[CHANGE OF CHARACTER OF INTERSYSTEMIC INTERACTIONS IN NEWBORN RAT PUPS UNDER CONDITIONS OF A DECREASE OF MOTOR ACTIVITY].

Interaction of slow-wave.rhythmic components of cardiac, respiratory.and motor activity was investigated in newborn rat pups on the first day after birth under normal conditions and after pharmacological depression of spontaneous periodic motor activity (SPMA) produced by injecting myocuran (myanesin) at low (100 mg/pg, i/p) and maximal (235 mg/pg, i/p) dosages. The data obtained allow to infer that in rat pups after birth the intersystemic interactions are realized mainly via slow-wave oscillations of about-one- and many-minute ranges whereas the rhythms of decasecond range do not play a significant role in integrative processes. Injection of miocuran at a dose causing no muscle relaxation and no inhibition of motor activity produces changes of the cardiac and respiratory rhythms as well as a transitory decrease of the magnitude of coordinate relations mediated by the rhythms of about-one- and many-minute ranges. The consequences of muscle relaxant injection were found to be more significant for intersystemic interactions with participation of the respiratory system. An increase of the dosage and, correspondingly, the total inhibition of SPMA is accompanied by reduction of the slow-wave components from the pattern of cardiac and respiratory rhythms. The cardiorespiratory interactions, more expressed in intact rat pups, are reduced in the about-one- and many-minute ranges of modulation whereas in the decasecond range of modulation they are slightly increased. Key words: early ontogenesis, intersystemic interactions, cardiac rhythm, respiration, motor activity, myocuran (myanesin).

Conformational flexibility of mephenesin.

The mephenesin molecule (3-(2-methylphenoxy)propane-1,2-diol) serves as a test bank to explore several structural and dynamical issues, such as conformational flexibility, the orientation of the carbon linear chain relative to the benzene plane, or the effect of substituent position on the rotational barrier of a methyl group. The molecule has been studied by rotational spectroscopy in the 4-18 GHz frequency range by Fourier-transform methods in a supersonic expansion. The experiment has been backed by a previous conformational search plus optimization of the lowest energy structures by ab initio and density functional quantum calculations. The three lowest-lying conformers that can interconvert to each other by simple bond rotations have been detected in the jet. Rotational parameters for all structures have been obtained, and methyl torsional barriers have been determined for the two lowest-lying rotamers. The lowest-lying structure of mephenesin is highly planar, with all carbon atoms lying nearly in the benzene ring plane, and is stabilized by the formation of cooperative intramolecular hydrogen bonding. An estimation of the relative abundance of the detected conformers indicates that the energetically most stable conformer will have an abundance near 80% at temperatures relevant for biological activity.

Mephenesin: abuse and dependence.

Mephenesin is a muscle relaxant with poorly documented clinical value. Its sedative properties have been known since its introduction on the French market. Cases of abuse and dependence have been reported, particularly since the early 2010s. Some adults were reported to be taking up to 12 g of mephenesin per day, the equivalent of an entire box. Most of them had a history of dependence on various other psychotropic drugs. Withdrawal symptoms, including tremor, anxiety, and aggression, have been reported in 3 patients. A woman who was taking no other drugs died of bronchial aspiration following mephenesin overdose. Painful muscle spasm is sometimes relieved by a short rest period, or paracetamol. Repeated requests for mephenesin should alert health professionals to the possibility of abuse. It is best to avoid mephenesin altogether, especially when the patient has a history of abuse or dependence.

Vestibular-mediated synaptic inputs and pathways to sympathetic preganglionic neurons in the neonatal mouse.

To assess when vestibulosympathetic projections become functional postnatally, and to establish a preparation in which vestibulosympathetic circuitry can be characterized more precisely, we used an optical approach to record VIIIth nerve-evoked synaptic inputs to thoracic sympathetic preganglionic neurons (SPNs) in newborn mice. Stimulation of the VIIIth nerve was performed in an isolated brainstem-spinal cord preparation after retrogradely labelling with the fluorescent calcium indicator Calcium Green 1-conjugated dextran amine, the SPNs and the somatic motoneurons (MNs) in the thoracic (T) segments T2, 4, 6, 8, 10 and 12. Synaptically mediated calcium responses could be visualized and recorded in individual SPNs and MNs, and analysed with respect to latency, temporal pattern, magnitude and synaptic pharmacology. VIIIth nerve stimulation evoked responses in all SPNs and MNs investigated. The SPN responses had onset latencies from 90 to 200 ms, compared with much shorter latencies in MNs, and were completely abolished by mephenesin, a drug that preferentially reduces polysynaptic over monosynaptic transmission. Bicuculline and picrotoxin, but not strychnine, increased the magnitudes of the SPN responses without changing the onset latencies, suggesting a convergence of concomitant excitatory and inhibitory synaptic inputs. Lesions strategically placed to test the involvement of direct vestibulospinal pathways versus indirect pathways within the brainstem showed that vestibulosympathetic inputs in the neonate are mediated predominantly, if not exclusively, by the latter. Thus, already at birth, synaptic connections in the vestibulosympathetic reflex are functional and require the involvement of the ventrolateral medulla as in adult mammals.

