POLYSENSORY RESPONSE CHARACTERISTICS OF DORSAL-ROOT GANGLION NEURONS THAT MAY SERVE SENSOR FUNCTIONS DURING MYOCARDIAL-ISCHEMIA

Objective: To determine the response characteristics of dorsal root ga nglion neurones that may serve sensory functions during myocardial isc haemia, Methods: Extracellular recordings were made from 54 spontaneou sly active and 5 normally quiescent dorsal root ganglion neurones (T-2 -T-5) in 22 anaesthetized open-chest dogs under control conditions and during epicardial mechanical or chemical stimulation and myocardial i schaemia. 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 stimul i. The 5 quiescent neurones responded only to chemical stimuli, Sponta neously active neurones associated with left ventricular mechanosensor y endings (37 neurones) generated four different activity patterns in response to similar mechanical stimuli (high or low pressure active, h igh-low pressure active, high-low pressure inactive), A fifth group ge nerated 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. Maxim um local mechanical or chemical stimuli enhanced activity to similar d egrees, as did ischaemia. Each ischaemia-sensitive neurone displayed u nique activity patterns in response to similar mechanical or chemical stimuli. Conclusions: Most myocardial ischemia-sensitive dorsal mot ga nglion neurones associated with epicardial neurites sense mechanical a nd multiple chemical stimuli, a small population sensing only mechanic al or chemical stimuli, Activity patterns generated by these neurones depend on their primary sensory characteristics or those of other neur ones that may converge on them, as well as the type and magnitude of t he stimuli that impinge upon their sensory fields, both normally and d uring ischaemia.