Comparison of arylalkylamine N-acetyltransferase and melatonin receptor type 1B immunoreactivity between young adult and aged canine spinal cord

Melatonin affects diverse physiological functions through its receptor and plays an important role in the central nervous system. In the present study, we compared immunoreactivity patterns of arylalkylamine N-acetyltransferase (AANAT), an enzyme essential for melatonin synthesis, and melatonin receptor type 1B (MT2) in the spinal cord of young adult (2~3 years) and aged (10~12 years) beagle dogs using immunohistochemistry and Western blotting. AANAT-specific immunoreactivity was observed in the nuclei of spinal neurons, and was significantly increased in aged dog spinal neurons compared to young adult spinal neurons. MT2-specific immunoreactivity was found in the cytoplasm of spinal neurons, and was predominantly increased in the margin of the neuron cytoplasm in aged spinal cord compared to that in the young adult dogs. These increased levels of AANAT and MT2 immunoreactivity in aged spinal cord might be a feature of normal aging and associated with a feedback mechanism that compensates for decreased production of melatonin during aging.

Neuronal Responses in the Globus Pallidus during Subthalamic Nucleus Electrical Stimulation in Normal and Parkinson's Disease Model Rats

Deep brain stimulation (DBS) of the subthalamic nucleus (STN) has been widely used as a treatment for the movement disturbances caused by Parkinson's disease (PD). Despite successful application of DBS, its mechanism of therapeutic effect is not clearly understood. Because PD results from the degeneration of dopamine neurons that affect the basal ganglia (BG) network, investigation of neuronal responses of BG neurons during STN DBS can provide informative insights for the understanding of the mechanism of therapeutic effect. However, it is difficult to observe neuronal activity during DBS because of large stimulation artifacts. Here, we report the observation of neuronal activities of the globus pallidus (GP) in normal and PD model rats during electrical stimulation of the STN. A custom artifact removal technique was devised to enable monitoring of neural activity during stimulation. We investigated how GP neurons responded to STN stimulation at various stimulation frequencies (10, 50, 90 and 130 Hz). It was observed that activities of GP neurons were modulated by stimulation frequency of the STN and significantly inhibited by high frequency stimulation above 50 Hz. These findings suggest that GP neuronal activity is effectively modulated by STN stimulation and strongly dependent on the frequency of stimulation.

Comparison of alpha-synuclein immunoreactivity in the spinal cord between the adult and aged beagle dog / 한국실험동물학회지

Alpha-synuclein (alpha-syn) is a presynaptic protein that is richly expressed in the central and peripheral nervous systems of mammals, and it is related to the pathogenesis of Parkinson's disease and other neurodegenerative disorders. In the present study, we compared the distribution of the immunoreactivity of alpha-syn and its related gliosis in the spinal cord of young adult (2-3 years) and aged (10-12 years) beagle dogs. We discovered that alpha-syn immunoreactivity was present in many neurons in the thoracic level of the aged spinal cord, however, its protein level was not distinct inform that of the adult spinal cord. In addition, ionized calcium-binding adapter molecule-1 (a marker for microglia) immunoreactivity, and not glial fibrillary acidic protein (a marker for astrocytes) immunoreactivity, was somewhat increased in the aged group compared to the adult group. These results indicate that alpha-syn immunoreactivity was not dramatically changed in the dog spinal cord during aging.

Odor-Dependent Hemodynamic Responses Measured with NIRS in the Main Olfactory Bulb of Anesthetized Rats

In this study, we characterize the hemodynamic changes in the main olfactory bulb of anesthetized Sprague-Dawley (SD) rats with near-infrared spectroscopy (NIRS, ISS Imagent) during presentation of two different odorants. Odorants were presented for 10 seconds with clean air via an automatic odor stimulator. Odorants are: (i) plain air as a reference (Blank), (ii) 2-Heptanone (HEP), (iii) Isopropylbenzene (IB). Our results indicated that a plain air did not cause any change in the concentrations of oxygenated (Delta[HbO2]) and deoxygenated hemoglobin (Delta[Hbr]), but HEP and IB induced strong changes. Furthermore, these odor-specific changes had regional differences within the MOB. Our results suggest that NIRS technology might be a useful tool to identify of various odorants in a non-invasive manner using animals which has a superb olfactory system.

