Ion transport across the frog olfactory mucosa: the action of cyclic nucleotides on the basal and odorant-stimulated states.
The action of cyclic nucleotides on the short-circuit current across the isolated bullfrog olfactory mucosa was studied both in the absence and presence of odorants. 8-Bromo-cAMP applied to the ciliated side of the mucosa caused a concentration-dependent, reversible increase in the basal short-circuit current, but not when it was applied to the submucosal side. The current had a sigmoidal concentration dependence described by the Hill equation. The magnitude of the odorant-evoked current was enhanced after bathing the ciliated side with cAMP analogs or modulators of intracellular cAMP. GTP gamma S added to the ciliated side increased the odorant-evoked current, while GDP beta S caused a decrease. Current transients induced by stimulating the ciliated side with either pulses of odorant or 8-bromo-cAMP were partially suppressed by amiloride, but only when amiloride and stimulant were presented simultaneously. Pulses of 8-bromo-cAMP and odorant presented simultaneously resulted in currents that added nonlinearly. In the absence of odorant, 8-bromo-cGMP caused a concentration-dependent decrease in net inward current that was reversed by 8-bromo-cAMP. Odorant-evoked currents were also reduced by 8-bromo-cGMP, and these could not be reversed by 8-bromo-cAMP. The results indicate that one type of olfactory transduction process involves the activation by cAMP of an inward current through an amiloride-sensitive apical ion channel and that this mechanism is mediated by a stimulatory G-protein.
Persaud
K C
KC
Department of Physiology and Biophysics, Medical College of Virginia, Richmond.
Heck
G L
GL
DeSimone
S K
SK
Getchell
T V
TV
DeSimone
J A
JA
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D000242:Cyclic AMP / Q000494:pharmacology; D006152:Cyclic GMP / Q000031:analogs & derivatives / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D019204:GTP-Binding Proteins / Q000378:metabolism; D009712:Nucleotides, Cyclic / Q000494:pharmacology*; D009812:Odorants; D009831:Olfactory Mucosa / Q000378:metabolism*; D011892:Rana catesbeiana
D009712:Nucleotides, Cyclic; D015124:8-Bromo Cyclic Adenosine Monophosphate; C016276:8-bromocyclic GMP; D000242:Cyclic AMP; D019204:GTP-Binding Proteins; D000262:Adenylyl Cyclases; D006152:Cyclic GMP