Oxytocin blocks the development of heroin-fentanyl cross-tolerance in mice

The development of cross-tolerance to an analgesic effect was observed between two mu-receptor agonists, heroin and fentanyl. Repeated treatments with heroin twice a day for 4 days resulted in a decreased nociceptive effect to fentanyl on day 5. The fentanyl dose-response line shifted to the right, and was considered to be a sign of the development of cross-tolerance. Peripheral treatment with oxytocin did not block the development of heroin-fentanyl cross-tolerance. However, intracerebroventricular administration of oxytocin blocked the development of tolerance, causing a leftward shift in the dose-response curve and supporting the assumption that oxytocin blocks the development of heroin-fentanyl cross-tolerance via CNS mechanisms.     

Estrogen blocks early T cell development in the thymus

PROBLEM: Pregnancy and estrogen are known to suppress B lymphopoiesis as well as lead to thymic involution in the mouse. Additionally, estrogen deficiency by oophorectomy reportedly causes a selective increase in the B220+ B cells in the murine bone marrow. The purpose of this study was to determine if estrogens played a regulatory role in T cell development. METHODS: The first experimental group consisted of 5-6-week-old Balb/c mice that received subcutaneous pellets of placebo, estriol, estradiol, or progesterone. The thymus glands were examined 2-4 weeks after treatment. The second group consisted of 6-week-old Balb/c mice who underwent either bilateral oophorectomy or a sham procedure. Two weeks after the surgery, extensive phenotypic characterization of the thymus and spleen cells was performed by flow cytometry using monoclonal antibodies to surface markers of T cell subsets. RESULTS: Estrogen treatment causes a dramatic reduction of thymic size and cellularity. All defined T cell subsets of CD4 and CD8 were reduced, with a disproportionate loss of CD4+CD8+ double positive cells. Examination of the triple negative (CD3-CD4-CD8-) subset revealed a striking loss of TN developmental progression of the early precursor cells. Based on the expression of CD44 (pgp-1) and CD25 (IL-2R alpha) markers, the TN thymic compartment was composed almost entirely of the earliest population (CD44+, CD25-), with the remaining maturational stages (CD44+, CD25+; CD44-, CD25+; CD44-, CD25-) depleted. In contrast, all T cell developmental stages in the thymus were found to be in normal proportions in the oophorectomized mice, with no differences in the splenic T and B cell subsets. CONCLUSIONS: The study demonstrates that estrogen but not progesterone blocks T cell development in the thymus. However, contrary to our expectation, estrogen deprivation by oophorectomy does not enhance T cell development.     

Effect of lipid solubility on the development of chronic cross-tolerance between ethanol and different alcohols and barbiturates

Tolerance to ethanol and cross-tolerance to other alcohols (n-propanol, n-butanol, t-butanol, isobutanol, t-amyl alcohol, n-amyl alcohol, and benzyl alcohol) and barbiturates (pentobarbital, secobarbital, amobarbital, thiopental, barbital and phenobarbital) that differ in lipid:water partition coefficient was examined in rats after chronic pretreatment with ethanol. Tolerance and cross-tolerance were studied with three different measures (hypothermia, tilt-plane, and rotarod). Tolerance to ethanol resulted in significant cross-tolerance to alcohols with low lipid solubility (n-propanol and t-butanol), whereas no cross-tolerance was seen with alcohols of high lipid solubility (isobutanol, n-amyl alcohol, t-amyl alcohol and benzyl alcohol). Cross-tolerance to n-butanol (which has intermediate lipid solubility) appeared to be metabolic rather than functional. Tolerance to ethanol also resulted in significant cross-tolerance to barbital and phenobarbital, but not to pentobarbital, secobarbital, amobarbital or thiopental. These studies suggest that lipid solubility is an important factor in relation to specificity of cross-tolerance to alcohols and barbiturates.     