Doublecortin-immunoreactive Neuroblasts in Each Layer of the Main Olfactory Bulb After Transient Cerebral Ischemia in Gerbils / 한국실험동물학회지

Neurogenesis in the adult brain occurs continuously throughout life. The main olfactory bulb (MOB) is the first central relay of the olfactory system. We examined proliferation of newly generated cells in each layer of the gerbil MOB after 5 min of transient cerebral ischemia using doublecortin (DCX), a marker of neuronal progenitors. Many DCX immunoreactive neuroblasts were found in the all layers of the MOBs of control and ischemia groups. Ten to 15 days after ischemia/reperfusion, no difference in numbers of DCX immunoreactive neuroblasts was found in the MOB. Thirty days after ischemia/reperfusion, significant increase of DCX immunoreactive cells was observed in all layers of ischemic MOB. This result indicates that neuroblasts increase in the MOB from 30 days after transient cerebral ischemia in gerbils.

Immunohistochemical Analysis of Calretinin and Parvalbumin in the Goat Main Olfactory Bulb / 대한해부학회지

The distributions of calretinin (CR)- and parvalbumin (PV)-immunoreactive neurons in the main olfactory bulb (MOB) of the goat were examined in this study. As in other animals, the goat MOB has a characteristic laminar structure with laminar types and distribution patterns in each layer. CR-immunoreaction was observed in all layers of the MOB, except for the olfactory nerve layer. Most of CR-immunoreactive neurons were observed in the glomerular and granule cell layers. Relatively small number of CR-immunoreactive neurons was detected in other layers. These CR-immunoreactive neurons were interneurons. PV-immunoreaction was detected in all layers. In contrast to CR, olfactory nerve bundles were immunostained with PV. Most of PV-immunoreactive neurons were distributed in the glomerular and granule cell layers. PV-immunoreactive neurons were interneurons. This result suggests that CR and PV may play important roles in the olfactory signal modulation through interneurons in the goat MOB.

NOTICE OF ERRATUM: Effects of Streptozotocin-Induced Type 1 Diabetes on Cell Proliferation and Neuronal Differentiation in the Dentate Gyrus; Correlation with Memory Impairment / 대한해부학회지

Choi JH et al. Effects of Streptozotocin-Induced Type 1 Diabetes on Cell Proliferation and Neuronal Differentiation in the Dentate Gyrus; Correlation with Memory Impairment. Korean J Anat (2009) 42(1): 41-48. Please note that there is error in the above article:On page 47 (ACKNOWLEDGEMENTS) on lines 39-40 in the right column, "(MOEHRD) (KRF-2007-8R07- 0301-064-S000100)" should be "(MOEHRD, Basic Research Promotion Fund) (KRF-2007-412-J00502)"

Changes in Calcium-binding Proteins in the Rat Hippocampus after Involuntary Treadmill Exercise / 대한해부학회지

In this study, we investigated the effects of treadmill exercise on hippocampal levels of calcium-binding proteins - calbindin D-28k (CB), calretinin (CR) and parvalbumin (PV) - using immunohistochemistry and Western blot analysis. At 6 weeks of age, male Wistar rats were put on a treadmill with or without running for 1 h/day/5 consecutive days at a pace of 22 m/min for a period of 5 weeks. In sedentary and exercise groups, CB immunoreaction was detected in granule cells of the dentate gyrus, mossy fibers, and CA1 pyramidal cells. In addition, CB immunoreaction was observed in interneurons of the CA1-3 region. Exercise significantly increased CB immunoreactivity in dentate granule cells, CA1 pyramidal cells and CA1-3 interneurons. CR immunoreaction was mainly observed in interneurons of the dentate gyrus and CA1-3 regions. Similar number of CR-immunoreactive neurons was observed in the exercise and sedentary groups. PV immunoreaction was detected in interneurons of the dentate gyrus and CA1-3 regions. PVimmunoreactive fibers were significantly increased in all regions of the hippocampus in the exercise group, as compared to the sedentary group. Similar to the immunohistochemical findings, protein levels of CB and PV were also increased in the exercise group compared to the sedentary group. These increases in CB and PV in the hippocampus may induce neuronal plasticity after treadmill exercise and may be related to the enhancement of synaptic plasticity in the hippocampus by exercise.