Organization of functional synaptic connections between medullary reticulospinal neurons and lumbar descending commissural interneurons in the neonatal mouse.

The medullary reticular formation (MRF) of the neonatal mouse is organized so that the medial and lateral MRF activate hindlimb and trunk motoneurons (MNs) with differential predominance. The goal of the present study was to investigate whether this activation is polysynaptic and mediated by commissural interneurons with descending axons (dCINs) in the lumbar spinal cord. To this end, we tested the polysynapticity of inputs from the MRF to MNs and tested for the presence of selective inputs from medial and lateral MRF to 574 individual dCINs in the L2 segment of the neonatal mouse. Reticulospinal-mediated postsynaptic Ca(2+) responses in MNs were reduced in the presence of mephenesin and after a midline lesion, suggesting the involvement of dCINs in mediating the responses. Consistent with this, stimulation of reticulospinal neurons in the medial or lateral MRF activated 51% and 57% of ipsilateral dCINs examined (255 and 352 dCINs, respectively) and 52% and 46% of contralateral dCINs examined (166 and 133 dCINs, respectively). The proportion of dCINs that responded specifically to stimulation of medial or lateral MRF was similar to the proportions of dCINs that responded to both MRF regions or to neither. The three responsive dCIN populations had largely overlapping spatial distributions. We demonstrate the existence of dCIN subpopulations sufficient to mediate responses in lumbar motoneurons from reticulospinal pathways originating from the medial and lateral MRF. Differential control of trunk and hindlimb muscles by the medullary reticulospinal system may therefore be mediated in part by identifiable dCIN populations.

Segmental patterns of vestibular-mediated synaptic inputs to axial and limb motoneurons in the neonatal mouse assessed by optical recording.

Proper control of movement and posture occurs partly via descending projections from the vestibular nuclei to spinal motor circuits. Days before birth in rodents, vestibulospinal neurons develop axonal projections that extend to the spinal cord. How functional these projections are just after birth is unknown. Our goal was to assess the overall functional organization of vestibulospinal inputs to spinal motoneurons in a brainstem-spinal cord preparation of the neonatal mouse (postnatal day (P) 0-5). Using calcium imaging, we recorded responses evoked by electrical stimulation of the VIIIth nerve, in many motoneurons simultaneously throughout the spinal cord (C2, C6, T7, L2 and L5 segments), in the medial and lateral motor columns. Selective lesions in the brainstem and/or spinal cord distinguished which tracts contributed to the responses: those in the cervical cord originated primarily from the medial vestibulospinal tracts but with a substantial contribution from the lateral vestibulospinal tract; those in the thoracolumbar cord originated exclusively from the lateral vestibulospinal tract. In the thoracolumbar but not the cervical cord, excitatory commissural connections mediated vestibular responses in contralateral motoneurons. Pharmacological blockade of GABA(A) receptors showed that responses involved a convergence of excitatory and inhibitory inputs which in combination produced temporal response patterns specific for different segmental levels. Our results show that by birth vestibulospinal projections in rodents have already established functional synapses and are organized to differentially regulate activity in neck and limb motoneurons in a tract- and segment-specific pattern similar to that in adult mammals. Thus, this particular set of descending projections develops several key features of connectivity appropriately at prenatal stages. We also present novel information about vestibulospinal inputs to axial motoneurons in mammals, providing a more comprehensive platform for future studies into the overall organization of vestibulospinal inputs and their role in regulating postural stability.

[Acute generalized exanthematous pustulosis induced by topical application of Algipan]. / Pustulose exanthématique aiguë généralisée induite par l'application d'Algipan.

