tan-67 and 7-benzylidenenaltrexone

Ultra-low-dose methionine-enkephalin-arginine-phenylalanine improves vagal transmission (vagotonic) and decreases heart rate via delta(1)-opioid receptors within the sinoatrial (SA) node. Higher doses activate delta(2)-opioid receptors, interrupt vagal transmission (vagolytic), and reduce the bradycardia. Preconditioning-like occlusion of the nodal artery produced a vagotonic response that was reversed by the delta(1)-antagonist 7-benzylidenaltrexone (BNTX). The following study tested the hypothesis that extended delta(1)-opioid receptor stimulation reduces subsequent delta(2)-receptor responses. The delta(2)-agonist deltorphin II was introduced in the SA node by microdialysis to evaluate delta(2) responses before and after infusion of the delta(1)-agonist TAN-67. TAN-67 reduced the vagolytic effect of deltorphin by two-thirds. When the delta(1)-antagonist BNTX was combined with TAN-67, the deltorphin response was preserved, suggesting that attrition of the prior response was mediated by delta(1) activity. When TAN-67 was omitted in time control studies, some loss of delta(2) responses was apparent in the absence of the delta(1) treatment. This loss was also eliminated by BNTX, suggesting that the attenuation of the response after deltorphin alone was also the result of delta(1) activity. Additional studies tested TAN-67 alone in the absence of prior deltorphin. When time controls were conducted without the initial deltorphin treatment, a robust vagolytic response was observed. When TAN-67 preceded the delayed deltorphin, the vagolytic response was eroded, indicating an independent effect of TAN-67. BNTX infused afterward was unable to restore the delta(2) response. These data support the conclusion that the loss of the delta(2) response resulted from reduced delta(2) activity mediated by continued delta(1)-receptor stimulation and not the arithmetic consequence of increased competition from that same delta(1) receptor.

Topics: Analgesics; Analgesics, Opioid; Animals; Benzylidene Compounds; Bradycardia; Dogs; Dose-Response Relationship, Drug; Enkephalin, Methionine; Female; Male; Microdialysis; Naltrexone; Narcotic Antagonists; Oligopeptides; Quinolines; Receptors, Opioid, delta; Sinoatrial Node; Stimulation, Chemical; Vagus Nerve

Local cardiac opioids appear to be important in determining the quality of vagal control of heart rate. Introduction of the endogenous opioid methionine-enkephalin-arginine-phenylalanine (MEAP) into the interstitium of the canine sinoatrial node by microdialysis attenuates vagally mediated bradycardia through a delta-opioid receptor mechanism. The following studies were conducted to test the hypothesis that a delta(2)-opiate receptor subtype mediates the interruption of vagal transmission. Twenty mongrel dogs were anesthetized and instrumented with microdialysis probes inserted into the sinoatrial node. Vagal frequency responses were performed at 1, 2, and 3 Hz during vehicle infusion and during treatment with the native agonist MEAP, the delta(1)-opioids 2-methyl-4aa-(3-hydroxyphenyl)-1,2,3,4,4a,5,12,12aalpha-octahydroquinolino[2,3,3- g]isoquinoline (TAN-67) and [d-pen(2,5)]-enkephalin (DPDPE), and the delta(2) opioid deltorphin II. The vagolytic effects of intranodal MEAP and deltorphin were then challenged with the delta(1)- and delta(2)-opioid receptor antagonists 7-benzylidenenaltrexone (BNTX) and naltriben, respectively. Although the positive control deltorphin II was clearly vagolytic in each experimental group, TAN-67 and DPDPE were vagolytically ineffective in the same animals. In contrast, TAN-67 improved vagal bradycardia by 30-35%. Naltriben completely reversed the vagolytic effects of MEAP and deltorphin. BNTX was ineffective in this regard but did reverse the vagal improvement observed with TAN-67. These data support the hypothesis that the vagolytic effect of the endogenous opioid MEAP was mediated by delta(2)-opioid receptors located in the sinoatrial node. These data also support the existence of vagotonic delta(1)-opioid receptors also in the sinoatrial node.

