Dystonia-like behaviors and impaired sensory-motor integration following neurotoxic lesion of the pedunculopontine tegmental nucleus in mice.

Introduction: The pedunculopontine nucleus (PPTg) is a vital interface between the basal ganglia and cerebellum, participating in modulation of the locomotion and muscle tone. Pathological changes of the PPTg have been reported in patients and animal models of dystonia, while its effect and mechanism on the phenotyping of dystonia is still unknown. Methods: In this study, a series of behavioral tests focusing on the specific deficits of dystonia were conducted for mice with bilateral and unilateral PPTg excitotoxic lesion, including the dystonia-like movements evaluation, different types of sensory-motor integrations, explorative behaviors and gait. In addition, neural dysfunctions including apoptosis, neuroinflammation, neurodegeneration and neural activation of PPTg-related motor areas in the basal ganglia, reticular formations and cerebellum were also explored. Results: Both bilateral and unilateral lesion of the PPTg elicited dystonia-like behaviors featured by the hyperactivity of the hindlimb flexors. Moreover, proprioceptive and auditory sensory-motor integrations were impaired in bilaterally lesioned mice, while no overt alterations were found for the tactile sensory-motor integration, explorative behaviors and gait. Similar but milder behavioral deficits were found in the unilaterally lesioned mice, with an effective compensation was observed for the auditory sensory-motor integration. Histologically, no neural loss, apoptosis, neuroinflammation and neurodegeneration were found in the substantia nigra pars compacta and caudate putamen (CPu) following PPTg lesion, while reduced neural activity was found in the dorsolateral part of the CPu and striatal indirect pathway-related structures including subthalamic nucleus, globus pallidus internus and substantia nigra pars reticular. Moreover, the neural activity was decreased for the reticular formations such as pontine reticular nucleus, parvicellular reticular nucleus and gigantocellular reticular nucleus, while deep cerebellar nuclei were spared. Conclusion: In conclusion, lesion of the PPTg could elicit dystonia-like behaviors through its effect on the balance of the striatal pathways and the reticular formations.

The two different effects of the potential neuroprotective compound minocycline on AMPA-type glutamate receptors.

BACKGROUND: Minocycline has demonstrated neuroprotective effects in experimental neurodegenerative diseases. The aim of this study was to investigate if there is any direct interaction between minocycline and the AMPA-type receptor channels, and to elucidate the underlying molecular pharmacological mechanisms. METHODS: The patch-clamp technique was used combined with an ultrafast solution exchange system to investigate the interaction of minocycline with recombinant AMPA-type glutamate receptor channels (homomeric GluR2flipGQ or nondesensitizing GluR2L504Y). RESULTS: Dose-dependent decreases in the relative peak current amplitude (rAmp) and the relative steady-state current (rC(des)) were found in coapplication experiments with GluR2L504Y receptors, but not in preincubation experiments. Furthermore, coapplication of 1 or 3 mmol/l minocycline showed a decrease in the fast time constant of current decay, and reopening currents were observed. But in the test with GluR2flipGQ receptors, rAmp, relative area under the curve and rC(des) increased with increasing concentrations of minocycline, and the steady-state time constant also increased when 3 µmol/l glutamate were used as agonist. CONCLUSION: Minocycline modulates AMPA-type receptor channels in a combination of a weaker open-channel block effect and a stronger potentiation effect, and the latter effect arises mainly from attenuating the extent of receptor desensitization.

Changes in extracellular pH affect glycine receptor channels expressed in HEK 293 cells.

Glycine receptors are expressed throughout the central nervous system working for inhibitory neurotransmission. Since fluctuations of the blood pH value occur under certain physiological and pathological conditions, we investigated the influence of the extracellular pH on glycine homomeric and heteromeric receptor functions using patch clamp in combination with the fast agonist application technique. Our results demonstrated that both alpha1 homomeric and alpha 1 beta heteromeric glycine receptors were remarkably inhibited under acidic extracellular pH. Under alkaline extracellular pH 8.5, there was also a negative functional effect. Desensitization was accelerated depending on pH and a rebound current was observed at an extremely acidic pH value. In double-pulse experiments on alpha1 homomeric receptors, a more rapid recovery of the glycinergic current was shown at pH 4.5 compared to current induced at a physiological pH of 7.2. Our study provided a potential cause for the impaired function of the glycine receptor channels during pH fluctuations occurring in the central nervous system, especially under pathological conditions such as epileptic seizure or ischaemia.

The interaction of the neuroprotective compounds riluzole and phenobarbital with AMPA-type glutamate receptors: a patch-clamp study.

BACKGROUND: Blockade of alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA)-type glutamate receptors is a promising pharmacological strategy in the treatment of neurodegenerative diseases. The aim of the study is to elucidate if there are direct interactions of riluzole and phenobarbital with AMPA-type receptor channels and to determinethe molecular pharmacological mechanisms. METHODS: The patch-clamp technique was used combining an ultrafast solution exchange system to investigate the interaction of riluzole and phenobarbital with recombinant AMPA-type glutamate receptor channels (homomeric GluR2flipGQ or nondesensitizing GluR2L504Y). RESULTS: A dose-dependent decrease in the relative peak current amplitude (rAmp) and the relative area-under-the-current curve (rAUC) were found after preincubation with 0.1 mmol/l or higher concentrations of riluzole. Furthermore, in coapplication experiments with GluR2L504Y, the application of 1 or 3 mmol/l riluzole showed a decrease in the current decay time constant, and a reopening current was observed at 3 mmol/l riluzole. Phenobarbital blocks AMPA receptor channels dose-dependently in the coapplication experiments, and reopening currents after removing glutamate and blocker were observed. A slight block effect after preincubation should indicate an additional competitive block effect. CONCLUSION: Riluzole and phenobarbital modulate AMPA-type receptor channels separately, which could be both characterized as a combination of open-channel block and competitive-block mechanism.