GDF11 knockdown downregulates SMURF1 to inhibit breast cancer progression by activation of p53 and inactivation of ERα signaling

Breast cancer (BC) is a prevalent neoplasm that occurs in women all over the world. Growth and differentiation factor 11 (GDF11) plays an essential role in cancer progression. This study focused on investigating the biological role and underlying mechanisms of GDF11 in BC. We detected the expression of GDF11 in 27 patients with BC and BC cell lines. Kaplan-Meier plotter was employed to analyze the relationship between GDF11 expression and overall survival (OS) of BC patients. The proliferative, migratory, invasive, and apoptotic abilities of T47D cells were examined. Correlation analysis of GDF11 with Smad ubiquitination regulatory factor 1 (SMURF1) was conducted. The association between GDF11 and the p53 pathway was analyzed by western blot and PFT-α (a p53 inhibitor)-mediated rescue assays. A brief analysis of the role of estrogen receptor alpha (ERα) signaling in BC progression was performed. The results showed that GDF11 was increased in BC tissues and cell lines, and the high expression of GDF11 was associated with the poor OS of BC patients. GDF11 knockdown inhibited the proliferation, migration, and invasion of T47D cells, but promoted cell apoptosis. Meanwhile, the GDF11 knockdown reduced the SMURF1 expression and invoked the p53 pathway activation. SMURF1 overexpression and PFT-α partially blocked the effects of GDF11 knockdown. In addition, GDF11 knockdown and SMURF1 silencing inhibited the activation of the ERα signaling pathway. In summary, GDF11 was involved in the progression of BC by regulating SMURF1-mediated p53 and ERα pathways, opening up a new way for BC treatment.

[Epidemiological features and diagnosis of malaria cases in Nantong City from 2015 to 2020]

OBJECTIVE

To investigate the epidemiological characteristics and diagnosis of malaria cases in Nantong City from 2015 to 2020, so as to provide insights into the prevention of re-establishment of imported malaria and consolidation of malaria elimination achievements in the city.

METHODS

The epidemic data of malaria in Nantong City from 2015 to 2020 were captured from the National Notifiable Disease Report System, the Information Management System for Parasitic Disease Control and individual epidemiological survey reports of malaria cases. The malaria parasite species, source of infections, population distribution, temporal distribution, spatial distribution and diagnosis of imported malaria cases were descriptively and statistically analyzed.

RESULTS

A total of 241 malaria cases were reported in Nantong City from 2015 to 2020, and all were overseas imported cases, including 191 cases with Plasmodium falciparum malaria (79.25%), 8 cases with P. vivax malaria (3.32%), 33 cases with P. ovale malaria (13.69%) and 9 cases with P. malaria malaria (3.73%). Overseas imported malaria cases acquired infections from 34 countries in Asia, Africa and Latin America, and 97.93% of the cases were infected in Africa, and 90.04% (217/241) were reported in Chongchuan District, Hai'an City and Haimen District. Imported malaria cases were aged from 20 to 68 years, and a median age of 45 (13) years, and 97.10% were male. The median duration between returning to China and malaria onset was 7 (9) days among all imported malaria cases, and the median duration from initial diagnosis to definitive diagnosis was 2 (2) days. There were 167 cases that were initially diagnosed as malaria, with a correct rate of 69.29%, and 53.53 (129/241) of malaria cases were diagnosed at city-level medical institutions and 41.49% (100/241) at county-level medical institutions. In addition, the proportion of malaria cases reported by city-level medical institutions increased from 39.62% in 2015 to 81.25% in 2020 (χ² = 6.94, P < 0.01).

CONCLUSIONS

The accuracy of initial malaria diagnosis requires to be improved in Nantong City. Malaria control knowledge should be specially given to migrant workers to shorten the duration of seeking medical care, and malaria training requires to be intensified among healthcare professionals to improve the diagnostic capability of imported malaria cases and the cure of severe P. falciparum malaria cases.

Peripheral Leptin Signaling Mediates Formalin-Induced Nociception

Accumulating evidence suggests that obesity is associated with chronic pain. However, whether obesity is associated with acute inflammatory pain is unknown. Using a well-established obese mouse model induced by a high-fat diet, we found that: (1) the acute thermal pain sensory threshold did not change in obese mice; (2) the model obese mice had fewer nociceptive responses in formalin-induced inflammatory pain tests; restoring the obese mice to a chow diet for three weeks partly recovered their pain sensation; (3) leptin injection induced significant phosphorylation of STAT3 in control mice but not in obese mice, indicating the dysmodulation of topical leptin-leptin receptor signaling in these mice; and (4) leptin-leptin receptor signaling-deficient mice (ob/ob and db/db) or leptin-leptin receptor pathway blockade with a leptin receptor antagonist and the JAK2 inhibitor AG 490 in wild-type mice reduced their nociceptive responses in formalin tests. These results indicate that leptin plays a role in nociception induced by acute inflammation and that interference in the leptin-leptin receptor pathway could be a peripheral target against acute inflammatory pain.

