A diffusible second messenger mediates one of the pathways coupling receptors to calcium channels in rat sympathetic neurons.
Muscarinic and alpha-adrenergic suppression of current through Ca2+ channels was studied in adult rat superior cervical ganglion neurons using whole-cell and cell-attached configurations of the patch-clamp technique. Oxotremorine methiodide suppressed ICa by both a rapid (much less than 1 s) and a slow (greater than 4 s) process, whereas norepinephrine suppressed ICa only by a rapid process. The slow muscarinic suppression could be prevented by adding 20 mM BAPTA, a Ca2+ chelator, to the recording pipette, whereas the adrenergic suppression was not affected. Muscarinic, but not alpha-adrenergic, receptors can couple to Ca2+ channels by a second messenger capable of diffusing into an on-cell patch. This signal seems not to be carried by intracellular Ca2+, cGMP, cAMP, or protein kinase C.
Bernheim
L
L
Department of Physiology and Biophysics, University of Washington, Seattle 98195.
Beech
D J
DJ
Hille
B
B
D000818:Animals; D015220:Calcium Channels / Q000502:physiology*; D004533:Egtazic Acid / Q000494:pharmacology / Q000031:analogs & derivatives; D004553:Electric Conductivity / Q000187:drug effects; D005728:Ganglia, Sympathetic / Q000502:physiology*; D066298:In Vitro Techniques; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D009474:Neurons / Q000502:physiology*; D009638:Norepinephrine / Q000494:pharmacology; D010095:Oxotremorine / Q000494:pharmacology; D015240:Phorbol 12,13-Dibutyrate / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects / Q000502:physiology*; D011976:Receptors, Muscarinic / Q000187:drug effects / Q000502:physiology*; D015290:Second Messenger Systems
D015220:Calcium Channels; D011942:Receptors, Adrenergic, alpha; D011976:Receptors, Muscarinic; D015240:Phorbol 12,13-Dibutyrate; D004533:Egtazic Acid; D010095:Oxotremorine; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid; D009638:Norepinephrine