Biomedical subjects

M Hamon

Publications and source records attributed to M Hamon.

At least 73 records · Page 4Linked to original sources

PubMed2000

[Role of serotonin and other neuroactive molecules in the physiopathogenesis of migraine. Current hypotheses].

The study of the mechanisms of action of the triptan group of drugs has largely contributed to the progress made in the understanding of the physiopathological processes that are possibly responsible for migraine. In this context, two discoveries have been especially important: 1) these anti-migraine drugs are specifically recognized by three main types of serotonin receptors (5-HT1B, 5-HT1D, and 5-HT1F); and 2) these receptors are present in the meninges, where they are expressed by both smooth muscle cells and/or endothelial cells of the vascular wall and/or the perivascular trigeminal to be deleted axon terminals. These two findings have led to the most currently accepted physiopathogenic hypothesis, whereby the migraine attack would start with an excitation of the perivascular trigeminal to be deleted fibers, which would then trigger the release of vasoactive peptides (substance P, calcitonin gene-related peptide/CGRP) within the dura mater. Locally, i.e., in the dura mater in particular, these substances can provoke vasodilatation (CGRP) and plasmatic extravasation (substance P) with platelet lysis and mast cell degranulation, thereby leading to the release of algogenic substances that excite the neighboring trigeminal fibers, and this neurogenic inflammatory response can progressivelly extend to the meninges as a whole. This reaction subsequently reaches the bulbar and thalamic nuclei and then the sensory cortex, where it is integrated and expressed as migraine pain. The aim of this article was to report the main findings on endogenous substances (serotonin, peptides, nitric oxide [NO], etc.) which appear to play a key role in this physiopathogenic sequence.

Animals↗

PubMed1999

5-HT1A autoreceptor desensitization by chronic ultramild stress in mice.

Electrophysiological and biochemical approaches were used to assess possible changes in central 5-HT neurotransmission in mice that had been subjected to chronic ultramild stress for 8 weeks. This treatment produced a significant decrease in the potency of the 5-HT1A agonist ipsapirone to inhibit the electrical activity of serotoninergic neurons in the dorsal raphe nucleus, without modifying 5-HT1A receptor binding in various brain areas. These data demonstrate that chronic ultramild stress triggers a long term and durable functional desensitization of somatodendritic 5-HT1A autoreceptors in mice.

Action Potentials↗

PubMed1999

Pyrroloquinoxaline derivatives as high-affinity and selective 5-HT(3) receptor agonists: synthesis, further structure-activity relationships, and biological studies.

The synthesis, pharmacological evaluation, and structure-activity relationships (SARs) of a series of novel pyrroloquinoxalines and heteroaromatic-related derivatives are described. The new pyrroloquinoxaline-related ligands were tested in rat cortex, a tissue expressing high density of 5-HT(3) receptors, and on NG108-15 cells and exhibited IC(50) values in the low nanomolar or subnanomolar range, as measured by the inhibition of [(3)H]zacopride binding. The SAR studies detailed herein delineated a number of structural features required for improving affinity. Some of the ligands were employed as "molecular yardsticks" to probe the spatial dimensions of the lipophilic pockets L1, L2, and L3 in the 5-HT(3) receptor cleft, while the 7-OH pyrroloquinoxaline analogue was designed to investigate hydrogen bonding with a putative receptor site H1 possibly interacting with the serotonin hydroxy group. The most active pyrroloquinoxaline derivatives showed subnanomolar affinity for the 5-HT(3) receptor. In functional studies ([(14)C]guanidinium accumulation test in NG108-15 hybrid cells, in vitro) most of the tested compounds showed clear-cut 5-HT(3) agonist properties, while some others were found to be partial agonists. Several heteroaromatic systems, bearing N-substituted piperazine moieties, have been explored with respect to 5-HT(3) affinity, and novel structural leads for the development of potent and selective central 5-HT(3) receptor agonists have been identified. Preliminary pharmacokinetic studies indicate that these compounds easily cross the blood-brain barrier (BBB) after systemic administration with a brain/plasma ratio between 2 and 20, unless they bear a highly hydrophilic group on the piperazine ring. None of the tested compounds showed in vivo anxiolytic-like activity, but potential analgesic-like properties have been possibly disclosed for this new class of 5-HT(3) receptor agonists.