[Long-term clinical efficacy of mild hypothermia therapy in neonates with hypoxic-ischemic encephalopathy: a Meta analysis]

OBJECTIVE

To systematically evaluate the long-term clinical efficacy and safety of mild hypothermia therapy in neonates with hypoxic-ischemic encephalopathy (HIE).

METHODS

All randomized controlled trials (RCTs) of mild hypothermia therapy for neonatal HIE from inception to March 2014 were retrieved from databases including Cochrane Library, PubMed, Embase, CBMdisc, and Wanfang Data. Meta analysis was performed using RevMan 5.1 Software.

RESULTS

Eight RCTs met the search criteria. The results of Meta analysis showed that, compared with the control group, systemic hypothermia significantly reduced the mortality rate and the incidence of growth delay (RR=0.73, 95% CI: 0.61-0.89; RR=0.70, 95%CI: 0.54-0.93); selective head or systemic hypothermia therapy significantly reduced the incidence of cerebral palsy (RR=0.65, 95%CI: 0.46-0.94; RR=0.67, 95%CI: 0.52-0.86) up to 12-24 months of age. One study reported that hypothermia reduced the mortality rate and the rate of a composite end point of death or severe disability compared with the control group at 6 to 7 years of age. The incidence of adverse events including sinus bradyarrhythmia, thrombocytopenia and hypoglycemia was significantly higher in the hypothermia group than in the control group, whereas the incidence of cardiac arrhythmia, hypotension, thrombosis or bleeding, hypokalemia, sepsis, and liver dysfunction showed no significant differences between the two groups.

CONCLUSIONS

Mild hypothermia therapy demonstrates a significant efficacy in children with HIE up to 12-24 months of age, but there is still a need for further research on childhood outcomes after mild hypothermia for neonatal HIE. This therapy has few adverse effects and a high clinical tolerability.

Control of P2X3 channel function by metabotropic P2Y2 utp receptors in primary sensory neurons

Purinergic signaling contributes significantly to pain mechanisms, and the nociceptor-specific P2X3 ATP receptor channel is considered a target in pain therapeutics. Recent findings suggesting the coexpression of metabotropic P2Y receptors with P2X3 implies that ATP release triggers the activation of both ionotropic and metabotropic purinoceptors, with strong potential for functional interaction. Modulation of native P2X3 function by P2Y receptor activation was investigated in rat dorsal root ganglia (DRG) neurons using whole cell patch-clamp recordings. Application of the selective P2Y receptor agonist UTP decreased peak amplitudes of α,β-meATP-evoked homomeric P2X3-mediated currents, but had no effect on heteromeric P2X2/3-mediated currents. Treatment with phospholipase C inhibitor U73122 significantly reversed P2X3 current inhibition induced by UTP-sensitive P2Y receptor activation. We previously reported the modulation of P2X receptors by phospholipids in DRG neurons and injection of exogenous phosphatidylinositol-4,5-bisphosphate (PIP(2)) fully reverses UTP-mediated regulation of P2X3 channel activity. Pharmacological as well as functional screening of P2Y receptor subtypes indicates the predominant involvement of P2Y2 receptor in P2X3 inhibition, and immunolocalization confirms a significant cellular coexpression of P2X3 and P2Y2 in rat DRG neurons. In summary, the function of P2X3 ATP receptor can be inhibited by P2Y2-mediated depletion of PIP(2). We propose that expression of P2Y2 purinoceptor in nociceptive sensory neurons provides an homeostatic mechanism to prevent excessive ATP signaling through P2X3 receptor channels.

[Molecular epidemiological and clinical feature of human metapneumovirus in children with acute lower respiratory tract infection in Changsha area from 2007 to 2011]

OBJECTIVE

To understand the epidemiological characteristics of human metapneumovirus (hMPV) infection in children with acute lower respiratory tract infection (ALRTI) in Changsha area, China.

METHODS

A total of 2613 nasopharyngeal aspirate (NPA) specimens were collected from hospitalized children with ARTIs between September 2007 and February 2011 (a period of 3.5 years) in Changsha area, Hunan Province, China. Respiratory specimens were screened for hMPV M gene by reverse-transcription polymerase chain reaction (RT-PCR). All RT-PCR positive' amplification products were confirmed by sequencing or analyzed and compared with those in GenBank known hMPV reference strain.

