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.

Age-Related Changes of Catalase Immunoreactivity in the Main Olfactory Bulbs of Wistar and Spontaneously Hypertensive Rats / 대한해부학회지

The reactive oxygen species (ROS) is well-known for the causative factors inducing ischemia, Parkinson's disease, Alzheimer, amylotrophic lateral sclerosis, hypertension and aging. Catalase (CAT) is an important endogenous antioxidant enzyme against ROS because it removes H2O2 during metabolic processes. Hence, we examined the age-related changes of CAT-immunoreactivity in the main olfactory bulbs (MOB) of the Wistar and spontaneous hypertensive rat (SHR) at various aging stages over 2 years periods; postnatal month 6 (PM 6), PM 12, PM 18 and PM 24. CAT immunoreactive (IR) neurons in Wistar rats were located in the glomerular layer (GL), external plexiform layer (EPL), internal plexiform layer (IPL) and granule cell layer (GCL). The number of CAT-IR neurons slightly decreased agedependently and nearly disappeared at PM 24. At PM 6 and PM 12, the CAT-IR neurons located in the EPL were morphologically identified as granule cells. However, at PM 18 and PM 24, CAT-IR neurons located in the EPL and mitral cell layer (MCL) were morphologically identified as tufted and mitral cells, respectively. CAT-IR neurons in the SHR were located in all layers of the MOB. The number of CAT-IR neurons and CAT immunoreactivity decreased agedependently and nearly disappeared especially in the GL and EPL at PM 24. These findings indicate that the decrease of CAT immunoreactivity may be one of the causative factors for increase of oxidative stress, and these damages may underlie age-related changes in the olfactory process. The early decrease of CAT immunoreactivity in the SHR than in the Wistar rat suggests that the early decreae of CAT may be associated with the cause of hypertensive neuronal damage.