David Mendelowitz Dept. of Pharmacology & Physiology 994-3466 [email protected].

David MendelowitzDept. of Pharmacology &

Physiology994-3466

[email protected]

Identification of Cardiac Vagal Neurons

XRITC – non-toxicfluorescent tracer

Nucleus Ambiguus

Cardiac Vagal Neurons

Identify the cellular mechanisms responsible for

the respiratory modulation of cardiac vagal neurons

20 mV

2.5 sec

Increased GABAergic input during inspiration is mediated by activation of 42 Nicotinic Receptors

Control DHE (3M)

1 sec

100pA

XII

CPM

XII

0GA

BA

Fre

q. (

Hz)

20

40

Unlike normal inspiration in which heart rate increases, during hypoxia gasps are evoked which elicit a pronounced bradycardia (decrease in HR)

Episodic Hypoxia Recruits an Excitatory Pathway to CVNs During Inspiration

Control Hypoxia 1 Hypoxia 2 Hypoxia 3

20 pA

1 s

Glutamatergic Frequency

0

1

2

3

4

5

-1 -2 -3 -4 -5 0 1 2 3 4-1 -2 -3 -4 -5 0 1 2 3 40

1

2

3

4

5

-1 -2 -3 -4 -5 0 1 2 3 40

1

2

3

4

5

-1 -2 -3 -4 -5 0 1 2 3 40

1

2

3

4

5

**

1 M Strychnine, 25 M Gabazine focally applied throughout experiment

50 mM APV, 50 mM CNQX added at end of experiment to block all events

CardiacVagalNeuron

Eupnic Inspiration

InhibitoryExcitatory

CardiacVagalNeuron

GABAGlycine

CardiacVagalNeuron

Inspiratory (gasping) inputsduring single episode ofhypoxia

InhibitoryExcitatory

CardiacVagalNeuron

GABAGlycine

CardiacVagalNeuron

Inspiratory (gasping) inputsduring intermittent episodesof hypoxia

InhibitoryExcitatory

CardiacVagalNeuron

Intermittent Hypoxia Alters Excitatory Neurotransmission to CVNs

No synaptic inputs

presynaptic42nicotinicreceptor

GABA

Ach

Glycine No synaptic inputs

Glutamate ?ROS

ROS generation by episodic hypoxia

Sp5

Sol

VLM

Amb

py

DMNX

4 V

p = 0.1-0.5p = 0.5-1

p < 0.1p < 0.05p < 0.01

C D

E

F

1.5

A

B

Tis

sue

pO2

(T

orr

)

0

100

200

300

400

0 10 20 30 40 50 60

Time (min)

Fo

ld I

ncr

eas

e D

CF

Inte

nsi

ty

1

2

Time DependentTempol

RVL

0 10 20 30 605040

Brainstem cardiorespiratory controlpertubations include: prenatal nicotine

exposure, hypoxia, hypercapniadisease focus: SIDS, sleep apnea

Methodologies include:• Patch clamping in in-vitro slice• Imaging (fluorescent)• In-vivo cardiorespiratory studies ie BP, HR,

inspiration (limited)

Techniques needed:• Single cell RT-PCR• siRNA (viral delivery)