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: