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Biomedical subjects

W D Bowen

Publications and source records attributed to W D Bowen.

At least 19 recordsLinked to original sources
PubMed1995

(E)-8-benzylidene derivatives of 2-methyl-5-(3-hydroxyphenyl)morphans: highly selective ligands for the sigma 2 receptor subtype.

The determination of the structure and function of the sigma receptor subtypes and their physiological role(s) has been impeded by the unavailability of selective ligands. We have developed a new class of sigma subtype selective receptor ligands that are (E)-8-benzylidene derivatives of the synthetic opioid (+/-)-, (+)-, and (-)-2-methyl-5-(3-hydroxyphenyl)morphan-7-one (1). The derivatives can be prepared by reaction of 1, (+)-1, and (-)-1 with the appropriate benzaldehyde under Claisen-Schmidt conditions. Incorporation of substituted (E)-8-benzylidene moieties onto the 7-keto precursor of (+)-2-methyl-5-(3-hydroxyphenyl)morphan, (+)-1, produces compounds (-)-2 through (-)-7 (5.8-32.0 nM, sigma 1), which have between a 25- and 131-fold increase in affinity for the sigma 1 receptor subtype relative to the keto precursor (+)-1 (Ki = 762 nM, sigma 1). Compound (-)-2 is the most selective of this group (16-fold) for the sigma 1 subtype versus sigma 2. Substitution of an (E)-8-benzylidene moiety onto the 7-keto precursor of (-)-2-methyl-5-(3-hydroxyphenyl)morphan, (-)-1, produces compounds (+)-2-(+)-9 (6.4-52.6 nM, sigma 2), which have at least a 475-3906-fold increase in affinity for the sigma 2 receptor subtype relative to the keto precursor (-)-1 (Ki = 25 x 10(3) nM). This enhancement of sigma 2 receptor affinity is accompanied by substantial selectivity of all of these dextrorotatory products for the sigma 2 relative to the sigma 1 subtype (32-238-fold), and thus, they are among the most sigma 2 selective compounds currently known. Furthermore, the sigma 1 subtype is highly enantioselective for the levorotatory isomers, (-)-2-(-)-7 (41-1034-fold), whereas the sigma 2 subtype is only somewhat enantioselective for the dextrorotatory isomers, (+)-2-(+)-7 (2.6-9.3-fold). All of these derivatives retain substantial affinity for the mu opioid receptor. Despite the high affinity of the dextrorotatory derivatives for the mu opioid receptor, the high affinity and selectivity for sigma 2 over sigma 1 sites will surely prove beneficial as tools for the delineation of the function and physiological role of sigma 2 receptors.

Animals↗
PubMed1995

Synthesis and sigma binding properties of 2'-substituted 5,9 alpha-dimethyl-6,7-benzomorphans.

The synthesis and sigma 1 and sigma 2 binding properties of several (+)- and (-)-2-benzyl- and 2-dimethylallyl-2'-substituted-5,9 alpha-dimethyl-6,7-benzomorphans (3 and 4) are presented. In agreement with previously reported binding data for 2-substituted 5,9 alpha-dimethyl-2'-hydroxy-6,7-benzomorphans (N-substituted-N-normetazocine), all (1S,5S,9S)-(+)-isomers showed higher affinity for the sigma 1 site than the corresponding (1R,5R,9R)-(-)-isomers. Replacement of the 2'-hydroxy group of (+)-2-benzyl-5,9 alpha-dimethyl-2'-hydroxy-6,7-benzomorphan [(+)-1f] with a 2'-NH2 and 2'-N(CH3)2 [(+)-3b and (+)-3c, respectively] had only a small effect on the sigma 1 Ki values. Changing the 2'-hydroxy group of (+)-1f to an H, F, Cl, Br, I, NHAc, or NHSO2CH3 resulted in a 5-fold or greater loss in potency. In contrast, replacement of the 2'-hydroxy group of (+)-2-(dimethylallyl)-5,9 alpha-dimethyl-2'-hydroxy-6,7-benzomorphan [(+)-1b, (+)-pentazocine] with a 2'-H or 2'-F group resulted in a 2-fold increase in potency. Conversion of (+)-1f to its 2'-desoxy analogue (+)-2d resulted in a 27.5-fold loss in affinity. This suggests that (+)-1f and other N-substituted benzomorphan analogues may be binding to single sigma 1 receptors in a different way or to different sigma 1 receptors. (-)-Pentazocine [(-)-1b] and its 2'-fluoro analogue, (-)-2-(dimethylallyl)-5,9 alpha-dimethyl-2'-fluoro-6,7-benzomorphan [(-)-4a] showed the highest potency for the sigma 2 binding site.

