Table 1Some electrophysiological properties of peripheral chemoreceptive NTS neurones
Excitatory response
Inhibitory response
Respiratory modulated
n
38
10
8
R.M.P. (mV)
−53.0±0.7
−51.8±1.7
−51.2±1.9
RIN (MΩ)
275±18
265±50
298±32
Ongoing activity (Hz)
2.4±0.4
1.9±0.7
2.4±0.4
Solitary tract stimulation
EPSP
IPSP
EPSP
Latency (ms)
5.2±0.4
23.8±4.3
4.4±1
n
17
4
6
Response to DP pulses (# tested):
30
8
5
Steady state
15
5
3
Augmenting
8
2
2
Adapting
7
1
0
Response to HP pulses:
Rebound excitation
20/32
1/8
5/6
Delayed excitation
11/32
2/8
0/6
There was no significant difference in resting membrane potential (R.M.P.), membrane input resistance (RIN) or ongoing activity between neurones displaying different synaptic responses to peripheral chemoreceptor stimulation. The latency of synaptic inputs to inhibitory response group cells was longer than those to neurones in the other two groups (P<0.05). Many excitatory response and respiratory modulated neurones exhibited rebound excitation following a HP pulse. Note: three of the 14 neurones in the excitatory response group displayed EPSP–IPSP sequence whereas three of seven neurones from the inhibitory group exhibited EPSP–IPSP to solitary tract stimulation. Abbreviations: DP, depolarising pulse injection; HP, hyperpolarising pulse injection; n, number of NTS neurones.