RESULTS

hMPV was detected in 135 (5.2%) out of the 2613 children. The detected rate was significantly different between male and female (chi2 = 8.007, P = 0.003). The majority of the hMPV-positive patients (63.2%) were 0-1 year old infants. The majority of hMPV-positive patients were detected during spring season. Seasonal distribution showed that subtype A2b circulated predominantly in winter and spring, subtype B2 circulated predominantly in summer and spring. The most common genotype in 135 hMPV-positive patients were A and B in human subjects in Changsha. The predominant genotype of hMPV changed over the 3.5 year study period from genotype A2b to combined A2b and B2, and to B2. The 66 (48.9%) out of the 135 hMPV-positive patients were found to be co-infected with other respiratory viruses, and human bocavirus (HBoV) was the most common additional respiratory virus.

CONCLUSION

These data suggest that some cases of acute lower respiratory infection in young children in Changsha area are related to hMPV and the majority of children infected with hMPV were less than 1 years old, the detected rate of boys was higher than that of girls. It circulated predominantly in spring. The subtype A2b genetic lineage and the subtype B1 genetic lineage of hMPV were revealed alternately in human subjects in Changsha area and the hMPV exhibited high co-infection rate with other respiratory viruses.

Neuropathic Nav1.3-mediated sensitization to P2X activation is regulated by protein kinase C

Background

Increased neuronal excitability and spontaneous firing are hallmark characteristics of injured sensory neurons. Changes in expression of various voltage-gated Na⁺ channels (VGSCs) have been observed under neuropathic conditions and there is evidence for the involvement of protein kinase C (PKC) in sensory hyperexcitability. Here we demonstrate the contribution of PKC to P2X-evoked VGSC activation in dorsal root ganglion (DRG) neurons in neuropathic conditions.

Results

Using the spinal nerve ligation (SNL) model of neuropathic pain and whole-cell patch clamp recordings of dissociated DRG neurons, we examined changes in excitability of sensory neurons after nerve injury and observed that P2X3 purinoceptor-mediated currents induced by α,β-meATP triggered activation of TTX-sensitive VGSCs in neuropathic nociceptors only. Treatment of neuropathic DRGs with the PKC blocker staurosporine or calphostin C decreased the α,β-meATP-induced Na⁺ channels activity and reversed neuronal hypersensitivity. In current clamp mode, α,β-meATP was able to evoke action-potentials more frequently in neuropathic neurons than in controls. Pretreatment with calphostin C significantly decreased the proportion of sensitized neurons that generated action potentials in response to α,β-meATP. Recordings measuring VGSC activity in neuropathic neurons show significant change in amplitude and voltage dependence of sodium currents. In situ hybridization data indicate a dramatic increase in expression of embryonic Na_v1.3 channels in neuropathic DRG neurons. In a CHO cell line stably expressing the Na_v1.3 subunit, PKC inhibition caused both a significant shift in voltage-dependence of the channel in the depolarizing direction and a decrease in current amplitude.

Conclusion

Neuropathic injury causes primary sensory neurons to become hyperexcitable to ATP-evoked P2X receptor-mediated depolarization, a phenotypic switch sensitive to PKC modulation and mediated by increased activity of TTX-sensitive VGSCs. Upregulation in VGSC activity after injury is likely mediated by increased expression of the Na_v1.3 subunit, and the function of the Na_v1.3 channel is regulated by PKC.

Radioembolization with yttrium microspheres for neuroendocrine tumour liver metastases

Background

90Y microsphere radioembolization is performed by injecting the microspheres through a hepatic artery catheter placed percutaneously via the femoral or brachial artery. This study assessed the efficacy of 90Y microsphere therapy for patients with unresectable neuroendocrine tumour liver metastases (NETLMs). Potential prognostic factors were analysed for their impact on overall survival.

Methods

A prospectively collected database for patients with NETLMs treated by 90Y microspheres in two centres from 2003 to 2008 was examined retrospectively. Serial radiographic evidence was collected during follow-up to assess response.

Results

Fifty-eight patients were included, 51 of whom had evaluable disease at most recent follow-up. Six patients achieved a complete response, 14 a partial response, 14 had stable disease and 17 had disease progression. Overall survival rates at 1, 2 and 3 years were 86, 58 and 47 per cent respectively; median survival was 36 (range 1–61) months. Extent of tumour involvement, radiographic response to treatment, extrahepatic disease and tumour grade were significant prognostic factors for overall survival.

Conclusion

90Y microsphere radioembolization achieved a radiographic response in a significant proportion of patients with NETLMs.

Subtype-specific regulation of P2X3 and P2X2/3 receptors by phosphoinositides in peripheral nociceptors

Background

P2X3 and P2X2/3 purinergic receptor-channels, expressed in primary sensory neurons that mediate nociception, have been implicated in neuropathic and inflammatory pain responses. The phospholipids phosphatidylinositol 4,5-bisphosphate (PIP₂) and phosphatidylinositol 3,4,5-trisphosphate (PIP₃) are involved in functional modulation of several types of ion channels. We report here evidence that these phospholipids are able to modulate the function of homomeric P2X3 and heteromeric P2X2/3 purinoceptors expressed in dorsal root ganglion (DRG) nociceptors and in heterologous expression systems.

