Biomedical subjects

J M Zajac

Publications and source records attributed to J M Zajac.

At least 37 records · Page 2Linked to original sources

PubMed1999

Nociceptin receptors in the rat spinal cord during morphine tolerance.

The anatomical localization of nociceptin receptors was examined by in vitro quantitative autoradiography techniques in rat spinal cord sections by using [(125)I-Tyr(14)]nociceptin. [(125)I-Tyr(14)]nociceptin appeared to interact with a single class of binding sites (K(D)=0.1 nM) present in the grey matter in all laminae of the spinal cord from cervical to sacral levels. Pre-incubation of sections in the presence of 150 mM NaCl, did not modify the radioligand affinity but significantly augmented the number of accessible binding sites and increased specific binding of [(125)I-Tyr(14)]nociceptin differentially on each laminae. In particular, the superficial layers of the dorsal horn exhibited the highest density of sites after pre-wash. Continuous intrathecal infusion of morphine produced a tolerance accompanied by a significant increase in nociceptin site density in the superficial layers. Thus, nociceptin binding sites may have different properties dependent upon the layer and may be up-regulated during the process of opioid-induced tolerance.

Amino Acid Sequence↗

PubMed1999

The neuropeptide FF analogue, 1DME, enhances in vivo met-enkephalin release from the rat spinal cord.

Behavioural studies have suggested that endogenous opioids mediate the antinociceptive action of neuropeptide FF (FLFQPQRF-NH2) at the spinal level in the rat. This hypothesis was directly assessed by investigating the effects of a NPFF analogue, 1DMe ([D-Tyr1,(NMe)Phe3]NPFF), on the spinal outflow of met-enkephalin-like material (MELM) in halothane-anaesthetised rats. Intrathecal infusion (0.1 ml/min) of 1DMe (0.1 microM-0.1 mM, for 45 min) produced a concentration-dependent increase in spinal MELM outflow which persisted for at least 90 min at the highest concentration tested. Intrathecal coadministration of the micro-opioid receptor antagonist CTOP (1 microM) did not significantly affect the spinal MELM overflow due to 0.1 mM 1DMe. In contrast, both naltrindole and nor-binaltorphimine, at concentrations (10 microM) that allow the selective blockade of alpha- and kappa-opioid receptors, respectively, significantly reduced the stimulatory effect of 1DMe on spinal MELM outflow. These data provide the first direct demonstration that met-enkephalin (among other opioid peptides) can mediate the antinociceptive action of NPFF at the spinal level in rats. In addition, they suggest that reciprocal excitatory interactions between opioids and opioid-modulatory factors (such as NPFF) participate in the physiological control of nociception.

Analgesics↗

PubMed1999

Enzymatic degradation of neuropeptide FF and SQA-neuropeptide FF in the mouse brain.

Degradation of neuropeptide FF (NPFF) and SQA-neuropeptide FF (SQA-NPFF) by mouse brain sections was investigated by using capillary electrophoresis with UV detection for the separation and the identification of the degradation products. The half disappearance time of SQA-NPFF was 2-fold greater than that of NPFF. NPFF was cleaved preferentially into an inactive metabolite, Gln-Arg-Phe-NH2, in the cerebrum slices. SQA-NPFF was hydrolyzed by an unidentified degrading activity to generate NPFF, and NPFF accounted for a larger part of SQA-NPFF degradation in the hindbrain and cervical spinal cord than in the cerebrum slices. These findings suggest that, depending on the brain regions, NPFF produced from SQA-NPFF could prolong the biologic effects of SQA-NPFF.

Animals↗

PubMed1999

Spinal effect of a neuropeptide FF analogue on hyperalgesia and morphine-induced analgesia in mononeuropathic and diabetic rats.