Animals↗
PubMed1995

Synthesis and sigma binding properties of 1'- and 3'-halo- and 1',3'-dihalo-N-normetazocine analogues.

The synthesis and sigma 1 and sigma 2 binding properties of several 1'- and 3'-halo- and 1',3'-dihalo-substituted analogues of (+)-N-benzyl- and (+)- and (-)-N-dimethylallyl-N-normetazocine are presented. Structure-activity relationship analyses of the binding data showed that halogen substitution at the 1'-position of these N-substituted N-normetazocine analogues had little effect on sigma 1 binding affinity, whereas 3'-halo substitution as well as 1',3'-dihalo substitution resulted in a reduction of affinity. sigma 2 affinity was increased by the presence of a 3'-bromo substituent in this series of (+)-N-substituted N-normetazocines.

Animals↗
PubMed1995

Synthesis and pharmacological characterization of 4-[125I]-N-(N-benzylpiperidin-4-yl)-4-iodobenzamide: a high affinity sigma receptor ligand for potential imaging of breast cancer.

The synthesis of [125I]-N-(N-benzylpiperidin-4-yl)-4-iodobenzamide (4-[125I]BP), a novel radiopharmaceutical that possesses high affinity for both sigma-1 and sigma-2 receptor subtypes, and its binding characteristics to MCF-7 breast cancer cells are described. To obtain high yields (with high specific activity) of radioiodinated ligand, (N-benzylpiperidin-4-yl)-4-tri-butylstannyl benzamide was synthesized. Radiolabeled 4-[125I]BP was prepared from tri-butylstannyl precursor with the use of chloramine-T or hydrogen peroxide as an oxidizing agent in high yields (71-86%). The competition binding studies of 4-[125I]BP in MCF-7 breast tumor cells with haloperidol and DTG (known sigma ligands) showed a dose-dependent displacement and high affinity binding (Ki = 4.6 and 56 nM, respectively), demonstrating that sigma receptors are expressed in MCF-7 breast tumor cells. Scatchard analysis of 4-[125I]BP binding in MCF-7 cells revealed saturable binding, with a Kd = 26 nM and a Bmax = 4000 fmol/mg protein. Furthermore, the Scatchard analysis of [3H]DTG binding in MCF-7 cells gave a Kd of 24.5 nM and a Bmax of 2071 fmol/mg of protein. The biodistribution and clearance of 4-[125I]BP was studied in rats. The radiopharmaceutical cleared quickly from the blood pool but rather slowly from the hepatobiliary system. The in vivo specificity was demonstrated by blocking the receptor binding in the presence of haloperidol. A decrease of 55, 63, 43, and 68% was found at 1 h postinjection in brain, kidney, heart, and lung, respectively. These results demonstrate that a high density of sigma receptors are expressed in MCF-7 cells and that radioiodinated 4-IBP may be useful for imaging breast cancer by targeting sigma sites.

Affinity Labels↗
PubMed1995

Ibogaine and its congeners are sigma 2 receptor-selective ligands with moderate affinity.