Effects of Streptozotocin-Induced Type 1 Diabetes on Cell Proliferation and Neuronal Differentiation in the Dentate Gyrus; Correlation with Memory Impairment / 대한해부학회지

We examined the effects of steptozotocin (STZ)-induced type 1 diabetes on cell proliferation and neuroblasts in the subgranular zone of the hippocampal dentate gyrus (SZDG) of male Wistar rats. Change in memory function was also investigated using the passive avoidance test. In the SZDG, Ki67 (a marker for cell proliferation) positive nuclei were significantly decreased at 2 and 3 weeks and slightly decreased at 4 weeks after STZ treatment. Doublecortin (DCX, a marker for neuronal differentiation)-immunoreactive (+) neuroblasts with tertiary dendrites were significantly decreased in the STZ-treated group compared to those in the vehicle-treated group. However, DCX+ neuroblasts without tertiary dendrites were abundant at 4 weeks after STZ treatment. In addition, retention latency time in STZ-treated group was similar to that of vehicle-treated group at 2 and 3 weeks after STZ treatment. However, the retention latency time was significantly decreased at 4 weeks after STZ treatment. These results suggest that STZ significantly reduced cell proliferation and neuroblasts at 2~3 weeks after STZ treatment, but not at 4 weeks after STZ treatment although memory impairment was detected at 4 weeks after STZ treatment. The gradual reduction of DCX+ neuroblasts with tertiary dendrites may be associated with the impairment of hippocampus-related memory function.

Real-time One-dimensional Brain-Computer Interface (BCI) Using Prefrontal Cortex Neuronal Activities of Rats

The aim of this study is to verify the feasibility of control of one-dimensional (1-D) rotating machine using neural activities of Prefrontal cortex (PFC) in a BCI system. In this study, adult male Sprague-Dawley rats received bilateral implantation of recording micro-electrodes in PFC area. The spontaneous activities of a pair of PFC neurons of water-deprived rats were encoded and converted through a triple-step threshold comparator algorithm to three commands for one-dimensional movement control of a robotic wheel for accessing water. Averaged activities of two PFC neurons were quantized in every 200 ms to four ranges of activities around the mean firing rates (+/-0.5 SD) and were converted to four values. After comparison of the values of two chosen neuron units, direction and speed of rotation were decided. Rats were trained to complete one-dimensional control task to obtain water reward. The results indicated the percentage of stop event increased alone with more training. Different brain activity significantly influenced total water-drinking duration and non-water-drinking duration. Events generated from neuronal activity differed according to variant experimental sessions. Correlation between two signal units impacted controlling performance. Overall, the results of this study suggest that rats were able to manipulate the 1-D BCI system by differentially modulating PFC single neuron activities according to different circumstances.

In vivo Performance Evaluation of Implantable Wireless Neural Signal Transmission System for Brain Machine Interface

A brain-machine interface (BMI) has recently been introduced to research a reliable control of machine from the brain information processing through single neural spikes in motor brain areas for paralyzed individuals. Small, wireless, and implantable BMI system should be developed to decode movement information for classifications of neural activities in the brain. In this paper, we have developed a totally implantable wireless neural signal transmission system (TiWiNets) combined with advanced digital signal processing capable of implementing a high performance BMI system. It consisted of a preamplifier with only 2 operational amplifiers (op-amps) for each channel, wireless bluetooth module (BM), a Labview-based monitor program, and 16 bit-RISC microcontroller. Digital finite impulse response (FIR) band-pass filter based on windowed sinc method was designed to transmit neural signals corresponding to the frequency range of 400 Hz to 1.5 kHz via wireless BM, measuring over -48 dB attenuated in the other frequencies. Less than +/-2% error by inputting a sine wave at pass-band frequencies for FIR algorithm test was obtained between simulated and measured FIR results. Because of the powerful digital FIR design, the total dimension could be dramatically reduced to 23x27x4 mm including wireless BM except for battery. The power isolation was built to avoid the effect of radio-frequency interference on the system as well as to protect brain cells from system damage due to excessive power dissipation or external electric leakage. In vivo performance was evaluated in terms of long-term stability and FIR algorithm for 4 months after implantation. Four TiWiNets were implanted into experimental animals' brains, and single neural signals were recorded and analyzed in real time successfully except for one due to silicon- coated problem. They could control remote target machine by classify neural spike trains based on decoding technology. Thus, we concluded that our study could fulfill in vivo needs to study various single neuron-movement relationships in diverse fields of BMI.

Classification of BMI Control Commands Using Extreme Learning Machine from Spike Trains of Simultaneously Recorded 34 CA1 Single Neural Signals

A recently developed machine learning algorithm referred to as Extreme Learning Machine (ELM) was used to classify machine control commands out of time series of spike trains of ensembles of CA1 hippocampus neurons (n=34) of a rat, which was performing a target-to-goal task on a two-dimensional space through a brain-machine interface system. Performance of ELM was analyzed in terms of training time and classification accuracy. The results showed that some processes such as class code prefix, redundancy code suffix and smoothing effect of the classifiers' outputs could improve the accuracy of classification of robot control commands for a brain-machine interface system.

