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Guanosine 3',5'‐cyclic monophosphate regulates calcium channels in neurones of rabbit vesical pelvic ganglia.
Author(s) -
Nishimura T,
Akasu T,
Krier J
Publication year - 1992
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1992.sp019394
Subject(s) - chemistry , biophysics , calcium , depolarization , medicine , endocrinology , reversal potential , guanosine , electrophysiology , patch clamp , biochemistry , biology , organic chemistry
1. The effects of dibutyryl guanosine 3',5'‐cyclic monophosphate (db‐cyclic GMP) were studied in vitro on calcium channels of neurones in rabbit vesical parasympathetic ganglia, using intracellular and single‐electrode voltage‐clamp recordings. 2. Db‐cyclic GMP (100 microM) caused membrane depolarization associated with a decrease in membrane input resistance and an after‐hyperpolarization associated with an increase in membrane input resistance. 3. Db‐cyclic GMP (0.01‐1 mM) caused a concentration‐dependent, transient inward current followed by a long‐lasting outward current. Membrane conductance was increased and decreased during the inward and outward currents, respectively. 4. The db‐cyclic GMP‐induced inward current was depressed in nominally calcium‐free solutions, by cobalt (1 mM) and nicardipine (10 microM). The mean reversal potentials of the inward current were +42 and ‐20 mV in the presence and absence of calcium in the external solution, respectively. 5. The db‐cyclic GMP‐induced inward current was not altered by lowering the external sodium concentration, raising external potassium concentration or by intracellular injection of caesium. 6. A calcium‐insensitive component of the db‐cyclic GMP‐induced current was increased by lowering the external chloride concentration and blocked by 4‐acetamido‐4'‐isothiocyanostilbene‐2,2'‐disulphonic acid, a chloride channel blocker. 7. Voltage‐dependent, high‐threshold calcium currents were depressed during the db‐cyclic GMP‐induced inward current and facilitated during the outward current. 8. Cyclic GMP was less potent than db‐cyclic GMP in causing both inward and outward currents or modulation of calcium currents. GTP, GDP, GMP, guanosine, 8‐bromoadenosine 3',5'‐cyclic monophosphate and forskolin did not alter the holding current or voltage‐dependent calcium currents. 9. It is concluded that intracellular cyclic GMP causes not only activation of resting calcium and chloride channels but also a transient depression followed by long‐lasting facilitation of voltage‐dependent calcium currents in neurones of vesical parasympathetic ganglia.