BACKGROUND: In most cases, acute generalized exanthematous pustulosis (AGEP) is a drug reaction. Even if several systemic drugs have been reported to be a causative agent, this clinical case has rarely been observed with a topical treatment. We report here a case of AGEP after topical application of Algipan. PATIENTS AND METHODS: A 51-year-old man consulted us for a skin rash with fever which started 72 h earlier. His personal history consisted only of lumbar pain and he was not under any oral medication. The skin rash was initially limited to the left hand and the back but quickly spread to the entire skin with multiple non-follicular pustules emerging on widespread and inflamed erythema. No systemic treatment was being taken prior the eruption. Nevertheless, 3 days before the skin rash appeared, the patient had applied Algipan to the lumbar area with his left hand. The whole clinical presentation leads us to diagnose Algipan-induced AGEP. The clinical signs improved rapidly. Patch tests performed 3 months later were positive for the whole product, thereby confirming our diagnosis. DISCUSSION: AGEP is drug-induced in more than 90% of cases, mostly after antibiotics, especially beta-lactams and macrolides. Algipan is a topical treatment containing mephenesin used for its analgesic and anti-inflammatory properties in adult muscular pain. No severe skin drug reactions due to this drug have been reported to date. Cases of AGEP induced by topical agents are rarely reported and our case is the first involving mephenesin. Our study suggests that topical mephenesin should be noted as a drug that may cause AGEP.

Validación de un método cromatográfico para la cuantificación de mefenesina en tabletas de producción nacional / A chromatographic method validation to quantify tablets Mephenesine of national production

Se realizó la validación de un método analítico por cromatografía líquida de alta eficiencia para la cuantificación de mefenesina en tabletas de 500 mg reformuladas recientemente. Con respecto a su aplicación al control de calidad, la validación incluyó los parßmetros linealidad, exactitud, precisión y selectividad. Los resultados fueron satisfactorios en el rango de 50-150 por ciento. Para su empleo en estudios posteriores de estabilidad química, se evaluó adicionalmente la selectividad para estabilidad y la sensibilidad. Los límites de detección y cuantificación estimados resultaron adecuados y el método fue selectivo frente a los posibles productos de degradación.

Authors made validation of an analytical method by high performance liquid chromatography (HPLC) for quantification of Mephenesine in recently reformulated 500 mg tablets. With regard to its application to quality control, validation included the following parameters: linearity, accuracy, precision, and selectivity. Results were satisfactory within 50-150 percent rank. In the case of its use in subsequent studies of chemical stability, the selectivity for stability and sensitivity was assessed. Estimated detection and quantification limits were appropriate, and the method was selective versus the possible degradation products.

Validación de un método cromatográfico para la cuantificación de mefenesina en tabletas de producción nacional / A chromatographic method validation to quantify tablets Mephenesine of national production

Se realizó la validación de un método analítico por cromatografía líquida de alta eficiencia para la cuantificación de mefenesina en tabletas de 500 mg reformuladas recientemente. Con respecto a su aplicación al control de calidad, la validación incluyó los parßmetros linealidad, exactitud, precisión y selectividad. Los resultados fueron satisfactorios en el rango de 50-150 por ciento. Para su empleo en estudios posteriores de estabilidad química, se evaluó adicionalmente la selectividad para estabilidad y la sensibilidad. Los límites de detección y cuantificación estimados resultaron adecuados y el método fue selectivo frente a los posibles productos de degradación(AU)

Authors made validation of an analytical method by high performance liquid chromatography (HPLC) for quantification of Mephenesine in recently reformulated 500 mg tablets. With regard to its application to quality control, validation included the following parameters: linearity, accuracy, precision, and selectivity. Results were satisfactory within 50-150 percent rank. In the case of its use in subsequent studies of chemical stability, the selectivity for stability and sensitivity was assessed. Estimated detection and quantification limits were appropriate, and the method was selective versus the possible degradation products(AU)

Fatal mephenesin intoxication.

This report describes a death related to the abuse of and intoxication by mephenesin. To the best of our knowledge, this is the first report case of lethal intoxication involving solely mephenesin and reporting mephenesin blood concentrations. The victim was a 48-year-old woman found unconscious at home. Resuscitation was unsuccessful. Toxicological analysis was performed on a blood sample collected during resuscitation. The results being negative, the body was exhumed for an autopsy, which revealed bronchial inhalation syndrome. Analysis in a second laboratory has revealed the presence of mephenesin in samples collected during autopsy. No other drug/toxin was found, and alcohol was negative. Reanalysis of the peripheral blood collected during resuscitation found a mephenesin concentration of 15.81 microg/mL (15-fold greater that the maximum concentration that would result from a single intake of a 500 mg formulation). The pathologist has concluded on a bronchial inhalation syndrome consecutive to a mephenesin overdose as the cause of death. The manner of this death is discussed in the light of the toxicological hair analysis and the medical past of the victim.

The synthesis of amphipathic prodrugs of 1,2-diol drugs with saccharide conjugates by high regioselective enzymatic protocol.