Ibogaine (12-methoxyibogamine) exhibited moderate affinity for sigma 2 sites (Ki = 201 nM) and low affinity for sigma 1 sites (Ki = 8554 nM), thus showing 43-fold selectivity for sigma 2 receptors. Tabernanthine (13-methoxyibogamine) and (+/-)-ibogamine had sigma 2 Ki = 194 nM and 137 nM, respectively. However, they showed 3- to 5-fold higher sigma 1 affinity compared to ibogaine, resulting in about 14-fold selectivity for sigma 2 sites over sigma 1. A potential ibogaine metabolite, O-des-methyl-ibogaine, had markedly reduced sigma 2 affinity relative to ibogaine (Ki = 5,226 nM) and also lacked significant affinity for sigma 1 sites. (+/-)-Coronaridine ((+/-)-18-carbomethoxyibogamine) and harmaline (1-methyl-7-methoxy-3,4-dihydro-beta-carboline) lacked significant affinity for either sigma subtype. Thus, sigma 2 receptors could play a role in the actions of ibogaine.

Animals↗
PubMed1995

CB-64D and CB-184: ligands with high sigma 2 receptor affinity and subtype selectivity.

Four members of a novel class of sigma (sigma) ligands were investigated for sigma subtype selectivity. (-)-1S,5S- and (+)-1R,5R-(E)-8-Benzylidene-5-(3-hydroxyphenyl)-2-methylmorphan-7- one (CB-64L and CB-64D, respectively) exhibited sigma 1 Ki = 10.5 nM and 3063 nM; sigma 2 Ki = 154 nM and 16.5 nM, respectively. The corresponding 3,4-dichloro derivatives, (-)-1S,5S- and (+)-1R,5R-(E)-8-(3,4-dichlorobenzylidene)-5-(3-hydroxyphenyl)-2-++ +methylmorphan-7 - one (CB-182 and CB-184, respectively) were also examined. CB-182 ((-)-isomer) showed sigma 1 and sigma 2 Ki = 27.3 nM and 35.5 nM, respectively, whereas CB-184 ((+)-isomer) exhibited sigma 1 and sigma 2 Ki = 7436 nM and 13.4 nM, respectively. Thus, the two sigma subtypes showed opposite enantioselectivity for these compounds, with (-) > (+) at sigma 1 and (+) > (-) at sigma 2. Importantly, CB-64D and CB-184 showed high sigma 2 affinity and, respectively, 185-fold and 554-fold selectivity for sigma 2 receptors over sigma 1. While high sigma 2 selectivity relative to sigma 1 was achieved with these compounds, they both exhibited high affinity at mu (mu) opioid receptors (Ki = 37.6 nM and 4.5 nM, respectively). Despite this, CB-64D and CB-184 will be useful tools for further characterization of sigma 2 receptors.

Animals↗
PubMed1995

Reductions in body weight following chronic central opioid receptor subtype antagonists during development of dietary obesity in rats.

Acute administration of long-acting general opioid antagonists reduces body weight and food intake in rats. In contrast, chronic administration of short-acting general opioid antagonists produces transient effects. The present study evaluated whether chronic central administration of selective long-acting antagonists of mu (beta-funaltrexamine, BFNA, 20 micrograms), mu1 (naloxonazine, 50 micrograms), delta1 ([D-Ala2,Leu5,Cys6]-enkephalin, DALCE, 40 micrograms), delta2 (naltrindole isothiocyanate, NTII, 20 micrograms) or kappa (nor-binaltorphamine, NBNI, 20 micrograms) opioid receptor subtypes altered weight and intake of rats exposed to a palatable diet of pellets, fat, milk and water, relative to pellet-fed and diet-fed controls. Diet-fed rats receiving chronic vehicle injections significantly increased weight (7-10%) and intake over the 11-day time course. Weight was significantly reduced over the time course in rats administered either BFNA (9%), naloxonazine (12%), DALCE (7%) or NTII (6%). Initial weight reductions failed to persist following chronic NBNI. All antagonists chronically reduced fat intake, but did not systematically alter total intake, pellet intake or milk intake relative to the pattern of weight loss. These data indicate that central mu, mu1, delta1, delta2, and, to a lesser degree, kappa receptors mediate long-term opioid modulation of weight even in animals maintained on diets that ultimately result in dietary obesity.