1DMe, a neuropeptide FF (NPFF) analogue, has been shown to produce antinociception and to enhance morphine analgesia in rats after intrathecal administration. To determine whether 1DMe could correct hyperalgesia and restore morphine efficacy in mononeuropathic (MN) and diabetic (D) rats we examined the spinal effect of 1DMe in MN and D rats without and after spinal blockade of mu- and delta-opioid receptors with CTOP and naltrindole, respectively. The influence of 1DMe on morphine-induced antinociception was assessed in the two models using isobolographic analysis. Whereas 1DMe intrathecally injected (0.1, 1, 7.5 microg rat(-1)) was ineffective in normal (N) rats, it suppressed mechanical hyperalgesia (decrease in paw pressure-induced vocalisation thresholds) in both MN and D rats. This effect was completely cancelled by CTOP (10 microg rat(-1)) and naltrindole (1 microg rat(-1)) suggesting that it requires the simultaneous availability of mu- and delta-opioid receptors. The combinations of morphine: 1DMe (80.6:19.4% and 99.8:0.2%, in MN and D rats, respectively) followed by isobolographic analysis, showed a superadditive interaction, relative to the antinociceptive effect of single doses, in D rats only. In N rats, the combination of morphine: 1DMe (0.5 mg kg(-1), i.v.: 1 microg rat(-1), i.t., ineffective doses) resulted in a weak short-lasting antinociceptive effect. These results show a different efficacy of 1DMe according to the pain model used, suggesting that the pro-opioid effects of the NPFF in neuropathic pain are only weak, which should contribute to hyperalgesia and to the impaired efficacy of morphine.

Analgesia↗

PubMed1999

A radioiodinated 7alpha-O-iodoallyl diprenorphine for mapping opioid receptors.

The aim of the current research has been to validate an original radioiodinated diprenorphine (DPN) derivative suitable for imaging studies of opioid receptors. [(125)I]7alpha-O-iodoallyl diprenorphine (7alpha-O-IA-DPN) was prepared by radioiododestannylation and in vitro and in vivo opioid receptor binding assays were performed with CDF1 mouse brains. In vitro binding studies showed high affinity (K(i)= 0.4 +/- 0.2 nM) for mouse brain membranes. In vivo studies showed 63% specific binding. Ex vivo autoradiography of brain sections confirmed high uptake and retention of [(125)I]7alpha-O-IA-DPN in regions rich in opioid receptors. This new radioiodinated DPN analogue appears to be a potential radioprobe for in vivo visualization of human cerebral opioid receptors with single photon emission computed tomography (SPECT).

Animals↗

PubMed1998

Anti-opioid efficacy of neuropeptide FF in morphine-tolerant mice.

The modulatory effects of 1DMe (d-Tyr-Leu-(NMe)Phe-Gln-Pro-Gln-Arg-Phe-NH2), an agonist of Neuropeptide FF (NPFF) receptors, on opioid antinociceptive activity have been compared in naive and tolerant mice in the tail-flick and the hot-plate tests. In naive mice, 1DMe alone had no effect on pain threshold but decreased dose-dependently (3-22 nmol) the analgesic activity of morphine in both tests. In tolerant mice, injections of 60-fold lower doses of 1DMe (0.05-0.5 nmol) reverse morphine-induced analgesia in the tail-flick test but this anti-opioid effect was no longer observed with the highest doses of 1DMe tested (3-22 nmol). In the hot-plate test, the anti-opioid action of 1DMe was not detected, whatever doses tested. Neither the NPFF-like immunoreactivity content of spinal cord and of olfactory bulbs, nor the density of NPFF receptors in olfactory bulbs, were altered. These results indicate that a chronic morphine treatment modifies the pharmacological properties of NPFF but the type of pain test is crucial in determining NPFF effects.

Animals↗

PubMed1998

Antisense oligonucleotides to human SQA-neuropeptide FF decrease morphine tolerance and dependence in mice.