Animals↗

PubMed1999

Long-term doxycycline-controlled expression of human tyrosine hydroxylase after direct adenovirus-mediated gene transfer to a rat model of Parkinson's disease.

Developments of technologies for delivery of foreign genes to the central nervous system are opening the field to promising treatments for human neurodegenerative diseases. Gene delivery vectors need to fulfill several criteria of efficacy and safety before being applied to humans. The ability to drive expression of a therapeutic gene in an adequate number of cells, to maintain long-term expression, and to allow exogenous control over the transgene product are essential requirements for clinical application. We describe the use of an adenovirus vector encoding human tyrosine hydroxylase (TH) 1 under the negative control of the tetracycline-sensitive gene regulatory system for direct injection into the dopamine-depleted striatum of a rat model of Parkinson's disease. This vector mediated synthesis of TH in numerous striatal cells and transgene expression was observed in a large proportion of them for at least 17 weeks. Furthermore, doxycyline, a tetracycline analog, allowed efficient and reversible control of transgene expression. Thus, the insertion of a tetracycline-sensitive regulatory cassette into a single adenovirus vector provides a promising system for the development of successful and safe therapies for human neurological diseases. Our results also confirm that future effective gene replacement approaches to Parkinson's disease will have to consider the concomitant transfer of TH and GTP-cyclohydrolase transgenes because the synthesis of the TH cofactor tetrahydrobiopterin may be crucial for restoration of the dopaminergic deficit.

Adenoviridae↗

PubMed1999

Novel potent and selective central 5-HT3 receptor ligands provided with different intrinsic efficacy. 2. Molecular basis of the intrinsic efficacy of arylpiperazine derivatives at the central 5-HT3 receptors.

Novel 5-HT3 receptor ligands were designed and synthesized with the aim of obtaining deeper insight into the molecular basis of the intrinsic efficacy of arylpiperazines interacting with the central 5-HT3 receptor. The newly synthesized compounds and some previously published compounds belonging to the same class of heteroarylpiperazines were tested for their potential ability to displace [3H]granisetron from rat cortical membranes. These 5-HT3 receptor binding studies revealed subnanomolar affinity in several of the compounds under study. The most active ligands were quipazine derivatives bearing a phenyl group in the 4-position and various oxygenated alkyl side chains in the 3-position of the quinoline nucleus. Qualitative and theoretical quantitative structure-affinity relationship studies were carried out, and the interaction model for the 5-HT3 ligands related to quipazine with their receptor, proposed in part 1 of the present work, was updated to incorporate the latest data. The potential 5-HT3 agonist/antagonist activity of 12 selected compounds was assessed in vitro on the 5-HT3 receptor-dependent [14C]guanidinium uptake in NG 108-15 cells. Their intrinsic efficacy ranged from the 5-HT3 full agonist properties of compounds 7a and 8h, i to those of partial agonists 10a,d and antagonists 8b,d,e, and 9c, d,h,i. The comparison between these functional data and those relative to the previously described compounds suggested that in this class of 5-HT3 ligands the intrinsic efficacy is modulated in a rather subtle manner by the steric features of the heteroaryl moiety.

Animals↗

PubMed1999

Characterization and distribution of Hxt1, a Na(+)/Cl(-)-dependent orphan transporter, in the human brain.

Rxt1, a transporter-like protein structurally related to the large family of Na(+)/Cl(-)-dependent carriers, was isolated from the rat brain. In the present study, Hxt1, the homologue of Rxt1, was isolated from human cortex cDNA. Comparison of their respective nucleotidic sequences revealed a 96% conservation between Hxt1 and Rxt1. Genetic mapping with human genome radiation hybrids allowed the location of the gene coding for Hxt1 between 323ya5 and 084xb3 AFM markers, on a portion of chromosome 1p which spans over 7 cM or 118 cRay. Northern blot analyses demonstrated that Hxt1 mRNA ( approximately 7.5 Kb) is expressed in the human brain but not in peripheral tissues. The immunodistribution of Hxt1 was determined with antibodies raised against the C-terminus of Rxt1. Hxt1 is concentrated in the cerebral cortex, caudate-putamen, substantia nigra, hippocampus, and cerebellum, appearing as a diffuse or a punctate labeling at the light microscope level. This regional and cellular distribution suggests that Hxt1, as its rat homologue, could be present in axon terminals of glutamatergic neurons. The high pressure of selection exerted upon this protein, its strategic anatomical and subcellular distributions suggest that this orphan transporter could be involved in critical functions in the central nervous system.