Oxytocin and milk removal are required for post-partum mammary-gland development

Following the introduction of a transvenous biatrial electrode configuration and a biphasic waveform for internal atrial defibrillation in patients in 1992, it was realized that the standard principles of efficient defibrillation derived from decades of ventricular defibrillation research would not provide painless atrial defibrillation in conscious patients. Over the last five years extensive experimental studies have addressed the risk of ventricular proarrhythmia from synchronized atrial shocks with reassuring results and the influence of the preceding R-R interval on the safety of atrial shocks has been established. Experimental atrial defibrillation research is now aimed at developing waveforms which are less painful and at exploring hybrid therapies including percutaneous right atrial compartmentalization by catheter ablation prior to atrial defibrillation and attempts at multisite pace-entrainment prior to and immediately following the delivery of perithreshold shocks.     

Peripheral morphine administration blocks the development of hyperalgesia and allodynia after bone damage in the rat

BACKGROUND: The current study aimed to assess whether local administration of morphine could block the development of hyperalgesia and allodynia in a rat model of osteotomy or bone damage. METHODS: Withdrawal responses to mechanical and thermal stimuli applied to the plantar surface of the hind paw were measured before and after bone damage. The bone was injured by drilling a 1-mm hole through the tibia during short-lasting general anesthesia. In separate groups of rats, the effects of administering morphine (20-80 microg), either into the marrow cavity or systemically, on the development of hyperalgesia and allodynia after bone damage were assessed. In an additional group of rats, a selective mu-opioid receptor antagonist, clocinnamox (0.15 mg), was administered into the marrow cavity before the administration of morphine (40 microg). RESULTS: In animals that received no drug treatment, hyperalgesia and allodynia peaked 2 h after injury. Injection of morphine (40 and 80 microg) into the marrow cavity immediately after bone injury prevented the development of hyperalgesia and allodynia. Clocinnamox (0.15 mg) injected into the marrow cavity before administration of morphine blocked the antihyperalgesic effect of morphine. CONCLUSION: This study shows that local application of a low dose of morphine effectively blocks the development of hyperalgesia and allodynia in a rat model of bone damage through mu-opioid receptor action. These findings provide further evidence that local application of morphine at the time of orthopedic surgery, bone graft, or bone marrow harvesting may reduce the amount of postoperative pain.     

Alpha-interferon inhibits the development of diabetes in NOD mice

The NOD mouse is a model of human IDDM, which is characterized by a cell-mediated autoimmune process resulting in spontaneous diabetes. Alpha-interferon (IFN-alpha) is thought to play a pathogenic role in this autoimmune process. We report that recombinant alpha-interferon (rIFN-alpha) administration decreases the development of spontaneous diabetes and the passive transfer of diabetes in NOD mice. Spontaneous diabetes was inhibited by IFN-alpha in a dose-dependent fashion. A dose of as little as 20 x 10(3) U inhibited diabetes development, while a dose of 100 x 10(3) U potently prevented diabetes (14% incidence vs. 70% incidence in control mice). Even at the termination of the experiment, nondiabetic mice administered rIFN-alpha maintained normal glucose tolerance. Islet inflammation was 65% lower in the pancreases of rIFN-alpha mice. rIFN-alpha administration decreased anti-islet effector cell bioactivity of spleen cells without inducing generalized immunosuppression. Passive transfer experiments demonstrated that the decreased anti-islet effector cell activity was not a direct action of rIFN-alpha on these cells. In conclusion, rIFN-alpha potently and paradoxically prevents diabetes by indirectly decreasing anti-islet effector cell activity and in turn the development of insulitis without inducing generalized immunosuppression. This work, which goes against our current understanding of the role of rIFN-alpha in autoimmunity, may have significant implications to further our understanding of the pathogenesis of IDDM and to further the development of novel modes to prevent the disease.     