Results

In dissociated rat DRG neurons, incubation with the PI3K/PI4K inhibitor wortmannin at 35 μM induced a dramatic decrease in the amplitude of ATP- or α,β-meATP-evoked P2X3 currents, while incubation with 100 nM wortmannin (selective PI3K inhibition) produced no significant effect. Intracellular application of PIP₂ was able to fully reverse the inhibition of P2X3 currents induced by wortmannin. In Xenopus oocytes and in HEK293 cells expressing recombinant P2X3, 35 μM wortmannin incubation induced a significant decrease in the rate of receptor recovery. Native and recombinant P2X2/3 receptor-mediated currents were inhibited by incubation with wortmannin both at 35 μM and 100 nM. The decrease of P2X2/3 current amplitude induced by wortmannin could be partially reversed by application of PIP₂ or PIP₃, indicating a sensitivity to both phosphoinositides in DRG neurons and Xenopus oocytes. Using a lipid binding assay, we demonstrate that the C-terminus of the P2X2 subunit binds directly to PIP₂, PIP₃ and other phosphoinositides. In contrast, no direct binding was detected between the C-terminus of P2X3 subunit and phosphoinositides.

Conclusion

Our findings indicate a functional regulation of homomeric P2X3 and heteromeric P2X2/3 ATP receptors by phosphoinositides in the plasma membrane of DRG nociceptors, based on subtype-specific mechanisms of direct and indirect lipid sensing.

Pro-nociceptive effects of neuromedin U in rat

The neuropeptide neuromedin U (NMU) has been shown to have significant effects on cardiovascular, gastrointestinal and CNS functions. The peptide was first isolated from the porcine spinal cord and later shown to be present in spinal cords of other species. Little is known about the distribution of neuromedin U receptors (NMURs) in the spinal cord and the spinal action of the peptide. Here we report on the expression of NMURs and a potential role in nociception in the rat spinal cord using a combination of behavioral and electrophysiological studies. Receptor autoradiography showed that NMU-23 binding was restricted to the superficial layers of spinal cord, a region known to be involved in the control of nociception. In situ hybridization analysis indicated the mRNA of NMUR2 was located in the same region (laminae I and IIo) as NMU-23 binding, while the mRNA for NMU receptor 1 was observed in a subpopulation of small diameter neurons of dorsal root ganglia. Intrathecal (i.t.) administration of neuromedin U-23 (0.4-4.0 nmol/10 microl) dose-dependently decreased both the mechanical threshold to von Frey hair stimulation and the withdrawal latency to a noxious thermal stimulus. Mechanical allodynia was observed between 10 and 120 min, peaking at 30 min and heat hyperalgesia was observed 10-30 min after i.t. administration of NMU-23. A similar mechanical allodynia was also observed following i.t. administration of NMU-8 (0.4-4 nmol/10 microl). A significant enhancement of the excitability of flexor reflex was induced by intrathecal administration of NMU-23 (4 nmol/10 microl). Evoked responses to touch and pinch stimuli were increased by 439+/-94% and 188+/-36% (P<0.01, n=6) respectively. The behavioral and electrophysiological data demonstrate, for the first time, a pro-nociceptive action of NMU. The restricted distribution of NMU receptors to a region of the spinal cord involved in nociception suggests that this peptide receptor system may play a role in nociception.

Selective depression of nociceptive responses of dorsal horn neurones by SNC 80 in a perfused hindquarter preparation of adult mouse

