W. Otto Friesen and Ruey-Jane FanDepartment of Biology
University of Virginia
University of Virginia in Charlottesville, Virginia
Identified Neurons in the CNS of Leeches
Supported by the NSF and the NIH
Leech CNS (~12,000 neurons—25% identified)• Head ganglion: sub and supraesophageal• Ventral nerve cord: M1 – M21 (400/ganglion)• Tail ganglion
Leech PNS (>20,000 neurons—clusters)• Photo-, chemo-, mechano-, and proprioreceptors• Stomatogastric neurons
Leech gross anatomy
CNS-- one midbody ganglion
400 neurons/segment
Cell 115
Dorsal and ventral maps
About 30% of neurons in midbody ganglia are identified
Peripheralmorphology
--sensory hairs
Approximately 100 sensory neurons/sensillum
Muscles
Circular, oblique, longitudinal, dorsoventral, cardiac, annulus erector
Describing identified neurons in leeches
Major identifiers – data partially complete
• Behavior [swim, crawl, shortening, bending, heart]• Type [sensory, motor, interneuron, modulatory]• Morphology [location, size, projection]• Physiology [impulses, activity, conductance]• Circuit interactions [chemical, electrical synapses]• Pharmacology [transmitters, receptors]• Size/Age/developmental stage• Experimental manipulations/preparations
Neuron morphology/dye coupling (DI-1)
Motoneuron DI-1soma injected with Alexa 488 and neurobiotinDorsal aspect,
posterior lateral packet
Leech neuron physiology: DI-1 et al.Swim oscillations
Physiological anatomy
Serotonin modulation
Non-spiking interactions
Functional interactions
Shifting cycle phase
Phase relationships
Circuit diagrams
Circuit data and physiology combined: Swim-initiation
Sensory
Trigger
Gating
Oscillator
Motoneuron
5 HTHormonal
5 HTSynaptic
Motoneuron
Trigger
Motoneuron
Swimming
Swimming
Oscillator
Gating
Gating
A.
B.
Pre
Post
Physiology relates to experimental methods/preparations
Summary of identified neurons
Green are swim-related excitatory cells; red are inhibitors
Identified neurons AIdentified neurons in the CNS of Hirudo medicinalis. Map Major axon Color Descriptionb Behavioral number projectionb codea involvementbc
Dorsal aspect Motoneurons (24 cell pairs)DE-3 CPNR green excitor of DLM swimming, LB
crawlingDE-5 CPNR green excitor of DLM swimming, LB
crawlingDE-18 CANR green swimmingDE-107 CANR green excitor of DLM swimming, LBVE-4 IPNR green excitor of VLM swimming, LB,
crawlingVE-8 CPNR green excitor of VLM swimming, LBVE-108 CANR green swimming, LBFE-109 CNR green excitor of lateral swimming, LB
dorsal-ventral FMFE-117 CNR green excitor of medial
dorsoventral FMDI-1 CNR red inhibitor of DLM swimming, LB,
crawlingDI-102 CNR red inhibitor of DLM swimming, LBVI-2 CNR red inhibitor of VLM swimming, crawlingVI-7 CNR red inhibitor of VLM swimmingVI-119 CNR red inhibitor of VLM swimmingFI-101 CNR red inhibitor of swimming, LB
Identified neurons BIdentified neurons in the CNS of Hirudo medicinalis. Map Major axon Color Descriptionb Behavioral number projectionb codea involvementbc
Dorsal aspect Motor Neurons (continued)CE-11 CNR blue excitor of CMCE-12 CNR blueCE-112 CNR blueL both CNR blue general excitor of LM crawlingDE-6 CNR blue excitor of DLM local
bendingLI-9 CNR blue inhibitor of LMLE-106 CNR blue excitor of lateral
LMOE-110 CNR blue excitor of OM local bendingOE-111 CNR blue
Interneurons (8 cell pairs)21 Green serotonergic, gating
swimming27 AIC Red oscillator
swimming240° phase
Identified neurons CIdentified neurons in the CNS of Hirudo medicinalis. Map Major axon Color Descriptionb Behavioral number projectionb codea involvementbc
Dorsal aspect interneurons (continued)28 AIC red oscillator swimming