Animals↗
PubMed1995

(+)-cis-N-(para-, meta-, and ortho-substituted benzyl)-N-normetazocines: synthesis and binding affinity at the [3H]-(+)-pentazocine-labeled (sigma 1) site and quantitative structure-affinity relationship studies.

sigma 1 receptor ligands have potential pharmacological significance as antipsychotic drugs, as tools in the study of drug-induced motor function disorders, and as radiopharmaceutical imaging agents for the noninvasive imaging of malignant tumors in human subjects. A series of substituted N-benzyl-N-normetazocines were synthesized and their binding affinity at the sigma 1 receptor evaluated in order to examine the details of the structure--affinity relationships (SAR) of a previously determined high-affinity lead compound, (+)-cis-N-benzyl-N-normetazocine (Ki = 0.67 nM). Variation in the benzyl substituents of these compounds produced a 1590-fold range in affinity at the sigma 1 receptor from the unsubstituted benzyl analog to the lowest affinity p-tert-butylbenzyl analog (Ki = 1066 nM). The nanomolar binding affinity for the sigma 1 receptor of (+)-cis-N-(4-fluorobenzyl)-N-normetzocine suggests that this analog may be a useful PET imaging agent.

Animals↗
PubMed1995

Sigma-1 and sigma-2 receptors are expressed in a wide variety of human and rodent tumor cell lines.

Thirteen tumor-derived cell lines of human and nonhuman origin and from various tissues were examined for the presence and density of sigma-1 and sigma-2 receptors. Sigma-1 receptors of a crude membrane fraction were labeled using [3H](+)-pentazocine, and sigma-2 receptors were labeled with [3H]1,3-di-o-tolylguanidine ([3H]DTG); in the presence or absence of dextrallorphan. [3H](+)-Pentazocine-binding sites were heterogeneous. In rodent cell lines (e.g., C6 glioma, N1E-115 neuroblastoma, and NG108-15 neuroblastoma x glioma hybrid), human T47D breast ductal carcinoma, human NCI-H727 lung carcinoid, and human A375 melanoma, [3H](+)-pentazocine bound to high- and low-affinity sites with Kd1 = 0.67-7.0 nM, Bmax1 = 25.5-108 fmol/mg protein, Kd2 = 127-600 nM, and Bmax2 = 942-5431 fmol/mg protein. However, [3H](+)-pentazocine bound to a single site in other cell lines. In human U-138MG glioblastoma, SK-N-SH neuroblastoma, and LNCaP.FGC prostate, Kd = 28-61 nM and Bmax = 975-1196 fmol/mg protein, whereas in ThP-1 leukemia Kd = 146 nM and Bmax = 1411 fmol/mg protein. The sigma-1-like nature of [3H](+)-pentazocine-binding sites was confirmed by competition studies which revealed high affinity for haloperidol and enantioselectivity for (+)-pentazocine over (-)-pentazocine. Interestingly, human MCF-7 breast adenocarcinoma showed little or no specific binding of [3H](+)-pentazocine, suggesting the absence of sigma-1 receptors in this cell line. All cell lines examined expressed a high density of sigma-2 receptors with Kd values for [3H]DTG ranging from 20 to 101 nM and Bmax values of 491 to 7324 fmol/mg protein. Competition studies indicated possible heterogeneity of sigma-2 receptors. While sites labeled by [3H]DTG in all cell lines tested exhibited affinity for haloperidol and preference for (-)-pentazocine over the (+)-enantiomer, human cell lines generally showed 4- to 7-fold lower affinity for haloperidol and approximately 10-fold lower affinity for (-)-pentazocine compared with the rodent cell lines. The high density of sigma-1 and sigma 2-binding sites in these cell lines suggests important cellular functions in cancer, as well as potential diagnostic utility for tumor-imaging agents which target sigma sites. These cell lines may be useful as model systems in which to study the functions of sigma sites in normal tissues, as well as their possible role in tumor biology.