Topics: Analgesics; Analgesics, Opioid; Animals; Benzylidene Compounds; Bradycardia; Dogs; Enkephalin, D-Penicillamine (2,5)-; Enkephalin, Methionine; Naltrexone; Narcotic Antagonists; Oligopeptides; Opioid Peptides; Quinolines; Receptors, Opioid, delta; Sinoatrial Node; Vagus Nerve

We investigated whether delta- and kappa-opioid agonists alter myocardial function, intracellular Ca(2+) concentration ([Ca(2+)](i)), and myofilament Ca(2+) sensitivity in intact guinea pig beating hearts and whether these effects are mediated by an opioid receptor. Intact guinea pig hearts were perfused with modified Krebs Ringer solution containing delta- (TAN-67) and kappa- (ICI-199441) opioid agonists in the absence and presence of delta- (BNTX) and kappa- (nor-BNI) opioid antagonists, respectively, while functional variables and [Ca(2+)](i) were recorded. TAN-67 (1 microM) and ICI-199441 (1 microM) decreased heart rate (P < 0.05). TAN-67 (1 microM) and ICI-199441 (1 micro M) decreased available [Ca(2+)](i) without changing developed left ventricular pressure (LVP) (P < 0.05). TAN-67 (1 microM) and ICI-199441 (1 microM) also caused a leftward shift in the curve of developed LVP as a function of available [Ca(2+)](i) (P < 0.05). ICI-199441 (1 microM) produced a steeper slope in the relation curve compared with baseline (P < 0.05). BNTX (1 microM) and nor-BNI (1 microM) blocked the effects of TAN-67 and ICI-199441, respectively. delta- and kappa-opioid agonists enhance myofilament Ca(2+) sensitivity despite decreasing available [Ca(2+)](i) in intact isolated guinea pig hearts, and these effects are mediated by delta- and kappa-opioid receptor stimulation.. Our results indicate that delta- and kappa-opioid agonists enhance myofilament Ca(2+) sensitivity despite decreasing available intracellular Ca(2+) concentrations in intact isolated guinea pig beating hearts, and these effects are mediated by delta- and kappa-opioid receptor stimulation.

Topics: Actin Cytoskeleton; Animals; Benzylidene Compounds; Blood Pressure; Calcium; Coronary Circulation; Guinea Pigs; Heart; Heart Rate; In Vitro Techniques; Kinetics; Naltrexone; Narcotic Antagonists; Pyrrolidines; Quinolines; Receptors, Opioid, delta; Receptors, Opioid, kappa; Stimulation, Chemical; Ventricular Function, Left

In the intestine, opioids produce antidiarrhoeal and constipating actions that are mediated by enteric neurones. Through interactions with opioid receptors (ORs) on submucosal neurones, opioids suppress active ion transport evoked by transmural electrical stimulation (TES) in mucosa-submucosa sheets from the porcine ileum. In this study, we examined the pharmacological characteristics of the previously described OR, which is sensitive to the delta1-OR antagonist 7-benzylidenenaltrexone and modulates neurogenic transepithelial ion transport in this tissue preparation. Increases in short-circuit current (Isc, a measure of active anion transport) evoked by TES in ileal mucosa-submucosa sheets were inhibited by opioid agonists possessing high selectivity for either delta- or micro-ORs including [d-Pen2,5]enkephalin (DPDPE), [d-Ala2, Glu4]deltorphin II, and [d-Ala2, N-Me-Phe4, Gly5-ol]enkephalin (DAMGO). As determined by the Schild analysis, the actions of these agonists were competitively inhibited by 7-benzylidenenaltrexone. The nonequilibrium micro-OR antagonist beta-funaltrexamine inhibited the actions of DAMGO only at a high concentration (1 microm) but did not alter DPDPE or deltorphin II action. At concentrations up to 10 microm, the nonequilibrium delta-OR antagonist naltrindole 5'-isothiocyanate did not alter the actions of delta- or micro-OR agonists. Radioligand binding analyses of neuronal homogenates from the ileal submucosa revealed that the nonselective OR ligand [3H]diprenorphine bound to two populations of specific binding sites. One of these sites possessed binding characteristics similar to the delta-OR. In summary, neurogenic ion transport in the porcine intestine is modulated by an OR which shares pharmacological characteristics of both micro- and delta-ORs and may represent a novel receptor entity.

