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Cascio MG, Valeri D, Tucker SJ, Marini P. A1-adenosine acute withdrawal response and cholecystokinin-8 induced contractures are regulated by Ca(2+)- and ATP-activated K(+) channels. Pharmacol Res 2015; 95-96:82-91. [PMID: 25836919 DOI: 10.1016/j.phrs.2015.03.014] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/07/2015] [Revised: 03/23/2015] [Accepted: 03/23/2015] [Indexed: 01/29/2023]
Abstract
In isolated guinea-pig ileum (GPI), the A1-adenosine acute withdrawal response is under the control of several neuronal signalling systems, including the μ/κ-opioid and the cannabinoid CB1 systems. It is now well established that after the stimulation of the A1-adenosine system, the indirect activation of both μ/κ-opioid and CB1 systems is prevented by the peptide cholecystokinin-8 (CCk-8). In the present study, we have investigated the involvement of the Ca(2+)/ATP-activated K(+) channels in the regulation of both acute A1-withdrawal and CCk-8-induced contractures in the GPI preparation. Interestingly, we found that: (a) the A1-withdrawal contracture is inhibited by voltage dependent Ca(2+)-activated K(+) channels, Kv, while it is enhanced by the voltage independent Ca(2+)-activated K(+) channels, SKCa; (b) in the presence of CCk-8, the inhibitory effect of the A1 agonist, CPA, on the peptide induced contracture is significantly enhanced by the voltage independent Ca(2+)-activated K(+) channel, SKCa; and (c) the A1-withdrawal contracture precipitated in the presence of CCk-8 is controlled by the ATP-sensitive potassium channels, KATP. Our data suggest, for the first time, that both Ca(2+)- and ATP-activated K(+) channels are involved in the regulation of both A1-withdrawal precipitated and CCk-8 induced contractures.
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Affiliation(s)
- Maria Grazia Cascio
- School of Medical Sciences, Institute of Medical Sciences, University of Aberdeen, Aberdeen, UK
| | - Daniela Valeri
- Department of Human Physiology and Pharmacology 'Vittorio Erspamer', University of Rome "La Sapienza", Rome, Italy
| | - Steven J Tucker
- School of Medical Sciences, Institute of Medical Sciences, University of Aberdeen, Aberdeen, UK
| | - Pietro Marini
- School of Medical Sciences, Institute of Medical Sciences, University of Aberdeen, Aberdeen, UK.
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Marini P, Romanelli L, Valeri D, Tucci P, Valeri P, Palmery M. Acute withdrawal induced by adenosine A1-receptor activation in isolated guinea-pig ileum: role of opioid receptors and effect of cholecystokinin. J Pharm Pharmacol 2010; 62:622-32. [DOI: 10.1211/jpp.62.05.0010] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
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Brundege JM, Williams JT. Increase in adenosine sensitivity in the nucleus accumbens following chronic morphine treatment. J Neurophysiol 2002; 87:1369-75. [PMID: 11877511 DOI: 10.1152/jn.00508.2001] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
There is a growing body of evidence suggesting that the neuromodulator adenosine is involved in drug addiction and withdrawal and that adenosine signaling pathways may offer new targets for therapeutic treatments of addiction. Recent studies have suggested that chronic exposure to drugs of abuse may alter adenosine metabolism in the nucleus accumbens, a brain region critically involved in drug addiction and withdrawal. The present study examined the effects of chronic morphine treatment on the ability of adenosine to inhibit excitatory postsynaptic currents in nucleus accumbens medium spiny neurons. It was found that chronic morphine treatment via subcutaneous implantation of morphine pellets in rats for 1 wk did not alter the level of adenosine-mediated tonic inhibition of nucleus accumbens excitatory synapses. However, chronic morphine treatment did induce a leftward shift in the adenosine dose-response curve, indicating an increase in the sensitivity of synaptic currents to exogenously applied adenosine. This shift was not due to a change in adenosine receptors or their effectors, because chronic morphine treatment had no effect on the dose-response relationship of a nonmetabolized adenosine receptor agonist. When adenosine transport was blocked, the ability of chronic morphine to shift the adenosine dose-response curve was eliminated. These experiments suggest that the increase in the sensitivity of nucleus accumbens synapses to the inhibitory effects of adenosine may be due to a decrease in adenosine transport. The identification of these changes in the adenosine system after chronic drug exposure may help identify new therapeutic strategies aimed at easing withdrawal from opioids.
