Spinal interaction between the highly selective µ agonist DAMGO and several δ opioid receptor ligands in naive and morphine-tolerant mice.

Since the discovery of opioid receptor dimers their possible roles in opioid actions were intensively investigated. Here we suggest a mechanism that may involve the µ-δ opioid heterodimers. The exact role of δ opioid receptors in antinociception and in the development of opioid tolerance is still unclear. While receptor up-regulation can be observed during the development of opioid tolerance no µ receptor down-regulation could be detected within five days. In our present work we investigated how the selective δ opioid receptor agonists and antagonists influence the antinociceptive effect of the selective µ receptor agonist DAMGO in naïve and morphine-tolerant mice. We treated male NMRI mice with 200 µmol/kg subcutaneous (s.c.) morphine twice daily for three days. On the fourth day we measured the antinociceptive effect of DAMGO alone and combined with delta ligands: DPDPE, deltorphin II (agonists), TIPP and TICPψ (antagonists), respectively, administered intrathecally (i.t.) in mouse tail-flick test. In naive control mice none of the δ ligands caused significant changes in the antinociceptive action of DAMGO. The treatment with s.c. morphine resulted in approximately four-fold tolerance to i.t. DAMGO, i.e. the ED50 value of DAMGO was four times as high as in naive mice. 500 and 1000 pmol/mouse of the δ1 selective agonist DPDPE enhanced the tolerance to DAMGO while 1000 pmol/mouse of the δ2 selective agonist deltorphin II did not influence the degree of tolerance. However, both δ antagonists TIPP and TICPψ potentiated the antinociceptive effect of i.t. DAMGO, thus they restored the potency of DAMGO to the control level. The inhibitory action of DPDPE against the antinociceptive effect of DAMGO could be antagonized by TIPP and TICPψ. We hypothesize that during the development of morphine tolerance the formation of µÎ´ heterodimers may contribute to the spinal opioid tolerance. δ ligands may affect the dimer formation differently. Those, like DPDPE may facilitate the dimer formation hence inhibit the antinociceptive effect of DAMGO by causing virtual µ receptor down-regulation. Ligands that do not affect the dimer formation do not influence antinociception either but ligands with the presumed capability of disconnecting the dimers may decrease the spinal tolerance to DAMGO.

A novel µ-opioid receptor ligand with high in vitro and in vivo agonist efficacy.

The aims of this study were to synthesize 14-O-Methylmorphine-6-O-sulfate (14-O-MeM6SU) and examine its opioid properties (potency, affinity, efficacy) in receptor ligand binding and isolated tissues (mouse vas deferens, MVD and rat vas deferens, RVD bioassays). The results were then compared to the parent compounds morphine-6-O-sulfate (M6SU) and morphine, as well as the �- opioid receptor (MOR) selective agonist peptide [D-Ala2,N-Me-Phe4,Gly-ol5]enkephalin (DAMGO). An additional objective was to compare the effect of subcutaneously (s.c.) or intracerebroventricularly (i.c.v.) administered 14-O-MeM6SU, M6SU and morphine in thermal nociception, rat tail-flick (RTF) test. In MVD, the EC50 (nM) value was 4.38 for 14-O-MeM6SU, 102.81 for M6SU, 346.63 for morphine and 238.47 for DAMGO. The effect of 14-O-MeM6SU and DAMGO was antagonized by naloxone (NAL) with Ke value 1-2.00 nM. The Emax values (%) were 99.10, 36.87, 42.51 and 96.99 for 14-O-MeM6SU, M6SU, morphine and DAMGO, respectively. In RVD 14-O-MeM6SU and DAMGO but not M6SU or morphine showed agonist activity. In binding experiments the affinity of 14-OMeM6SU, M6SU, morphine and DAMGO for MOR was 1.12, 11.48, 4.37 and 3.24 nM, respectively. The selectivity of 14-O-MeM6SU was κ/µ= 269 and δ/µ= 9. In G-protein activation experiments, 14-O-MeM6SU and DAMGO showed higher Emax values than M6SU or morphine. S.c. or i.c.v-injected 14-O-MeM6SU, M6SU and morphine produced a dose and time-dependent increase in RTF response latency. 14-O-MeM6SU was the most potent. Our results showed that introduction of 14-O-Me in M6SU increased the binding affinity, agonist potency, and most importantly, the intrinsic efficacy (Emax).

