Cellular Neurobiology BIPN140

Transcription

1 Cellular Neurobiology BIPN140 2nd Midterm Exam Will be Ready for Pickup Next Monday By the elevator on the 3 rd Floor of Pacific Hall (waiver) Exam Depot Window at the north entrance to Pacific Hall (no waiver) Mon-Fri, 11:00 AM to 3:00 PM Chih-Ying s ffice Hour: Monday, 1:00-2:00 PM, Bonner Hall 4146 BIPN140 Lecture 15: The Chemical Senses 1. lfactory System 2. lfactory Receptors & Transduction Mechanism Su (FA16)

2 Three Stages of Information Processing (Afferent) external or internal (Efferent) external or internal

3 S dimethyl sulfide S S dimethyl disulfide butanal acetic acid, ethyl ester acetic acid, methyl ester 1-hydroxy-2-propanone acetate furan 2-vinylfuran 2-furfurylfuran 3,4-hexanedione 1-acetyloxy-2-butanone S H N N thiophene 2,5-dimethylpyrrole N 2-ethyl-6-methylpyrazine N N S H S 4-methylthiazole acetic acid butyrolactone 4-methylthiazole dor space is boundless and dimensionless Vision: wavelength; Hearing: frequency Number of pure odorants is unknown. Which two odorants are more similar to one another? (Goldstein, Sensation and Perception, 8 th edition)

4 The Nobel Prize in Physiology or Medicine 2004 was awarded jointly to Richard Axel and Linda Buck "for their discoveries of odorant receptors and the organization of the olfactory system" dorant Receptor Proteins (Fig. 15.9) The Nobel Prize in Physiology or Medicine 2004 was awarded jointly to Richard Axel and Linda Buck "for their discoveries of odorant receptors and the organization of the olfactory system"

5 Molecular Mechanisms of lfactory Transduction (Fig ) NCKX4 Anoctamin 2 (Ano2) Structure and Function of the lfactory Epithelium (Fig )

6 rganization of the Human lfactory System (Fig. 15.1) lfactory learning Innate olfactory behavior & aggression lfactory memory Reproduction lfactory information processing: convergent evolution ne receptor from a large gene family Glomerular structure Multiple higher brain targets (Su et al., Cell, 2009)

7 dorant Receptor Neuron Selectivity (Fig ) odorant (Malnic et al., Cell, 1999) Combinatorial code: each RN recognizes multiple odorants and one odorant is recognized by multiple RN types. dor identity is likely encoded by the activation pattern of RNs. Anosmia (Box. 15A)

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9 Many primary sensory cells are grouped together lfactory Sensilla Pheromone Sensilla Humidity Sensilla Auditory Scolopidia (Su et al, Nature, 2012) (based on Thistle et al, Neuron, 2012) Taste Sensilla Taste Buds (Kim & Wang, Current Biology, 2016) (Bechstedt & Howard, Current Biology, 2008) (Weiss et al, Neuron, 2011) (Yarmolinsky et al, Cell, 2009) Fly olfaction sensillum Antenna Maxillary palp (Su et al., Cell, 2009)

10 A detailed map of fly RNs basiconic coeloconic trichoid ab11 ab12 (de Bruyne et al, Neuron, 2001; Couto et al, Current Biology, 2005; Benton et al, Cell, 2009; Kwon et al, Current Biology, 2010) Activation of one RN inhibits its neighbor 2-hep (37 Hz) (34 Hz) (r85b-rpr) (Su et al., Nature, 2012)

11 Communication between grouped RNs is bidirectional Does lateral inhibition require central processing??

12 lfactory computation without a synapse Conventional means of neuronal communication Chemical Synapse Gap Junction

13 Communication without a synapse (Shanbhag et al, International Journal of Insect Morphology and Embryology, 1999) (Shanbhag et al, Arthropod Structure & Development, 2000) Ephaptic coupling Electrical interactions that arise from the close apposition of neuronal processes from two or a few neurons. (Jefferys, Physiol Reviews, 1995) (Vermeulen and Rospars, Eur Biophys J, 2004)

14 Model: ephaptic coupling (Adapted from Vermeulen and Rospars, Eur Biophys J, 2004) Why are fly RNs compartmentalized? Communication by sharing the same environment Each sensillum type as a processing unit in olfactory computation What is the functional output of those processing units? Do they process information about odor identity and/or the valence of the odor? What is the functional impact of those processing units on olfactory behavior? (Couto et al, Current Biology, 2005)

15 Ephaptic interaction is asymmetrical: A > B 3D reconstruction of a labeled RN and its neighbor 1 µm

16 3D reconstruction of a labeled RN and its neighbor 1 µm Large-spiked neuron has large soma than their (Angela Tsang, Ben Damasco and Renny Ng )

17 Fig. 1. Lateral inhibition of RNs Fig. 4. Lateral inhibition does not require synapses.

18 Fig. 5. Lateral inhibition in a sensillum modulates behavior.