Detailed electrophysiological characterisation of spinal opioid receptors in the mouse has been limited due to various technical difficulties. In this study, extracellular single unit recordings were made from dorsal horn neurones in a perfused spinal cord with attached trunk-hindquarter to investigate the role of delta-opioid receptor in mediating nociceptive and non-nociceptive transmission in mouse. Noxious electrical shock, pinch and heat stimuli evoked a mean response of 20.8+/-2.5 (n=10, P<0.005), 30.1+/-5.4 (n=58, P<0.005) and 40.9+/-6.3 (n=29, P<0.005) spikes per stimulus respectively. In 5 of 22 cells, repetitive noxious electrical stimuli applied to the hindpaw for 20 s produced a progressive increase in spike number, the phenomenon known as 'wind-up' and/or hyperactivity. When the selective delta-opioid receptor agonist (+)-4-[(alpha R)-alpha-((2S,5R)-4-allyl-2,5-dimethyl-1-piperazinyl)-3-methoxybenzyl]-N,N-diethylbenzamide (SNC 80) was perfused for 8-10 min, these evoked nociceptive responses were reversibly depressed. SNC 80 (2 microM) depressed the nociceptive responses evoked by electrical shock, pinch and heat by 74.0+/-13.7% (n=8, P<0.01), 66.5+/-16.6% (n=10, P<0.01) and 74.1+/-17.0% (n=10, P<0.01) respectively. The maximum depression by 5 microM SNC 80 was 92.6+/-6.8% (n=3). SNC 80 at 5 microM also completely abolished the wind-up and/or hypersensitivity (n=5). The depressant effects of SNC 80 on the nociceptive responses were completely blocked by 10 microM naloxone (n=5) and 3 microM 17-(cyclopropylmethyl)-6,7-dehydro-4,5 alpha-epoxy-14 beta-ethoxy-5 beta-methylindolo [2',3':6',7'] morphinan-3-ol hydrochloride (HS 378, n=8), a novel highly selective delta-opioid receptor antagonist. Interestingly, HS 378 (3 microM) itself potentiated the background activity and evoked responses to pinch and heat by 151.8+/-38.4% (P<0.05, n=8), 34.2+/-6.1% (P<0.01, n=7) and 45.5+/-11.8% (P<0.05, n=5) respectively. In contrast, the responses of non-nociceptive dorsal horn neurones were not inhibited by SNC 80 at a dose of up to 10 microM (n=5). These data demonstrate that delta-opioid receptor modulate nociceptive, but not non-nociceptive, transmission in spinal dorsal horn neurones of the adult mouse. The potentiation of neuronal activity by HS 378 may reflect an autoregulatory role of the endogenous delta-opioid in nociceptive transmission in mouse.

Photon statistics of random lasers with resonant feedback

We have measured the photon statistics of random lasers with resonant feedback. With an increase of the pump intensity, the photon number distribution in a single mode changes continuously from Bose-Einstein distribution at the threshold to Poisson distribution well above the threshold. The second-order correlation coefficient drops gradually from 2 to 1. By comparing the photon statistics of a random laser with resonant feedback and that of a random laser with nonresonant feedback, we illustrate very different lasing mechanisms for the two types of random lasers.

Spinal delta-opioid receptors mediate suppression of systemic SNC80 on excitability of the flexor reflex in normal and inflamed rat

Due to low central nervous system (CNS) bioavailability of delta-opioid peptides, little is known about the effect of systemic administration of delta-opioid receptor ligands. The present study examined the effect of non-peptidergic delta-opioid receptor agonists, (+)-4-[(alphaR)-alpha-((2R,5R)-4-Allyl-2,5-dimethyl-1-piperazinyl)-3-methoxybenzyl]-N,N-diethylbenzamide (SNC80) and (-)dibenzoyl-L-tartaric acid salt (SNC86), on the activity of alpha-motoneurons in decerebrate-spinal rats. The flexor reflex was facilitated by C-afferent conditioning inputs, shown by a decrease in mechanical threshold and increase in touch- and pinch-evoked responses. Systemic administration of SNC80 (10 micromol/kg) prevented and reversed the neuronal hyperactivity. We further examined the effect of this agonist on the hypersensitivity of the flexor reflex induced by intraplantar injection of Freund's adjuvant. SNC80 dose-dependently (1, 3, 5 and 10 micromol/kg) increased the mechanical threshold and decreased touch-, pinch- and Abeta-afferent inputs-evoked responses. Similar effects were seen with SNC86 (5 micromol/kg). Pretreatment with either naloxone (20 micromol/kg, i.p.) or (Cyclopropylmethyl)-6,7-dehydro-4,5alpha-epoxy-14beta-ethoxy-5beta-methylindolo [2',3':6',7']morphinan-3-ol hydrochloride (SH378; 5 micromol/kg, intraarterially (i.a.)), a novel selective delta-opioid receptor antagonist, completely abolished the anti-hypersensitivity effect of SNC80. The effect of SNC80 remained following intrathecal administration of mu-opioid receptor antagonist D-Phe-Cys-Tyr-D-Trp-Orn-Thr-Pen-Thr-NH(2) (CTOP; 1.5 nmol). These results indicate that systemic injection of SNC80 exerted antihypersensitivity in models of both acute and tonic nociception and these effects are mediated mainly through a spinal delta-opioid mechanism.

Pattern of marine mass extinction near the Permian-Triassic boundary in South China

The Meishan section across the Permian-Triassic boundary in South China is the most thoroughly investigated in the world. A statistical analysis of the occurrences of 162 genera and 333 species confirms a sudden extinction event at 251.4 million years ago, coincident with a dramatic depletion of delta13C(carbonate) and an increase in microspherules.