Transgenic expression of Fas in T cells blocks lymphoproliferation but not autoimmune disease in MRL-lpr mice

Fas is a member of the TNF receptor family. Binding of Fas ligand to Fas induces apoptosis in Fas-bearing cells. Fas is expressed in various cells, including thymocytes, peripheral T cells, and activated B cells. The mouse lpr mutation is a loss of function mutation of Fas. MRL-lpr/lpr mice develop lymphadenopathy and splenomegaly, and produce multiple autoantibodies, which results in autoimmune disease. In this report, we describe the establishment of a line of Fas transgenic MRL-lpr mice in which mouse Fas cDNA was expressed using the T cell-specific murine lck promoter. The transgenic mice expressed functional Fas in thymocytes and peripheral T cells, but not in B cells. The transgenic mice did not accumulate abnormal T cells (Thy-1+ B220+), but still accumulated B cells (Thy-1- B220+); they produced a large quantity of Igs (IgG1 and IgG2a), including anti-DNA Abs, and developed glomerulonephritis. These results suggest that autoreactive or activated B cells must be killed through Fas expressed in the B cells by the Fas ligand expressed in activated T cells.     

Postnatal development of delta-opioid receptor subtypes in mice

1. The density and affinity of binding sites for the delta-selective opioid ligands [3H]-[D-Ala2, Asp4]deltorphin (DELT-I), [3H]-[D-Ala2Glu4]-deltorphin (DELT-II), [3H]-[D-Pen2,D-Pen5]enkephalin (DPDPE), and [3H]-naltrindole (NTI) were determined in whole brain from 10, 15, 25 and 60 day-old C57BL mice. 2. At all ages, the analyses of the homologous displacement curves, gave best fits to single rather than to multiple site models. The binding capacity (Bmax) labelled by [3H]-NTI was about one half that labelled by [3H]-DELT-I, [3H]-DELT-II and [3H]-DPDPE. In 25 and 60 day-old mouse brain the DPDPE Bmax was 25% less than the deltorphin-II Bmax. 3. In saturation experiments, specific binding of [3H]-DELT-I on adult mouse brain homogenates was best fitted by a two-site model (34%, high affinity site, Kd = 1.08 nM and 66% low affinity sites, Kd = 39.9 nM). 4. DPDPE produced a biphasic inhibition of specific [3H]-DELTI-I binding, from 15 days of age onwards. The relative percentage of high and low affinity sites was 72% and 28% in 15 day-, 65% and 35% in 25 day- and 30% and 70% in 60 day-old mice. 5. In adult mouse brain labelled with [3H]-DELT-I, DELT-II recognized 71% of high-affinity and 29% of low-affinity sites DELT-I and DPDPE produced monophasic inhibition of specific [3H]-DELT-II binding to brain homogenates of adult mice. 6. These data suggest that a sub-population of delta-sites (probably the delta 2-subtype), recognized by DELT-I, with high affinity for DELT-II and low affinity for DPDPE develops from 25 days onward. 7. In electrically stimulated mouse vas deferens (MVD) the rank order of potency of the three delta-agonists was: DELT-I > DELT-II > DPDPE in 10 day-old mice: and DELT-I- DELT-II > DPDPE, from 25 days onward. During this time, the potency of DELT-II increased about 15 fold whereas the potency of DELT-I and DPDPE increased only 5 times. The higher efficacy of DELT-II could depend on receptor maturation towards the delta 2-subtype.     

Oxytocin release and milk removal in ruminants

Before milking, less than 20% of the milk yielded by dairy cows is stored within the cistern, where it is immediately available for removal. Most of the milk is available for the milking machine only after milk ejection, which occurs in response to tactile teat stimulation and oxytocin release. For complete milk removal, milk ejection is necessary throughout the entire milking process. The continuation of stimulatory effect of the milking machine until the end of milking is, therefore, essential. Premilking teat stimulation causes induction of alveolar milk ejection before the start of milking. Thus, bimodal milk flow curves (i.e., interruption of milk flow after removal of the cisternal milk) are avoided. Continual ejection of milk is dependent on the presence of elevated oxytocin concentrations during the entire milking. Any interruption of the milk ejection process can disturb milk removal. Disruption of milk removal can be caused by peripheral inhibition of oxytocin effects on the mammary gland or by inhibition of oxytocin release by the central nervous system. Peripheral inhibition is induced by elevated concentrations of catecholamines through stimulation of alpha-adrenergic receptors in the mammary gland, likely via changes in ductal resistance. Inhibition of oxytocin release by the central nervous system has been observed in primiparous cows immediately after parturition, during peak estrus, and during milking in unfamiliar surroundings; concentrations of beta-endorphin and cortisol are elevated in this situation. However, the role of endogenous opioid peptides in the inhibition of oxytocin release in cows remains unclear. In conclusion, during machine-milking, the physiological requirements of the cows need to be considered, and, most importantly, stressors must be minimized.     