Adenocarcinoma↗
PubMed1995

Prenatal and postnatal transfer of fatty acids from mother to pup in the hooded seal.

Unlike most mammals, hooded seal (Cystophora cristata) pups are born with a substantial layer of adipose tissue. Subsequently, during the brief lactation period of only 4 days, fasting mothers mobilize enormous amounts of lipid from blubber and secrete milk (60% fat) at rates of 10 kg.day-1. Pups gain 7 kg.day-1 due primarily to the deposition of fat in blubber. We measured blubber content and fatty acid composition of blubber and milk in hooded seal mother-pup pairs at birth and over the 4-day lactation period to examine the nature and source of fetal lipids, the incorporation of maternal blubber fatty acids into milk lipid, and patterns of fatty acid deposition in suckling young. The fatty acid composition of the blubber of the newborn was notably different from that of its mother. Fetal deposition was likely due to a combination of both fetal synthesis and direct placental transfer of maternal circulating fatty acids. The blubber of the newborn was characterized by high levels (> 90% of total fatty acids) of saturated and monounsaturated fatty acids of primarily endogenous origin. In particular, the fetus appeared to have high delta-9 desaturase activity as evidenced by the large amounts of 14:1n-5 (4.2%) and 16:1n-7 (37.0%) in newborn blubber compared to maternal blubber (0.2% and 14.1%, respectively). Nevertheless, essential and long-chain polyunsaturated fatty acids of the n-3 and n-6 families, which could only have originated by direct transfer from the mother, comprised > 7% of pup blubber fatty acids and indicated greater rates of placental transfer than found in humans. In hooded seal mothers, rapid lipid transfer during the brief lactation period appeared to be facilitated by direct incorporation of mobilized fatty acids into milk. Although some differences in proportions of specific fatty acids were found between milk and maternal blubber, most of these differences declined over the course of lactation. However, selective mobilization of 20:5n-3 from maternal blubber into milk was apparent throughout lactation and resulted in elevated levels in pup blubber at weaning compared to maternal blubber. Ingested fatty acids were deposited directly and without modification into the blubber of pups, and by 4 days the fatty acid composition of pup blubber was virtually identical to that of the milk consumed.

Animals↗
PubMed1995

Sigma receptors are expressed in human non-small cell lung carcinoma.

N-(2-piperidinoethyl)4-iodobenzamide), IPAB, was used to characterize sigma receptors in non-small cell lung cancer (NSCLC) cell lines. 125IPAB bound with high affinity to large cell carcinoma (NCI-H1299), adenocarcinoma (NCI-H838), and lung carcinoid (NCI-H727) cell lines. Specific IPAB binding was inhibited with high affinity by haloperidol (Ki = 0.6 nM), IPAB (Ki = 14 nM) and 1,3-ditolyl guanidine (DTG) (Ki = 40 nM). Relative to other receptor ligands, IPAB was not readily internalized at 37 degrees C. IPAB had little effect on the growth of NSCLC cells. Scintigraphic imaging studies using 131IPAB in nude mice bearing NCI-H838 xenografts visualized the tumor at 24 or 30 hours after injection. These results suggest that sigma receptors which are present on NSCLC cells may be used as external markers for imaging tumors in vivo.

Animals↗
PubMed1995

Cytotoxic effects of sigma ligands: sigma receptor-mediated alterations in cellular morphology and viability.

