Comparação de inibições medulares entre indivíduos com doença de Parkinson e saudáveis / Comparison of spinal inhibitions between parkisonian and helathy individuals

O objetivo do presente estudo foi comparar os níveis de inibição pré-sináptica (IPS) e inibição recíproca (IR) entre indivíduos com Doença de Parkinson e saudáveis e, a correlação entre essas inibições e a rigidez muscular e a severidade clínica de indivíduos com Doença de Parkinson (avaliadas através da Escala Unificada de Avaliação da Doença de Parkinson). Foram avaliados 11 indivíduos nos estágios 2 e 3 da doença e 13 indivíduos saudáveis pareados pela idade. A IPS foi menor em indivíduos com Doença de Parkinson (31,6%) do que em saudáveis (67,1%) (p = 0,02). A IR não diferiu entre indivíduos com Doença de Parkinson (26,9%) e saudáveis (27,6%) (p = 0,91). Adicionalmente, não foram detectadas correlações entre os níveis de IPS com a rigidez e a severidade clínica (p > 0,05). Portanto, mecanismos inibitórios não explicam totalmente a rigidez muscular e a severidade clinica da doença. Alterações entre ativação de músculos agonistas e antagonistas parecem estar relacionadas a influências supraespinhais anormais nos mecanismos espinhais decorrentes da doença...

The purposes of the present study were to compare presynaptic inhibition (PI) and disynaptic reciprocal inhibition (DRI) levels between parkinsonians and healthy individuals and to verify the correlation of such inhibitions with muscle rigidity and clinical severity (assessed by the Unified Parkinson Disease Rating Scale). We evaluated 11 parkinsonians in stages 2 and 3 of the disease and 13 healthy individuals matched for age. The PI was significant lower in parkinsonians (31.6%) than in healthy individuals (67.1%) (p = 0.02). The DRI did not differ between parkinsonians (26.9%) and healthy individuals (27.6%) (p = 0.91). Furthermore, no significant correlation was observed between PI with muscle rigidity and clinical severity (p > 0.05). Therefore, inhibitory mechanisms do not fully explain the cause of muscle rigidity and clinical severity of parkinsonians. Changes between the activation of agonist and antagonist muscles seem to be caused by abnormal supraspinal influence on spinal mechanisms...

Roles of metabotropic glutamate receptors on excitatory synaptic transmission in rat trigeminal caudal neurons

Muscarine M2 Receptor-mediated Presynaptic Inhibition of GABAergic Transmission in Rat Meynert Neurons

Cholinergic modulation of GABAergic spontaneous miniature inhibitory postsynaptic currents (mIPSCs) by the activation of muscarine receptors was investigated in mechanically dissociated rat nucleus basalis of the Meynert neurons using the conventional whole-cell patch recording configuration. Muscarine (10microM) reversibly and concentration-dependently decreased mIPSC frequency without affecting the current amplitude distribution. Muscarine action on GABAergic mIPSCs was completely blocked by 1microM methoctramine, a selective M2 receptor antagonist, but not by 1microM pirenzepine, a selective M1 receptor antagonist. NEM (10microM), a G-protein uncoupler, attenuated the inhibitory action of muscarine on GABAergic mIPSC frequency. Muscarine still could decrease GABAergic mIPSC frequency even in the Ca2+-free external solution. However, the inhibitory action of muscarine on GABAergic mIPSCs was completely occluded in the presence of forskolin. The results suggest that muscarine acts presynaptically and reduces the probability of spontaneous GABA release, and that such muscarine-induced inhibitory action seems to be mediated by G-protein-coupled M2 receptors, via the reduction of cAMP production. Accordingly, M2 receptor-mediated disinhibition of nBM neurons might play one of important roles in the regulation of cholinergic outputs from nBM neurons as well as the excitability of nBM neurons themselves.

Effects and mechanism of PNS on synaptic transmission in hippocampal CA1 region of rat / 中草药

Objective To investigate the effects of Panax notoginseng saponins(PNS)on both the excitatory and inhibitory synaptic transmission in the pyramidal neurons in hippocampal CA1 region of rats.Methods Wistar male rats(3—4 weeks)were killed by cervical dislocation and hippocampal slices(400 ?m)were prepared,blind whole-cell voltage-clamp recordings were performed on the CA1 pyramidal cells in hippocampal slices to examine and analyze the effects of PNS(0.05—0.4 g/L)on CA1 afferent fiber-evoked excitatory postsynaptic currents(EPSCs)and inhibitory postsynaptic currents(IPSCs),respectively.Moreover,the Schaffer collateral/commissural pathway was stimulated with paired pulses(interpulse interval was 50 ms)and the paired-pulse facilitation(PPF)was analyzed by EPSC2/EPSC1(P2/P1)ratio.Results PNS(0.1—0.4 g/L)significantly depressed amplitude of EPSCs in neurons in the hippocampal CA1 region(P0.05).Conclusion The inhibitory effect of PNS on EPSCs in hippocampal CA1 pyramidal neurons is not due to the reinforcement of the inhibiting interneurons.It may be a result of direct inhibition on excitatory synaptic transmission.The increasing of P2/P1 ratio after PNS application suggests that PNS depresses the excitatory synaptic transmission by presynaptic mechanism.