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Affiliation(s)
- James M Brundege
- The Vollum Institute, Oregon Health Sciences University, 31812 SW Sam Jackson Park Road, Portland, OR 97201, USA.
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Mundey MK, Ali A, Mason R, Wilson VG. Pharmacological examination of contractile responses of the guinea-pig isolated ileum produced by mu-opioid receptor antagonists in the presence of, and following exposure to, morphine. Br J Pharmacol 2000; 131:893-902. [PMID: 11053208 PMCID: PMC1572416 DOI: 10.1038/sj.bjp.0703659] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2000] [Revised: 07/30/2000] [Accepted: 08/14/2000] [Indexed: 11/09/2022] Open
Abstract
We have assessed the potential of several mu-opioid receptor antagonists to elicit a response in the guinea-pig isolated ileum in the presence of, and following overnight exposure to, morphine. Naloxone, D-Phe-Cys-Tyr-D-Trp-Orn-Thr-Pen-Thr-NH(2) (CTOP), (-)-5, 9alpha-diethyl-2-(3-furyl-methyl)-2'-hydroxy-6,7-benzomorphan (MR2266), but not D-Phe-Cys-Tyr-D-Trp-Arg-Thr-Pen-Thr-NH(2) (CTAP), produced a transient inhibition of electrically-evoked contractions of the guinea-pig ileum. The effect of 1 microM CTOP, but not that to MR2266, was inhibited by 1 microM somatostatin. Naloxone (0.3 microM), CTOP (3 microM), CTAP (3 microM) and MR2266 (0.3 microM) antagonized the inhibitory effect of morphine on electrically-evoked contractions of the guinea-pig to a similar degree and, following 60 min exposure to morphine, produced non-sustained contractions. The response to 3 microM CTOP was significantly smaller than that to 3 microM CTAP. None of the antagonists produced a response in the absence of morphine. Following overnight exposure of the ileum to 0.3 microM morphine (4 degrees C), and repeated washing to remove the agonist, all four antagonists elicited non-sustained contractions. However, the responses to 3 microM CTOP and 0.3 microM MR2266 were significantly smaller than those elicited by 0.3 microM naloxone and 3 microM CTAP. Somatostatin (1 microM) significantly reduced naloxone-induced contractions, but not those to CTAP. While all four mu-opioid antagonists elicited contractions in the presence of, and following prolonged exposure to, morphine, differences between them were noted which may be a consequence of non-opioid actions.
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Affiliation(s)
- M K Mundey
- School of Biomedical Sciences, The Medical School, Queen's Medical Centre, University of Nottingham, Nottingham NG7 2UH
| | - A Ali
- School of Biomedical Sciences, The Medical School, Queen's Medical Centre, University of Nottingham, Nottingham NG7 2UH
| | - R Mason
- School of Biomedical Sciences, The Medical School, Queen's Medical Centre, University of Nottingham, Nottingham NG7 2UH
| | - V G Wilson
- School of Biomedical Sciences, The Medical School, Queen's Medical Centre, University of Nottingham, Nottingham NG7 2UH
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Characterization and tissue location of the neural adenosine receptor in the rat ileum. Br J Pharmacol 1999. [PMID: 10205018 DOI: 10.1038/sj.bjp.0702411].] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
1. The aim of the present investigation was to characterize and determine the tissue location of the adenosine receptors present in the rat ileum using a method that detects drug action on the cholinergic nerves innervating the longitudinal and circular muscles. 2. The non-selective adenosine agonist, NECA (10 and 100 nM) caused significant concentration-related reductions in the circular muscle responses to transmural stimulation over the frequency range of 2.5-40 Hz, but did not affect the responses of the longitudinal muscle, nor did it reduce the muscle responses of the guinea-pig ileum. 3. The affinity order of antagonists at inhibiting the effect of NECA on the circular muscle was: CPDPX>8-PT>DMPX with apparent pA2 values of 9.31, 7.54 and 5.63 respectively. CPDPX (10-100 nM) caused parallel displacements of the concentration-effect curves to CPA with a pKb value of 9.15 and Schild slope of 1.03. 4. The agonists previously tested in the rat jejunum peristaltic reflex preparation were also shown to inhibit responses of the rat ileum in the following decreasing order of potency: CPA>NECA>2-CADO>R-PIA>S-PIA>>PAA. In addition, CHA and CCPA were also potent agonists. NECA (100 nM) and CPA (32 nM) did not inhibit carbachol (1 microM)-induced tone of tissues pre-treated with TTX (1 microM). 5. In conclusion, the rat ileum contains inhibitory A1 adenosine receptors situated on cholinergic nerve endings innervating the circular muscle.
