david mendelowitz dept. of pharmacology & physiology 994-3466 [email protected]
TRANSCRIPT
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)