Effects of bicarbonate buffer on acetylcholine-, adenosine 5'triphosphate-, and cyanide-induced responses in the cat petrosal ganglion in vitro.
Acetylcholine (ACh), adenosine 5'-triphosphate (ATP) and sodium cyanide (NaCN) activate petrosal ganglion (PG) neurons in vitro, and evoke ventilatory reflexes in situ, which are abolished after bilateral chemosensory denervation. Because in our previous experiments we superfused the isolated PG with solutions free of CO2/HCO3- buffer, we studied its effects on the PG responses evoked in vitro. PGs from adult cats were superfused at a constant pH, with HEPES-supplemented (5 mM) saline with or without CO2/HCO3- (5%/26.2 mM) buffer, and carotid (sinus) nerve frequency discharge (fCN) recorded. Increases in fCN evoked by ACh, ATP and NaCN in CO2- free saline were significantly reduced (P < 0.05, Wilcoxon test) when CO2/HCO3- was present in the superfusion medium. Thus, the presence of CO2/HCO3- buffer appears to reduce PG neurons sensitivity to ACh, ATP and NaCN, an effect that may underlie the lack of ventilatory reflexes after bilateral chemodenervation.
Soto
Carolina R
CR
Laboratorio de Fisiología Celular, Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Casilla 653, Santiago, Chile.
Arroyo
Jorge
J
Alcayaga
Julio
J
D000109:Acetylcholine / Q000378:metabolism / Q000494:pharmacology*; D000255:Adenosine Triphosphate / Q000378:metabolism / Q000494:pharmacology*; D000818:Animals; D001639:Bicarbonates / Q000737:chemistry / Q000494:pharmacology*; D002021:Buffers; D002245:Carbon Dioxide / Q000494:pharmacology; D002339:Carotid Arteries / Q000294:innervation; D002344:Carotid Body / Q000187:drug effects; D002415:Cats; D003714:Denervation; D004791:Enzyme Inhibitors; D005071:Evoked Potentials / Q000187:drug effects; D017950:Ganglia, Sensory / Q000187:drug effects* / Q000502:physiology; D005930:Glossopharyngeal Nerve / Q000187:drug effects* / Q000502:physiology; D006531:HEPES / Q000737:chemistry / Q000494:pharmacology*; D012966:Sodium Cyanide / Q000378:metabolism / Q000494:pharmacology*
D001639:Bicarbonates; D002021:Buffers; D004791:Enzyme Inhibitors; D002245:Carbon Dioxide; D000255:Adenosine Triphosphate; D000109:Acetylcholine; D012966:Sodium Cyanide; D006531:HEPES