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Coupar IM. Characterization and tissue location of the neural adenosine receptor in the rat ileum. Br J Pharmacol 1999; 126:1269-75. [PMID: 10205018 PMCID: PMC1565885 DOI: 10.1038/sj.bjp.0702411] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
1. The aim of the present investigation was to characterize and determine the tissue location of the adenosine receptors present in the rat ileum using a method that detects drug action on the cholinergic nerves innervating the longitudinal and circular muscles. 2. The non-selective adenosine agonist, NECA (10 and 100 nM) caused significant concentration-related reductions in the circular muscle responses to transmural stimulation over the frequency range of 2.5-40 Hz, but did not affect the responses of the longitudinal muscle, nor did it reduce the muscle responses of the guinea-pig ileum. 3. The affinity order of antagonists at inhibiting the effect of NECA on the circular muscle was: CPDPX>8-PT>DMPX with apparent pA2 values of 9.31, 7.54 and 5.63 respectively. CPDPX (10-100 nM) caused parallel displacements of the concentration-effect curves to CPA with a pKb value of 9.15 and Schild slope of 1.03. 4. The agonists previously tested in the rat jejunum peristaltic reflex preparation were also shown to inhibit responses of the rat ileum in the following decreasing order of potency: CPA>NECA>2-CADO>R-PIA>S-PIA>>PAA. In addition, CHA and CCPA were also potent agonists. NECA (100 nM) and CPA (32 nM) did not inhibit carbachol (1 microM)-induced tone of tissues pre-treated with TTX (1 microM). 5. In conclusion, the rat ileum contains inhibitory A1 adenosine receptors situated on cholinergic nerve endings innervating the circular muscle.
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Affiliation(s)
- I M Coupar
- Department of Pharmaceutical Biology and Pharmacology, Victorian College of Pharmacy, Monash University, Parkville, Australia
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Abbracchio MP, Burnstock G. Purinergic signalling: pathophysiological roles. JAPANESE JOURNAL OF PHARMACOLOGY 1998; 78:113-45. [PMID: 9829617 DOI: 10.1254/jjp.78.113] [Citation(s) in RCA: 321] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
In this review, after a summary of the history and current status of the receptors involved in purinergic signalling, we focus on the distribution and physiological roles of purines and pyrimidines in both short-term events such as neurotransmission, exocrine and endocrine secretion and regulation of immune cell function, and long-term events such as cell growth, differentiation and proliferation in development and regeneration. Finally, the protective roles of nucleosides and nucleotides in events such as cancer, ischemia, wound healing, drug toxicity, inflammation and pain are explored and some suggestions made for future developments in this rapidly expanding field, with particular emphasis on the involvement of selective agonists and antagonists for purinergic receptor subtypes in therapeutic strategies.
