Biomedical subjects

J F Kachur

Publications and source records attributed to J F Kachur.

At least 37 records · Page 2Linked to original sources

PubMed1991

Enantiomers of oxybutynin: in vitro pharmacological characterization at M1, M2 and M3 muscarinic receptors and in vivo effects on urinary bladder contraction, mydriasis and salivary secretion in guinea pigs.

The major side effects of racemic oxybutynin (OXY), which is used in the treatment of urinary incontinence are dry mouth (xerostomia) and blurred vision (mydriasis). Highly purified enantiomers of OXY [(R)OXY, (S)OXY] were compared with the racemate both in vitro in functional studies and in vivo in guinea pigs to evaluate their pharmacological action relative to their adverse effects. The affinity of (R)OXY and (S)OXY for different muscarinic receptor subtypes was determined using field stimulated rabbit vas deferens (M1) and guinea pig atria (M2) or bladder (M3) strips. Stereoselective antimuscarinic effects [(R)OXY greater than or equal to (R/S) OXY much greater than (S)OXY] were evident at all three receptor subtypes; the isomeric ratio [(S)OXY/(R)OXY] ranged from 12 to 88. Both (R)OXY and (R/S)OXY were slightly more selective (2-4-fold, P less than .01) for M1 and M3 relative to M2 muscarinic receptors. Stereoselectivity was also evident in vivo for volume-induced urinary bladder contractions as measured by cystometrogram parameters [(S)OXY/(R)OXY approximately 21], mydriasis [(S)OXY/(R)OXY approximately 136] and salivary gland secretory responses [(S)OXY/(R)OXY approximately 30]. The absolute potencies of (R)OXY or (R/S)OXY for mydriasis and salivation were similar to those for inhibition of intravesical bladder pressure. Also, (R)OXY and (R/S)OXY equipotently antagonized cholinergic-mediated CNS effects in mice. Collectively, the data suggest that the activity of (R/S)OXY resides predominantly in the (R)-enantiomer. However, it appears that (R)OXY may offer no significant pharmacological advantage over (R/S)OXY in terms of its principal therapeutic and side effect profile.

Animals↗

PubMed1991

Monochloramine, a neutrophil-derived oxidant, stimulates rat colonic secretion.

Neutrophil-derived oxidants may be involved in inflammatory bowel disease. Stable oxidants formed by halogenation of primary amines (e.g., monochloramine, NH2Cl) are extremely potent and may be of major importance in the pathophysiological response in inflammatory bowel disease. We tested the effects of NH2Cl relative to other oxidants on muscle-stripped rat colon under short-circuit conditions. Serosal addition of the oxidants evoked a concentration-dependent increase in short-circuit current (Isc). The EC50 values were 3.2 microM for NH2Cl, 6.5 microM for HOCl and 6.5 microM for H2O2. Responses to NH2Cl and H2O2 were abolished by removal of Cl- or Ca++. Unidirectional 36Cl- flux measurements showed that both oxidants (50 microM) evoked significant decreases in net chloride absorption. Tetrodotoxin (0.5 microM) and atropine (0.5 microM) partially inhibited the initial phase of the response to 50 microM NH2Cl; tetrodotoxin completely inhibited and atropine partially inhibited the response to 50 microM H2O2. Piroxicam (5 microM) inhibited the increase in Isc to 50 microM NH2Cl and H2O2 by 20-45% and 90%, respectively. Serosal prostaglandin E2 levels were significantly increased after the addition of 50 microM NH2Cl and H2O2. The morphological response to NH2Cl consisted of changes in mucosal depth and crypt architecture. In conclusion, at concentrations found in inflamed tissue, both NH2Cl and H2O2 increase Isc probably by stimulating release of arachidonate metabolites and neurotransmitter(s). NH2Cl also may act directly on the epithelial cell to stimulate Isc and evoke Cl- secretion.

Animals↗

PubMed1990

In vitro and in vivo antimuscarinic effects of (-)cis 2,3-dihydro-3-(4-methylpiperazinylmethyl)-2-phenyl-1,5 benzothiazepin-4-(5H)one HCl (BTM-1086) in guinea pig peripheral tissues.

