Influence of Sodium Humate on the Growth Performance, Diarrhea Incidence, Blood Parameters, and Fecal Microflora of Pre-Weaned Dairy Calves

This study aimed to evaluate the effects of the administration of sodium humate (NaH) on the growth performance, diarrhea incidence, and fecal microflora of pre-weaned Holstein calves. In a 53-day experiment, forty healthy newborn female calves were randomly allocated to the following four treatment groups: (1) control (basal diet); (2) 1-gram NaH (basal diet extra orally supplemented with 1 g of NaH dissolved in 100 mL of milk or milk replacer daily); (3) 3-gram NaH (basal diet extra orally supplemented with 3 g of NaH dissolved in 100 mL of milk or milk replacer daily); and (4) 5-gram NaH (basal diet extra orally supplemented with 5 g of NaH dissolved in 100 mL of milk or milk replacer daily). NaH was mixed with milk (d 2–20) or milk replacer (d 21–53). Calves in the 5-gram NaH group had a higher ADG during d 1 to 21 and d 21 to 53 than the other groups did (p < 0.05). Fecal scores and diarrheal incidence were significantly lower in the 3-gram and 5-gram NaH groups than the 1-gram NaH and control groups during d 1 to 20 (p < 0.05). The serum IgA, IgG and IL-4 concentrations, and T-SOD and T-AOC activities were higher, and the serum IL-6, TNF-α, D-lactic acid, and MDA concentrations were lower in the 5-gram NaH group than the control group (p < 0.05). Furthermore, NaH supplementation increased the abundances of Bifidobacterium and Lactobacillus but decreased the abundance of Escherichia coli in feces (p < 0.05). These encouraging findings indicated that supplementation with 5 g of NaH effectively improved the immune status, antioxidant capacity, and intestinal beneficial bacteria, and further improved the growth performance and reduced the diarrhea incidence of the pre-weaned dairy calves.

Combined supplementation of sodium humate and glutamine reduced diarrhea incidence of weaned calves by intestinal microbiota and metabolites changes

This study was conducted to investigate the effects of combined supplementation of sodium humate (HNa) and glutamine (Gln) on growth performance, diarrhea incidence, serum parameters, intestinal microbiome, and metabolites of weaned calves. In Exp. 1, 40 calves were randomly assigned to four treatments: 1) NC (negative control, basal diet), 2) 1% H+1% G (basal diet extra orally gavaged with 1 g of HNa and 1 g of Gln daily), 3) 3% H+1% G (basal diet extra orally gavaged with 3 g of HNa and 1 g of Gln daily), and 4) 5% H+1% G (basal diet extra orally gavaged with 5 g of HNa and 1 g of Gln daily). The HNa and Gln were together mixed with 100 mL of milk replacer (51 to 58 d of age) or water (59 to 72 d of age) and orally administrated to each calf from a bottle before morning feeding. In a 21-d trial, calves on the 5% HNa+1% Gln group had higher (P < 0.05) average daily gain (ADG) and lower (P < 0.05) diarrhea incidence than those in the control group. In Exp. 2, 20 calves were randomly assigned to two treatments fed with a basal diet and a basal diet supplemented with 100 mL of 5% HNa+1% Gln. In a 21-d trial, calves supplemented with HNa and Gln had higher (P < 0.05) ADG, IgG concentration and glutathione peroxidase (GSH-Px), and total antioxidant capacity (T-AOC) activities in the serum, but lower (P < 0.05) diarrhea incidence, as well as serum diamine oxidase (DAO), D-isomer of lactic acid (D-lac), tumor necrosis factor-α (TNF-α), and malondialdehyde (MDA) concentrations compared with control group. Results of intestinal microbiota indicated that supplementation with HNa and Gln significantly increased (P < 0.05) the abundance of intestinal beneficial microbiota. Moreover, supplementation with HNa and Gln altered 18 metabolites and enriched 6 Kyoto Encyclopedia of Genes and Genomes pathways in weaned calves. In conclusion, combined supplementation with HNa and Gln could decrease diarrhea incidence of weaned calves via altering intestinal microbial ecology and metabolism profile.

