ATP- and ACh-induced responses in isolated cat petrosal ganglion neurons.
Chemoreceptor (glomus) cells of the carotid body are synaptically connected to the sensory nerve endings of petrosal ganglion (PG) neurons. In response to natural stimuli, the glomus cells release transmitters, which acting on the nerve terminals of petrosal neurons increases the chemosensory afferent discharge. Among several transmitter molecules present in glomus cells, acetylcholine (ACh) and adenosine 5'-triphosphate (ATP) are considered to act as excitatory transmitter in this synapse. To test if ACh and ATP play a role as excitatory transmitters in the cat CB, we recorded the electrophysiological responses from PG neurons cultured in vitro. Under voltage clamp, ATP induces a concentration-dependent inward current that partially desensitizes during 20-30 s application pulses. The ATP-induced current has a threshold near 100 nM and saturates between 20-50 muM. ACh induces a fast, inactivating inward current, with a threshold between 10-50 muM, and saturates around 1 mM. A large part of the population of PG neurons (60%) respond to both ATP and ACh. Present results support the hypothesis that ACh and ATP act as excitatory transmitters between cat glomus cells and PG neurons.
Alcayaga
Carmen
C
Programa Disciplinario de Fisiología y Biofísica, ICBM, Facultad de Medicina, Universidad de Chile, Avda. Independencia 1027, Santiago, Chile. calcayag@med.uchile.cl
Varas
Rodrigo
R
Valdés
Viviana
V
Cerpa
Verónica
V
Arroyo
Jorge
J
Iturriaga
Rodrigo
R
Alcayaga
Julio
J
D000109:Acetylcholine / Q000378:metabolism* / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000378:metabolism* / Q000494:pharmacology; D000818:Animals; D002344:Carotid Body / Q000187:drug effects / Q000378:metabolism*; D002415:Cats; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology; D017950:Ganglia, Sensory / Q000187:drug effects / Q000378:metabolism*; D005930:Glossopharyngeal Nerve / Q000187:drug effects / Q000378:metabolism*; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009475:Neurons, Afferent / Q000187:drug effects / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D011984:Sensory Receptor Cells / Q000187:drug effects / Q000378:metabolism; D013569:Synapses / Q000187:drug effects / Q000378:metabolism; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology
D000255:Adenosine Triphosphate; D000109:Acetylcholine