Neuropeptide FF (Phe-Leu-Phe-Gln-Pro-Gln-Arg-Phe-NH2) is able to modulate opioid analgesia. Intracerebroventricular treatment for 5 days with antisense-oligodeoxynucleotides complementary to the sequence of human SQA-neuropeptide FF (Ser-Gln-Ala-Phe-Leu-Phe-Gln-Pro-Gln-Arg-Phe-NH2) precursor gene or by mismatch-oligodeoxynucleotides did not change the antinociceptive activity of morphine in the mouse tail flick test. In contrast, antisense- but not mismatch-oligodeoxynucleotides attenuated significantly the tolerance to the analgesic activity of morphine and the withdrawal syndrome precipitated by naloxone in morphine-treated mice. These treatments with oligodeoxynucleotides did not modify neuropeptide FF-immunoreactivity content in whole brain but repeated injections of an agonist of neuropeptide FF receptors increased the intensity of morphine tolerance. These results demonstrate the important role of neuropeptide FF in opioid pharmacodependence.

Amino Acid Sequence↗

PubMed1998

Biochemical, cellular and pharmacological activities of a human neuropeptide FF-related peptide.

We report on the biochemical, cellular and pharmacological activities of SQA-neuropeptide FF (Ser-Gln-Ala-Phe-Leu-Phe-Gln-Pro-Gln-Arg-Phe-NH2), a peptide sequence contained in the human neuropeptide FF (neuropeptide FF, Phe-Leu-Phe-Gln-Pro-Gln-Arg-Phe-NH2) precursor. Quantitative autoradiography revealed that, in the superficial layers of the rat spinal cord, SQA-neuropeptide FF displayed the same high affinity for [125I]1DMe ([125I]D-Tyr-Leu-(NMe)Phe-Gln-Pro-Gln-Arg-Phe-NH2) binding sites (Ki = 0.33 nM) as did neuropeptide FF (Ki = 0.38 nM). In acutely dissociated mouse dorsal root ganglion neurones, SQA-neuropeptide FF reduced by 40% the depolarisation-induced rise in intracellular Ca2+ as measured with the Ca2+ indicator, Fluo-3. In mice, 1DMe and SQA-neuropeptide FF dose-dependently inhibited the antinociceptive effect of intracerebroventricular (i.c.v.) injections of morphine, but SQA-neuropeptide FF was less potent than 1DMe. Furthermore, SQA-neuropeptide FF, as well as 1DMe, produced marked hypothermia following third ventricle injections in mice. These data demonstrate that the human peptide, SQA-neuropeptide FF, exhibits biochemical and pharmacological properties similar to those of neuropeptide FF or neuropeptide FF analogues, and belongs to the neuropeptide FF family.

Analgesics, Opioid↗

PubMed1998

Neuropeptide FF, pain and analgesia.

Neuropeptide FF (Phe-Leu-Phe-Gln-Pro-Gln-Arg-Phe-NH2) and the octadecapeptide neuropeptide AF (Ala-Gly-Glu-Gly-Leu-Ser-Ser-Pro-Phe-Trp-Ser-Leu-Ala-Ala-Pro-Gln-Arg-Phe -NH2) were isolated from bovine brain, and were initially characterized as anti-opioid peptides. They can oppose the acute effects of opioids and an increase in their brain concentrations may be responsible for the development of tolerance and dependence to opioids. Numerous experiments suggest a possible neuromodulatory role for neuropeptide FF. A precursor protein has been identified, in particular in human brain. Neuropeptide FF immunoreactive neurons are present only in the medial hypothalamus, and the nucleus of the solitary tract, and in the spinal cord in the superficial layers of the dorsal horn and areas around the central canal. Depolarization induces a Ca2+-dependent release of neuropeptide FF immunoreactivity from the spinal cord. Neuropeptide FF acts through stimulation of its own receptors and high densities of specific binding sites are found in regions related either to sensory input and visceral functions or to the processing of nociceptive messages. In both isolated dorsal root ganglion neurons and CA1 pyramidal neurons of the hippocampus, neuropeptide FF has little effect of its own but reverses the effects of mu-opioid receptor agonists. In agreement with the hypothesized anti-opioid role of neuropeptide FF, supraspinal injection lowers the nociceptive threshold and reverses morphine-induced analgesia in rats. Furthermore, immunoneutralization of neuropeptide FF increases endogenous and exogenous opioid-induced analgesia. Similarly, microinfusion of neuropeptide FF or neuropeptide FF analogs into the nucleus raphe dorsalis, the parafascicular nucleus, or the ventral tegmental area has no effect on the nociceptive threshold but inhibits the analgesia induced by co-injected morphine. Furthermore, infusion of neuropeptide FF into the parafascicular nucleus or the nucleus raphe dorsalis reverses the analgesic effect of morphine infused into the nucleus raphe dorsalis or the parafascicular nucleus, respectively, demonstrating remote interactions between neuropeptide FF and opioid systems. By contrast, intrathecal administration of neuropeptide FF analogs induces a long lasting, opioid-dependent analgesia and potentiates the analgesic effect of morphine. Analgesic effects of neuropeptide FF after supraspinal injection could also be observed, for example during nighttime. In young mice, (1DMe)Y8Famide (D.Tyr-Leu-(NMe)Phe-Gln-Pro-Gln-Arg-Phe-NH2), a neuropeptide FF analog, increases delta-opioid receptor-mediated analgesia. These findings indicate that neuropeptide FF constitutes a neuromodulatory neuronal system interacting with opioid systems, and should be taken into account as a participant of the homeostatic process controlling the transmission of nociceptive information.

