Hindbrain Neurons

Question:• How will the alteration of input affect neurons in

the CNS dedicated to inner ear sensory input processing?

• By manipulating the ear, either by removing it or by adding extra ears, we can determine the effects of afferents on their target neuron(s) in the CNS

Mauthner Cell• Single, large, pair of reticulospinal neurons at the

level of the ear in the hindbrain of most aquatic animals

• Important component of the C-start escape response

25µm

Mauthner Cell• Early, but not late, ear ablation has been shown to

result in the absence of the Mauthner cell• Has been suggested to be a surgical artifact

• Surviving Mauthner cells show a reduction in dendritic branching

• Previous studies each only focused on a single time point of ear removal• I removed the ear at various time points in development to

answer the following questions:

Mauthner Cell Questions• 1) Is there a critical period of a Mauthner cell during

which it depends on the ear for survival?

• 2) Does the stage at which the ear is removed affect the degree of dendritic branching of surviving Mauthner cells?

Dendritic Branching following ear loss

Control Remove and Replace Ear

Ear Removed at Placode (Stage 26) Ear Removed at Late Otic Vesicle (Stage 40)

25µm

23 Terminal Branches 26 Terminal Branches 19 Terminal Branches 24 Terminal Branches

24 Terminal Branches 3 Terminal Branches 32 Terminal Branches 9 Terminal Branches

Dendritic Branching with extra ear

50µm

Extra Ear

50µm

21 Terminal Branches 33 Terminal Branches

Control Remove-Replace RemovePlacode (24-26)

Remove Early Otic Vesicle (27-30)

Remove Late Otic Vesicle (31-40)

Extra Ear0

5

10

15

20

25

30

35

Treatment

Num

ber o

f Den

driti

c Bra

nche

s

Dendritic Branching

*** p < 0.001

n = 12 n = 12 n = 12 n = 12n = 12

*** ******

*

n = 10

ControlTreated

* p < 0.05

Control Remove-Replace Remove Placode(24-26)

Remove Early Otic Vesicle

(27-30)

Remove Late Otic Vesicle

(27-30)

Extra Ear

t-test