Effects of sodium humate and glutamine combined supplementation on growth performance, diarrhea incidence, blood parameters, and intestinal microflora of weaned calves

This experiment was conducted to investigate the effects of sodium humate (HNa) and glutamine (Gln) alone or combined supplementation on growth performance, diarrhea incidence, blood parameters, and intestinal microflora of weaned Holstein calves. In a 14-day experiment, 40 calves at 51 ± 3 days of age were randomly allocated to four treatment groups: (1) NC (basal diet), (2) NC + 5% HNa, (3) NC + 1% Gln, and (4) NC + 5% HNa + 1% Gln. Calves combined supplementation with HNa and Gln had a higher (P < .05) ADG, serum concentration of glucose (GLU), IgA, and IgG but lower fecal scores, diarrhea incidence, serum concentration of TNF-α, and IL-10 compared with NC group (P < .05). Compared with NC group, HNa + Gln group showed higher (P < .05) serum GSH and T-AOC activities but lower (P < .05) concentration of MDA and D-lac. Furthermore, the abundances of Prevotella ruminicola, Bifidobacterium, and Lactobacillus in rectal digesta were increased (P < .05), but the Escherichia coli was significantly decreased. In conclusion, combined supplementation with HNa and Gln can effectively improve the immune status, antioxidant capacity, and intestinal microflora of the weaned calves while reducing diarrhea incidence.

Effects of cellular prion protein on rapid eye movement sleep deprivation-induced spatial memory impairment

The effects of cellular prion protein on rapid eye movement sleep deprivation-induced spatial memory impairment were investigated, and the related mechanisms explored. Male C57BL/6 mice were randomly divided into four groups: environment control, sleep deprivation control, sleep-deprived-plasmid adeno-associated virus-green fluorescent protein group, and sleep-deprived-plasmid adeno-associated virus-cellular prion protein-green fluorescent protein group. Overexpression of cellular prion protein was induced by stereotaxic injection of adeno-associated viral plasmids-CAG-enhanced green fluorescent protein-cellular prion protein-Flag (a small label, which can be detected with corresponding tagged antibodies) into the hippocampus. Sleep-deprived mice were allowed no rapid eye movement sleep for 72 hours. Morris water maze was used to assess the effects of cellular prion protein on spatial learning and memory. The expression of amyloid-β was also investigated in all groups. The sleep-deprived- plasmid adeno-associated virus- cellular prion protein-green fluorescent protein group spent significantly more time in a goal quadrant compared with the sleep-deprived- plasmid adeno-associated virus-green fluorescent protein group. Sleep deprivation resulted in increased amyloid-β in the hippocampus, which was reversed by the overexpression of hippocampus cellular prion protein. Overexpression of cellular prion protein in the hippocampus rescues rapid eye movement sleep deprivation-induced spatial memory impairment in mice. It is shown that amyloid-β in the hippocampus might be one of the mechanisms.

Association between neuropeptide oxytocin and male infertility

PURPOSE

To investigate the relationship between oxytocin (OT) and male infertility, serum OT baseline concentration and oxytocin receptor (OTR) gene expression in fertile and infertile men were investigated.

METHODS AND PATIENTS

Twenty obstructive azoospermia patients, twenty five idiopathic asthenozoospermia patients, twenty idiopathic oligozoospermia patients and twenty healthy subjects were taken into consideration. Serum OT baseline concentration was determined by radioimmunoassay. Moreover, serum concentration of luteinizing hormone (LH), follicle-stimulating hormone (FSH) and testosterone (T) were determined by chemoluminescence to evaluate the correlation with OT. OTR gene promotor and OTR mRNA expressions were determined by polymerase chain reaction and reverse transcriptase-polymerase chain reaction, respectively. OTR protein expression was also performed by Western Blot.