Topics: Amphibian Proteins; Animals; Anions; Benzamides; Benzylidene Compounds; Biological Transport, Active; Carrier Proteins; Diprenorphine; Dose-Response Relationship, Drug; Electric Stimulation; Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; Enkephalin, D-Penicillamine (2,5)-; Female; Gastrointestinal Motility; Ileum; Intestinal Mucosa; Male; Naltrexone; Neurons, Afferent; Oligopeptides; Piperazines; Quinolines; Receptors, Opioid, delta; Receptors, Opioid, mu; Swine; Tritium

The objective of the present study was to investigate the role of delta(1)-opioid receptors in mediating cardioprotection in isolated chick cardiac myocytes and to investigate whether protein kinase C and mitochondrial ATP-sensitive K(+) (K(ATP)) channels act downstream of the delta(1)-opioid receptor in mediating this beneficial effect. A 5-min preexposure to the selective delta(1)-opioid receptor agonist (-)-TAN-67 (1 microM) resulted in less myocyte injury during the subsequent prolonged ischemia compared with untreated myocytes. 7-Benzylidenenaltrexone, a selective delta(1)-opioid receptor antagonist, completely blocked the cardioprotective effect of (-)-TAN-67. Naltriben methanesulfonate, a selective delta(2)-opioid receptor antagonist, had only a slight inhibitory effect on (-)-TAN-67-mediated cardioprotection. Nor-binaltorphimine dihydrochloride, a kappa-opioid receptor antagonist, did not affect (-)-TAN-67-mediated cardioprotection. The protein kinase C inhibitor chelerythrine and the K(ATP) channel inhibitors glibenclamide, a nonselective K(ATP) antagonist, and 5-hydroxydecanoic acid, a mitochondrial selective K(ATP) antagonist, reversed the cardioprotective effect of (-)-TAN-67. These results suggest that the delta(1)-opioid receptor is present on cardiac myocytes and mediates a potent cardioprotective effect via protein kinase C and the mitochondrial K(ATP) channel.

Topics: Adenosine Triphosphate; Alkaloids; Animals; Benzophenanthridines; Benzylidene Compounds; Cells, Cultured; Chick Embryo; Enzyme Inhibitors; Glyburide; Heart; Ischemia; Ischemic Preconditioning, Myocardial; Mitochondria, Heart; Myocardium; Naltrexone; Narcotic Antagonists; Phenanthridines; Potassium Channel Blockers; Protein Kinase C; Quinolines

Stimulation of the delta(1)-opioid receptor confers cardioprotection to the ischemic myocardium. We examined the role of protein kinase C (PKC) after delta-opioid receptor stimulation with TAN-67 or D-Ala(2)-D-Leu(5)-enkephalin (DADLE) in a rat model of myocardial infarction induced by a 30-min coronary artery occlusion and 2-h reperfusion. Infarct size (IS) was determined by tetrazolium staining and expressed as a percentage of the area at risk (IS/AAR). Control animals, subjected to ischemia and reperfusion, had an IS/AAR of 59.9 +/- 1.8. DADLE and TAN-67 administered before ischemia significantly reduced IS/AAR (36.9 +/- 3.9 and 36.7 +/- 4.7, respectively). The delta(1)-selective opioid antagonist 7-benzylidenenaltrexone (BNTX) abolished TAN-67-induced cardioprotection (54.4 +/- 1.3). Treatment with the PKC antagonist chelerythrine completely abolished DADLE- (61.8 +/- 3.2) and TAN-67-induced cardioprotection (55.4 +/- 4.0). Similarly, the PKC antagonist GF 109203X completely abolished TAN-67-induced cardioprotection (54.6 +/- 6.6). Immunofluorescent staining with antibodies directed against specific PKC isoforms was performed in myocardial biopsies obtained after 15 min of treatment with saline, chelerythrine, BNTX, or TAN-67 and chelerythrine or BNTX in the presence of TAN-67. TAN-67 induced the translocation of PKC-alpha to the sarcolemma, PKC-beta(1) to the nucleus, PKC-delta to the mitochondria, and PKC-epsilon to the intercalated disk and mitochondria. PKC translocation was abolished by chelerythrine and BNTX in TAN-67-treated rats. To more closely examine the role of these isoforms in cardioprotection, we utilized the PKC-delta selective antagonist rottlerin. Rottlerin abolished opioid-induced cardioprotection (48.9 +/- 4.8) and PKC-delta translocation without affecting the translocation of PKC-alpha, -beta(1), or -epsilon. These results suggest that PKC-delta is a key second messenger in the cardioprotective effects of delta(1)-opioid receptor stimulation in rats.