120° phase33 AIC red oscillator swimming
240° phase115 PCC red oscillator swimming, LB
0° phase123 PIC red oscillator swimming
0° phase125 PIC blue excitor, receives LB
Input from P cells34 blue interacts with
T cells, S cellsMechanosensory cellsPv INR, IC yellow mechanosensory responds to
pressureNv INR, IC yellow mechanosensory responds to
noxious
Neurosecretory cells50 IC pink secretary neuron LB, feeding
Identified neurons DIdentified neurons in the CNS of Hirudo medicinalis. Map Major axon Color Descriptionb Behavioral number projectionb codea involvementbc
Ventral aspect Motoneurons (6 cell pairs) AE CNR blue annuli erector change skin
surfacefrom smooth to
ridgedCV CNR blue excitor of crawling
ventrolateral CMHE INR blue cardiac rhythmic control HN
M3-19 movementAP CNR blue input from P cell crawling152 CNR blue CM excitor crawling166 CNR blue CM inhibitor crawling
Interneurons (20 paired, 4 unpaired cells)61 IC green serotonergic swimming gating
2 ganglia204 Fn green gating swimming,
crawling, unpaired behavioral decision205 Fn green gating swimming
unpaired, M9
Identified neurons EIdentified neurons in the CNS of Hirudo medicinalis. Map Major axon Color Descriptionb Behavioral number projectionb codea involvementbc
Ventral aspect Interneurons (continued) 208 IC (unpaired) green oscillator swimming60 IC (2 ganglia) red oscillation 240° swimming151 IC (NR) blue non-spiking153 CANR blue excitatory photo reception,
photo-sensory input swimming
-oscillation 180° 154 blue photo-sensory photo reception157 CC blue EPSP long latency LB159 PIC blue EPSP long latency LB, crawling160 blue shifts swim phase, swimming?
no oscillation161 IC blue EPSP from P cell LB162 IC blue EPSP from P cell LB169 CC blue EPSP long latency swimming, LB201 CC blue receives inhibition water motion202 CC blue receives excitation water motion
from SMRs detection213 AIC blue ascending crawling215/216 blue receives excitation photosensory
(ipsi-) sensillum 7
Identified neurons FIdentified neurons in the CNS of Hirudo medicinalis. Map Major axon Color Descriptionb Behavioral number projectionb codea involvementbc
Ventral aspect Interneurons (continued) 212 ACC blue EPSP from P cell LB
218 IC blue Spontaneous EPSP LB258 INR blue large soma crawlingS Fn blue LB, shortening,
learning, crawlingHN IC blue inhibitor IN control of heartbeat
(M1-M7)Mechanosensory cell (7 cell pairs)T IC (NR) yellow responds to tactile touch reception
(Tl, Tv, Td) stimuli
P IC (NR) yellow responds to moderate pressure reception
(Pd, Pv) body wall stimuli
N IC (NR) yellow responds to noxious nociception(Nv, Nd) body wall stimuli, gut
Neurosecretory cell (2 cell pairs)R (Retzius) IC,NR, IC pink serotonergic swimming, feeding
muscle relaxation50 (Leydig) IC, NR pink LB, feeding
Identifiers and descriptors for leeches• Identifier: cell name and location• Animal: genus, species, variety • Cell_group: CNS, PNS, glial cell, muscle• Cell_type: Interneuron, motoneuron, sensory, secretory• Distribution: paired, unpaired, cluster• Soma_location: brain, midbody ganglion, tail brain, periphery• Coordinates: dorsal, ventral, packet designation• Morphology: soma size, neurite branching, axon projection
Interacts_with: chemical, electrical• Homolog_of: contralateral, serial homologs• Innervates: muscles types• Resting_potential: value, with range• Spontaneous_AP: frequency, amplitude• Bursting: frequency, burst duration, impulse frequency, condition• Receptive_field_modality: type of modality, submodality • Receptive_field:• Releases_transmitter: • Receptors:• Behavior:
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