RESULTS

Serum OT baseline concentrations in infertile groups were significantly higher than in fertile group (F0.05/2(2,82) = 8.29, p < 0.001). Serum baseline concentration of OT was not correlated with that of LH, FSH and T. There was no significant difference in gene sequences of OTR gene promotor and OTR mRNA when comparing infertile patients with fertile. Human OTR was in the form of oligomers and monomers, and the oligomers were in the majority containing tetramers and hexamers. Monomer expression was significantly higher in idiopathic asthenozoospermia and idiopathic oligozoospermia than that in obstructive azoospermia and control group (F0.05/2(2,82) = 115.50, p < 0.001). There was no significant difference in oligomer expression between different groups, but 20% of idiopathic asthenozoospermia cases showed a decrease.

CONCLUSIONS

Significantly different OT baseline concentrations and OTR expressions between fertile and infertile men strongly suggest that OT/OTR system is likely to be linked with male infertility, providing new insights into the pathogenesis and treatment of male infertility.

G protein-coupled inwardly rectifying potassium channels in dorsal root ganglion neurons

AIM

G protein-coupled inwardly rectifying potassium channels (GIRK) are important for neuronal signaling and membrane excitability. In the present study, we intend to find whether GIRK channels express functionally in adult rat dorsal root ganglion (DRG) neurons.

METHODS

We used RT-PCR to detect mRNA for 4 subunits of GIRK in the adult DRG. The whole-cell patch clamp recording was used to confirm GIRK channels functionally expressed.

RESULTS

The mRNA for the 4 subunits of GIRK were detected in the adult DRG. GTPgammaS enhanced inwardly rectifying potassium (K+) currents of the DRG neurons, while Ba2+ inhibited such currents. Furthermore, the GIRK channels were shown to be coupled to the GABA(B) receptor, a member of the G protein-coupled receptor family, as baclofen increased the inwardly rectifying K+ currents.

CONCLUSION

GIRK channels are expressed and functionally coupled with GABA(B) receptors in adult rat DRG neurons.

Detection of constitutive heterodimerization of the integrin Mac-1 subunits by fluorescence resonance energy transfer in living cells

Macrophage differentiation antigen associated with complement three receptor function (Mac-1) belongs to beta2 subfamily of integrins that mediate important cell-cell and cell-extracellular matrix interactions. Biochemical studies have indicated that Mac-1 is a constitutive heterodimer in vitro. Here, we detected the heterodimerization of Mac-1 subunits in living cells by means of two fluorescence resonance energy transfer (FRET) techniques (fluorescence microscopy and fluorescence spectroscopy) and our results demonstrated that there is constitutive heterodimerization of the Mac-1 subunits and this constitutive heterodimerization of the Mac-1 subunits is cell-type independent. Through FRET imaging, we found that heterodimers of Mac-1 mainly localized in plasma membrane, perinuclear, and Golgi area in living cells. Furthermore, through analysis of the estimated physical distances between cyan fluorescent protein (CFP) and yellow fluorescent protein (YFP) fused to Mac-1 subunits, we suggested that the conformation of Mac-1 subunits is not affected by the fusion of CFP or YFP and inferred that Mac-1 subunits take different conformation when expressed in Chinese hamster ovary (CHO) and human embryonic kidney (HEK) 293T cells, respectively.

Involvement of dynorphin A in the inhibition of morphine physical dependence by N-nitro-L-arginine in rats

OBJECTIVE

To investigate the involvement of immunoreactive-dynorphin A in the inhibitory effect of N-nitro-L-arginine on the morphine physical dependence in rats.

METHODS

The rats were rendered dependent on morphine by subcutaneous administration of morphine solution three times daily in a manner of dose increment of 5 mg.kg(-1) for 6 days. The degree of morphine physical dependence was monitored by scoring the abstinence syndromes precipitated by 5 mg.kg(-1) naloxone of the rats. The expression levels of immunoreactive dynorphin A in tissues were determined using a radioimmunoassay.