The morphological effects of several neuroleptics as well as other novel and prototypic sigma ligands were examined by addition to cultures of C6 glioma cells. Sigma ligands caused loss of processes, assumption of spherical shape, and cessation of cell division. The time course and magnitude of this effect were dependent on the concentration of sigma ligand. Continued exposure to sigma compounds ultimately resulted in cell death. However, the morphological effect was reversible when sigma ligand was removed shortly after rounding. The potency of compounds to produce these effects generally correlated with binding affinity at sigma receptors of C6 glioma cell membranes labeled with [3H](+)-pentazocine. At a concentration of 100 microM, haloperidol, reduced haloperidol, fluphenazine, perphenazine, trifluoperazine, BD737, LR172, BD1008, and SH344 produced significant effects in 3-6 hr of exposure. Other compounds, such as trifluperidol, thioridazine, and (-)-butaclamol, produced significant effects by 24 hr of exposure. Despite the requirement of micromolar concentrations of ligand (some compounds were effective at 30 microM), the effect showed a remarkable specificity for compounds exhibiting sigma receptor binding affinity. Neuroleptics lacking potent sigma affinity [e.g., (-)-sulpiride, (+)-butaclamol, and clozapine] and other compounds that lack significant sigma affinity but that are agonists or antagonists at dopamine, serotonin, adrenergic, glutamate, phencyclidine, GABA, opiate, or muscarinic cholinergic receptors were without effect on cellular morphology at concentrations up to 300 microM over a period of 72 hr. Likewise, blockers and activators of Na+, K+, and Ca2+ channels and a monoamine oxidase inhibitor devoid of sigma affinity were without effect. Interestingly, 1,3-di-o-tolylguanidine (DTG), (+)-3-(3-hydroxyphenyl)-N-(1-propyl)piperidine [(+)-3-PPP], (+)-pentazocine, (+)-cyclazocine, and other sigma-active benzomorphans and morphinans appeared inactive in up to 72 hr of culture. However, these compounds interacted synergistically with a subeffective dose of BD737 (30 microM) to produce effects usually in 6 hr or less. Also, the pH of the culture medium had a profound effect on the activity of sigma compounds. Increasing the pH from the normal range of 7.2-7.4 to pH 8.3-8.5 shifted the dose curves (30, 100, 300 microM) for all sigma compounds to the left. Under these conditions, DTG, (+)-3-PPP, and benzomorphans produced effects in 24 hr or less.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1994

Rat liver and kidney contain high densities of sigma 1 and sigma 2 receptors: characterization by ligand binding and photoaffinity labeling.

Rat liver and kidney were investigated for the presence of sigma (sigma) receptor subtypes by radioligand binding with three highly selective sigma probes and by photoaffinity labeling using [3H]azido-di-o-tolylguanidine ([3H]azido-DTG). [3H](+)-Pentazocine, a highly selective sigma 1 probe, bound to sites in liver membranes with Kd = 7.5 nM and Bmax3 = 2929 fmol/mg protein. [3H](+)-Pentazocine binding sites in kidney had Kd = 23.3 nM and Bmax = 229 fmol/mg protein. [3H]1,3-Di-o-tolylguanidine ([3H]DTG) and [3H](+)-3-(3-hydroxyphenyl)-N-(1-propyl)piperidine ([3H](+)-3-PPP) label both sigma 1 and sigma 2 receptors. Parameters for [3H]DTG in the liver were Kd = 17.9 nM and Bmax = 11,895 fmol/mg protein. Similar parameters were observed for [3H](+)-3-PPP, Kd = 51.9 nM and Bmax = 11,070 fmol/mg protein. [3H]DTG bound to rat kidney with Kd = 45.8 nM and Bmax = 1190 fmol/mg protein. The observation that either [3H]DTG or [3H](+)-3-PPP and [3H](+)-3-PPP labeled a higher number of sites relative to [3H](+)-pentazocine suggested that liver and kidney contain both subtypes of sigma receptor. This was confirmed by competition studies vs. [3H](+)-pentazocine and [3H]DTG (in the presence of dextrallorphan to mask sigma 1 sites). In both tissues, [3H](+)-pentazocine labeled sites with high affinity for haloperidol and enantioselectivity for (+)-benzomorphans over (-)-benzomorphans. [3H]DTG + dextrallorphan labeled sites in both tissues which also had high affinity for haloperidol, but which had the characteristic sigma 2 property of low affinity for (+)-benzomorphans and enantioselectivity for (-)-benzomorphans over the corresponding (+)-isomer. Similar results were obtained with [3H](+)-3-PPP + dextrallorphan. Several novel aryl diamines, such as 1S,2R-cis-N-[2-(3,4-dichlorophenylethyl]-N-methyl-2- (1-pyrrolidinyl)cyclohexylamine (BD737) and N-[2-(3,4-dichlorophenyl)ethyl]-N-methyl-2-(1-pyrrolidinyl)ethylamine (BD1008), bound to both sites with high affinity. Photoaffinity labeling with 10 nM [3H]azido-DTG resulted in specific labeling of polypeptides of 25 kDa and 21.5 kDa. Dextrallorphan (100 nM or 500 nM) completely blocked labeling of the 25 kDa polypeptide, but had no effect on labeling of the lower molecular weight protein. (+)-10,11-Dihydro-5-methyl-5H-dibenzo[a,d]cyclohepten-5,10- imine((+)-MK-801) had no effect on labeling of either polypeptide. These data are consistent with the notion that the 25 kDa and 21.5 kDa proteins represent sigma 1 and sigma 2 receptors, respectively.(ABSTRACT TRUNCATED AT 400 WORDS)