Lactation performance of mothers with contrasting nutritional status in rural Kenya.

Breastmilk yields and its composition during the first 6 months of lactation were measured in 46 women with low weight-for-height during the third trimester of pregnancy (WH minus group) and in 52 mothers with good weight-for-height in the same period (WH plus group). On average WH minus mothers produced 695 g per 24 hours and WH plus mothers 790 g. In the WH minus group yield was affected by feeding frequency, season, mother's energy intake during lactation and infant's weight-for-age. In the WH plus group feeding frequence, parity and sex were the affecting variables (male infants consumed more milk). The difference in yield between WH minus and WH plus mothers corrected for feeding frequency, sex and season was significant but was only 80 g per 24 hours. Protein and lactose concentrations in milk were in both groups comparable with that of British mothers, fat concentrations were lower.

PIP: Breastmilk yields and its composition during the 1st 6 months of lactation were measured in 46 women with low weight-for-height during the 3rd trimester of pregnancy (WH minus group) and in 52 mothers with good weight-for-height in the same period (WH group). On the average, WH minus mothers produced 695 g/24 hours and WH plus mothers 790 g. In the Wh minus group, yield was affected by feeding frequency, season, mother's energy intake during lactation, and infant's weight-for-age. In the WH plus group, feeding frequency, parity, and sex were the variables affecting outcome (male infants consumed more milk). The difference in yield between WH minus and WH plus mothers corrected for feeding frequency, sex, and season was significant but was only 80 g/24 hours. Protein and lactose concentrations in milk were in both groups comparable with that of British mothers, and fat concentrations were lower.

Serum cholesterol changes during pregnancy and puerperium in African and Asian women.

PIP: This study investigated the levels of serum total cholesterol among urban African and Asian vegetarian and Asian nonvegetarian women ranging in age from 18 to 35. All were before 26 weeks of gestation. A group of nonpregnant, nonlactating women of the same ethnic origins was included as control. Venous blood samples were collected at 26 weeks and 37 weeks of gestation and within 24 hours after delivery. Levels in cord blood samples were also analysed. All blood samples collected were nonfasting. African women when compared with Asian nonvegetarians were found to have a significantly lower serum cholesterol level (p.02). No difference was observed between African and Asian vegetarians. Asian vegetarians had a lower level than Asian nonvegetarians (p.05). No statistical differences were observed among the 3 groups at 26 weeks of gestation. All 3 groups showed a progressive increase in serum total cholesterol levels as pregnancy advanced. From 26 to 37 weeks of gestation an increase was found of 18%, 4% and 6% for the Asian nonvegetarian, Asian vegetarian and African women, respectively. On average, a drop in cholesterol levels was observed within 24 hours after delivery: 11% decrease for Asian nonvegetarians, 9% for Asian vegetarians, and 3% for Africans. No statistical differences were found in the serum total cholesterol levels measured in the cord blood samples of the 3 groups. Lower levels of cholesterol among vegetarians may be due to higher intake of leafy vegetables and cereals.^ieng

Identification of human CML target. HLA-B locus (B12) antigen variants defined by CTL generated between B locus-identical (B12) responder-stimulator pairs.

The genetics of human CML targets were studied by seven CTL generated in combinations iun which the responder/stimulator difference was limited to one (or two) HLA-A, -B, or -C antigens. Unstimulated peripheral blood lymphocytes were used as targets. CTL sensitized against antigens A11, Aw31, or B17 lysed all cells bearing the respective target from a large panel of cells from unrelated individuals. Hence, at least one CTL clone was directed against the HLA antigen molecule. However, all CTL also exerted cross-kill to cells not sharing the stimulating HLA antigen. For two CTL, the target of the cross-kill was not clarified. Five CTL were found where the cross-kill was directed against antigen HLA-B12 (Bw44 and Bw45). All these cTL were generated in R/S pairs identical for B locus antigens (Bw44/Bw35 heterozygotes). The individual CTL lysed different parts of the panel of B12-positive target cells. The interpretation is that these CTL detect subtypes of HLA antigens, but alternative possibilities are also considered. Four B12 subtypes are described, tentatively designated as B12-related CML targets. Identification of HLA-B-related CML targets represent CML "typing" of HLA-antigen differences that were not detected serologically. The subtypes can now be tested for their possible functional significance.