RESULTS

Intraperitoneal injection of 5 mg.kg(-1) N-nitro-L-arginine suppresses most of the withdrawal symptoms of morphine dependent rats. N-nitro-L-arginine can elevate the expression of immunoreactive dynorphin.

CONCLUSIONS

Chronic N-nitro-L-arginine administration can inhibit the development of morphine physical dependence in a manner of dose-dependence, which is significantly related to its role of regulating the endogeneous dynorphin system.

[The expression of ciliary neurotrophic factor in facial nucleus after long-term facial denervation]

OBJECTIVE

To explore the expression and distribution of Ciliary neurotrophic factor (CNTF) mRNA and its protein in the facial motoneuron in order to clarify its functional state after long-term facial denervation.

METHOD

The facial nerves on the right sides were cut in dogs. Brain stems were removed and sectioned, and sections were separately used for histochemistry, immunohistochemistry and in situ hybridization of CNTF. The facial motoneurons were identified by Nissl staining. The count and intense of positive reactive motoneurons were measured by computer image processing system.

RESULT

Transection of the facial nerve led to a very marked reduce in the count and intense of CNTF mRNA positive reactive motoneurons, and reached the minimal levels at week 3. CNTF immunoreactivity increased rapidly and reached the maximal levels at also week 3. At week 4, a significant increase in CNTF mRNA expression and decrease in CNTF immunoreactivity were observed. At week 6, both CNTF mRNA and its protein expression were significantly less than those of unlesioned contralateral sides. Although a little difference between at week 12 and at 32 was observed, the motoneurons were generally stable in the expression level of CNTF mRNA and its protein, and in the size and count after 12 weeks, with 78%, 84.4%, 80.9% and 83.7% respectively as compared with the unlesioned contralateral facial motoneurons.

CONCLUSION

The results indicated that although degenerating changes occurred in the facial motoneurons after long-term facial denervation, the ciliary neurotrophic factors activity of the lesioned motoneurons was still maintained at a certain level.

[Effect of Salvia miltiorrhiza on neuropeptide Y1-36 and calcitonin gene-related peptide in neonatal rats with hypoxia-ischemic brain injury]

OBJECTIVE

To observe the effects of Salvia miltiorrhiza (SM) on levels of neuropeptide Y1-36 and calcitonin gene-related peptide immune reactive substances (ir-NPY, ir-CGRP) in blood plasma and pons-oblongata after hypoxia-ischemic brain injury (HIBI) in neonatal rats.

METHODS

Seven-day old rats were randomized into HIBI group (A), HIBI + SM group (B) and sham operation group(C). And each group was subdivided into 4 subgroups according to the different time after operation. 0.5 ml SM was injected intraperitoneally immediately and every 12 hrs afterwards. Changes of ir-NPY and ir-CGRP levels in plasma and pons-oblongata were observed immediately and 12, 24 and 48 hrs after HIBI by radioimmunoassay.

RESULTS

Plasma levels of ir-NPY and ir-CGRP in different times after HIBI were all significantly raised but those in pons-oblongata were either raised or lowered to a certain degree. Part of the elevated ir-NPY could be reversed by SM injection.

CONCLUSION

Central and peripheral neuropeptide Y1-36 and calcitonin gene-related peptide take part in the pathophysiological process of HIBI, SM could partially reverse the abnormal post-HIBI elevation of ir-NPY, which may be one of the pathways of SM in promoting recovery of damaged brain function.

