Role of vascular endothelial growth factor as a critical neurotrophic factor for the survival and physiology of motoneurons

Vascular endothelial growth factor(VEGF)was discovered by its angiogenic activity.However,during evolution,it appeared earlier as a neurotrophic factor required for the development of the nervous system in invertebrates lacking a circulatory system.We aimed at reviewing recent evidence indicating that VEGF has neuroprotective effects in neurons exposed to a variety of insults.Of particular interest is the link established between VEGF and motoneurons,especially after the design of the VEGFδ/δmutant mice.These mice are characterized by low levels of VEGF and develop muscle weakness and motoneuron degeneration resembling amyotrophic lateral sclerosis.The administration of VEGF through several routes to animal models of amyotrophic lateral sclerosis delays motor impairment and motoneuron degeneration and increases life expectancy.There are new recent advances in the role of VEGF in the physiology of motoneurons.Our experimental aims use the extraocular(abducens)motoneurons lesioned by axotomy as a model for studying VEGF actions.Axotomized abducens motoneurons exhibit severe alterations in their discharge activity and a loss of synaptic boutons.The exogenous administration of VEGF to axotomized abducens motoneurons,either from the transected nerve or intraventricularly,fully restores the synaptic and discharge properties of abducens motoneurons,despite being axotomized.In addition,when an anti-VEGF neutralizing antibody is delivered from the muscle to intact,uninjured abducens motoneurons,these cells display alterations in their discharge pattern and a loss of synaptic boutons that resemble the state of axotomy.All these data indicate that VEGF is an essential neurotrophic factor for motoneurons.

A novel implantable multichannel silicon-based microelectrode

Silicon-based microelectrodes have been confirmed to be helpful in neural prostheses. The fabricated 7-channel silicon-based microelectrode was feasible to be implanted into the brain cortex. The manufacturing process by micro-electromechanical system （MEMS） technology was detailed with four photolithographic masks. The microscopic photographs and SEM images indicated that the probe shank was 3 mm long, 100μm wide and 20 μm thick with the recording sites spaced 120μm apart for good signal isolation. To facilitate the insertion and minimize the trauma, the microelectrode is narrowed down gradually near the tip with the tip taper angle of 6 degrees. Curve of the single recording site impedance versus frequency was shown by test in vitro and the impedance declined from 150.5 kΩ to 6.0 kΩ with frequency changing from 10 k to 10 MHz.