The potency and selectivity of (-)cis-2,3-dihydro-3-(4-methylpiperazinylmethyl)-2-phenyl-1,5 benzothiazepin-4-(5H)one HCl (BTM-1086) for muscarinic receptor subtypes was compared in functional assay systems, in guinea pig peripheral tissues, to known reference drugs: atropine (nonselective), pirenzepine (M1), AF-DX 116 (M2) and HHSiD (M3). Like atropine, BTM-1086 was a potent, nonselective, competitive muscarinic antagonist with no detectable antispasmodic activity in urinary bladder or ileal muscle. In vivo, in the guinea pig cystometrogram, BTM-1086 depressed intravesical bladder pressure (PvesP) with the same efficacy and potency as oxybutynin, a drug used clinically for the treatment of urinary incontinence. The pharmacological profile of BTM-1086, however, suggests that it may not be suitable for development for bladder dysfunction disorders.

Animals↗

PubMed1990

Synthesis of some 3-(1-azabicyclo[2.2.2]octyl) 3-amino-2-hydroxy-2-phenylpropionates: profile of antimuscarinic efficacy and selectivity.

A series of 3-quinuclidinyl atrolactate [3-(1-azabicyclo[2.2.2]octyl) 2-hydroxy-2-phenylpropionate, QNA] derivatives in which the methyl group of the parent is substituted with a tertiary amino substituent was prepared and tested for antimuscarinic activity. In general, potency was markedly decreased, although the morpholinyl and thiomorpholinyl derivatives retained significant activity. These compounds were also examined for muscarinic receptor subtype selectivity. Their subtype selectivities were comparable to that of (R,R)-QNA. The results of this investigation suggest possible differences in the accessory binding sites of the proteinaceous receptor subtypes.

Animals↗

PubMed1990

Characterization of Ile,Ser-bradykinin-induced changes in short-circuit current across rat colon.

The effects of Ile,Ser-bradykinin (TK) on electrolyte secretion across mucosa of rat distal colon were determined and compared to those of bradykinin (BK). A segment of colon stripped of muscularis was mounted in an Ussing chamber for monitoring short-circuit current (Isc). Serosal application of TK and BK produced a concentration-dependent and transient increase in Isc with EC50(nM) values of 2.0 +/- 0.6 and 1.7 +/- 0.7, respectively. At a concentration of 1.0 microM, TK produced a maximal response of 130 +/- 18 compared to 75 +/- 13 microA/cm2 for BK. Increases in Isc induced by BK and TK were significantly (P less than .001) inhibited (90 +/- 4% for BK and 87 +/- 5% for TK) by serosal addition of bumetanide (10 microM). The lipoxygenase/cyclooxygenase inhibitor, eicosa-5,8,11,14-tetraynoic acid (0.1 mM), inhibited (P less than .01) the response to BK by 67 +/- 9% and to TK by 51 +/- 8%. Moreover, the cyclooxygenase inhibitor indomethacin (5.0 microM) significantly (P less than .05) inhibited the Isc response to 1.0 nM BK and 1.0 nM TK. Atropine (1.0 microM) did not block the effects of either kinin. Finally, the BK antagonist D-Arg0[Hyp3,Thi5,8,DPhe7]-bradykinin (2.0 microM) competitively antagonized the effect of BK and TK, shifting the concentration curve competitively to the right by 6-fold and 16-fold respectively. Another BK antagonist, [D-Phe7]-bradykinin (20 microM), also exhibited similar blockade effects. In this model, although some differences exist, BK and TK appear to act by the same mechanism, which may involve arachidonic acid metabolites.

Animals↗

PubMed1990

Regulation of guinea pig ileal electrolyte transport by M3-muscarinic acetylcholine receptors in vitro.