Oxytocin mediates the inhibitory action of acute lithium on the morphine dependence in rats

The role of central oxytocin in inhibitory action of lithium on the development of morphine dependence was behavioral investigated in rats. Acute lithium could enhance the morphine-induced analgesia in rats with or without chronic morphine treatment; this effect could be inhibited by intraventricular injection of oxytocin antagonist d (CH(2))(5)-Tyr (Me)-[Orn(8)]-Vasotocin (OVT). Lithium could attenuate naloxone-precipitated withdrawal signs in morphine dependent rats. The reduction of the expression of naloxone-precipitated withdrawal signs by lithium was reversed by ICV of OVT. The lithium significantly inhibited the conditioned place preference (CPP) induced by morphine, which inhibitory action of lithium could also reverse by ICV injection of OVT. These results suggested that lithium might inhibit the physical dependence on morphine as well as psychological dependence in rats, and that this inhibitory effect of lithium on the development of morphine dependence might be associated with oxytocin systems in the central nervous system.

The expression of G-protein-gated inwardly rectifying K+ channels GIRK1 and GIRK2 mRNAs in the supraoptic nucleus of the rat and possible role involved

The expression of G-protein-gated inwardly rectifying K channels subunits GIRK1 and GIRK2 mRNAs in the supraoptic nucleus (SON) was investigated in the rat by in situ hybridization with non-radioactive dig-labeled cRNA probes. Double-labeled methods were used to study the co-localization of GIRK1 and 2 and oxytocin (OT) and vasopressin (AVP) in the SON. The present study revealed wide and intense expression of GIRK1 and GIRK2 mRNAs with high overlapping in the SON, indicating the heterologous channel of GIRK1/GIRK2 was a major functional channel in the SON. Given that 100% of OT-positive and 95% of (AVP)-positive neurons in the SON expressed GIRK1/GIRK2 mRNAs, it is possible that GIRK1/GIRK2 channel, activated through G-protein coupled receptors, may be involved in the inhibitory regulation of the release of OT and AVP from the SON.

Chronic morphine treatment inhibits oxytocin synthesis in rats

The changes of oxytocin content and mRNA expression in some nuclei were investigated in morphine-dependent rats using radioimmunoassay (RIA) and in situ hybridization (ISH). After chronic administration of morphine, the oxytocin content in supraoptic nucleus (SON) and nucleus accumbens (NAc) decreased, and increased in the ventral tegment area (VTA) and locus coeruleus (LC), but did not change in other nuclei including the paraventricular nucleus (PVN), lateral septum (SEPTUM), raphe magnus nucleus (NRM) and periaquaductal gray (PAG). In morphine-L dependent rats, naloxone increased the levels of oxytocin in SON and PVN, but decreased that in LC. ISH first showed that chronic morphine treatment inhibited the oxytocin synthesis in SON but not in PVN. The present study demonstrates that chronic morphine treatment alters the brain oxytocin system, suggesting that oxytocin might contribute to the behavioral and neuroendocrine responses to morphine.

Distinct domains of IFNalpha mediate immune and analgesic effects respectively

Interferon-alpha (IFNalpha) is not only an immunoregulatory factor, but is also an analgesic molecule. The analgesic effect of IFNalpha was mediated by mu opioid receptor. After the 129th Tyr residue of human IFNalpha was mutated to Ser, the antiviral activity almost disappeared, but there still remained a strong analgesic activity that could be blocked by naloxone. These results indicate that there exist distinct domains in the IFNalpha molecule, which mediate immune and analgesic effects respectively, and suggest that there are different receptor mechanisms inducing immune and analgesic effects of IFNalpha. However, although the antiviral activity of IFNalpha decreased to 34.1% of wild type IFNalpha after the 122nd Tyr residue was changed to Ser, the analgesic activity of this mutant was lost completely. There were significant cross reactivities between INFalpha and anti-opioid sera. These studies show strong structural and functional similarities between INFalpha and opioid peptides, and inferred that the analgesic domain locates around the 122nd Tyr residue of IFNalpha molecule in tertiary structure.

