Minocycline cannot protect neurons against bilirubin-induced hyperexcitation in the ventral cochlear nucleus.
Excitotoxicity has been suggested to play an important role in many central nervous system diseases, particularly in bilirubin encephalopathy. Minocycline treatment has been proposed to be one of the most promising potential therapies for excitotoxicity-induced neurological disorders. However, some key questions, such as the electrophysiological effect of minocycline on neuronal excitability and hyperexcitation in pathological conditions, require clarification. In this study, using patch-clamp techniques, we showed that bilirubin increased the frequency of both spontaneous excitatory postsynaptic currents (sEPSCs) and neuronal firing in isolated ventral cochlear nucleus (VCN) neurons at postnatal days 11-14 (P11-14) in rats but it did not affect the amplitude of sEPSCs or glutamate-activated (I(Glu)) currents. However, minocycline had no effect on sEPSC frequency or I(Glu) amplitude. Furthermore, minocycline pretreatment did not abolish bilirubin-induced sEPSC potentiation or neuron firing. These data suggest that minocycline does not affect excitatory synaptic transmission or hyperexcitation induced by bilirubin in VCN neurons. From these results, we propose that the neuroprotective efficacy of minocycline, if it can protect neurons against neurotoxicity induced by substances like bilirubin, is mediated by either an alternative mechanism or downstream events post neuronal hyperexcitation. Certainly, additional investigation of the neuroprotective effects of minocycline is required before embarking on further clinical trials.
Department of Otorhinolaryngology, Affiliated Sixth People's Hospital of Shanghai Jiaotong University, 600 Yishan Road, Shanghai 200233, China.
Chun-Yan
CY
Li
Hai-Bo
HB
Shi
Hai-Bo
HB
Ye
Ning-ying
NY
Song
Shan-Kai
SK
Yin
D000818:Animals; D017209:Apoptosis / Q000502:physiology; D001663:Bilirubin / Q000097:blood / Q000633:toxicity*; D018846:Excitatory Amino Acids / Q000378:metabolism*; D018698:Glutamic Acid / Q000633:toxicity*; D008911:Minocycline / Q000627:therapeutic use*; D009336:Necrosis; D009474:Neurons / Q000378:metabolism / Q000473:pathology* / Q000502:physiology; D018696:Neuroprotective Agents / Q000627:therapeutic use; D018408:Patch-Clamp Techniques / Q000379:methods; D051381:Rats; D017207:Rats, Sprague-Dawley; D009435:Synaptic Transmission / Q000502:physiology; D020651:Ventral Thalamic Nuclei / Q000166:cytology / Q000473:pathology* / Q000502:physiology
D018846:Excitatory Amino Acids; D018696:Neuroprotective Agents; D018698:Glutamic Acid; D008911:Minocycline; D001663:Bilirubin