Amino Acid Sequence↗

PubMed1999

Key role of 5-HT1B receptors in the regulation of paradoxical sleep as evidenced in 5-HT1B knock-out mice.

The involvement of 5-HT1B receptors in the regulation of vigilance states was assessed by investigating the spontaneous sleep-waking cycles and the effects of 5-HT receptor ligands on sleep in knock-out (5-HT1B-/-) mice that do not express this receptor type. Both 5-HT1B-/- and wild-type 129/Sv mice exhibited a clear-cut diurnal sleep-wakefulness rhythm, but knock-out animals were characterized by higher amounts of paradoxical sleep and lower amounts of slow-wave sleep during the light phase and by a lack of paradoxical sleep rebound after deprivation. In wild-type mice, the 5-HT1B agonists CP 94253 (1-10 mg/kg, i.p.) and RU 24969 (0.25-2.0 mg/kg, i.p.) induced a dose-dependent reduction of paradoxical sleep during the 2-6 hr after injection, whereas the 5-HT1B/1D antagonist GR 127935 (0.1-1.0 mg/kg, i.p.) enhanced paradoxical sleep. In addition, pretreatment with GR 127935, but not with the 5-HT1A antagonist WAY 100635, prevented the effects of both 5-HT1B agonists. In contrast, none of the 5-HT1B receptor ligands, at the same doses as those used in wild-type mice, had any effect on sleep in 5-HT1B-/- mutants. Finally, the 5-HT1A agonist 8-OH-DPAT (0.2-1.2 mg/kg, s.c.) induced in both strains a reduction in the amount of paradoxical sleep. Altogether, these data indicate that 5-HT1B receptors participate in the regulation of paradoxical sleep in the mouse.

Analysis of Variance↗

PubMed1999

Adaptive changes of serotonin 5-HT2A receptors in mice lacking the serotonin transporter.

The serotonin transporter (5-HTT) plays a key-role in the control of serotoninergic neurotransmission and is the target of some antidepressants. Possible adaptive changes in brain 5-HT2A receptors were investigated in knock-out mice that do not express the 5-HTT. Autoradiographic labeling of these receptors by the selective antagonist [3H]MDL 100,907 and saturation experiments with cortical membranes revealed: (1) a new localization of these receptors in the external field of striatum (possibly in striosomes); (2) regional variations in adaptive changes in the density of 5-HT2A receptors in 5-HT(-/-) mutants (-30-40% in the claustrum, cerebral cortex and lateral striatum; no significant change in the striatum core) as compared to wild-type mice.

Adaptation, Physiological↗

PubMed1999

Induction of serotonin transporter by hypoxia in pulmonary vascular smooth muscle cells. Relationship with the mitogenic action of serotonin.

-The increased delivery of serotonin (5-hydroxytryptamine, 5-HT) to the lung aggravates the development of hypoxia-induced pulmonary hypertension in rats, possibly through stimulation of the proliferation of pulmonary artery smooth muscle cells (PA-SMCs). In cultured rat PA-SMCs, 5-HT (10(-8) to 10(-6) mol/L) induced DNA synthesis and potentiated the mitogenic effect of platelet-derived growth factor-BB (10 ng/mL). This effect was dependent on the 5-HT transporter (5-HTT), since it was prevented by the 5-HTT inhibitors fluoxetine (10(-6) mol/L) and paroxetine (10(-7) mol/L), but it was unaltered by ketanserin (10(-6) mol/L), a 5-HT2A receptor antagonist. In PA-SMCs exposed to hypoxia, the levels of 5-HTT mRNA (measured by competitive reverse transcriptase-polymerase chain reaction) increased by 240% within 2 hours, followed by a 3-fold increase in the uptake of [3H]5-HT at 24 hours. Cotransfection of the cells with a construct of human 5-HTT promoter-luciferase gene reporter and of pCMV-beta-galactosidase gene allowed the demonstration that exposure of cells to hypoxia produced a 5.5-fold increase in luciferase activity, with no change in beta-galactosidase activity. The increased expression of 5-HTT in hypoxic cells was associated with a greater mitogenic response to 5-HT (10(-8) to 10(-6) mol/L) in the absence as well as in the presence of platelet-derived growth factor-BB. 5-HTT expression assessed by quantitative reverse transcriptase-polymerase chain reaction and in situ hybridization in the lungs was found to predominate in the media of pulmonary artery, in which a marked increase was noted in rats that had been exposed to hypoxia for 15 days. These data show that in vitro and in vivo exposure to hypoxia induces, via a transcriptional mechanism, 5-HTT expression in PA-SMCs, and that this effect contributes to the stimulatory action of 5-HT on PA-SMC proliferation. In vivo expression of 5-HTT by PA-SMC may play a key role in serotonin-mediated pulmonary vascular remodeling.