[Distinct structural bases of the immunoregulatory and central analgesic effects of IFNalpha]

Interferon-alpha (IFNalpha), a cytokine, is also an analgesic molecule. There is significant cross reactivity between IFNalpha and anti-opioid sera, suggesting a strong antigenic relatedness between human IFNalpha molecules and opioid peptides. Different structural basis of the immunoactivity and analgesic effect of IFNalpha can be demonstrated by different reactivities of the two reactions towards different mutants of IFNalpha obtained by using the site-directed mutagenesis. When the 129th Tyr residue of human IFNalpha was mutated to Ser, the immunoactivity of the mutant almost disappeared, while the strong analgesic activity still persisted, which could be blocked by naloxone. These results indicate that there exist distinct domains in the IFNalpha molecule, which mediate immune and analgesic effects differentially, and that the receptor mechanism underlying immune and analgesic effects of IFNalpha may be different.

Leu-enkephalin induced by IL-2 administration mediates analgesic effect of IL-2

Interleukin-2 (IL-2) was found to have an analgesic effect in both central and peripheral nervous systems. This effect is related to opioid receptors and mediated mainly by IL-2 directly binding to opioid receptors. Using radioimmunoassay, the content of Leu-enkephalin (LEK) in some nuclei were measured at intervals after the injection of IL-2 into the lateral ventricle of rats. Levels of LEK increased in both paraventricular hypothalamic nucleus (PVN) and locus ceruleus (LOC) after IL-2 administration, suggesting that the analgesic effect of IL-2 is also related to the change of LEK in PVN and LOC induced by IL-2 administration.

Analgesic effect of interferon-alpha via mu opioid receptor in the rat

Using the tail-flick induced by electro-stimulation as a pain marker, it was found that pain threshold (PT) was significantly increased after injecting interferon-alpha (IFN alpha) into the lateral ventricle of rats. This effect was dosage-dependent and abolished by monoclonal antibody (McAb) to IFN alpha. Naloxone could inhibit the analgesic effect of IFN alpha, suggesting that the analgesic effect of IFN alpha be related to the opioid receptors. Beta-funaltrexamine (beta-FNA), the mu specific receptor antagonist could completely block the analgesic effect of IFN alpha. The selective delta-opioid receptor antagonist, ICI174,864 and the kappa-opioid receptor antagonist, nor-BNI both failed to prevent the analgesic effect of IFN alpha. IFN alpha could significantly inhibit the production of the cAMP stimulated by forskolin in SK-N-SH cells expressing the mu-opioid receptor, not in NG108-15 cells expressing the delta-opioid receptor uniformly. The results obtained provide further evidence for opioid activity of IFN alpha and suggest that this effect is mediated by central opioid receptors of the mu subtype. The evidence is consistent with the hypothesis that multiple actions of cytokines, such as immunoregulatory and neuroregulatory effects, might be mediated by distinct domains of cytokines interacting with different receptors.

Interleukin-2: structural and biological relatedness to opioid peptides

Interleukin (IL)-2 is not only an immunoregulatory factor, but also an analgesic molecule. There are distinct domains of immune and analgesic functions in the IL-2 molecule. The analgesic domain is located around the 45th Tyr residue of human IL-2 in tertiary structure. Antiopioid (beta-endorphin, Leu-enkephalin, Met-enkephalin and dynorphin A1-13) sera partially neutralized the analgesic activity of IL-2. Monoclonal antibody against the IL-2 receptor alpha subunit (Tac) could not block the analgesic activity of IL-2. There existed cross-reactivity between IL-2 and antiopioid sera by indirect ELISA. These studies show strong structural and biological similarities between IL-2 and opioid peptides. The tertiary structure around the 45th residue of IL-2 composes the analgesic domain that is similar to that of endogenous opioids. These results are consistent with the hypothesis that multiple domains of cytokines serve as the structural bases for the immunoregulatory and neuroregulatory effects of cytokines.

Levels of immunoreactive dynorphin A1-13 during development of morphine dependence in rats

AIM

To study the relationship between the levels of immunoreactive dynorphin A1-13 (ir-dynorphin A1-13) and the degree of morphine dependence.

