Neurons were Stimulated Using a Piezo-Electric Controlled

Heat-Polished Glass Pipette

Perforated PatchConfiguration

Neurons 1 day in culture

Tests:1. Series 2m increments2. Repeated stimulus

Characterisation of Mechanically Activated Currents in Dorsal Root

Ganglia Neurons

• LJ Drew, TM Jessell, JN Wood &

P Cesare

Capsaicin Sensitive and Insensitive Neurons are Differentially Responsive to Mechanical Stimulation

Caps + Rapidly adapting

Caps - Rapidly adapting

Caps - Slowly adapting

0

12

-3000

0

-600

0

-500

0

Stimuli

Inward Currents

Time (msec)

Cu

rre

nt

Am

plit

ud

e (

pA

)

Displacement (m)

0

1000

2000

3000

0 2 4 6 8 10 12

0 300

pA

m

Blockade of MA Currents by Ruthenium Red and Gadolinium in Different Subpopulations

Caps + Rapidly adaptingCaps - Rapidly adaptingCaps - Slowly adapting

0.1 1 10 100

0

100

Log10 [Gd3+] (M)

% In

hib

itio

n

50

0.1 1 10 100

0

50

100

Log10 [Ruthenium Red] (M)

MA Currents in Subsets of DRG Neurons are Differentially Modulated by Ca2+

-100

-50

0

+50

+100

% C

on

tro

l (2m

M C

a2

+)

5mM Ca2+

0mM Ca2+

Caps -Caps +

-1000

-500

0

Caps -

-800

-400

0

Control0mM Ca2+

5mM Ca2+

Caps +

pA

pA

MA Currents Are Acutely Inhibited by Cytochalasin B (10M) in Capsaicin Insensitive Neurons

Caps - Caps + 0

20

40

60

80

100%

Co

ntr

ol

P = 0.0001

Are MA Currents ASIC Mediated?

• ASIC2 and ASIC3 KO Mice show moderate changes in mechanosensitivity.– Magnitude of MA currents does not correlate with rapidly

adapting low pH evoked currents.– MA currents are not modulated by low pH.– MA currents are not sensitive to Amiloride.– MA currents are blocked by 300M Zn2+.

Conclusions• Important aspects of the mechanosensitive

phenotype of DRG neurons are maintained in vitro.

• Pharmacology: MA Currents are mediated by closely related ion channels in low- and high-threshold neurons.

• Ca2+ modulation reveals diversity in MA current modulation.

• Sensitivity of ion channels may be determined by cytoskeletal tethering.