Polysensory response characteristics of dorsal root ganglion neurones that may serve sensory functions during myocardial ischaemia.
OBJECTIVE
To determine the response characteristics of dorsal root ganglion neurones that may serve sensory functions during myocardial ischaemia.


METHODS
Extracellular recordings were made from 54 spontaneously active and 5 normally quiescent dorsal root ganglion neurones (T2-T5) in 22 anaesthetized open-chest dogs under control conditions and during epicardial mechanical or chemical stimulation and myocardial ischaemia.


RESULTS
The activity of 78% of spontaneously active and all quiescent neurones with left ventricular sensory fields was modified by left ventricular ischaemia. Forty-six spontaneously active neurones (85%) were polysensory with respect to mechanical and chemical stimuli. The 5 quiescent neurones responded only to chemical stimuli. Spontaneously active neurones associated with left ventricular mechanosensory endings (37 neurones) generated four different activity patterns in response to similar mechanical stimuli (high or low pressure active, high-low pressure active, high-low pressure inactive). A fifth group generated activity which was not related to chamber dynamics. Adenosine, adenosine 5'-triphosphate, substance P and bradykinin modified 72, 61, 65 and 63% of the spontaneously active neurones, respectively. Maximum local mechanical or chemical stimuli enhanced activity to similar degrees, as did ischaemia. Each ischaemia-sensitive neurone displayed unique activity patterns in response to similar mechanical or chemical stimuli.


CONCLUSIONS
Most myocardial ischemia-sensitive dorsal root ganglion neurones associated with epicardial neurites sense mechanical and multiple chemical stimuli, a small population sensing only mechanical or chemical stimuli. Activity patterns generated by these neurones depend on their primary sensory characteristics or those of other neurones that may converge on them, as well as the type and magnitude of the stimuli that impinge upon their sensory fields, both normally and during ischaemia.
Huang
M H
MH
Department of Physiology and Biophysics, Dalhousie University, Halifax, NS, Canada.
Horackova
M
M
Negoescu
R M
RM
Wolf
S
S
Armour
J A
JA
D000241:Adenosine / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D001920:Bradykinin / Q000494:pharmacology; D004285:Dogs; D005260:Female; D005727:Ganglia, Spinal / Q000503:physiopathology*; D008297:Male; D017202:Myocardial Ischemia / Q000503:physiopathology*; D009474:Neurons / Q000187:drug effects / Q000502:physiology; D013268:Stimulation, Chemical; D013314:Stress, Mechanical; D013373:Substance P / Q000494:pharmacology; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology*
D013373:Substance P; D000255:Adenosine Triphosphate; D000241:Adenosine; D001920:Bradykinin