Search

Tunicamycin (TM) induces endoplasmic reticulum (ER) stress and inhibits N-glycosylation in cells. ER stress is associated with neuronal death in neurodegenerative disorders, such as Parkinson’s disease and Alzheimer’s disease, and most patients complain of the impairment of olfactory recognition. Here we examined the effects of TM on aversive olfactory learning and the underlying synaptic plasticity in the main olfactory bulb (MOB). Behavioral experiments demonstrated that the intrabulbar infusion of TM disabled aversive olfactory learning without affecting short-term memory. Histological analyses revealed that TM infusion upregulated C/EBP homologous protein (CHOP), a marker of ER stress, in the mitral and granule cell layers of MOB. Electrophysiological data indicated that TM inhibited tetanus-induced long-term potentiation (LTP) at the dendrodendritic excitatory synapse from mitral to granule cells. A low dose of TM (250 nM) abolished the late phase of LTP, and a high dose (1 μM) inhibited the early and late phases of LTP. Further, high-dose, but not low-dose, TM reduced the paired-pulse facilitation ratio, suggesting that the inhibitory effects of TM on LTP are partially mediated through the presynaptic machinery. Thus, our results support the hypothesis that TM-induced ER stress impairs olfactory learning by inhibiting synaptic plasticity via presynaptic and postsynaptic mechanisms in MOB. [ABSTRACT FROM AUTHOR]

Abstract: Objective: In the United States and European countries, the University of Pennsylvania Smell Identification Test (UPSIT), the Quick Smell Identification Test (Q-SIT), a shorter version of the UPSIT, and “Sniffin’ Sticks” are widely used for testing olfaction. The odor stick identification test for Japanese (OSIT-J) has been manufactured in Japan. This was followed by the development of “Open Essence,” consisting of cards that make use of sealed odorants. This study examined the usefulness of Open Essence in young volunteers with normal olfaction. Method: The participants were 176 medical students in their clinical clerkships at the Department of Otolaryngology, Kochi Medical School Hospital. There were 111 males and 65 females, with a median age of 24 years (range 22–42 years). The olfactory function of all participants was confirmed as normal by screening with T&T olfactometry. Before beginning Open Essence, the subjects were asked to answer a questionnaire on their olfaction and habits. Results: Females had significantly better smell identification than males. Of the 12 odorants, “perfume” and “cooking gas” were difficult to identify, because perfume involves different imagery and the compounds that give the smell of gas are readily volatilized. In contrast, all participants recognized “curry” and “menthol,” probably because they are received as both somatosensory stimuli and smell. Conclusions: These results suggest that, with improvement, Open Essence might be used for testing olfaction in Japanese subjects. [Copyright &y& Elsevier]

Objective: To investigate the differences in regions of brain activation in response to olfactory stimulation by functional magnetic resonance imaging in conditions of prior warning of an odor and without. Methods: Participants were 17 normal right-handed volunteers; 8 participants received prior warning of the odor (informed condition) and 9 participants were not pre-warned (naïve condition). The odorant used was isovaleric acid. Results: In the informed condition with prior warning, activation was observed in the putamen extending to the insula, amygdala, and inferior frontal gyrus, and there was instant reification of the odor, while in the naïve condition without prior warning, activation was observed in the anterior cingulate cortex, entorhinal cortex, putamen and inferior frontal gyrus, and recognition of the odor was difficult. Conclusions: These results suggest that the condition prior to olfactory stimulation, i.e., with or without prior warning, can affect recognition and regions of brain activation in response to olfactory stimulation using isovaleric acid. Differences in recognition and regions of brain activation between both conditions could be associated with response latencies, or degree of attention, expectation and/or concentration. [ABSTRACT FROM AUTHOR]

Olfaction plays an important role in social recognition in most mammals. Central arginine vasopressin (AVP) plays a role in this olfaction-based recognition. The high level of expression of AVP receptors in the accessory olfactory bulb (AOB) at the first relay of the vomeronasal system highlights the importance of AVP signaling at this stage. We therefore analyzed the effects of AVP on the synaptic plasticity of glutamatergic transmission from mitral cells to granule cells in AOB slices from male mice. To monitor the strength of the glutamatergic transmission, we measured the maximal initial slope of the lateral olfactory tract-evoked field potential, which represents the granule cell response to mitral cell activation. AVP paired with 100-Hz stimulation that only produced short-term potentiation enhanced the induction of long-term potentiation (LTP) in a dose-dependent manner. AVP-paired LTP was blocked by the selective AVP receptor 1a (AVPR1a) antagonist, d(CH 2 ) 5 [Tyr(Me) 2 ]AVP (Manning compound), but not by the AVPR1b antagonist SSR149415, and it was mimicked by the selective AVPR1a agonist [Phe 2 , Ile 3 , Orn 8 ]-vasopressin. We further examined the effect of AVP on the reciprocal transmission between mitral and granule cells by stimulating a mitral cell and recording the evoked inhibitory postsynaptic currents (IPSCs) from the same cell using conventional whole-cell patch-clamp techniques. AVP reduced the reciprocal IPSCs triggered by endogenous glutamate release from the excited mitral cell. These results suggest that AVP promotes the induction of LTP at the mitral-to-granule cell synapse via the activation of AVPR1a through an as-yet-to-be-determined mechanism in the AOB of male mice. [ABSTRACT FROM AUTHOR]