Bradykinin-induced modulation of calcium signals in rat dorsal root ganglion neurons in vitro.
We used combined patch-clamp-microfluorimetric recordings to examine the effects of bradykinin on [Ca2+]i transients and the Ca2+ current (ICa) in rat dorsal root ganglion neurons in vitro. Bradykinin increased [Ca2+]i in approximately 20% of dorsal root ganglion cells examined and inhibited the ICa in approximately 65% of dorsal root ganglion cells. Bradykinin also inhibited the ICa when [Ca2+]i was buffered with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid or when Ba2+ was the charge carrier. When ICa's of increasing duration were elicited in these neurons, [Ca2+]i transients were produced that increased in amplitude but eventually approached an asymptote at longer voltage steps. Similarly, the amplitude of the [Ca2+]i transient also approached an asymptote in current-clamp recordings when cells were induced to fire a large number of action potentials. The bradykinin-induced inhibition of the amplitude of the [Ca2+]i transient was more pronounced at shorter voltage steps. At pulse durations that produced asymptotic [Ca2+]i signals, bradykinin no longer decreased the amplitude of the rise in [Ca2+]i, although it still reduced the ICa. In current-clamp recordings, bradykinin also reduced the [Ca2+]i signal that accompanied the generation of action potentials, but again bradykinin was more effective for shorter spike trains. Bradykinin also depolarized the majority of neurons (65%). The reduction in [Ca2+]i produced by bradykinin in sensory neurons may be an important factor contributing to bradykinin-induced excitation of primary sensory afferents.
Bleakman
D
D
Department of Pharmacological and Physiological Sciences, University of Chicago, Illinois 60637.
Thayer
S A
SA
Glaum
S R
SR
Miller
R J
RJ
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D001920:Bradykinin / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000187:drug effects; D002478:Cells, Cultured; D005727:Ganglia, Spinal / Q000187:drug effects* / Q000378:metabolism; D011189:Potassium Chloride / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains
D015220:Calcium Channels; D011189:Potassium Chloride; D001920:Bradykinin; D002118:Calcium