Amino Acid Sequence↗

PubMed1998

Affinity of neuropeptide FF analogs to opioid receptors in the rat spinal cord.

Several high-affinity analogs of neuropeptide FF (Phe-Leu-Phe-Gln-Pro-Gln-Arg-Phe-NH2, NPFF) exhibiting both supraspinal anti-opioid and spinal analgesic activities were studied for their abilities to interact with specific mu, delta, and kappa opioid binding in the rat spinal cord. Measurements by quantitative receptor autoradiography in the superficial layers of the spinal cord revealed that NPFF analogs tested have only a low affinity for opioid receptors since Ki values ranged from 5 to 400 microM. Taking into account the high efficacy of NPFF after intrathecal injection, these results indicate that analgesic effects of NPFF did not result from opioid receptor stimulation.

Analgesics, Opioid↗

PubMed1997

Effects of neuropeptide FF on intestinal motility and temperature changes induced by endotoxin and platelet-activating factor.

Several effects of bacterial endotoxins involve an opioid pathway and neuropeptide FF is an endogenous peptide known to modulate opioid activity, mainly in the central nervous system. The aim of this study was to investigate in rats the role of central neuropeptide FF receptors in intestinal motor disturbances and body temperature changes induced by endotoxins and platelet-activating factor (PAF), a major endotoxin mediator. Rats were fitted with intestinal electrodes, an intraperitoneal thermistor probe and an intracerebroventricular (i.c.v.) cannula for long-term use. E. coli endotoxin (100 microg/kg, i.v.) disrupted the cyclic pattern of intestinal migrating myoelectric complexes and induced a biphasic increase in body temperature while PAF (25 microg/kg, i.p.) disrupted the migrating myoelectric complexes and induced hypothermia for about 2 h. The neuropeptide FF analog, (1 DME)Y8Fa (D-Tyr-D-Leu[N-Me]-Phe-Gln-Pro-Gln-Arg-Phe-NH2) administered i.c.v. 40 and 100 microg/kg reduced the duration of migrating myoelectric complex disruption induced by endotoxin and PAF and abolished the PAF-induced hypothermia. Only at the dose of 100 microg/kg did (1 DME)Y8Fa change the biphasic endotoxin-induced hyperthermia into a monophasic increase. Naloxone (1 mg/kg, s.c.) reduced only the duration of migrating myoelectric complex disruption induced by endotoxin. These results indicate that central neuropeptide FF modulates the intestinal motor disturbances and changes in body temperature induced by endotoxin and PAF. Its action against endotoxin may involve an anti-opioid pathway whereas its action against PAF does not.

Animals↗

PubMed1997

Neuropeptide FF receptors control morphine-induced analgesia in the parafascicular nucleus and the dorsal raphe nucleus.