Animals↗

PubMed1999

Identification and characterization of a zinc finger gene (ZNF213) from 16p13.3.

During our search for the familial Mediterranean fever (FMF) gene, we identified by cDNA selection a 1.2 kb cDNA fragment representing a novel human gene that is expressed in a wide variety of tissues. This gene spans approx. 8.0 kb genomic DNA and has seven exons. Its 3' untranslated region contains a long tandem repeat that gives rise to a polymorphism with two alleles of approx. 1.1 kb and 1.0 kb, with the 1.1 kb allele in strong linkage disequilibrium with FMF in patients of different ethnic backgrounds. However, both genetic and mutational analyses have excluded this gene as the one responsible for FMF. The predicted 424 amino acid protein, designated ZNF213, contains three C2H2 zinc fingers, a Kruppel associated A box and a leucine rich motif (LeR domain/SCAN box), strongly suggestive of a transcription factor.

Amino Acid Sequence↗

PubMed1999

Chronic alnespirone-induced desensitization of somatodendritic 5-HT1A autoreceptors in the rat dorsal raphe nucleus.

The effects of long-term (7, 14 or 21 days) administration of the 5-HT1A receptor agonist alnespirone [5 mg/(kg day), i.p.] on the binding characteristics of 5-HT1A, 5-HT2A and 5-HT3 receptors, and the functional status of 5-HT1A autoreceptors were assessed using biochemical and electrophysiological approaches in rats. Whatever the treatment duration, the specific binding of [3H]8 hydroxy-2-(di-n-propylamino)tetralin ([3H]8-OH-DPAT), [3H]trans,4-[(3Z)3-(2-dimethylaminoethyl) oxyimino-3(2-fluorophenyl) propen-1-yl] phenol hemifumarate ([3H]SR 46349B), and [3H]S-zacopride to 5-HT1A, 5-HT2A and 5-HT3 receptors, respectively, were unaltered in all the brain areas examined. In contrast, in vitro electrophysiological recordings performed 24 h after the last injection of alnespirone showed that the potency of the 5-HT1A receptor agonist, 8-OH-DPAT, to depress the firing of serotoninergic neurons in the dorsal raphe nucleus, was significantly reduced after a 21-day treatment with alnespirone. However, no changes were noted after a 7-day or 14-day treatment. These data indicate that desensitization of somatodendritic 5-HT1A autoreceptors is a selective but slowly developing adaptive phenomenon in response to their chronic stimulation in rats.

Animals↗

PubMed1999

Toward autologous ex vivo gene therapy for the central nervous system with human adult astrocytes.

The combination of gene transfer techniques and cell transplantation is a promising approach to deliver therapeutic molecules into the CNS. To optimize gene transfer systems, several neural and nonneural cell types are currently under investigation. Among these cells, astrocytes are particularly well suited because of their CNS origin, their efficient secretory mechanisms, and their role as neuronal support. Most importantly, the use of human adult astrocytes as cellular vehicles for ex vivo gene transfer may open the way to autologous transplantation, thus obviating immunological rejection and the side effects of immunosuppressors. In the present study, we report the ability of these cells to be expanded and genetically modified in vitro. Astrocytes derived from human adult cerebral cortex were grown and maintained in vitro as pure primary cultures for at least 10 months. In addition, cells were efficiently transduced by an adenoviral vector encoding human tyrosine hydroxylase (hTH) under the negative control of the tetracycline-based regulatory system (tet-off). The infected cells synthesized large amounts of active hTH and released L-dopa. In addition, doxycycline, a potent analog of tetracycline, efficiently regulated transgene expression. This work is a first step toward the development of therapeutic strategies based on the use of genetically engineered human adult astrocytes for autologous transplantation in human neurodegenerative diseases and CNS trauma.