Interactions of nicotinic and muscarinic acetylcholine receptors / 中国药理学通报

Nicotinic and muscarinic acetylcholine receptors have the same endogenous ligand ACh and are distributed together in many tissues, so it is reasonable to believe that there must be some interactions existed between them. The functions of muscarinic receptors in the tissues innervated by the parasympathetic cholinergic postfibers, can be modulated by the ganglionic nicotinic receptors through stimulating ACh release. In ganglia, the postsynaptic nicotinic receptor activities can be modulated by the presynaptic muscarinic and nicotinic autoreceptors through regulating ACh release. Moreover, The functions of muscarinic receptors can be changed by nicotinic receptor desensitization or blockade. The two types of receptor act on each other and keep in a varied homeostasis of cholinergic nervous system.

THE INHIBITORY EFFECT OF STIMULATION IN PERIAQUEDUCTAL GREY ON NEURONS IN SPINAL DORSAL HORN AND ITS RELATION TO PAG-CDP / 西安交通大学学报(医学版)

The cord dorsum potential evoked by stimulation in the ventrolateral aspect of periaqueductal grey (PAG-CDP) was recorded from the dorsal surface of the spinal lumbosacral cord in rats. PAG stimulation with the same parameters as for producing PAG-CDP inhibited the C discharges of convergent neurons in spinal dorsal horn. There was a positive correlation between the time course of the inhibitory effect of PAG on convergent neurons and the duration of the slow wave of PAG-CDP. a positive correlation also presented between the latencies of the PAG inhibition and the slow wave. Furthermore, the PAG inhibition did not appear when the intensity of PAG stimulation was below the threshold of PAG-CDP. These results indicate that the presynaptic inhibition is involved in the PAG inhibition of the C discharges of convergent neurons in spinal dorsal horn.

INFLUENCES OF CONDITIONING STIMULI OF PERIPHERAL NERVE ON C-FIBRE AFFERENT TERMINAL EXCITABILITY IN SPINAL TOADS / 西安交通大学学报(医学版)

The antidromic C waves elicited by stimulating the entry zone of the dorsal root were recorded in spinal toads. Influences if conditioning stimuli in 60 T from sciatic nerve on antidromic C waves were observed. The conditioning stimuli produced marked increace in the excitability of the C-afferent terminals. The increased excitability possessed two phases. The results indicat that periphiral primary afferent A and C-fibres can produce presynaptic inhibition in C-fibre terminals.

THE EFFECT OF REMOTE SEGMENTAL ELECTRO-ACUPUNCTURE ON THE FLEXION REFLEX POTENTIAL AND THE DORSAL ROOT POTENTIAL / 西安交通大学学报(医学版)

Deseription was given of the effect of electric acupuncture of Neiguan point on the flexion reflex potential (FRP) of the hindlimbs and the dorsal root potential (DRP). On the intact and awake rats, the graded train stimulation (three pulses, 5ms interval, 0.5ms duration) was given to the sural nerve (a pure cutancous n(?), the C-FRP and C-DRP with their proper amplitudes (70～80% maximum) were obtained on the hamstring nerve (a group of nerves innervating the hindlimb flexors) and L5 dorsal root respectively. Then the electric acupuncture with low freqency and low intensity (4Hz, 1～3V)and low freqency and high intensity ( 4Hz, 20～40V), lasting 5 minutes, was given to the ipsilateral Neiguan point. After acupuncture, the amplitudes of both C-FRP and C-DRP decreased without change of their latebcues. The former one declined heavier and recovered slower than the latter one did. The A-FRP and A-DRP were not affected. Te result of the experiment suggests that the ipsilatcral Neiguan point cletric acupuncture can induce hindlimb's analgesia, the presynaptic inhibition might be involved in the mechanism of such analgesia.

THE DRP EVOKED BY MUSCLE SPINDLE AFFERENTS AND ITS EFFECTS ON THE DRP VRP EVOKED BY STIMULATING N. PERONAEUS / 西安交通大学学报(医学版)

Using the bullforg and toad in experi ments, and making the dorsal root potential (DRP) and ventral rool potential (VRP) as the indexes of the presynaptic inhibition, we examined and analysed the central effects produced by the spindle a fferents during stretching muscle. The results indicat that, aftet muscle paralysis, the phase DRP recorded on dorsal root simultanesously with stretching M. Semitendinosus is produced by spindle afferents, so it is named spindle-DRP'. The characteristic of the spindle-DRP has been discussed in detail. Meanwhile it was found that continual spindle afferents could increase the DRP evoked by electro-stimulating N. peronaeus, can decrease the nerve VRP evoked in this way. These results suggest that the spindle afferents are involved in the acupuncture anaesthesia, perhaps through the presynaptic inhibition. This result may be a new data for the research of the theory of presynaptic inhibition and the principle of acupuncture anaesthesia.