Topics: Acetophenones; Alkaloids; Analgesics; Animals; Benzophenanthridines; Benzopyrans; Benzylidene Compounds; Enkephalin, Leucine-2-Alanine; Enzyme Activation; Enzyme Inhibitors; Heart Rate; Indoles; Ischemic Preconditioning, Myocardial; Isoenzymes; Male; Maleimides; Myocardial Infarction; Myocardial Ischemia; Myocardial Reperfusion Injury; Myocardium; Naltrexone; Narcotic Antagonists; Phenanthridines; Protein Kinase C; Protein Kinase C-delta; Quinolines; Rats; Rats, Wistar; Receptors, Opioid, delta

Topics: Animals; Antioxidants; Benzamides; Benzylidene Compounds; Dose-Response Relationship, Drug; Drug Therapy, Combination; Free Radicals; Humans; Ischemic Preconditioning, Myocardial; Myocardial Ischemia; Naltrexone; Narcotic Antagonists; Oxygen; Piperazines; Quinolines; Rats; Receptors, Opioid, delta; Tiopronin

Opioids have been shown to produce both an early and delayed phase of cardioprotection; however, the signaling pathways involved, particularly in the delayed response, have not been well defined. Therefore, we investigated the potential of BW373U86 (BW), a potent delta opioid agonist, to produce delayed cardioprotection and characterized the role of opioid receptors and oxygen-derived free radicals (OFRs) in this delayed response. All rats underwent 30 min of ischemia followed by 2 h of reperfusion. The rats were divided into four groups. First, rats were pretreated with selective opioid receptor antagonists or the antioxidant, 2-mercaptopropionyl glycine (2-MPG), in the presence of BW and allowed to recover for 24 h before the ischemia-reperfusion protocol. Second, rats were pretreated with BW, allowed to recover for 24 h, and subsequently treated with either opioid antagonists or 2-MPG, 10 min prior to the ischemia-reperfusion protocol. Third, rats underwent ischemic preconditioning (IPC) (1x5 min occlusion) both with and without 2-MPG to determine the role of OFRs in acute cardioprotection. Fourth, rats were pretreated with TAN-67, an opioid agonist known to signal through the delta1 opioid receptor in the presence and absence of 2-MPG. Control rats were injected with saline and allowed to recover for 24 h. BW produced a bell-shaped dose-related reduction in infarct size with a maximal reduction observed at 0.1 mg/kg v control (16+/-3%v 60+/-3%, P<0.001). Surprisingly, the delayed protection induced by BW was only partially blocked by pretreatment with the delta1-selective antagonist, BNTX; however, it was completely blocked by pretreatment with 2-MPG (47+/-5%, P<0.001). Only naloxone given acutely inhibited the protective effects of BW; however, at the dose used, 2-MPG partially reduced the protective effect of acute IPC. TAN-67 (0.1 mg/kg) also produced a significant reduction in infarct size compared to control (18+/-4%v 60+/-3%, P<0.001). This protection was blocked by pretreatment with 2-MPG (42+/-4%, P<0.001). These data suggest that BW and TAN-67 mediate delayed cardioprotection via a free radical mechanism that appears to be only partially dependent on delta opioid receptor stimulation. Furthermore, it is the early burst in OFRs that is crucial to initiating the protective effect.