Rapid development of tolerance to the hypothermic effect of ethanol in mice

The hypothermic response to i.p. injection of ethanol (2.0-4.0 g/kg) in mice was found to be attenuated by a single equivalent ethanol injection given 24 hr earlier. The diminished hypothermic response was not an artifact since it could not be attributed to changes in body weight and was independent of familiarity with test environment and procedures. A parallel shift in the dose-response curve was found. It appears, therefore, that the reduced change in body temperature is indicative of tolerance. If the second ethanol injection was given 48 or 72 hr later, tolerance could no longer be seen. With injections spaced 24 hr apart, a third administration of ethanol did not further increase the tolerance seen after the second injection. Since blood ethanol levels did not differ in tolerant and nontolerant mice, and since tolerance was already present 10 min after the second ethanol injection, a functional rather than a metabolic tolerance is likely.     

Genes on the X chromosome affect development of collagen-induced arthritis in mice

Susceptibility to collagen-induced arthritis (CIA) in mice is associated with a class II gene in MHC (Aq) but also with unknown genes outside MHC. Investigated here is the influence of genes on the X chromosome as well as the role of the X-linked immunodeficiency (xid) mutation. Reciprocal male F1 hybrids, bred to be heterozygous or homozygous for Aq, showed a genetic influence in their susceptibility to develop CIA. Crosses were made between B10.G, B10.Q, DBA/1, SWR/J, C3H.Q and CBA/Ca, and all F1 mice were castrated to avoid sex hormone modulation of the susceptibility. A differential timing of arthritis onset and severity were seen in the reciprocal F1 males. An exception was the reciprocal F1 male offspring from SWR/J and DBA/1 crosses which differed only in disease severity late in the course of the disease. The female F1 crosses did not show the same pattern of differential susceptibility to CIA as the F1 males. To exclude the possible influence of the Y chromosome, F1 males of reciprocal crosses were back-crossed to the parental strains creating offspring with equal X chromosomes but divergent Y chromosomes. No difference in development of arthritis was observed in these. The influence of the xid mutation was investigated next. The xid loci from the CBA/N mouse was bred into DBA/1 strain which is highly susceptible to CIA. The resulting congenic DBA/1-xid strain was resistant to induction of CIA and did not develop an antibody response to type II collagen. We conclude that polymorphic genes on the X chromosome modulate susceptibility to CIA. The results from the experiments with mice carrying xid mutations confirm that such immune modulating genes exist on the sex chromosomes.     

Partial mediation of strange-male-induced pregnancy blocks by sexual activity in mice (Mus musculus).

Novel male house mice (Mus musculus) can disrupt early pregnancy in females. Previous research (e.g., A. E. Storey; see record 1986-16382-001) focused on pheromonal rather than behavioral mediation of this phenomenon. In Experiment 1, novel males were housed with females shortly after insemination. Litter production was negatively correlated with the males' sexual activity. Experiment 2 replicated this finding with a larger sample. In Experiment 3, females were exposed to castrated males. Testosterone-treated males completely blocked pregnancy, whereas untreated males did not. In Experiment 4, castrated testosterone-treated males were presented at intervals after insemination. Pregnancy was totally blocked at Days 3 and 4 and mostly blocked at Days 1 and 2 but was less affected at Days 5 and 6. In Experiment 5, females were exposed through a wire-mesh grid to castrated males. Pregnancies occurred in all conditions, even with testosterone-treated males. These data suggest a role for sexual activity in male-induced pregnancy blocks. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Role of androgens in testicular tumor development in inhibin-deficient mice