Affinity Labels↗
PubMed1994

Relative immunocompetence of the newborn harbour seal, Phoca vitulina.

The immune system of many mammalian species is not fully developed at birth, with newborns obtaining temporary immunological protection from maternal antibodies. Little is known of the immune system of the harbour seal, and developmental aspects of its immune system have not been systematically studied. We collected blood and milk samples from nine free-ranging mother-pup pairs throughout the lactation period on Sable Island, Canada, in an effort to characterise developmental aspects of the immune system of this newborn pinniped. Pup lymphocytes responded stronger to the mitogens concanavalin A, phytohaemagglutinin, and pokeweed mitogen than the lymphocytes of their mothers. In contrast to newborn cats and dogs, newborn seal pups developed high specific antibody responses after immunisation with an inactivated rabies vaccine. Circulating levels of total IgG in newborn pups were low (3% of maternal levels), but increased rapidly after colostrum intake (to 65% of maternal levels after 15 days). A similar pattern of increase in pup serum was observed for phocine distemper virus specific antibodies which had been detected in the serum and milk of mothers, suggesting that the transfer of colostral antibodies is an important feature of temporary protection for the pup. We speculate that the relative immunocompetence of the harbour seal at birth reflects an adaptation to its relatively short nursing period and limited maternal care.

Animals↗
PubMed1994

Lack of involvement of delta-1 opioid receptors in the development of physical dependence on morphine in mice.

Previously, we have shown that the development of physical dependence on morphine in mice is inhibited substantially by treatment of mice with the highly selective, nonequilibrium delta-2 opioid receptor antagonist, naltrindole-5'-isothiocyanate. With the availability of the highly selective, nonequilibrium delta-1 opioid receptor antagonist, [D-Ala2,Leu5,Cys6]enkephalin, it was possible, in the present report, to examine the possible involvement of delta-1 opioid receptors in the development of opiate dependence. Mice were made physically dependent on morphine by s.c. implantation of morphine pellets (75-mg free base) for 3 days. The degree of dependence was quantified by determining the ED50 values of naloxone to precipitate withdrawal jumping and diarrhea. Neither sign of opiate withdrawal was affected by chronic treatment of animals with [D-Ala2,Leu5,Cys6]enkephalin during the morphine implant period. The data suggest that delta-1, as opposed to delta-2, opioid receptors are not involved in the development of physical dependence on morphine. This fact takes on added significance because the recently cloned delta opioid receptors appear to be the delta-2 subtype and the present data together with previous findings suggest that the cloned receptors may be proper models for the study of opiate dependence.