Adenoviridae↗

PubMed1999

Limited inhibition of 5-HT1A receptor expression in the rat brain by antisense RNA and oligodesoxynucleotides.

The efficiency of antisense approaches to produce a selective regional inhibition of the expression of brain 5-HT1A receptors was tested in the rat. In vivo ICV injections of modified antisense oligodesoxynucleotides yielded at most an 18% specific decrease in 5-HT1A receptor expression in the hippocampus only, as measured by [3H]8-OH-DPAT autoradiographic labeling. In vitro, when 5-HT1A receptors were transiently expressed in LLC-PK1 cells, co-transfection with antisense RNA encoding plasmids resulted in a marked reduction (50-70%) in the density of 5-HT1A binding sites. In vivo stereotaxic injections of the same constructs into the hippocampus, but not in the raphe, which contains 5-HT1A autoreceptors, were shown to produce a approximately 20% reduction in local 5-HT1A receptor density. These data show that antisense strategies could be used to inhibit 5-HT1A receptors expression in the rat hippocampus, but with a limited efficacy.

Animals↗

PubMed1999

Delta(2)-opioid receptor mediation of morphine-induced CCK release in the frontal cortex of the freely moving rat.

Numerous pharmacological data have been accumulated in support of the existence of physiological interactions between cholecystokinin (CCK) and opioids in the central nervous system. With the aim of further characterizing these interactions, an in vivo microdialysis approach was used to directly assess the possible influence of opioids on the extracellular levels of CCK-like material (CCKLM) in the frontal cortex of the awake, freely moving rat. Systemic administration of a high dose of morphine (10 mg/kg i.p.) produced a marked increase (up to +200%) of cortical CCKLM outflow, and this effect could be completely prevented by systemic (1.5 mg/kg i.p.) as well as intracortical (10 microM) administration of the opioid receptor antagonist naloxone. The opioid receptors activated by morphine appeared to be of the delta type because the intracortical infusion of naltrindole (10 microM) also prevented the effect of morphine, whereas CTOP (10 microM), a selective mu-opioid receptor antagonist, and nor-binaltorphimine (10 microM), a selective kappa-opioid receptor antagonist, were inactive. In addition, naltriben (10 microM), which acts selectively at the delta(2) subtype, also abolished the stimulatory effect of morphine on cortical CCKLM outflow, whereas 7-benzylidenenaltrexone (10 microM), a selective delta(1)-opioid receptor antagonist (10 microM), did not alter the morphine effect. Conversely, the direct stimulation of cortical delta(2)-opioid receptors by local infusion of [D-Ala(2)] deltorphin II mimicked the stimulatory effect of systemic morphine on CCKLM outflow. These data indicate that delta(2)-opioid receptors play a key role in opioid-CCK interactions in the rat frontal cortex.

Analgesics, Opioid↗

PubMed1999

Serotonin and tolerance to delay of reward in rats.

RATIONALE: Tolerance to delay of gratification, taken to reflect impulsiveness, has been proposed to be under the preferential control of central serotonin (5-HT) processes. OBJECTIVE: The present study further examined the effects of drugs which directly or indirectly alter 5-HT transmission, on behaviour controlled by a delayed positive reinforcer. METHODS: Rats were given the choice in a T-maze between two magnitudes of reward: small (two food pellets) and immediate versus large (ten pellets) but delayed. When a 15-s waiting period was imposed in the arm leading to the large reward, rats selected this arm on 65-70% of the trials. This frequency was reduced to less than 40% when the large reward was delayed by 25 s. RESULTS: In rats whose ascending 5-HT pathways had been lesioned by infusion of 5,7-dihydroxytryptamine (5,7-DHT) into the dorsal raphe, the introduction of the 15-s delay contingency resulted in a transient larger reduction of the frequency of choice of the now-delayed reward, compared to sham operated controls. In contrast, choice behaviour of rats given 5,7-DHT into the substantia nigra did not differ from controls. para-Chlorophenylalanine (pCPA, 150 mg/kg IP, daily for 3 days), a 5-HT synthesis inhibitor, bretazenil (0.5-8 mg/kg IP), a benzodiazepine (BZD) receptor partial agonist, and muscimol (0.25-1 mg/kg IP), a GABA(A) receptor agonist, induced a shift toward immediate reward. In contrast to the other BZDs, alprazolam (1-2 mg/kg IP) enhanced the frequency of choice of the large-but-25 s-delayed reward. Similar increased preference for the large-but-delayed reward was induced by the selective 5-HT reuptake inhibitors, fluoxetine (4-8 mg/kg IP) and fluvoxamine (4 mg/kg IP). The full 5-HT(1A) receptor agonist, 8-OH-DPAT (0.015-0.5 mg/kg IP) enhanced the frequency of choice of the large reward delayed by 25 s, whereas the partial agonists, buspirone (1-4 mg/kg IP), ipsapirone (0.5-1 mg/kg IP) and MDL 73005EF (1-2 mg/kg SC), and the antagonist, WAY 100635 (4 mg/kg SC), reduced the number of choices of the large reward delayed by 15 s. Unexpectedly, WAY 100635 (2 mg/kg), which had no effect on choice whatever the delay, did not counteract the increased tolerance to delay induced by 8-OH-DPAT (0.06 mg/kg) and further reduced the frequency of choice of the large-but- 15 s-delayed reward induced by ipsapirone (0.5 mg/kg). CONCLUSIONS: These effects on tolerance to delay may be accounted for by a subtle balance between the opposing functional consequences of pre- versus post-synaptic 5-HT(1A) receptor activation or blockade. Overall, the present results provide further support to the idea that 5-HT processes participate in the control of impulsive-related behaviour, as assessed from tolerance to delay of reward in this particular T-maze procedure.