To understand gonadal tumor development, we have previously created a mouse model in which mice deficient in the inhibins develop gonadal sex cord-stromal tumors with essentially 100% penetrance. These tumors develop as early as 4 weeks of age and cause cancer cachexia-like symptoms and subsequent death in the inhibin-deficient mice. Gonadectomized inhibin-deficient mice eventually develop adrenal cortical tumors with nearly 100% penetrance. These studies have identified inhibin as a novel secreted tumor suppressor protein with specificity for the gonads and adrenal glands. Sex steroids have been implicated to influence gonadal tumor development in humans and mice. To determine the role of androgens in gonadal tumorigenesis in inhibin-deficient male mice, we have used a genetic intercross strategy, breeding inhibin alpha mutant mice with tfm (testicular feminization, a naturally occurring androgen receptor mutant) carrying females to eventually generate compound mutant male mice that lack inhibins and carry the tfm mutation. These compound mutant mice, like inhibin-deficient mice, continue to develop testicular tumors and the accompanying cancer cachexia-like wasting syndrome. Consistent with these findings, elevated levels of activins A and B secreted from the gonadal tumors are seen in the adult compound mutant mice as well as the secondary pathological consequences of these high activin levels in the livers and glandular stomachs. However, in contrast to male mice lacking only inhibin, in which essentially 100% of the testicular tumors are hemorrhagic, 65% of the tumors in these compound mutant male mice are less hemorrhagic, and approximately 50% of the compound mutants live longer than 17 weeks of age (95% of the male mice lacking only inhibin die by 12 weeks). These results suggest that androgens are not required for testicular tumor development in inhibin-deficient mice, but may play a regulatory role in testicular tumor progression.     

Effects of GABAB receptor antagonism on the development of pentylenetetrazol-induced kindling in mice

In our previous studies, the yeast Endomyces fibuliger LU677 was found to degrade amygdalin in bitter apricot seeds. The present investigation shows that E. fibuliger LU677 produces extracellular beta-glycosidase activity when grown in malt extract broth (MEB). Growth was very good at 25 degrees C and 30 degrees C and slightly less at 35 degrees C. When grown in MEB of pH 5 and pH 6 with addition of 0, 10 or 100 ppm amygdalin, E. fibuliger produced only slightly more biomass at pH 5, and was only slightly inhibited in the presence of amygdalin. Approximately, 60% of the added amygdalin was degraded (fastest at 35 degrees C) during an incubation period of 5 days. Supernatants of cultures grown at 25 degrees C and pH 6 for 5 days were tested for the effects of pH and temperature on activity (using amygdalin, linamarin and prunasin as substrates). Prunase activity had two pH optima (pH 4 and pH 6), amygdalase and linamarase only one each at pH 6 and pH 4-5 respectively. The linamarase activity evolved earlier than amygdalase (2 days and 4 days respectively). The data thus indicate the presence of at least two different glycosidases having different pH optima and kinetics of excretion. In the presence of amygdalin, lower glycosidase activities were generally produced. However, the amygdalin was degraded from the start of the growth, strongly indicating an uptake of amygdalin by the cells. The temperature optimum for all activities was at 40 degrees C. Activities of amygdalase (assayed at pH 4) and linamarase (at pH 6) evolving during the growth of E. fibuliger were generally higher in cultures grown at 25 degrees C and 30 degrees C. TLC analysis of amygdalin degradation products show a two-stage sequential mechanism as follows: (1) amygdalin to prunasin and (2) prunasin to cyanohydrin.     

Conditioned morphine tolerance in the rat: Absence of a compensatory response and cross-tolerance with stress.

In 4 experiments with 193 male Holtzman rats, evidence was obtained that tolerance development to morphine analgesia occurred most rapidly when morphine delivery was paired with salient contextual cues. Contextual cues previously paired with morphine did not elicit conditioned drug-compensatory responses when presented to nondrugged Ss. These results were obtained by different analgesia assessments, with different drug-administration analgesia-test latencies, and in environments differing with respect to stress level. Stress level influenced nociceptive response, as it was found that the combination of bright illumination, white noise, and a strong odor resulted in antinociception in the absence of drug. Ss that had a history of receiving morphine in this stressful context were tolerant to this stress-induced antinociception but only when morphine was present in their systems. In the final 2 studies, this antinociception, which was cross-tolerant with morphine, was characterized with respect to naloxone reversibility and brain levels of met- and leu-enkephalin as determined by radioimmunoassay. (87 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Oxytocin inhibits the uptake of serotonin into uterine mast cells