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Affiliation(s)
- M P Abbracchio
- Institute of Pharmacological Sciences, University of Milan, Italy
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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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Hancock DL, Coupar IM. Functional characterization of the adenosine receptor mediating inhibition of peristalsis in the rat jejunum. Br J Pharmacol 1995; 115:739-44. [PMID: 8548171 PMCID: PMC1908508 DOI: 10.1111/j.1476-5381.1995.tb14995.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
1. The non-selective adenosine agonist, 5'-N-ethylcarboxamidoadenosine (NECA), is a potent inhibitor of morphine withdrawal diarrhoea in rats. More recently we found that NECA exerts its antidiarrhoeal effect by inhibiting secretion in both the jejunum and ileum and also by inhibiting peristalsis in the ileum. The specific aim of this study was to characterize the receptor in the rat jejunum mediating inhibition of peristalsis via functional studies using a range of metabolically stable adenosine analogues based on the pharmacological criteria of relative agonist and antagonist potencies. 2. Peristalsis in the rat isolated jejunum was achieved by raising the pressure to between 7-11 cmH2O for 3 min followed by a 3 min rest period (pressure at zero). The mean rate of peristalsis during inflation was 7.3 +/- 0.1 peristaltic waves per 3 min and this rate remained consistent for up to 30 min, in 5 separate tissues. The inhibitory effects of the adenosine analogues were quantified by expressing their effects as a % reduction in the mean number of peristaltic contractions derived from the control tissues. 3. The rank order of agonist potency to reduce the rate of peristalsis was: N6-cyclopentyladenosine (CPA) > NECA > R(-)-N6-(2-phenylisopropyl)adenosine (R-PIA) > chloroadenosine (2-CADO) > S-PIA > 2-phenylaminoadenosine (CV-1808). This order complies well with the rank order of agonist potency that represents the activation of the A1 receptor subtype (CPA > R-PIA = CHA = > NECA > 2-CADO > S-PIA > CV-1808). 4. The selective A1 adenosine antagonist 1,3-dipropyl-8-cyclopentylxanthine (DPCPX) and the nonselective adenosine antagonist 8-phenyltheophylline (8-PT) at their respective concentrations of 10 nM and 2 microM caused parallel rightward shifts in the concentration-response curve to the non-selective Al/A2 agonist NECA. DPCPX was significantly more potent at inhibiting NECA than 8-PT as revealed by their apparent pA2 values; DPCPX (9.5) and 8-PT (7.26). The high affinity of DPCPX relative to that of 8-PT suggests the presence of an Al and not an A2B receptor. In addition, the high affinity of DPCPX(pA2:9.37) against the selective Al agonist CPA, further confirms the presence of the Al receptor subtype.5. In this study we found that the Al adenosine receptor is involved in regulating in vitro peristalsis which is different from the adenosine receptor regulating inhibition of secretion (A2B) in the same region of intestine of the same species. We propose that A2B adenosine agonists could be of clinical value in the management of diarrhoea that is due to microbiological organisms where antimotility effects are not desired.
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Affiliation(s)
- D L Hancock
- Department of Pharmaceutical Biology and Pharmacology, Victorian College of Pharmacy, Monash University, Parkville, Victoria, Australia
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Abstract
This study aimed to determine whether the antidiarrhoeal effect of the mixed A1/A2 adenosine agonist NECA (5'-N-ethylcarboxamido adenosine) is due to inhibition of intestinal fluid transport or to contractility. Intestinal secretion was stimulated in anaesthetized rats by intra-arterial infusions of PGE2 (4 micrograms min-1) or vasoactive intestinal peptide (0.8 micrograms min-1). NECA reversed PGE2-induced secretion in the jejunum (ED50 16 micrograms kg-1) and ileum (ED50 21 micrograms kg-1, i.v.) and inhibited VIP-induced secretion in the jejunum (ED50 21.5 micrograms kg-1). NECA inhibited twitch responses (0.1 Hz, 1 ms, IC50 11.2 nM) but not tetanic contractions at 10 Hz of the transmurally stimulated guinea-pig ileum. Likewise, NECA (10 microM) did not inhibit frequency-related contractions over the range of 2.5 to 40 Hz of rat jejunum or ileum. However, NECA was shown to be a potent inhibitor (30 nM) of the peristaltic reflex in the rat ileum. The results indicate that adenosine receptors are involved in modulating peristalsis as well as the secretory activity of the mucosa in the rat small intestine.