5,7-Dihydroxytryptamine↗

PubMed1999

Direct coronary stenting without balloon predilation in acute coronary syndromes.

BACKGROUND: This prospective, observational study was designed to evaluate the feasibility and the safety of a new strategy for stenting in acute coronary syndromes: direct stent implantation without predilation of the culprit lesion. This strategy might reduce both the cost of the procedure and the rate of no-reflow, a phenomenon that is more frequently observed during dilation of unstable plaques. METHODS AND RESULTS: Between September 1997 and March 1998, 122 carefully selected patients with unstable angina or acute myocardial infarction were included in this study. Highly calcified lesions and vessels with excessive proximal tortuosity were excluded. The procedure was successful in 96% of cases. In 5 cases the stent failed to pass through the stenosis and was successfully retrieved in the guiding catheter in 3 cases. In 2 cases the stent was lost in the peripheral circulation. Transient no-reflow occurred in only 3 cases and was rapidly reversed by rescue use of an intracoronary bolus injection of a glycoprotein IIb/IIIa receptor inhibitor in 2 cases. A patient treated by primary angioplasty with cardiogenic shock on admission died 48 hours after the initial procedure because of irreversible cardiac failure. One-month clinical follow-up was obtained by telephone for all patients; no major coronary events occurred during this period. CONCLUSIONS: Direct coronary stenting without balloon predilation can be safely performed in acute coronary syndrome-related lesions in selected patients. A randomized, controlled study is warranted to confirm the promising results of this pilot study, especially regarding the low rate of the no-reflow phenomenon.

Aged↗

PubMed1999

Prevention by 5-HT1A receptor agonists of restraint stress- and yohimbine-induced release of cholecystokinin in the frontal cortex of the freely moving rat.

In line with the idea that cholecystokinin (CCK) is involved in anxiety-related behaviours, previous investigations showed that stressful conditions and an 'anxiogenic' drug, yohimbine, increased the cortical release of CCK like-material (CCKLM) in awake rats, and that this effect could be prevented by diazepam. Here, we investigated whether other anxiolytic drugs such as 5-HT1A receptor agonists could also affect cortical CCKLM release. Indeed, neither buspirone (1 mg/kg i.p.), alnespirone (1 mg/kg i.p.) nor lesopitron (3 mg/kg i.p.) affected, on their own, CCKLM release. However, pretreatment with the latter drugs completely abolished the stimulatory effect of restraint stress on the peptide outflow. As expected of the involvement of 5-HT1A receptors, tertatolol (10 mg/kg i.p) markedly reduced the inhibitory effect of buspirone on restraint stress-evoked CCKLM overflow. On the other hand, pretreatment with buspirone, alnespirone or lesopitron also inhibited the stimulatory effect of yohimbine (5 mg/kg i.p.) on cortical CCKLM outflow. These data support the idea that the anxiolytic action of 5-HT1A receptor agonists could be mediated, at least partly, through their inhibitory influence on cortical CCK-ergic systems.

Adrenergic alpha-Antagonists↗

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↗