The ability of (1DMe)Y8Fa (D.Tyr-Leu-(NMe)Phe-Gln-Pro-Gln-Arg-Phe-NH2), a selective neuropeptide FF analog resistant to enzymatic degradation, to control morphine-induced analgesia was investigated in rat after microinfusion into the dorsal raphe nucleus and the nucleus parafascicularis of the thalamus. Infusion of (1DMe)Y8Fa (2.5 nmol) in the nucleus raphe dorsalis did not modify the animal response in the tail-immersion test but significantly reversed analgesia induced by coinjected morphine (27 nmol). Similarly, (1DMe)Y8Fa (5 nmol) inhibited morphine effects in the hot-plate test after co-injection into the parafascicular nucleus. Furthermore, (1DMe)Y8Fa injected into the parafascicular nucleus attenuated analgesia induced by morphine injected into the nucleus raphe dorsalis and similarly, the neuropeptide FF analog in the nucleus raphe dorsalis decreased the effects of 27 nmol morphine injected in the parafascicular nucleus. The density of neuropeptide FF receptors did not decrease in the nucleus raphe dorsalis after lesion of serotonergic neurons by 5,7-dihydroxytryptamine. However, after this lesion, (1DMe)Y8Fa injected in the nucleus raphe dorsalis was no longer able to modify analgesic effects of morphine in hot-plate and tail-immersion tests. Similarly, the serotonin (5-HT) depletion induced by a systemic administration of para-chlorophenylalanine did not modify morphine analgesia microinjected into the nucleus raphe dorsalis and the parafascicular nucleus but blocked the ability of (1DMe)Y8Fa to reverse morphine effects in both nuclei. These data show that neuropeptide FF exerts anti-opioid effects directly into both the nucleus raphe dorsalis and the parafascicular nucleus and acts also at distance on opioid functions. Furthermore, anti-opioid effects of neuropeptide FF require functional serotonergic neurons although neuropeptide FF receptors are not carried on these neurons.

5,6-Dihydroxytryptamine↗

PubMed1997

Hypothermic effects of neuropeptide FF analogues in mice.

The effects of neuropeptide FF (NPFF) and its analogues on mouse body temperature were examined. In a thermoneutral environment, administration of NPFF (Phe-Leu-Phe-Gln-Pro-Gln-Arg-Phe-NH2), 1DMe ([D.Tyr1, (N.Me)Phe3] NPFF), and 3D ([D.Tyr1, D.Leu2, D.Phe3] NPFF) in the third ventricle produced marked hypothermia. The effect of 1DMe was dose-dependent, and 45 nmol decreased body temperature by 5.6 degrees C. This effect was more pronounced when mice were placed at 4 degrees C. Hypothermia was not reversed by naloxone, an opioid antagonist, and was not modified by morphine. After 5 days of chronic treatment with 1DMe, mice did not became tolerant to the hypothermic effect. These results indicate that central NPFF receptors may control body temperature independently from opioid functions.

Animals↗

PubMed1997

Differential modulation of mu- and delta-opioid antinociception by neuropeptide FF receptors in young mice.

The ability of neuropeptide FF (NPFF) to modulate mu- and delta-opioid-induced analgesia by intracerebroventricular administration was compared in adults and 14-day-old mice. In adults, opioid-induced analgesia was predominantly mediated by mu-receptors whereas mu- and delta-receptors were equally involved in pups. An NPFF analog, 1 DMe, reduced the analgesic effect of DAGO and [D.Ala2]deltorphin-I, mu and delta selective agonists respectively. However, a high dose of 1DMe (22 nmol) increased both morphine and [D.Ala2]deltorphin-I-induced analgesia. Dose-response curves for 1DMe in the presence of naltrindole or naltrexone, delta- and mu-opioid selective antagonists respectively, indicate that 1DMe preferentially reversed mu-receptor-mediated but increased delta-receptor-mediated analgesia. These findings demonstrate differences in control of mu- and delta-induced analgesia by NPFF receptors.

Age Factors↗

PubMed1997

Neuropeptide FF receptors of mouse olfactory bulb: binding properties and stimulation of adenylate cyclase activity.