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Affiliation(s)
- I M Coupar
- Unit of Addictive Drug Research, School of Pharmaceutical Pharmacology, Victorian College of Pharmacy, Monash University, Parkville, Australia
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Dionyssopoulos T, Hope W, Coupar IM. Effect of adenosine analogues on the expression of opiate withdrawal in rats. Pharmacol Biochem Behav 1992; 42:201-6. [PMID: 1631178 DOI: 10.1016/0091-3057(92)90516-i] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The aim of this study was to test whether convergent dependence occurs in vivo. The adenosine A1 receptor agonist N6-[(R)-1-methyl-2-phenylethyl]adenosine (R-PIA), the A2 agonist 2-(phenylamino)adenosine (CV-1808), the nonselective A1, A2 agonist (adenosine-5'-ethylcarboxamide (NECA), and the alpha 2-adrenoceptor agonist clonidine were screened (each at 30, 100, and 300 micrograms/kg, SC) for their ability to alter naloxine-precipitated withdrawal signs in morphine-dependent rats. The results indicate that there is convergent dependence involving opioid and adenosine A1 receptors on those effects expressed by withdrawal diarrhoea, paw-shakes, teeth-chattering, body-shakes, and jumping. Further, dependence expressed by body-shakes involves convergence involving A1 receptors, as well as alpha 2-adrenoceptors; while A1 receptors are involved in dependence expressed by jumping, stimulation of alpha 2-adrenoceptors augments this sign. Adenosine analogues may be of clinical value for detoxification of opiate addicts.
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Affiliation(s)
- T Dionyssopoulos
- Unit of Addictive Drug Research, School of Pharmacology, Victorian College of Pharmacy, Parkville, Australia
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Chahl LA. Effects of putative neurotransmitters and related drugs on withdrawal contractures of guinea-pig isolated ileum following brief contact with [Met5]enkephalin. Br J Pharmacol 1990; 101:908-12. [PMID: 1982231 PMCID: PMC1917839 DOI: 10.1111/j.1476-5381.1990.tb14179.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: 12/29/2022] Open
Abstract
1. Brief exposure for 2 min of guinea-pig isolated ileum to [Met5]enkephalin (MEnk) and noradrenaline has been shown previously to produce withdrawal contractures on washout of the agonist or addition of naloxone (MEnk) or phentolamine (noradrenaline). 2. The present study was undertaken to investigate firstly, whether other putative neurotransmitters and/or related drugs which inhibit transmitter release also produced withdrawal responses following 2 min contact with the ileum and secondly, whether they affected the opioid withdrawal response. 3. Adenosine (1-5 microM), but not U-50,488H (1-5 microM), somatostatin (0.01-5 microM), ocreotide (1-5 microM), baclofen (1-25 microM) or dopamine (5, 50 microM), produced a contracture on washout following 2 min contact with the ileum. The adenosine (5 microM) washout contracture, in common with MEnk and noradrenaline washout contractures, was inhibited by the substance P antagonist, spantide (10 microM). 4. Added 30 s before washout at a concentration of 5 microM, noradrenaline, U-50,488H, adenosine, somatostatin and ocreotide significantly inhibited the washout withdrawal response following 2 min contact of the ileum with MEnk, 1 microM. A higher concentration of baclofen, 250 microM, also inhibited this response. 5. The naloxone (1 microM)-precipitated withdrawal response following contact of the ileum with MEnk, 1 microM, for 2 min, was inhibited only by noradrenaline (5 microM) and U-50,488H (5 microM). 6. It is concluded that during naloxone-precipitated opioid withdrawal an additional population of enteric motor neurones is recruited which is not involved in the washout withdrawal response and these neurones have less diversity of presynaptic receptors mediating inhibition of transmitter release than cholinergic motor neurones.
