Modulation of Neuronal Activity on Intercalated Neurons of Amygdala Might Underlie Anxiolytic Activity of a Standardized Extract of Centella asiatica ECa233.

GABAergic intercalated neurons of amygdala (ITCs) have recently been shown to be important in the suppression of fear-like behavior. Effects of ECa233 (a standardized extract of Centella asiatica), previously demonstrated anxiolytic activity, were then investigated on ITCs. Cluster of GABAergic neurons expressing fluorescence of GFP was identified in GAD67-GFP knock-in mice. We found that neurons of medial paracapsular ITC were GABAergic neurons exhibiting certain intrinsic electrophysiological properties similar to those demonstrated by ITC neurons at the same location in C57BL/6J mice. Therefore, we conducted experiments in both C57BL/6J mice and GAD67-GFP knock-in mice. Excitatory postsynaptic currents (EPSCs) were evoked by stimulation of the external capsule during the whole cell patch-clamp recordings from ITC neurons in brain slices. ECa233 was found to increase the EPSC peak amplitude in the ITC neurons by about 120%. The EPSCs in ITC neurons were completely abolished by the application of an AMPA receptor antagonist. Morphological assessment of the ITC neurons with biocytin demonstrated that most axons of the recorded neurons innervated the central nucleus of the amygdala (CeA). Therefore, it is highly likely that anxiolytic activity of ECa233 was mediated by increasing activation, via AMPA receptors, of excitatory synaptic input to the GABAergic ITC leading to depression of CeA neurons.

Expression of secreted phosphoprotein 1 (osteopontin) in human sensorimotor cortex and spinal cord: Changes in patients with amyotrophic lateral sclerosis.

Secreted phosphoprotein 1 (SPP1, also known as osteopontin) is expressed in large pyramidal neurons in the primary motor cortex (M1) of certain primate species, including macaque monkeys, but not of rodents. Based on this, we suggested that SPP1 expression may reflect the functional or structural specialization of highly developed corticospinal systems. In the present study, we further characterized SPP1 in the human central nervous system by investigating its expression in the primary somatosensory cortex (S1) and spinal cord, in addition to M1. Although a small number of SPP1-positive pyramidal neurons were observed in S1, the number was smaller than that in M1. In the cervical segment of the spinal cord, SPP1 was principally expressed in choline acetyltransferase-positive motor neurons in lamina IX. We also examined SPP1 expression in patients with amyotrophic lateral sclerosis (ALS), a disease characterized by the degeneration of motor neurons. When SPP1 expression was compared in neurons of the same size range, expression in both M1 and the spinal cord of ALS patients was lower than that of subjects without ALS. SPP1 expression was especially reduced in surviving large neurons in both M1 and the spinal cord of ALS patients. The results further support the concept that SPP1 has a role in the specialization of motor projection neurons and suggest that its reduced expression may be implicated in the neurodegeneration seen in ALS.

Causal Link between the Cortico-Rubral Pathway and Functional Recovery through Forced Impaired Limb Use in Rats with Stroke.

Intensive rehabilitation is believed to induce use-dependent plasticity in the injured nervous system; however, its causal relationship to functional recovery is unclear. Here, we performed systematic analysis of the effects of forced use of an impaired forelimb on the recovery of rats after lesioning the internal capsule with intracerebral hemorrhage (ICH). Forced limb use (FLU) group rats exhibited better recovery of skilled forelimb functions and their cortical motor area with forelimb representation was restored and enlarged on the ipsilesional side. In addition, abundant axonal sprouting from the reemerged forelimb area was found in the ipsilateral red nucleus after FLU. To test the causal relationship between the plasticity in the cortico-rubral pathway and recovery, loss-of-function experiments were conducted using a double-viral vector technique, which induces selective blockade of the target pathway. Blockade of the cortico-rubral tract resulted in deficits of the recovered forelimb function in FLU group rats. These findings suggest that the cortico-rubral pathway is a substrate for recovery induced by intensive rehabilitation after ICH. SIGNIFICANCE STATEMENT: The research aimed at determining the causal linkage between reorganization of the motor pathway induced by intensive rehabilitative training and recovery after stroke. We clarified the expansion of the forelimb representation area of the ipsilesional motor cortex by forced impaired forelimb use (FLU) after lesioning the internal capsule with intracerebral hemorrhaging (ICH) in rats. Anterograde tracing showed robust axonal sprouting from the forelimb area to the red nucleus in response to FLU. Selective blockade of the cortico-rubral pathway by the novel double-viral vector technique clearly revealed that the increased cortico-rubral axonal projections had causal linkage to the recovery of reaching movements induced by FLU. Our data demonstrate that the cortico-rubral pathway is responsible for the effect of intensive limb use.

Reorganization of sensory pathways after neonatal hemidecortication in rats.

We investigated ascending somatosensory pathways in neonatally hemidecorticated rats. Injection of an anterograde tracer, biotinylated dextran amine (BDA), into the contralesional dorsal root ganglions revealed ipsilateral projections to the dorsal column nuclei (DCN) in hemidecorticated rats as well as in normal rats. Injection of BDA into the DCN on the same side revealed that while most axons projected to the contralateral thalamus, some axons were detected in the ipsilateral thalamus in hemidecorticated rats while such projections were rarely detected in normal rats. The results suggest that aberrant ipsilateral projections of DCN neurons contralateral to the lesion developed after the hemidecortication.