Topics: Animals; Antioxidants; Benzamides; Benzylidene Compounds; Dose-Response Relationship, Drug; Free Radicals; Ischemic Preconditioning, Myocardial; Male; Myocardial Ischemia; Myocardial Reperfusion; Naltrexone; Narcotic Antagonists; Piperazines; Quinolines; Rats; Rats, Sprague-Dawley; Receptors, Opioid, delta; Tiopronin

Opioids have been previously shown to confer short-term cardioprotection against a prolonged ischemic insult. Therefore, the present study was designed to determine whether opioids can induce a delayed or "second window" of cardioprotection and to assess the potential involvement of the mitochondrial KATP channel. All rats were subjected to 30 minutes of ischemia and 2 hours of reperfusion (I/R). Control animals, injected with saline 24 hours before I/R, elicited an infarct size/area at risk (IS/AAR) of 62.9+/-3.4. TAN-67, a delta1-opioid receptor agonist, was administered 10 or 30 mg/kg IP 12, 24, 48, or 72 hours before I/R. TAN-67 (10 mg/kg) 12- or 24-hour pretreatment did not significantly reduce IS/AAR (62.1+/-6.3 and 43.3+/-7.3, respectively). Similarly, 12-hour pretreatment with TAN-67 (30 mg/kg) did not reduce IS/AAR (60.0+/-5.6); however, 24-hour pretreatment significantly reduced IS/AAR (34.5+/-5.9). Forty-eight-hour pretreatment with TAN-67 maximally reduced IS/AAR (29.2+/-7.0), and opioid-induced cardioprotection was lost after 72-hour pretreatment (61.7+/-3.8). TAN-67-induced cardioprotection could be abolished by pretreatment with the selective delta1-opioid receptor antagonist 7-benzylidenenaltrexone, BNTX, administered either 30 minutes before TAN-67 given 48 hours before I/R or 10 minutes before I/R in rats previously treated for 48 hours with TAN-67 (59.6+/-3.1 and 58.7+/-3.5, respectively). The involvement of the KATP channel was investigated with 2 inhibitors: glibenclamide, a nonselective KATP channel inhibitor, and 5-hydroxydecanoic acid, selective for the mitochondrial KATP channel in rabbits. Glibenclamide, administered 30 minutes before I/R in 48-hour TAN-67-pretreated rats, completely abolished cardioprotection (60. 4+/-3.2). Similarly, 5-hydroxydecanoic acid, administered 5 minutes before I/R in rats pretreated 48 hours previously with TAN-67, completely abolished cardioprotection (57.8+/-2.5). These results suggest that delta1-opioid receptor stimulation, 24 to 48 hours before an ischemic insult, produces a delayed cardioprotective effect that is possibly the result of mitochondrial KATP channel activation.

Topics: Analgesics; Animals; Benzylidene Compounds; Blood Pressure; Coronary Circulation; Glyburide; Hypoglycemic Agents; Ischemic Preconditioning, Myocardial; Male; Mitochondria; Myocardial Infarction; Myocardial Ischemia; Myocardial Reperfusion Injury; Myocardium; Naltrexone; Narcotic Antagonists; Potassium Channels; Quinolines; Rats; Rats, Wistar; Receptors, Opioid, delta