Metabotropic glutamate receptor antagonists, like GABA(B) antagonists, potentiate dorsal root-evoked excitatory synaptic transmission at neonatal rat spinal motoneurons in vitro

Recordings of whole-cell synaptic current responses elicited by electrical stimulation of dorsal roots were made from motoneurons, identified by antidromic invasion, in isolated spinal cord preparations from five- to eight-day-old Wistar rats. Supramaximal electrical stimulation of the dorsal root evoked complex excitatory postsynaptic currents with mean latencies (+/- S.E.M.) of 6.1 +/- 0.26 ms, peak amplitude of -650 +/- 47 pA and duration of 4.30 +/- 0.46 s (n=34). All phases of excitatory postsynaptic currents were potentiated to approximately 20% above control levels in the presence of the metabotropic glutamate receptor antagonists S-2-amino-2-methyl-4-phosphonobutanoate (MAP4; 200 microM; n=15) and 2S, 1'S,2'S-2-methyl-2-(carboxycyclopropyl)glycine (MCCG; 200 microM; n=9). A similar level of potentiation was produced by the GABA(B) receptor antagonist 3-N[1-(S)-(3,4-dichlorophenyl)ethyl]amino-2-(S)-hydroxypropyl-P-benzyl-p hosphinic acid (CGP55845; 200 nM; n=5). MAP4 (200 microM) produced a six-fold rightward shift in the concentration-effect plot for the depressant action of the metabotropic glutamate receptor agonist S-2-amino-4-phosphonobutanoate (L-AP4), whereas CGP55845 produced no significant change in the potency of L-AP4. MAP4 did not antagonize the depressant actions of baclofen (n=8), 1S,3S-1-aminocyclopentane-1,3-dicarboxylate (n=4) or 2-S,1'S,2'S-2-(carboxycyclopropyl)glycine (n=4). The metabotropic glutamate receptor antagonists produced no change in the holding current of any of the neurons, indicating that they had no significant postsynaptic excitatory actions. These results are the first to indicate a possible physiological role for metabotropic glutamate receptors in the spinal cord. Like GABA(B) receptors, they control glutamatergic synaptic transmission in the segmental spinal pathway to motoneurons. This is likely to be a presynaptic control mechanism.

Antagonism of mGlu receptors and potentiation of EPSCs at rat spinal motoneurones in vitro

The patch-clamp technique has been used to record synaptic responses, elicited by electrical stimulation of dorsal roots, in 28 single motoneurones of in vitro spinal cord preparations from neonate (P5 to P8) rats. The effects of (RS)-alpha-methyl-4-phosphonophenylglycine (MPPG) (200 microM), a potent antagonist at L-2-amino-4-phosphonobutanoate (AP4)-sensitive receptors, and (RS)-alpha-methyl-4-carboxyphenylglycine (MCPG) (500 microM), which is a less selective antagonist of mGluRs, were tested on EPSCs alone and as antagonists of AP4-induced depression of EPSCs. The EC50 for depression of EPSCs by AP4 (1.16 +/- 0.12 microM, n = 8) was increased to 18.9 +/- 0.7 microM (n = 6) by MPPG. MCPG (500 microM) had no significant effect on the depressant potency of AP4. Under control conditions, EPSCs had mean peak amplitudes of 983 pA +/- 64 SEM and mean charge transferred of 306 +/- 37 pC (n = 28). These values were increased significantly (p < 0.05) to 1168 +/- 68 pA and 363 +/- 39 pC by MPPG (n = 6), and 1150 +/- 54 pA and 358 +/- 33 pC (n = 6) by MCPG. There was no significant difference between the enhancement of the initial peak of the EPSCs (mean latency from stimulus artifact 5.9 +/- 0.3 ms) and later components, suggesting mGluRs to be present on primary afferent terminals presynaptic to motoneurones as well as in pathways via interneurones. These results are consistent with the presence of at least two types of presynaptic mGluR that modulate release of glutamate in segmental pathways convergent onto motoneurones. These receptors appear to be activated by interstitial glutamate tonically present in the present preparations.

Effect of raised Mg2+ on the antidromic activation of immature rat spinal motoneurones in vitro

Currents elicited by electrical stimulation of the ventral root were recorded from motoneurones of the immature rat spinal cord in vitro using the patch pipette technique. Control medium contained Ca2+ (1.5 mM) and Mg2+ (0.75 mM). In nine preparations the mean amplitude of antidromic current responses was 5.12 +/- 0.41 nA. Raising Mg2+ (EC50 9.6 +/- 1.1 mM) to levels up to 50 mM produced an all-or-none maximal depression of the current responses by 69 +/- 1%. These levels of Mg2+ depressed currents elicited by depolarizing command steps by only 30% and compound action potentials recorded in ventral roots by only 17%. It is concluded that raised Mg2+ caused conduction block from the initial segment to the soma dendritic region of motoneurones. This non-synaptic depressant action of raised Mg2+ should be considered when raised Mg2+ is used in order to specifically block synaptic activity in vitro.