To determine the muscarinic receptor subtype mediating guinea pig ileal mucosal electrolyte secretion, we compared the potencies (Kb) of selective M1 (pirenzepine) (PZ), M2 (AF-DX 116, methoctramine), and M3 [4-diphenylacetoxy-N-methylpiperidine methiodide (4-DAMP), hexahydrosiladifenidol (HHSiD)] antagonists as inhibitors of carbachol-induced reductions in guinea pig atrial heart rate and ileal longitudinal muscle contractions, responses mediated by M2 and M3 receptors, respectively. Pretreatment with all five muscarinic antagonists shifted the carbachol concentration-response curve to the right, in a manner suggesting competitive antagonism. The following affinity profiles (Kb, nM) were obtained for: 1) ileal mucosa: 4-DAMP (2.7) greater than HHSiD (23.0) greater than PZ (110) greater than or equal to methoctramine (395) greater than AF-DX 116 (784); 2) atrial heart rate: 4-DAMP (9.5) congruent to methoctramine (11) greater than AF-DX 116 (63) greater than HHSiD (222) greater than PZ (256); and 3) ileal longitudinal muscle: 4-DAMP (3.1) greater than HHSiD (21) greater than PZ (143) greater than methoctramine (388) greater than or equal to AF-DX 116 (482). The selectivity profiles of these antagonists suggest that muscarinic receptors in the ileal mucosa more closely resemble those in the ileal muscle (M3) than those in atrial muscle (M2). Moreover, M1-muscarinic receptors appear to be relatively unimportant in mediating the effects of carbachol on short circuit current (ISC). Carbachol-induced increases in ISC were also unaffected by pretreatment with 0.5 microM tetrodotoxin, suggesting that electrolyte transport in the guinea pig ileal mucosa may be mediated, in part, by postsynaptic M3-muscarinic receptors on the enterocytes.

Animals↗

PubMed1989

Kinins as mediators of intestinal secretion.

Kinins are small peptides that have diverse biological actions. Concentrations of kinins in the nanomolar or subnanomolar range induce intestinal smooth muscle contraction and evoke mucosal electrolyte secretion. Hyperkininemia is associated with effects on gastrointestinal motility and intestinal mucosal inflammation. Bradykinin and kallidin are the predominant kinins with effects on the gastrointestinal tract of mammals. Bradykinin stimulates chloride ion secretion by the guinea pig and rabbit ileum, rabbit colon, rat colon and monolayers of human HCA-7 cells. Kinins directly or indirectly stimulate phospholipase A2 and phospholipase C. Cells in the lamina propria of the mucosa (e.g., fibroblasts, mast cells, leukocytes), by liberating cyclooxygenase and lipoxygenase metabolites of arachidonic acid, are involved in the kinin response; direct effects on epithelial cells cannot be ruled out, however. Antagonists now exist for kinin receptors. Based on studies with these antagonists in smooth muscle preparations, two subgroups of kinin receptor have been identified. The B2-type receptor appears to be responsible for both the contraction of ileal muscle and ileal secretion. Kinins are probably more important as pathophysiological rather than as physiological mediators. They may amplify the effect of inflammatory products that induce intestinal secretion. The precise involvement of kinins in clinical mucosal secretory states and diarrhea will require quantitative assessment of their levels during each phase of mucosal inflammation. Additional studies on the mechanism of action of kinins will be essential in designing therapy to mitigate the symptoms associated with mucosal inflammation.

Animals↗

PubMed1988

R and S enantiomers of oxybutynin: pharmacological effects in guinea pig bladder and intestine.

Oxybutynin (Ditropan) is widely utilized in treatment of incontinence due to neurogenic bladder dysfunction. We prepared its R and S enantiomers and evaluated their antimuscarinic, Ca++-channel antagonistic and spasmolytic effects in guinea pig detrusor strips and ileal longitudinal muscle. Ussing chambers were used to assess inhibition of carbachol-induced mucosal Cl-secretion in vitro. The enantiomers and the racemate were also tested in in vivo preparations for local anesthetic activity and for antimuscarinic activity in the slow filling cystometrogram. Stereoselective antimuscarinic effects [R)OXY:(R/S)OXY:(S)OXY) were evident for isolated ileal longitudinal (0.12:1.0:4.5) and bladder detrusor muscle (0.5:1.0:13) isolated ileal mucosa (0.2:1:8.9) and acetylcholine stimulated phosphoinositide turn-over in vitro (0.24:1.0:39). Stereoselectivity was also evident for the volume-induced contractions of the cystometrogram in vivo (0.7:1:15). In contrast, no stereoselectivity was observed for Ca++-channel antagonism, spasmolytic and local anesthetic properties of (R/S)OXY and its enantiomers.

Anesthetics, Local↗

PubMed1988

Antihistaminic and antimuscarinic effects of amitriptyline on guinea pig ileal electrolyte transport and muscle contractility in vitro.

