinity for prazosin (KI = 7.9 nmol/L). 3. [3H]-p-Aminoclonidine bound to an apparent single site (KD = 5.2 nmol/L; Bmax = 72.4 fmol/mg protein), when 10 mumol/L phentolamine defined non-specific binding. When 1 mumol/L of the potent and selective alpha 2-adrenoceptor antagonist 2-methoxyidazoxan was included in the incubate, no specific binding was detected. We therefore conclude that under the conditions of this experiment [3H]-p-aminoclonidine binds only to alpha 2-adrenoceptors in the dog kidney. 4. [3H]-Idazoxan bound to two sites, with a higher (KD = 0.95 nmol/L; Bmax = 43.9 fmol/mg protein) and lower (KD = 9.1 nmol/L; Bmax = 93.8 fmol/mg protein) affinity, respectively, when 1 mmol/L phentolamine defined non-specific binding. When 10 mumol/L GTP gamma S was included in the incubate, the low affinity site was unaffected but the maximum binding at the higher affinity site was reduced by 79%. 2-Methoxyidazoxan displaced [3H]-idazoxan in a monophasic manner and with low potency (IC50 = 11.5 mumol/L). Yohimbine, efaroxan, clonidine, rilmenidine, guanabenz and idazoxan itself displaced [3H]-idazoxan in a complex manner; the slope of the displacement curves being less than unity. 5. We conclude that the dog kidney contains a heterogeneous population of alpha 2-adrenoceptors that can be labelled either with [3H]-rauwolscine or [3H]-p-aminoclonidine. The dog kidney also contains a heterogeneous population of non-adrenoceptor imidazoline-preferring binding sites of the I2-subtype, that can be labelled with [3H]-idazoxan. The binding site for which [3H]-idazoxan has the highest affinity appears to be coupled to a guanine nucleotide binding regulatory protein.
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Affiliation(s)
- R G Evans
- Emily E. E. Stewart Renal Laboratory, Baker Medical Research Institute, Prahran, Victoria, Australia
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Hollecker M, Marshall DL, Harvey AL. Structural features important for the biological activity of the potassium channel blocking dendrotoxins. Br J Pharmacol 1993; 110:790-4. [PMID: 7694758 PMCID: PMC2175942 DOI: 10.1111/j.1476-5381.1993.tb13881.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
1. Dendrotoxins from mamba snake venoms are small proteins that block neuronal K+ channels. In order to investigate structural features associated with their biological activity, partially folded versions of dendrotoxins I and K from black mamba (Dendroaspis polylepis) were prepared by selectively reducing one or more of their three S-S bonds. 2. The modified toxins were tested for ability to compete with 125I-labelled native toxin I to high affinity binding sites on rat brain synaptosomal membranes and for the ability to increase acetylcholine release in a neuromuscular preparation. 3. Binding affinity increased progressively as the toxins folded to the native conformation and the most biologically active of the modified species were those in which only the disulphide bond between residues 14 and 38 was not formed. These intermediates had native-like conformations as determined by circular dichroism but still had about 5-10 times lower affinity than native toxins. 4. Addition of negatively charged groups to block the free sulthydryls at positions 14 and 38 caused a further, marked loss of activity. 5. The results are consistent with the existence of two important regions in the dendrotoxin molecules. The region containing two of the disulphide bonds (around Cys5-Cys55 and Cys30-Cys51) and much of the secondary structure is essential for the binding affinity of the toxins, while the region around Cys14 and Cys38, equivalent to part of the antiprotease site of the homologous protease inhibitor from bovine pancreas (BPTI), plays an important role in the potency of dendrotoxins.
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Affiliation(s)
- M Hollecker
- Centre de Biophysique Moléculaire, CNRS, Orleans, France
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De Luca A, Coupar IM. Difenoxin and loperamide: studies on possible mechanisms of intestinal antisecretory action. NAUNYN-SCHMIEDEBERG'S ARCHIVES OF PHARMACOLOGY 1993; 347:231-7. [PMID: 8386327 DOI: 10.1007/bf00169273] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Experiments have been performed to determine whether the antisecretory (antidiarrhoeal) actions of difenoxin and loperamide are mediated by enteric neurones. An iso-osmotic perfusion solution was circulated around the lumen of the jejunum of anaesthetised rats. Vasoactive intestinal peptide was infused intra-arterially to induce net fluid secretion which was inhibited by difenoxin (ED50, 0.23 mg/kg) and loperamide (ED50, 0.5 mg/kg). However, neither were able to restore the fluid transport rate to the control level of absorption. The antisecretory effects of difenoxin (0.77 mg/kg) and loperamide (0.6 mg/kg) were blocked by the opiate receptor antagonist naloxone (2 mg/kg). Their effects were also abolished by pretreatment with the 5-HT synthesis inhibitor p-chlorophenylalanine (PCPA; 200 mg/kg; with desmethylimipramine given beforehand to protect noradrenergic nerves and enhance 5-HT depletion). The effect of difenoxin was blocked with methiothepin (1 mg/kg) and methysergide (30 micrograms/kg) but not ketanserin (30 micrograms/kg), ritanserin (30 mg/kg), ondansetron (10 micrograms/kg) or ICS 205-930 (3 mg/kg). None of the above 5-HT receptor antagonists modified the antisecretory effect of loperamide. The antisecretory effect of difenoxin but not loperamide was prevented by phentolamine (2 mg/kg) and by pretreatment with 6-hydroxy-dopamine (150 mg/kg total). It is concluded that both difenoxin and loperamide inhibit net fluid secretion by indirect mechanisms. It is proposed that the initial action is on enteric mu-opiate receptors and that this results in the release of 5-HT. In the case of difenoxin, the 5-HT may act on 5-HT1-like receptors to release noradrenaline.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- A De Luca
- Monash University, Unit of Addictive Drug Research, School of Pharmacology, Victorian College of Pharmacy, Parkville, Australia
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Affiliation(s)
- J P Hieble
- Department of Pharmacology, Smith Kline Beecham Pharmaceuticals, King of Prussia, Pennsylvania
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