The effects of selective mu-, delta- and kappa-opioid receptor agonists and antagonists on the discriminative stimulus properties of methamphetamine were examined in rats that had been trained to discriminate between methamphetamine (0.4 mg/kg) and saline. Methamphetamine produced a dose-related increase in methamphetamine-appropriate responses in all of the rats. In generalization tests, neither morphine (a mu-opioid receptor agonist: 0.3-10 mg/kg) nor 3,4-dichloro-N-[2-(1-pyrrolidinyl)cyclohexo]benzeneacetamide (U50,488H: a kappa-opioid receptor agonist: 1.0-8.0 mg/kg) generalized to the discriminative stimulus properties of methamphetamine. A newly synthesized non-peptide selective delta-opioid receptor agonist 2-methyl-4aalpha-(3-hydroxyphenyl)-1,2,3,4,4a,5,12,12aalpha- octahydroquinolino(2,3,3,-g)isoquinoline (TAN-67: 32 mg/kg) partially generalized (70% methamphetamine-appropriate responses) to the discriminative stimulus properties of methamphetamine. In combination tests, pretreatment with the mu- and kappa-opioid receptor antagonists, beta-funaltrexamine (9.0 mg/kg) and nor-binaltorphimine (10 mg/kg), respectively, had little or no influence on the discriminative stimulus properties of methamphetamine. In contrast, pretreatment with naltrindole (a non-selective delta-opioid receptor antagonist: 3.0 mg/kg) or naltriben (a selective delta2-opioid receptor antagonist: 1.0 mg/kg), but not with 7-benzylidenenaltrexone (a selective delta1-opioid receptor antagonist: 0.5 and 1.0 mg/kg), significantly attenuated the discriminative stimulus properties of methamphetamine. However, naltrindole (3.0 mg/kg) did not significantly attenuate the discriminative stimulus properties of methamphetamine at a higher training dose (1.0 mg/kg). Our findings may have some bearing on the relative importance of the role of delta-opioid (especially delta2-opioid) receptors in the discriminative stimulus properties of a low dose of methamphetamine.

Topics: Animals; Benzylidene Compounds; Central Nervous System Stimulants; Discrimination, Psychological; Dose-Response Relationship, Drug; Male; Methamphetamine; Naltrexone; Quinolines; Rats; Rats, Inbred F344; Receptors, Opioid, delta

The effect of 2-methyl-4a alpha-(3-hydroxyphenyl)-1,2,3,4,4a,5,12, 12a alpha-octahydroquinolino [2,3,3,-g]isoquinoline (TAN-67), a selective non-peptide delta opioid receptor agonist, on the morphine-induced place preference was examined in mice. Morphine (1-5 mg/kg, s.c.) produced a dose-related place preference in mice. In contrast, administration of TAN-67 (5-20 mg/kg, s.c.) did not result in a preference for either the drug- or vehicle-associated place. When TAN-67 (5-20 mg/kg, s.c.) was coadministered with morphine (1 mg/kg, s.c.), the morphine-induced place preference was enhanced dose dependently, and this effect of TAN-67 was suppressed by the pretreatment with naltrindole (1 mg/kg, s.c.), a nonselective delta opioid receptor antagonist, 7-benzylidenenaltrexone (0.05 and 0.5 mg/kg, s.c.), a selective delta 1 opioid receptor antagonist, and naltriben (0.05 and 0.5 mg/kg, s.c.), a selective delta 2 opioid receptor antagonist. In biochemical study, morphine (1 mg/kg, s.c.) or TAN-67 (20 mg/kg, s.c.) alone did not modify dopamine turnover in the limbic forebrain. Coadministration of TAN-67 (20 mg/kg, s.c.) with morphine (1 mg/kg, s.c.) increased DA turnover in the limbic forebrain. This increase in DA turnover in the limbic forebrain was suppressed by pretreatment with naltrindole (1 mg/kg, s.c.) or 7-benzylidenenaltrexone (0.5 mg/kg, s.c.), but not by naltriben (0.5 mg/kg, s.c.). Our results demonstrate that coadministration of TAN-67 with morphine enhances the morphine-induced place preference via activation of both delta 1 and delta 2 opioid receptors, suggesting that both delta 1 and delta 2 opioid receptors may modulate the morphine-induced rewarding effect. In addition, we also found that although both delta 1 and delta 2 opioid receptors may be implicated in the modulation of rewarding effect of morphine, the mechanisms involved may be different for each receptor subtypes, i.e., mu-delta 1 interaction may mainly modulate the rewarding effect of morphine by enhancing neurotransmission of mesolimbic dopamine neurons, although modulation by mu-delta 2 opioid receptor interaction may involve some other dopamine-independent mechanisms.

Topics: Analgesics; Animals; Benzylidene Compounds; Dopamine; Dose-Response Relationship, Drug; Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; Enkephalins; Limbic System; Male; Mice; Morphine; Naltrexone; Quinolines; Receptors, Opioid, delta; Reward