Amitriptyline, a tricyclic antidepressant, was tested for antimuscarinic and antihistamine effects against bethanechol and histamine-stimulated contractility and secretion in the guinea pig ileum in vitro. Comparisons were made with muscarinic-receptor antagonists, as well as with H1 and H2 histamine-receptor antagonists. Amitriptyline (0.01-5.0 microM) produced a parallel rightward shift in the concentration-response curves to histamine in muscle (Ki 0.4 nM) and mucosa (Ki 450 nM). The H1-receptor antagonists pyrilamine and diphenhydramine were less potent against histamine in the muscle and more potent against histamine in the mucosa than was amitriptyline. The H2-receptor antagonist cimetidine was ineffective in the muscle and mucosa. Amitriptyline (0.1-2 microM) also produced a parallel rightward shift in the concentration-response curve to bethanechol in muscle (Ki 133 nM) and mucosa (Ki 143 nM). Against bethanechol, in both tissues, atropine and 4-diphenylacetoxy-N-methyl piperidine methiodide were more potent competitive antagonists than was amitriptyline. Pirenzepine produced a competitive blockade of bethanechol in the muscle and a noncompetitive blockade in the mucosa. The data indicate that amitriptyline exerts more potent antihistaminic effects on guinea pig ileal muscle than the mucosa but that the tricyclic drug is equipotent as an antimuscarinic in both tissues.

Amitriptyline↗

PubMed1987

Synthesis and pharmacologic properties of 6-succinylcodeine.

In our search for a ligand to be used for affinity chromatography in the separation of putative, codeine-specific receptors, we have synthesized a pharmacologically active codeine derivative, 6-succinylcodeine (Ib). The structure of the compound has been confirmed. It is markedly less toxic than the parent compound, codeine (Ia), and has significantly weaker antitussive properties in the cat. On the other hand, its antinociceptive properties in the mouse and effects on guinea pig ileum are comparable to those of codeine. An interesting pharmacological property of Ib is its hypotensive effect in both cats and rhesus monkeys. The compound has been successfully coupled to an aminoalkyl agarose matrix. When coupled to the matrix, the drug loses its capacity to cause contraction of the guinea pig ileum but this property is restored upon alkaline hydrolysis of the coupled beads. Whether the diminished antitussive properties, as compared to the parent compound, or the loss of capacity to inhibit guinea pig ileum contractility when coupled to agarose would limit its usefulness for affinity chromatography of codeine-specific receptors is being investigated.

Analgesics↗

PubMed1987

Bradykinin receptors: functional similarities in guinea pig gut muscle and mucosa.

It is well established that bradykinin can stimulate mucosal electrolyte transport. However, the receptor type which mediates this effect has not been fully characterized. Recent studies have suggested that bradykinin and related kinins may act at two types of receptors designated as B1 and B2. We have determined the effect of bradykinin on electrolyte secretion across guinea pig ileal mucosa and longitudinal muscle in vitro in the presence and absence of D-Phe7-bradykinin (B2 antagonist) and des-Arg9-(Leu8)-bradykinin (B1 antagonist). The B2 antagonist (less than 100 microM) did not affect resting muscle tension or basal electrolyte transport but at 6-30 microM it caused a parallel rightward shift in the concentration-response curves to bradykinin in the mucosa (Ki = 4 microM) and muscle (Ki = 6 microM). Changes in electrolyte transport and muscle contractility evoked by bethanechol and substance P were not affected by the B2 antagonist (30 microM) in either the muscle or the mucosa. Moreover, changes in electrolyte transport and muscle contractility produced by bradykinin were not altered by the B1 antagonist (30 microM). Finally, the B1 agonist des-Arg9-bradykinin (10 nM-1 microM) was not active in either preparation. These data suggest that under normal conditions, ileal secretion and smooth muscle contractility in the guinea pig are regulated by B2-type bradykinin receptors.

Animals↗

PubMed1987

Effect of dextromethorphan and levomethorphan on gastric emptying and intestinal transit in the rat.

Dextromethorphan and levomethorphan were evaluated using 51Cr as a marker for their effects on gastric emptying and intestinal transit in the rat. Levomethorphan at 10 mg/kg i.p. and 10 and 50 mg/kg p.o. significantly (P less than or equal to .05) inhibited gastric emptying; dextromethorphan did not inhibit gastric emptying at p.o. doses up to 100 mg/kg or i.p. doses up to 10 mg/kg. Naloxone (1 mg/kg i.p.) significantly antagonized the effect of p.o. levomethorphan (50 mg/kg). Levomethorphan (10 and 50 mg/kg p.o. and 1 and 10 mg/kg i.p.) significantly inhibited intestinal transit. Dextromethorphan significantly inhibited intestinal transit after p.o. (10, 50, 100, 200 mg/kg) and i.p. (50 mg/kg) administration. As in the case of gastric emptying, naloxone inhibited the effect of levomethorphan but did not alter the effect of dextromethorphan. Naloxone itself (1 mg/kg i.p.) did not affect gastric emptying or intestinal transit. The results suggest that levomethorphan exerts inhibitory effects on intestinal transit and gastric emptying that are probably mediated partly through an opiate mechanism whereas the effects of dextromethorphan may be mediated through a nonopiate mechanism of action.

