Research On In Vivo Bioelectronic Nose Based On Mammalian Olfaction And How Olfactory Dysfunction Affects Gustation

Odor detection plays an unreplaceable role in food safety,environment monitoring,searching for drugs or explosives and diagnosing diseases.Traditional electronic noses are able to accomplish these missions to some extent.Yet their performances are far less than biological olfactory systems in many ways,such as detecting range,sensitivity and selectivity.Based on implantable electrode and brain-computer interface,the in vivo bioelectronic nose takes advantage of the intact mammalian olfactory system and thus has the potential to rival or even surpass biological olfactory systems in odor detection and discrimination.However,the in vivo bioelectronic nose is far from being applied to the mentioned areas for certain reasons.First,the neurons recorded by the implanted electrode are random and may be irresponsive to the designated odor.Second,the system requires several large instruments,which makes it almost impossible to be utilized to practical applications outside labs.Third,the in vivo bioelectronic nose system takes the olfactory system as a“black box”because the chemical sensory systems of mammals are not fully understood for now,which results in many limitations of this system.To increase the possibilities of recording responsive neurons,this study,based on previous researches on in vivo bioelectronic nose by our group,combines advanced technologies like manganese-enhanced magnetic resonance imaging and genetic engineering.Also,“olfaction-navigated rat-robot”is proposed and a wearable system for olfactory electrophysiological recording and animal motion control is introduced in this study.Meanwhile,how pentobarbital anesthesia affects the neural activities in the olfactory bulb(OB)and how olfactory dysfunction affects bitter detection areinvestigated.The results are expected to be helpful for our understanding of biological olfaction and gustation.The main innovative contents of this dissertation are listed as follows:1.The manganese-enhanced MRI(MEMRI)is used to investigate odor maps and to guide the implantation of the electrodes for in vivo bioelectronic nose.Before our works,electrode localization during implantation relies on the researchers' experiences,resulting in an unreliable success rate of recording neurons responsive to the designated odors.The goal of this research is to determine the optimal electrode implantation sites for electrophysiological recordings by using the technique of MEMRI at 3T and 7T.By implanting electrodes in the regions where Mn2+accumulates,signals responsive to the odors are recorded,thus a novel odor detection system with high specificity and high sensitivity is developed.2.A novel in vivo bioelectronic nose is developed using transgenic technology,which further improves the feasibility of the in vivo bioelectronic nose to detect a designated odorant.Electrode localization guided by manganese enhanced MRI is not accurate to the level of a neuron or a glomerulus.So this study aims to transform as many neurons as possible to be responsive to the designated odorant.An adenovirus vector is engineered with the gene of ODR-10,an olfactory receptor protein of C.elegans.The vector is applied to the right naris of the rat.The olfactory sensory neurons(OSNs)infected by the virus functionally express the receptor and respond to butanedione.The induced signals are transmitted to the OB and recorded by the electrode.The results of electrophysiological recordings show that the percentage of neurons responsive to butanedione has increased due to the transgenic procedure and is much higher than the percentage of transfected neurons,but few neurons responses to other odorants.The feasibility of the in vivo bioelectronic nose to detect a designated odorant is highly improved using this technique.3.The concept of the“olfaction-navigated rat-robot"is proposed and a wearable system for high-quality olfactory electrophysiological recording and effective animal motion control is designed.To get rid of wires and large equipment,a wearable system is developed based on Wi-Fi for electrophysiological recording.The system supports 8 input channels,as well as 8 output channels for electrical stimulation.the device is small in size and light in weight.The battery can support recording for 4 hours or stimulation for several days.The results show that the quality of long-term signal recording is high.By applying voltage or current pulses in medial forebrain bundle,barrel cortex and dorsolateral periaqueductal gray,the control of the rat's marching,turning and halting is achieved.The widths and amplitudes of the pulses are found to affects the speed of the rat's marching speed.The working life of the system is up to a month.The system allows the in vivo bioelectronic nose to be used in non-lab environment.4.How pentobarbital anesthesia affects the neural activities in the OB and spike durations are investigated.Although the mechanisms of different anesthetics influencing neural activities in the olfactory system is not systematically studied,all related researches reported that anesthesia affects olfactory neural activities.The influences of pentobarbital anesthesia in the olfactory neural activities are investigated in this study.The results show that in conscious state,the firings pyramidal neurons(PNs)and interneurons(INs)are coupled to the respiration-locked rhythm(RR).The difference of the respiratory phases where their firings are coupled indicates their positions in the olfactory pathway.Anesthesia abolished the coupling between the IN firings and the RR and significantly impaired that between the PN firings and the RR.Moreover,we found that the spike durations of PNs were prolonged by anesthesia.The results showed that spontaneous neural firing patterns and spike waveforms were modulated by brain state,suggesting the neural basis of different olfactory processing ability in different states.5.Olfaction impairment model is constructed and how it affects bitter detection is investigated using behavioral and electrophysiological analysis.Olfaction and gustation are the most important chemical sensory systems,whose impairment is highly related with neurodegenerative diseases.There are few reports on olfactory dysfunction affecting the functionality of gustation for now.In this study,olfaction dysfunction model is constructed by nasal irrigation of zinc sulfate.In the two-bottle test,the rats drink more quinine after their olfaction is impaired,indicating declined sensitivity of bitterness.Simultaneous recordings from the OBs and gustatory cortex(GCs)on both sides show that olfactory impairment has a strong impact on gustation.After olfaction impairment,the ? oscillations,RR and the coupling between them are decreased in varying levels in the OBs and GCs.Olfaction impairment also decreases the responses of ? oscillations.