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Affiliation(s)
- L A Chahl
- Neuropharmacology Laboratory, Faculty of Medicine, University of Newcastle, N.S.W., Australia
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Taylor DA, Leedham JA, Doak N, Fleming WW. Morphine tolerance and nonspecific subsensitivity of the longitudinal muscle myenteric plexus preparation of the guinea-pig to inhibitory agonists. NAUNYN-SCHMIEDEBERG'S ARCHIVES OF PHARMACOLOGY 1988; 338:553-9. [PMID: 2907611 DOI: 10.1007/bf00179329] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
1. The sensitivity of the longitudinal smooth muscle/myenteric plexus (LM/MP) to agonists which reduce the amplitude of neurogenic contractions was studied in preparations obtained from animals implanted with either placebo or morphine (75 mg/pellet) pellets 7 days prior. 2. Tolerance or subsensitivity to morphine was observed following chronic treatment with morphine and was revealed as a rightward shift of the concentration-response curve to morphine. The degree of tolerance decayed modestly with time after removal from a morphine containing environment suggesting a time dependence for the loss of subsensitivity to morphine. 3. LM/MP preparations from animals pretreated with morphine also developed subsensitivity to the inhibitory effects of the purine analogue, 2-chloroadenosine. Subsensitivity to 2-chloroadenosine was seen as a parallel rightward shift of the concentration-response curve in morphine-tolerant preparations. The magnitude of the loss in sensitivity was comparable to that observed to morphine. 4. A reduction in sensitivity of the LM/MP following chronic treatment with morphine was also observed to the inhibitory effects of the alpha2 adrenoceptor agonists, clonidine and xylazine. In contrast to the results obtained with morphine and 2-chloroadenosine, the development of subsensitivity to alpha2 adrenoceptor agonists was characterized by a marked reduction in slope and a depression of the maximum response. 5. These data suggest that myenteric neurons possess spare receptors for morphine and 2-chloroadenosine but not for clonidine and xylazine. Furthermore, the studies support the idea that tolerance is associated with a general cellular change or adaptation which impacts on all of these inhibitory substances in such a way as to reduce their efficacy.
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Affiliation(s)
- D A Taylor
- Department of Pharmacology and Toxicology, West Virginia University Health Sciences Center, Morgantown 26506
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Adenylate cyclase supersensitivity: a general means of cellular adaptation to inhibitory agonists? Trends Pharmacol Sci 1987. [DOI: 10.1016/0165-6147(87)90124-6] [Citation(s) in RCA: 60] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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Wauquier A, Van Belle H, Van den Broeck WA, Janssen PA. Sleep improvement in dogs after oral administration of mioflazine, a nucleoside transport inhibitor. Psychopharmacology (Berl) 1987; 91:434-9. [PMID: 3108923 DOI: 10.1007/bf00216007] [Citation(s) in RCA: 35] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Mioflazine, a nucleoside transport inhibitor, was given PO to dogs at doses of 0.04-10 mg/kg. Sixteen hour polygraphic sleep recordings were made and analysis and sleep stage classification was done by computer. Mioflazine decreased wakefulness and increased slow wave sleep, but did not affect the latencies of either REM sleep or slow wave sleep. This increased sleep was due to an increase in the number of light and deep slow wave sleep epochs. The effect lasted for about 8 h. The decreased wakefulness and increased slow wave sleep could be antagonized by the adenosine antagonist caffeine (2.5 and 10 mg/kg, PO); however, there was not a pure antagonistic effect. It might be that the enhancement of slow wave sleep is due to an activation of brain adenosine receptors. This is the first report of a drug acting on adenosine that given orally improves sleep. Mioflazine might be the prototype of substances worth considering for the treatment of a variety of sleep disorders.