Animals↗

PubMed1986

Pharmacological effects of 1,2,3,5,6,10b-hexahydropyrido[2,3g]indolizine, a bridged-nicotine analog.

The racemate of a bridged-nicotine (BN) analog was synthesized and resolved into its enantiomers for pharmacological comparisons to (+)- and (-)-nicotine. The EC50 values for (-)- and (+)-nicotine and (-)- and (+)-BN were 4, 170, 53 and 400 microM, respectively, for producing contractions of guinea-pig ilea. (-)-Nicotine was an effective antinociceptive agent in the mouse tail-flick procedure at i.v. doses of 0.1-0.3 mg/kg, whereas the isomers of BN failed to alter tail-flick response in doses up to 5 mg/kg. (-)-Nicotine (0.01-0.3 mg/kg, i.v.) increased blood pressure and decreased heart rate in anesthetized rats. Neither (+)- nor (-)-BN altered blood pressure and heart rate in rats in this dosage range. At doses of 3-100 mg/kg, (+)-BN produced an increase in blood pressure without changing heart rate, while (-)-BN decreased both blood pressure and heart rate. Bridging the pyrrolidine and pyridine rings decreased biologic activity and did not result in stereoselectivity greater than that observed with (+)- and (-)-nicotine. It appears that there may be subpopulations of nicotine receptors to which the isomers of BN do not interact.

Analgesics↗

PubMed1986

Morphine dependence and diabetes. II. Alterations of normorphine potency in the guinea-pig ileum and mouse vas deferens and of ileal morphine dependence by changes in glucose concentration.

The effects of glucose in vitro at concentrations of 100, 200 and 400 mg/dl on responses of the guinea-pig ileum and mouse vas deferens to opiates were studied. Responses of the electrically stimulated ileum to normorphine were significantly reduced (IC50 values: 26.3 +/- 4.3, 40.5 +/- 3.7 and 71.8 +/- 16.6 nM) as the glucose concentration increased, whereas the potency of normorphine was not affected by equimolar substitutions of glucose with the nonmetabolizable sugar 3-O-methylglucose. The potency of naloxone to induce withdrawal contractions of ilea incubated in Ringer's solution for 3 or 4.5 hr with 1 microM morphine was also significantly decreased as the concentration of glucose in the incubations increased, indicating a reduction of acute dependence development by high glucose. The potency of normorphine was also reduced by increasing concentrations of glucose in electrically stimulated vasa deferentia from nondiabetic (db/m+, m+/m+) C57BL/KsJ mice (IC50 values: 0.53 +/- 0.01, 0.77 +/- 0.01 and 1.84 +/- 0.03 nM), but not in vasa deferentia from their diabetic (db/db) littermates. These results support our hypothesis that the decreased sensitivity to morphine and decreased development of physical dependence on morphine in in vivo models of diabetes reported previously by our laboratory is due primarily to the hyperglycemia associated with diabetes.

Animals↗

PubMed1986

Effect of dextromethorphan on guinea pig ileal contractility in vitro: comparison with levomethorphan, loperamide and codeine.

Dextromethorphan (DM) was tested for its effect on the contractility of the guinea pig ileum in vitro. Comparisons were made with levomethorphan, levorphanol, codeine and loperamide. DM and codeine inhibited the contractions of the electrically stimulated ileum, with IC50 values of 15 and 8 microM, respectively. The inhibitory effect of DM, in contrast to codeine, was not blocked by the opiate antagonist naloxone. Pretreatment (8, 50 and 100 microM) with DM and its I-isomer levomethorphan reduced in a dose-dependent fashion both phasic and tonic contractions produced by maximally effective concentrations of carbachol and 80 mM KCl. Pretreatment (8, 50 and 100 microM) with codeine, dextrorphan or levorphanol, unlike DM, did not reduce carbachol or KCl-induced contractions. The concentration-response curves to calcium in K+ depolarized ileum were shifted to the right in a parallel manner suggesting competitive antagonism for DM (pA2 5.3), levomethorphan (pA2 5.3) and loperamide (pA2 6.6). Codeine and levorphanol (8, 50 and 100 microM) did not antagonize calcium-induced contractions. In two assays of calmodulin-dependent processes DM was inactive (IC50 greater than 1 mM), whereas trifluoperazine and calmidazolium (standard calmodulin antagonists) were active in the micromolar range. In summary, these data suggest that DM, through a nonopiate mechanism, antagonizes gut contractility possibly by "stabilizing" neuronal and/or muscle cell membranes.