A comparison of the effects of selective metabotropic glutamate receptor agonists on synaptically evoked whole cell currents of rat spinal ventral horn neurones in vitro

1. Whole cell synaptic currents were recorded under voltage clamp from a total of 54 ventral horn neurones held near to their resting potential by the patch clamp technique in immature rat spinal cord preparations in vitro. Twenty eight neurones were identified, by antidromic invasion from ventral roots, as motoneurones. Excitatory postsynaptic currents (e.p.s.cs) of peak amplitude -480 pA +/- 66 s.e. mean and -829 +/- 124 pA were evoked respectively from the unidentified ventral horn neurones and the motoneurones in response to maximal activation of the segmental dorsal root. 2. The e.p.s.cs were depressed reversibly by the metabotropic glutamate agonists 1S3S-1-aminocyclopentane-1,3-dicarboxylate (1S3S-ACPD) (EC50 17.1 microM +/- 0.3 s.e. mean, n = 14) and L-2-amino-4-phosphonobutanoate (L-AP4) (EC50 = 2.19 +/- 0.19 microM, n = 15). Since both agonists independently produced more than 90% depression it is likely that the receptors that mediate their effects are present on the same presynaptic terminals. 3. When the Mg2+ concentration was raised from 0.75 mM to 2.75 mM together with the addition of 50 microM D-2-amino-5-phosphonopentanoate (AP5), a treatment which would increase the proportion of monosynaptic component in the e.p.s.c. the concentration-effect plots for both 1S3S-ACPD (EC50 1.95 +/- 0.4 microM, n = 8) and L-AP4 (EC50 0.55 +/- 0.20 microM, n = 7) were shifted to the left, suggesting that monosynaptic e.p.cs of primary afferents to ventral horn neurones are more susceptible to L-AP4 and 1S3S-ACPD than are other synapses in polysynaptic pathways. 4. lS3S-ACPD (20 and 50 microM) also caused mean sustained inward currents of 95 +/- 31 pA (n = 6) and248 +/- 49 pA (n = 10) respectively. In the combined presence of AP5 (50 microM) and Mg2+ (2.75 mM) themean response to 50 microM lS3S-ACPD was reduced to 106+/- 18 pA (n = 4). In the presence of tetrodotoxin(1 microM) the corresponding value was 48 +/- 6 pA (n = 4). Similar sustained inward currents produced by N-methyl-D-aspartate (NMDA) were almost abolished to < 10 pA in the presence of AP5 and 2.75 mMMg2+. In the presence of tetrodotoxin the maximum inward current produced by NMDA was undiminished. Thus a large component of the excitatory action of lS3S-ACPD was mediated at non-NMDA receptors both directly at the patch-clamped neurones and indirectly by synaptic relay.

Antagonism of baclofen-induced depression of whole-cell synaptic currents in spinal dorsal horn neurones by the potent GABAB antagonist CGP55845

The potencies of two GABAB receptor antagonists P-[3-aminopropyl]- P-diethoxymethyl-phosphinic acid (CGP35348) and the novel compound 3-N[1-(S)-(3,4-dichlorophenyl)ethyl]amino-2-(S)-hydroxypropyl-P- benzyl-phosphinic acid (CGP55845) have been compared in an in vitro spinal cord preparation. They have been tested as antagonists of baclofen-induced depression of EPSCs of patch-clamped dorsal horn neurons following electrical stimulation of dorsal roots. Mean EC50 values for the depressant action of baclofen were increased by 50- and 140-fold respectively in the presence of CGP35348 (200 microM) (n = 5) and CGP55845 (100 nM) (n = 4). This potency of CGP55845 is > 1000-fold higher than that reported previously for other GABAB receptor antagonists.

Lumbosacral spinal neurons in the cat that are candidates for being activated by collaterals from the spinocervical tract