Affinity Labels↗
PubMed1993

Characterization of a (+)-azidophenazocine-sensitive sigma receptor on splenic lymphocytes.

A study was undertaken to structurally define and functionally assess sigma receptors on splenocytes using the highly selective sigma ligand (+)-azidophenazocine. Radioreceptor assays under reduced lighting show (+)-azidophenazocine can effectively block the binding of sigma ligands [3H]haloperidol (IC50 = 30 nM, Ki = 19.0 nM) and [3H](+)-pentazocine (IC50 = 40 nM, Ki = 350 nM), but not the dopamine (D2) ligand [3H]spiperone (IC50 > 5 microM) to splenic lymphocytes. [3H](+)-1-Propyl-3-(3-hydroxyphenyl)piperidine ([3H](+)-PPP) sites (Kd = 40.8 nM, Bmax = 2.32 pmol/mg) were also present on these lymphocytes. Additional studies using [3H](+)-azidophenazocine indicated the presence of saturable sites (Kd = 29.7 nM, Bmax = 760 fmol/mg) on splenic lymphocytes. There are no significant differences in affinity between sites found on T-enriched (Kd = 59 +/- 47 nM) and B-enriched lymphocytes (Kd = 23 +/- 5 nM). Photoaffinity labeling studies of splenocyte membranes with [3H](+)-azidophenazocine revealed a protein migrating at an apparent m.w. of 57 kDa under reducing and nonreducing conditions on SDS-PAGE. The labeling was specific because pretreatment with unlabeled haloperidol, (+)-PPP, 1,3 di(2-tolyl)guanidine, (+)-pentazocine, and (+)-azidophenazocine before cross-linking competed away > 75% of the radioactivity associated with the protein, whereas (-)-pentazocine and naloxone were significantly less effective. This data together with the observation that both (+)-azidophenazocine or haloperidol inhibit Con A-induced production of IFN by splenocytes, indicates that lymphocytes possess a biologically relevant sigma receptor.

Affinity Labels↗
PubMed1992

Central opioid receptor subtype antagonists differentially alter sucrose and deprivation-induced water intake in rats.

The present study compared the effectiveness of centrally-administered opioid receptor subtype antagonists to inhibit intake of either a 10% sucrose solution under ad libitum conditions, or water following 24 h of water deprivation. Full dose-response functions were evaluated over a 1 h period for the following antagonists: naltrexone (general: 1-50 micrograms), nor-binaltorphamine (Nor-BNI, kappa: 1-20 micrograms), beta-funaltrexamine (beta-FNA, mu: 1-20 micrograms), naltrindole (delta 2: 1-20 micrograms), [D-Ala2, Leu5, Cys6]-enkephalin (DALCE, delta 1: 10-40 micrograms) and naloxonazine (mu 1: 10-50 micrograms). Naltrexone significantly and dose-dependently inhibited both sucrose intake (64-67%) and deprivation-induced water intake (53-67%). Nor-BNI significantly and dose-dependently inhibited sucrose intake (53-55%), but failed to significantly affect (28%) deprivation-induced water intake. beta-FNA significantly and dose-dependently inhibited both sucrose intake (31-34%) and deprivation-induced water intake (36-50%). Naltrindole failed to significantly alter either sucrose intake (24%) or deprivation-induced water intake (16%). Whereas DALCE significantly, but transiently (15-20 min) inhibited sucrose intake (28%), it failed to significantly alter deprivation-induced water intake (14%). Naloxonazine significantly, but transiently (5-10 min) stimulated sucrose intake at low doses (26%), but non-significantly reduced sucrose intake at higher doses (20%). Naloxonazine failed to significantly alter deprivation-induced water intake (16% reduction). These data indicate that whereas the kappa and mu 2 binding sites participate in the opioid modulation of sucrose intake, the mu 2 binding site participates in the opioid modulation of deprivation-induced water intake.

Animals↗