Neuropeptide FF (NPFF) receptors have been characterized in mouse olfactory bulb membranes by using [125I][1DMe]Y8Fa. The specific binding of this NPFF analogue was time and concentration dependent, reversible, saturable, and of high affinity (Kd = 0.022 nM, Bmax = 56.4 fmol/mg protein). In olfactory bulb membranes, NaCl increased the affinity of [125I][1DMe]Y8Fa by decreasing the dissociation rate constant (k-1). In contrast, the nonhydrolyzable analogue of GTP, Gpp[NH]p, decreased the maximal number of binding sites suggesting a coupling of NPFF receptors to a G-protein. In mouse olfactory bulb and spinal cord membranes, NPFF analogues stimulated adenylate cyclase activity in a time- and dose-dependent manner, whereas in the cerebellum, which does not possess NPFF receptors, low cAMP production was stimulated by NPFF. Our data are consistent with guanine nucleotide binding protein regulation of NPFF receptors positively coupled to adenylate cyclase.

Adenylyl Cyclases↗

PubMed1997

Autoradiographic characterization of rat spinal neuropeptide FF receptors by using [125I][D.Tyr1, (NMe)Phe3]NPFF.

The binding properties of neuropeptide FF (NPFF) receptors were investigated in different laminae of the rat spinal cord by using quantitative autoradiography and [125I][D.Tyr1, (NMe)Phe3]NPFF as radioligand. In the superficial layers, the specific binding of [125I][D.Tyr1, (NMe)Phe3]NPFF was time-dependent, reversible, and saturable (KD = 0.1 nM). Preincubation of spinal sections increased the maximal number of [125I][D.Tyr1, (NMe)Phe3]NPFF binding sites. Bestatin, an inhibitor of aminopeptidases, increased significantly the apparent affinity of NPFF. Optimal binding of [125I][D.Tyr1, (NMe)Phe3]NPFF was observed in the presence of 120 mM NaCl in all laminae of the spinal cord. No significant differences were noted in the salt dependence in laminae I-II, IV-V, and X, and the pharmacological profile of [125I][D.Tyr1, (NMe)Phe3]NPFF binding was similar in each laminae. These results do not support the existence of NPFF receptors subtypes differentially localized in different area of the spinal cord. Our data reveal the effects of tissue treatments on binding characteristics of NPFF receptors and indicate that [125I][D.Tyr1, (NMe)Phe3]NPFF is a useful radioactive probe for the characterization of NPFF receptors in discrete brain areas.

Animals↗

PubMed1997

Evaluation of [125I]7 alpha-O-iodoallyl diprenophine as a new potential SPECT opioid receptor imaging agent.

A new iodinated diprenorphine analog, [125I]7 alpha-O-iodoallyl diprenorphine ([125I]7 alpha-O-IA-DPN), was prepared by iododestannylation and characterized. As an opioid antagonist, this agent showed very high affinity (Ki = 0.4 +/- 0.2 nM) and 63% of specific binding by in vitro and in vivo binding studies. Inhibition curves indicated that this tracer labeled with the same affinities to three opioid receptors (mu = delta = kappa). The findings demonstrate that this proposed compound appears to be potential radioprobe for future study of opioid receptors by in vivo SPECT.

Animals↗

PubMed1996

Neuropeptide FF reverses the effect of mu-opioid on Ca2+ channels in rat spinal ganglion neurones.

Single neurones isolated from spinal ganglia of young rats were loaded with Fluo3, a fluorescent indicator of intracellular Ca2+ concentration. In 27 of 47 neurones the depolarization-evoked rise in fluorescence was reduced by 47.8 +/- 3.3% by prior perfusion with DAGO (1 microM, 30 s) a mu-opioid agonist. In 12 neurones an analogue of neuropeptide FF ((1DMe)Y8Fa, 10 nM, 30 min) did not affect the Ca2+ response to depolarization. (1DMe)Y8Fa reversed the effect of DAGO by 63 +/- 8% in seven of these 12 neurones. We conclude that stimulation of neuropeptide FF receptors antagonizes mu-opioid modulation of Ca2+ channels at the cellular level.

Analgesics↗