METHODS

The levels of ir-dynorphin A1-13 in discrete brain regions, spinal cord, and plasma in rats were determined by radioimmunoassay, and the degree of morphine dependence was assessed by scoring withdrawal signs on d 3, d 6, and d 12.

RESULTS

Morphine injection s.c. decreased the levels of ir-dynorphin A1-13 in spinal cord, pituitary, and plasma. The levels of ir-dynorphin A1-13 in hippocampus and hypothalamus were increased. No changes in cortex, midbrain, cerebellum, pons, and medulla were observed. With continuous injection of morphine, withdrawal signs scores were increased on d 6, but there was no difference between the scores of d 6 and d 12.

CONCLUSION

The changes of the levels of endogenous ir-dynorphin A1-13 in pituitary, spinal cord, and plasma were compatible with the degree of morphine dependence.

[Possible mechanism of the analgesic effect of interleukin-2 in central nervous system]

The monoclonal antibody against IL-2R (Tac) could not block the analgesic effect of IL-2, and IL-2 mutant that could not bind to beta subunit of IL-2 receptor still had capability of increasing the pain threshold of rats. All these facts suggest that the analgesic effect of IL-2 in CNS is not mediated through the IL-2 receptor, and that the immune and analgesic effects of IL-2 are mediated through different receptor mechanisms. It is suggested that there are common antigenic determinants and similar structure between IL-2 and endogenous opioid peptides (EOP). This implies that the analgesic effect of IL-2 might be mediated by interaction between IL-2 and opioid receptors in CNS. Using radioimmunoassay the contents of EOP of different nuclei were measured at different times after injecting IL-2 into the lateral ventricle of rats. The results suggested that the analgesic effect of IL-2 may be related to beta-EP and LEK in arcuate hypothalamic nucleus, paraventricular hypothalamic nucleus and locus ceruleus.

[Role of locus coeruleus in analgesia caused by stimulation of supraoptic nucleus]

The effects of stimulation of supraoptic nucleus (SON) on the changes of oxytocin (OT), arginine vasopressin (AVP), norepinephrine (NE) and serotonin (5-HT) in the perfusate of locus coeruleus (LC) and changes of pain threshild (PT) were studied by methods of microinjection, radioimmunoassay (RIA) and high pressure liquid chromatography (HPLC) technique. The results showed that the OT contents at 30, 60 and 90 min after stimulation, that of AVP at 30 min and 5-HT at 60 min were increased significantly, while the NE contents at 30 and 60 min were decreased markedly. Injection of V1 antagonist into LC did not affect the analgesic effect caused by administration of L-glutamic acid (L-Glu) into SON, which, however, could be partially inhibited by V2 antagonist or even reversed by OT antagonist. The above results suggested that the analgesic effect due to stimulation of SON is caused by increase of 5-HT and decreases of NE in the LC though the action of OT released by SON on OT and V2 receptor in LC.

Antinociceptive effect of intracerebroventricular injection of a tetrapeptide Asn-Ala-Gly-Ala in rats

The antinociceptive effect of intracerebroventricular injection (icv) of Asn-Ala-Gly-Ala (NAGA), a partial sequence of beta-lipotropin, was studied in rats. The potassium iontophoresis-induced tail flick was used to measure the pain threshold. The antinociceptive effect of NAGA, which was dose-dependent (icv, 0.03-0.24 mumol/rat) and long-lasting (90 min), was reversed by naloxone (icv, 0.26 mg.kg-1) and inhibited by anti-MEK serum (titre: 1:5000, 5 microliters) or anti-LEK serum (titre: 1:5000, 5 microliters). NAGA-induced antinociception was scarcely affected by anti-beta-EP serum (titre: 1:30,000, 5 microliters) or anti-Dyn A1-13 serum (titre: 1:30,000, 5 microliters). It was suggested that the antinociceptive effect of NAGA may be associated with the release of met-enkephalin and leu-enkephalin in rat brain.