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Hoffman BB, Chang H, Dall'Aglio E, Reaven GM. Desensitization of adenosine receptor-mediated inhibition of lipolysis. The mechanism involves the development of enhanced cyclic adenosine monophosphate accumulation in tolerant adipocytes. J Clin Invest 1986; 78:185-90. [PMID: 3013937 PMCID: PMC329548 DOI: 10.1172/jci112550] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Adipocytes contain adenosine receptors, termed A1 receptors, which inhibit lipolysis by decreasing adenylate cyclase activity. The inhibition of lipolysis by adenosine agonists in vivo acutely suppresses the plasma concentrations of free fatty acids (FFA) and triglycerides. We have found that infusions of the adenosine receptor agonist phenylisopropyladenosine (PIA) initially decreases plasma FFA concentrations; however, with prolonged exposure (6 d), rats become very tolerant to the effects of the drug. Adipocytes isolated from epididymal fat pads from PIA-infused rats have altered lipolytic responses. When lipolysis is stimulated with a relatively high concentration of isoproterenol (10(-7) M), PIA does not inhibit lipolysis in adipocytes from the infused animals. However, PIA inhibits isoproterenol-stimulated cyclic AMP (cAMP) accumulation in adipocytes from the infused rats although with decreased sensitivity compared with controls. The explanation for the impaired antilipolytic effect appears to be due to the fact that isoproterenol-stimulated cAMP accumulation is markedly increased in cells from infused rats. Indeed, basal lipolysis and lipolysis stimulated with lower concentrations of isoproterenol (10(-9), 10(-8) M) are effectively inhibited by PIA. cAMP accumulation is greatly increased in adipocytes from infused rats when stimulated by isoproterenol, ACTH, and forskolin. The results have some striking analogies to changes induced in nerve cells by prolonged exposure to narcotics. These data suggest that tolerance to PIA develops in adipocytes as a consequence of enhanced cAMP accumulation.
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Abstract
Shaking movements, similar to those made by a dog when wet, were elicited in rats by immersion in ice-water, injections of icilin, a chemical that produces sensations of cold, and naloxone-precipitated morphine withdrawal. Adenosine and 2-chloroadenosine produced dose-dependent inhibition of shaking to ice-water and icilin. The 2-chloroadenosine effect was mediated centrally because the ICV dose required to produce inhibition was not effective when given IP. Caffeine antagonized the inhibitory effects of adenosine and 2-chloroadenosine. 2-Chloroadenosine suppressed morphine-abstinence shaking as well as the body weight loss that normally accompanies withdrawal.
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Abstract
Adenosine and the methylxanthines have marked and opposite effects on behavior both of which are now thought to be mediated by cell surface adenosine receptors present in brain. These receptor sites have now been characterized using simple radioreceptor ligand binding techniques. Pharmacologic, autoradiographic and behavioral studies involving adenosine and the methylxanthines strongly suggest a neuromodulatory role for adenosine and indicate that adenosinergic neurons constitute an important central nervous system depressant system. A key component of the adenosinergic system is the adenosine uptake site which represents the inactivation mechanism for receptor mediated adenosine action. The adenosine uptake site can be identified as distinct from the adenosine receptor using a specific ligand. The two key components of the adenosine system, i.e., the receptor and uptake site, can therefore be studied using simple binding techniques. This should facilitate the development of new drugs specific for each system. Adenosine agonists can be expected to have sedative, anticonvulsant and anxiolytic actions whereas adenosine antagonists such as caffeine have stimulant and anxiogenic properties. Adenosine uptake blockers should have pharmacologic actions similar to adenosine agonists. The adenosinergic system, therefore, offers unique opportunities for developing new and potentially useful clinical agents.
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Ahlijanian MK, Takemori AE. Effects of (-)-N6-(R-phenylisopropyl)-adenosine (PIA) and caffeine on nociception and morphine-induced analgesia, tolerance and dependence in mice. Eur J Pharmacol 1985; 112:171-9. [PMID: 2992993 DOI: 10.1016/0014-2999(85)90493-5] [Citation(s) in RCA: 76] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
(-)-N6-(R-phenylisopropyl)-adenosine (PIA) was shown to possess analgesic activity in both the tail flick and acetic acid writhing assays. The analgesic actions of PIA were antagonized by caffeine in a dose-dependent manner. An apparent pA2 analysis in vivo suggested that the antagonism by caffeine was not competitive. Subanalgesic doses of PIA potentiated morphine-induced analgesia, tolerance and dependence. Caffeine antagonized these effects of morphine. PIA attenuated while caffeine exacerbated opiate withdrawal. While a low dose of caffeine antagonized PIA effects on withdrawal, a low dose of PIA did not antagonize the effects of caffeine. These results indicate that PIA can facilitate, and caffeine can antagonize the actions of morphine and that caffeine may be exerting some of its actions independent of adenosine receptor antagonism.
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Cowan A. Opioids: past, present and future. Trends Pharmacol Sci 1984. [DOI: 10.1016/0165-6147(84)90345-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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