Post-ischemic Time-dependent Activity Changes of Hippocampal CA1 cells of the Mongolian Gerbils

Changes of single unit activity of CA1 hippocampus region were investigated in anesthetized Mongolian gerbils for six days following transient ischemia. Ischemia was produced immediately before the implantation of micro-wire recording electrodes. In control animals receiving pseudo-ischemic surgery, neither spontaneous neuronal activities (5.70+/-0.4 Hz) nor the number of recorded neurons per animal changed significantly for six days. Correlative firings among simultaneously recorded neurons were weak (correlation coefficient >0.6) in the control animals. Animals subjected to ischemia exhibited a significant elevation of neural firing at post-ischemic 12 hr (9.95+/-0.9 Hz) and day 1 (8.48+/-0.8 Hz), but a significant depression of activity at post-ischemic day 6 (1.84+/-0.3 Hz) when compared to the activities of non-ischemic control animal. Ischemia significantly (correlation coefficient <0.6) increased correlative firings among simultaneously recorded neurons, which were prominent especially during post-ischemic days 1, 2 and 6. Although the numbers of spontaneously active neurons recorded from control group varied within normal range during the experimental period, those from ischemic group changed in post-ischemic time-dependent manner. Temporal changes of the number of cells recorded per animal between control group and ischemic group were also significantly different (p = 0.0084, t = 3.271, df = 10). Cresyl violet staining indicated significant loss of CA1 cells at post-ischemic day 7. Overall, we showed post-ischemic time-dependent, differential changes of three characteristics, including spontaneous activity, network relationship and excitability of CA1 cells, suggesting sustained neural functions. Thus, histological observation of CA1 cell death till post-ischemic day 7 may not represent actual neuronal death.

Interhemispheric Modulation on Afferent Sensory Transmission to the Ventral Posterior Medial Thalamus by Contralateral Primary Somatosensory Cortex

Single unit responses of the ventral posterior medial (VPM) thalamic neurons to stimulation were monitored in anesthetized rats during activation of contralateral primary somatosensory (SI) cortex by GABA antagonist. The temporal changes of afferent sensory transmission were quantitatively analyzed by poststimulus time histogram (PSTH). Mainly, afferent sensory transmission to VPM thalamus was facilitated (15 neurons of total 23) by GABA antagonist (bicuculline) applied to contralateral cortex, while 7 neurons were suppressed. However, when ipsilateral cortex was inactivated by GABA agonist, musimol, there was significant suppression of afferent sensory transmission of VPM thalamus. This suppressed responsiveness by ipsilateral musimol was not affected by bicuculline applied to contralateral cortex. These results suggest that afferent transmission to VPM thalamus may be subjected to the interhemispheric modulation via ipsilateral cortex during inactivation of GABAergic neurons in contralateral SI cortex.

Changes of afferent transmission to the SI cortex by transient co-stimulation of receptive field center and outside in anesthetized rats

We have characterized the aftereffects of impulse activities on the transmission of afferent sensory to the primary somatosensory (SI) cortex of the anesthetized rats (n=22). Following conditioning stimulation (CS, 10 sec, either 5 Hz or 200 Hz) to the receptive field (RF), quantitative determination of the changes of afferent sensory transmission was done by generating post-stimulus time histogram of unit response to the testing stimulation (TS, at 0.5 Hz) to the RF center (RFC) for 60 min. In one group of experiments, CS was delivered to the RF center (RFC). In another group of experiments, CSs were simultaneously given to both RFC and RF outside (RFO, either forepaw or hindpaw). CS of 5 Hz to RFC exerted irreversible facilitation of sensory transmissions evoked by TS. Simultaneous CSs of 5 Hz to RFC and hindpaw RFO exerted reversible suppression of afferent transmission. However, CSs of 5 Hz to RFC and forepaw RFO did not significantly altered afferent sensory transmission to SI cortex neurons. CS of 200 Hz to RFC exerted irreversible suppression of sensory transmissions up to 60 min of experimental period. Simultaneous CSs of 200 Hz to RFC and RFO did not significantly altered afferent sensory transmission to SI cortex neurons. The profiles of CS-induced modulation of afferent sensory transmission were significantly different between two CS conditions. Thus, this study suggests that activity-dependent modulation of afferent transmission from a RF center to the SI cortex may be significantly altered when remote body part was simultaneously activated.