Ventricular sensory neurons in canine dorsal root ganglia: effects of adenosine and substance P.
Effects elicited by adenosine and substance P on ventricular sensory endings of 14 dorsal root ganglion afferent neurons were studied in situ in anesthetized dogs. Sensory-field application of adenosine (1 microM) increased the activity of these neurons by 179%. Application of a nonspecific adenosine antagonist to epicardial sensory fields suppressed ongoing activity in all 14 neurons by 39%. Application of an A1- or A2-adenosine-receptor antagonist suppressed activity generated by 10 of these neurons by 44 and 59%, respectively. Adenosine applied after A1- or A2-receptor blockade increased activity in 10 neurons by 131 and 145%, respectively, indicating that A1- and A2-receptor effects were not additive. Application of substance P (1 microM) to identified sensory fields increased activity in 12 of these neurons by 169%, whereas application of a substance P-receptor antagonist reduced activity generated by these neurons by 75%. Myocardial ischemia increased activity of nine neurons associated with left ventricular sensory fields by 320%, an effect that was counteracted by the nonspecific adenosine-receptor antagonist. It is concluded that A1- and A2-adenosine receptors, as well as substance P receptors, are present on ventricular epicardial sensory nerve endings of dorsal root ganglion neurons that are tonically active during normal states, becoming further activated during ischemia.
Huang
M H
MH
Department of Physiology and Biophysics, Faculty of Medicine, Dalhousie University, Halifax, Nova Scotia, Canada.
Sylvén
C
C
Horackova
M
M
Armour
J A
JA
D000241:Adenosine / Q000494:pharmacology*; D000818:Animals; D002120:Calcium Channel Agonists / Q000494:pharmacology; D002121:Calcium Channel Blockers / Q000494:pharmacology; D004285:Dogs; D005260:Female; D005727:Ganglia, Spinal / Q000166:cytology / Q000502:physiology*; D006321:Heart / Q000502:physiology*; D006352:Heart Ventricles; D008297:Male; D017202:Myocardial Ischemia / Q000473:pathology / Q000503:physiopathology; D009206:Myocardium / Q000166:cytology; D009475:Neurons, Afferent / Q000187:drug effects* / Q000502:physiology*; D010496:Pericardium / Q000294:innervation; D018047:Receptors, Purinergic P1 / Q000378:metabolism; D013373:Substance P / Q000494:pharmacology*
D002120:Calcium Channel Agonists; D002121:Calcium Channel Blockers; D018047:Receptors, Purinergic P1; D013373:Substance P; D000241:Adenosine