Lumbosacral spinal neurons activated via the spinocervical tract were stained by intracellular injection of horseradish peroxidase in cats anaesthetized with chloralose and paralysed with gallamine triethiodide. The neurons were activated orthodromically by single shock stimulation of the ipsilateral dorsolateral funiculus at the second to third cervical segment, but not from the rostral part of the first cervical segment. Twenty nine cells were recovered from the histological material and subsequently reconstructed from transverse sections. Sixteen cells (55%) had axons that projected ipsilaterally to the lateral funiculus and their somata were located in two regions of the spinal cord, one group in the dorsal horn (laminae IV-V) and the other in the intermediate gray matter (laminae VI-VII). The axons of 10 of these cells gave off collaterals, and in seven of them the collaterals ramified in the grey matter deep to the cell body. The axons of five cells (17%) projected medially towards the central canal, four crossing the mid line in the ventral white commissure and ascending in the contralateral ventral funiculus. Only one of these cells had an axon collateral that crossed into the contralateral dorsal horn. Of the remaining eight cells, three had no obvious long axons but had many local axon collaterals, the axons of three cells were not stained, one had an axon projecting towards the ipsilateral ventral funiculus and one was a motoneuron and its axon projected into a ventral root. A feature of the dendritic trees of many cells was their wide spread in the mediolateral and/or the dorsoventral directions, although no dendrites reached dorsally into lamina II. Twenty-two cells (76%) were excited by moving hairs and by noxious pinch, three (10%) by hair movement alone, two (7%) by noxious pinch and pressure, and for two cells (7%) no receptive field could be found. It is concluded that not only postsynaptic dorsal column neurons receive input from the spinocervical tract but also other cells in the dorsal and ventral horns and the intermediate gray matter. Possible identities for these cells are discussed.

Physiological and morphological characteristics of cat masticatory motoneurons--intracellular injection of HRP

The physiology and morphology of masticatory motoneurons of adult cats were examined by the methods of intracellular recording and intracellular injection of horseradish peroxidase. Masseter and jaw-opening motoneurons were identified by intracellular recordings of the antidromic response following stimulation of the masseter and mylohyoid nerves, respectively. An excitatory postsynaptic potential (EPSP) was recorded from masseter neurons by stimulation of the masseter nerve with stimulus intensity below threshold for antidromic response. In contrast, the EPSP was not recorded from jaw-opening motoneurons by stimulation of the mylohyoid nerve with stimulus intensity below threshold for antidromic response. Patterns of postsynaptic potentials (PSPs) in the masseter motoneurons following stimulation of the tooth pulp or periodontal afferents were classified into 4 types: hyperpolarization (n = 40), depolarization-hyperpolarization (n = 9), hyperpolarization-depolarization (n = 5), and depolarization with spike potentials (n = 10). On the other hand, patterns of the PSPs in the jaw-opening motoneurons following stimulation of the same afferents were classified into two types: depolarization with spike potentials (n = 19), and hyperpolarization (n = 5). Twenty-five masseter and 7 jaw-opening motoneurons and an intranuclear neuron were reconstructed from serial sections in the transverse plane. On the basis of dendritic morphology, the masseter motoneurons could be classified into two major groups, type I (n = 15) and type II (n = 9), whereas two neurons were found to constitute a separate category of the masseter motoneuron. The dendritic distributions of all the jaw-opening motoneurons examined were generally similar and there was no indication of the existence of subtypes, whereas there were 2 or 3 subgroups in type I and type II masseter motoneurons. Type I masseter neurons had primary dendrites which extended radially in all directions, and the whole profile of their dendritic trees presented a spherical and an egg-shaped appearance. In type II masseter neurons, the origin of primary dendrites was bipolar or tripolar, and the whole profile of their dendritic trees presented a hemispherical and mirror-imaged, funnel-shaped appearance. The other two masseter motoneurons had a particular dendritic tree which was much simpler in configuration, with less tapering or branching than those of other neurons examined. In contrast, the dendritic profiles of all the jaw-opening motoneurons were similarly organized and showed vertically oriented dendritic trees which were more developed in the dorsomedial than in the ventrolateral direction.(ABSTRACT TRUNCATED AT 400 WORDS)

Morphology of single mesencephalic trigeminal neurons innervating masseter muscle of the cat

The morphology of functionally identified single axons of mesencephalic trigeminal neurons was studied in the cat by the method of intra-axonal injection of horseradish peroxidase (HRP). Each axon can be divided into united (U), peripheral (P) and central branches (C). The united axon (U) descends from its soma within the tract of the trigeminal mesencephalic nucleus to the dorsal aspect of the trigeminal motor nucleus (Vmo), where it splits into peripheral and descending central branches with a Y-shaped bifurcation. The peripheral axon (P) joins the motor root of the trigeminal nerve to exit the brainstem. The central axon (C) travels caudally within the juxtatrigeminal regions (or lateral reticular formation). All 3 branches issue axon collaterals that distribute terminal boutons within the dorsolateral subdivision of Vmo, supra- and intertrigeminal regions. Collaterals emanating from the central axon (C) except for its proximal segment travel ventrolaterally within the juxtatrigeminal regions, and send their terminal branches into the lateral boundaries adjacent to the spinal trigeminal nucleus. The trajectory of terminal branches distinguishes group Ia afferents from the possible group II afferents. The majority of terminal boutons are found to distribute in the supra- and intertrigeminal regions for group II afferent fibers and in the dorsolateral subdivision of Vmo for group Ia afferents.