The uptake of serotonin (5HT) into mouse uterine horns, the localization of sites at which this amine could be stored and the effect of oxytocin on 5HT uptake were studied. To analyze the characteristics of the 5HT uptake process, the tissue was incubated with [3H]serotonin. The uptake of [3H]5HT was Na+ dependent and saturable (Kmapp: 166 +/- 15 nM, Vmax: 404 +/- 25 fmol/mg tissue, 30 min (diestrous); and Km: 165 +/- 39 nM, Vmax: 276 +/- 43 fmol/mg tissue, 30 min (estrous), n = 6), and was inhibited by imipramine, fluoxetine and 6-nitroquipazine (IC50: 2; 0.09 and 0.5 nM, respectively). In the myometrium the main 5HT uptake process was localized in uterine mast cells. This was determined by treating the uterine horns with 6-hydroxydopamine, by using an immunocytochemical approach and by studying the outflow of 3H under the action of stimuli directed to either mast cells (compound 48/80: 10 microgram/ml) or sympathetic nerves (high K+: 100 mM and veratridine: 20 microM) in uterine preparations. Oxytocin inhibited [3H]5HT uptake into uterine mast cells during estrus, but not in ovarectomized mice treated with progesterone. Maximal inhibition was attained at 0.03 nM, with a significant reduction in both Kmapp and Vmax (87 +/- 15 nM and 184 +/- 36 fmol/mg tissue/30 min, n = 3, respectively). This effect was reversed by the addition of OVT16, an oxytocin antagonist, at a concentration of 4 nM (Kmapp 158 +/- 35 nM, Vmax: 278 +/- 24 fmol/mg tissue, 30 min, n = 3). These findings support a new potential role of oxytocin and mast cells as a local regulators of serotonin bioavailability in myometrium. Because serotonin is recognized as an important endogenous uterotonic compound, this effect could be considered as an indirect action of oxytocin that may contribute to its potency as a labor inducer after genomic effects of estrogens are expressed in uterine tissue.     

Gene disruption in mice: models of development and disease

Gene targeting technology in mice by homologous recombination has become an important method to generate loss-of-function of genes in a predetermined locus. Although the inactivation is limited to irreversible alteration of chromosomal DNA and a surprising variety of genes have given unexpected and disappointing results, modification of the basic technology now provides additional choices for a more specific and variety of manipulations of the mouse genome. This includes conditional cell-type specific gene targeting, knockin technique and the induction of the specific balanced chromosomal translocations. In the past decade this technique not only generated a wealth of knowledge concerning the roles of growth factors, oncogenes, hormone receptors and Hox genes but also helped to produce animal models for several human genetic disorders. In the future it may provide more powerful and necessary tools to dissect the psychiatric disorders, understanding the complex central nervous system and to correct the inherited disorders.     

Effects of cocaine on fetal and postnatal development in mice

The goal of the current investigation was to study the effect of in utero exposure of cocaine on fetal and postnatal development. 48 adult female NIH Swiss mice were used as experimental animal models. Each of the 24 mice were injected intraperitoneally with cocaine HCl at a daily dose level of 45 mg/kg (body weight). Each of the 24 control animals were daily injected with saline. One week after the treatment started, one male was introduced into each female cage. The day the vaginal plug was found was recorded as day one of pregnancy. Both cocaine treated and saline treated animals were subdivided into three subgroups each with 8 animals in each subgroup. Subgroup one was used to obtain midgestational (11 day) fetuses, subgroup two was used to obtain full term fetuses (18 day) and subgroup three was used to obtain pups. Individual fetal weights were taken and each fetus was examined for developmental anomalies. Midgestational fetuses exposed to cocaine had lower body weights than those of the controls. The full term fetuses, however, had similar weight in both experimental and control groups. The pups were weighed every 2 days from day 2 to day 16. The pups showed a slightly wider range of weights in the cocaine treated group as they matured to 16 days. All fetuses and pups revealed no soft tissue anomaly which, along with the weight data, supported our earlier findings.