Actins↗

PubMed1985

Comparison of the ability of opioid analgesics to increase endogenous opioid-like activity in the cerebrospinal fluid of rabbits.

We have previously demonstrated that the acute administration of morphine increases the level of endogenous substances, which have antinociceptive activity, in cerebrospinal fluid (CSF). The present study was conducted to determine whether other opioid analgesics exert a similar effect. CSF was withdrawn from the cisterna magna of anesthetized rabbits before and after s.c. injections of meperidine, pentazocine, levorphanol and methadone, and was bioassayed for opioid-like activity in the mouse tail-flick and phenylquinone writhing tests. The opioid-like activity of CSF taken 60 min after meperidine (50 mg/kg) was significantly increased in both bioassays, and the CSF level of meperidine was insufficient to account for this effect. Pentazocine (25-75 mg/kg) also significantly increased opioid-like activity in rabbit CSF, but the effects of methadone (5-10 mg/kg) and levorphanol (20 mg/kg) were less marked. Dextrorphan (20 mg/kg), diazepam (10 mg/kg) and pentobarbital (20 mg/kg) administration did not significantly increase opioid-like activity in CSF. It is concluded that the antinociceptive action of some opioid analgesics in rabbits may be mediated in part by the release of endogenous antinociceptive substances.

Animals↗

PubMed1985

Inhibition of muscarinic receptor binding and acetylcholine-induced contraction of guinea pig ileum by analogues of 5'-(isobutylthio)adenosine.

(Isobutylthio)adenosine (SIBA, 1) and its derivatives have been shown to produce a variety of biological effects on the basis of the hypothesis that such agents act directly as inhibitors of transmethylation reactions, as inhibitors of S-adenosylhomocysteine hydrolase, or as inhibitors of polyamine biosynthesis. We report here the ability of selected analogues of SIBA to inhibit the binding of the muscarinic antagonist quinuclidinyl benzilate (QNB) to cultured N4TG1 neuroblastoma cells and to antagonize the acetylcholine-induced contraction of guinea pig ileum. The most potent inhibitors were 5'-deoxy-5'-(isobutylthio)-1-deazaadenosine (1-deaza-SIBA, 5) and 5'-deoxy-5'-(isobutylthio)-3-deazaadenosine (3-deaza SIBA, 3), while the parent nucleoside SIBA and the carbocyclic derivative 5'-(isobutylthio)-3-deazaaristeromycin were less active. The same agents had no effect on the nicotinic receptors of NG108-15 neuroblastoma X glioma hybrid cells. The acyclic derivative 9-[[2-(isobutylthio)ethoxy]methyl]adenine, 3-deazaadenosine, 5'-(isobutylthio)tubercidin, and 5'-(isobutylamino)adenosine were inactive at the 1-mM level. These results suggest that SIBA and 3-deaza-SIBA may have profound effect on membrane-mediated phenomenon, including inhibition of muscarinic receptor binding.

Acetylcholine↗

PubMed1984

Pentazocine-tripelennamine ("T's and Blues") substitution studies in morphine-dependent rodents.

Tripelennamine, pentazocine and various pentazocine-tripelennamine combinations were tested for their ability to substitute for morphine in morphine-dependent rodents. Rats and mice were rendered physically dependent on morphine by the Drug-Admixed Food Method. Pentazocine produced a dose-related partial suppression of morphine withdrawal signs in mice, as well as in both mildly and severely dependent rats. Tripelennamine did not suppress morphine withdrawal signs, but rather aggravated them. Furthermore, tripelennamine did not potentiate the ability of pentazocine to suppress morphine withdrawal signs. It is concluded that the primary reason for the reported "street" abuse of the tripelennamine-pentazocine combinations is not related to any remarkable ability of the combination to effectively suppress the discomfort of heroin withdrawal.

Animals↗