Local homogeneity of tonotopic organization in the primary auditory cortex of marmosets.

Marmoset has emerged as a useful nonhuman primate species for studying brain structure and function. Previous studies on the mouse primary auditory cortex (A1) showed that neurons with preferential frequency-tuning responses are mixed within local cortical regions, despite a large-scale tonotopic organization. Here we found that frequency-tuning properties of marmoset A1 neurons are highly uniform within local cortical regions. We first defined the tonotopic map of A1 using intrinsic optical imaging and then used in vivo two-photon calcium imaging of large neuronal populations to examine the tonotopic preference at the single-cell level. We found that tuning preferences of layer 2/3 neurons were highly homogeneous over hundreds of micrometers in both horizontal and vertical directions. Thus, marmoset A1 neurons are distributed in a tonotopic manner at both macro- and microscopic levels. Such organization is likely to be important for the organization of auditory circuits in the primate brain.

[Effects of emodin on oxidative stress and inflammatory response in rats with acute spinal cord injury].

This paper was aimed to investigate the effects of emodin on oxidative stress and inflammatory response in rats with acute spinal cord injury（SCI）, and to explore the protective mechanism of emodin on neurons after SCI. Rat SCI models were established using a modified Allen's method. One hundred and ninety five Sprague-Dawley rats were randomly divded into sham (group A), model (group B), emodin group of 20 mg·kg⁻¹(group C), emodin group of 40 mg·kg⁻¹(group D), emodin group of 80 mg·kg⁻¹(group E). Functional recovery was evaluated using the Basso-Beattie-Bresnahan (BBB) scale and inclined plate test on the 3rd, 7th, 14th and 28th day. On the 7th day after SCI, neuron nylon body was observed with toluidine blue staining. The changes of myelinated nerve fibers were observed by transmission electron microscope. Nrf2, HO-1, NQO1, GFAP, NF-κB protein were detected by Western blot. The content of TNF-α, IL-1ß, IL-6 were detected by ELISA. Immunofluorescence staining was performed to observe the expression of the GFAP, NG2 and ED-1. The BBB and inclined plate scores of group C, D and E were higher than group B on the 7th, 14th, 28th day,the difference was statistically significant (P<0.05). On the 7th day, Nylon Body of group B and C started to fuse,the fusion of group D and E were significantly alleviated than group B and C. Transmission electron microscope showed that the changes of demyelination were obvious in group B and C, group D and E were significantly improved than group B and C. Western blot showed that Nrf2, HO-1, GFAP, NF-κB protein expression,group C, D, E compared with group B, NQO1 protein expression, group D, E compared with group B, the difference was statistically significant (P<0.05). ELISA showed that the content of TNF-α, IL-6,group C, D, E compared with group B,the content of IL-1ß,group D, E compared with group B, the difference was statistically significant (P<0.05)；Immunofluorescence showed that the expressions of GFAP and NG2 in group C, D and E were higher than that in group B, and the group D and E were more obvious. The expression of ED-1 in group C, D, E were decreased significantly compared with group B. Emodin has protective effect on neurons after SCI. The mechanism may connect with activting Nrf2-ARE pathway, reducing the expression of NF-κB, ED-1, TNF-α, IL-1ß, IL-6, and promoting the expression of GFAP and NG2.

[Effects of tanshinone â ¡A sulfonate on nerve regeneration after cryopreserved sciatic nerve allograft in rats].

In order to investigate the protective effect of tanshinone ⅡA sulfonate on the sciatic nerve activty in rats after cryopreservation as well as the nerve regeneration and functional recovery after allograft and its possible mechanism, Sprague-Dawley (SD) rats were divded into four groups at different doses of tanshinone ⅡA sulfonate (A 0 mg·L⁻¹, B 80 mg·L⁻¹, C 160 mg·L⁻¹, D 480 mg·L⁻¹) cryopreserved at -80 °C for 24 weeks. Fresh control group nerve segments were harvested without cryopreservation. The ultrastructure and the viable cells of the nerve segments after cryopreservation were observed by electron microscopy, calcein-AM/propidium iodide staining, respectively. The expression of Bax and Bcl-2 was detected by Western blot. After cryopreservation, the nerve segments were cultured in vitro for one week, the mRNA and protein level of NGF and GDNF were detected by PCR and Western blot respectively. In addition, the above four cryopreserved groups transplanted to the Wistar rats by allografting (A', B', C', D'). At 16-week postoperation, muscle compound action potential latency and nerve conduction velocity were examined by electrophysiological. The number and the thickness of myelinated nerve fibers were analyzed by toluidine blue staining. The ultrastructure of the sciatic nerve by electron microscopy was observed. According to the results, after the cryopreserved for 24 weeks, compared with groups A and B, the nerve demyelination and vacuolation were weak, and the more viable cells, the decreased Bax and increased Bcl-2, the increased NGF and GDNF in group C and D. At 16-week poseoperation, the results demonstrated that the more larger and thickly regenerated myelinated axons, the shorter latency of muscle compound action potentials and higher nerve conduction velocity in groups C' and D' compared with groups A' and B'. According to these results, tanshinone ⅡA sulfonate exerted a significant protective effect on the viability of the nerves during cryopreservation at -80 °C and promoted nerve regeneration and functional recovery after transplantation especially in middle- and high-dose of tanshinone ⅡA sulfonate.

Distinct neuron populations for simple and compound calls in the primary auditory cortex of awake marmosets.

Marmosets are highly social non-human primates that live in families. They exhibit rich vocalization, but the neural basis underlying this complex vocal communication is largely unknown. Here we report the existence of specific neuron populations in marmoset A1 that respond selectively to distinct simple or compound calls made by conspecific marmosets. These neurons were spatially dispersed within A1 but distinct from those responsive to pure tones. Call-selective responses were markedly diminished when individual domains of the call were deleted or the domain sequence was altered, indicating the importance of the global rather than local spectral-temporal properties of the sound. Compound call-selective responses also disappeared when the sequence of the two simple-call components was reversed or their interval was extended beyond 1 s. Light anesthesia largely abolished call-selective responses. Our findings demonstrate extensive inhibitory and facilitatory interactions among call-evoked responses, and provide the basis for further study of circuit mechanisms underlying vocal communication in awake non-human primates.