A facile, high regioselective enzymatic synthesis approach for the preparation of amphipathic prodrugs with saccharides of mephenesin and chlorphenesin was developed. Firstly, transesterification of two drugs with divinyl dicarboxylates with different carbon chain length was performed under the catalysis of Candida antarctica lipase acrylic resin and Lipozyme in anhydrous acetone at 50 degrees C, respectively. A series of lipophilic derivatives with vinyl groups of mephenesin and chlorphenesin were prepared. The influences of different organic solvents, enzyme sources, reaction time, and the acylation reagents on the synthesis of vinyl esters were investigated. And then, protease-catalyzed high regioselective acylation of D-glucose and D-mannose with vinyl esters of mephenesin and chlorphenesin gave drug-saccharide derivatives in good yields. The studies of lipophilicity and hydrolysis in vitro of prodrugs verified that drug-saccharide derivatives had amphipathic properties, and both lipophilic and amphipathic drug derivatives had obvious controlled release characteristics.

Spinal ventral root after-discharges as a pain index: involvement of NK-1 and NMDA receptors.

Nociceptive signals are transmitted to the spinal dorsal horn via primary afferent fibers, and the signals induce withdrawal reflexes by activating spinal motoneurons in the ventral horn. Therefore, nociceptive stimuli increase motoneuronal firing and ventral root discharges. This study was aimed to develop a method for the study of pain mechanisms and analgesics by recording ventral root discharges. Spinalized rats were laminectomized in the lumbo-sacral region. The fifth lumbar ventral root was sectioned and placed on a pair of wire electrodes. Multi unit efferent discharges from the ventral root were increased by mechanical stimulation using a von Frey hair applied to the plantar surface of the hindpaw. The low-intensity mechanical stimuli increased the discharges during stimulation (during-discharges) without increasing the discharges after cessation of stimulation (after-discharges), and the high-intensity mechanical stimuli increased both during- and after-discharges. Pretreatment with resiniferatoxin, an ultrapotent analogue of capsaicin, halved during-discharges and eliminated after-discharges, suggesting that after-discharges are generated by heat- and mechanosensitive polymodal nociceptors. Ezlopitant, a neurokinin-1 (NK-1) receptor antagonist, but not its inactive enantiomer, selectively reduced the after-discharges. Ketamine, an N-methyl-D-aspartate (NMDA) receptor antagonist, preferentially reduced the after-discharges, demonstrating that NK-1 and NMDA receptors mediate the after-discharges. Morphine reduced the after-discharges without affecting during-discharges. By contrast, mephenesin, a centrally acting muscle relaxant, reduced both during- and after-discharges. There results suggest that simultaneous recordings of during- and after-discharges are useful to study pain mechanisms and analgesics as well as to discriminate the analgesic effects from the side effects such as muscle relaxant effects.

Presynaptic GABAergic control of the locomotor drive in the isolated spinal cord of neonatal rats.

The in vitro newborn rat isolated brain stem/spinal cord preparation was used to study the involvement of presynaptic inhibition in the control of the synaptic locomotor drive. The recording chamber was partitioned with Vaseline walls to separate the L1-L2 locomotor network from the motoneurons in the lower segments. When locomotor like activity was induced by bath applying a mixture of N-methyl-D-L-aspartate and serotonin to the L1-L2 segments, intracellular recordings of L3-L5 motoneurons show an alternating pattern of monosynaptic excitatory glutamatergic and inhibitory glycinergic inputs known as the locomotor drive. Gamma-aminobutyric acid (GABA), baclofen and muscimol (respectively GABA(B) and GABA(A) agonists) superfused on the L3-L5 segments depressed the synaptic locomotor drive of motoneurons during the ongoing activity. On the contrary, the GABA(B) receptor antagonist CGP35348 enhanced the locomotor drive, which suggests that an endogenous release of GABA occurs during locomotor-like activity. Baclofen, unlike muscimol and GABA, did not affect the passive membrane properties and the firing discharge of synaptically isolated motoneurons. Baclofen and muscimol acted on the two phases (inhibitory and excitatory) of the synaptic drive. The effects of GABAergic agonists on the whole locomotor activity were tested. When superfused on the L3-L5 part of the cord, they affected only the L5 burst amplitude. When bath-applied to the L1-L2 network, GABA and muscimol decreased the amplitude of the L2 and L5 bursts and increased the locomotor period while baclofen had significant effects only on the period. It was concluded that GABA modulates the information conveyed by the L1-L2 network to its target motoneurons presynaptically via GABA(B) and possibly GABA(A) receptors and postsynaptically, via GABA(A) receptors.