Facilitating effect of CCK on nicotinic neurotransmission in cat pancreatic ganglion.
Previous studies have demonstrated the presence of cholecystokinin (CCK)-like peptides in nerve terminals surrounding ganglion neurons of the cat pancreas. The present study was undertaken to determine the effect of cholecystokinin octapeptide (CCK-8) on ganglionic transmission. Recordings were made intracellularly in vitro from ganglion neurons in isolated pieces of the pancreas. Sulfated CCK-8 (S-CCK-8) and nonsulfated CCK-8 initiated or increased ongoing fast excitatory postsynaptic potential (fEPSP) activity, an effect antagonized by hexamethonium. Superfusion of S-CCK-8 in concentrations ranging from 10(-11) to 10(-8) M significantly augmented the amplitude of nerve-evoked subthreshold fEPSPs without a significant change in either membrane potential or membrane input resistance. S-CCK-8 (10(-8)M) also increased the quantal content and quantal size of nerve-evoked fEPSPs and increased the response to exogenously applied acetylcholine (ACh). Concentrations of S-CCK-8 higher than 10(-8)M caused depolarization and an increase in membrane input resistance, an effect unaltered by a low-Ca+, high-Mg2+ solution. It was concluded that S-CCK-8 potentiated nicotinic transmission by facilitating release of ACh from preganglionic nerve terminals and by increasing the postsynaptic membrane sensitivity to ACh.
Ma
R C
RC
Department of Physiology and Biophysics, Mayo Clinic and Mayo Foundation, Rochester, Minnesota 55905, USA.
Szurszewski
J H
JH
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D002415:Cats; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation; D005071:Evoked Potentials / Q000187:drug effects / Q000502:physiology; D005728:Ganglia, Sympathetic / Q000502:physiology*; D018738:Hexamethonium / Q000494:pharmacology; D008564:Membrane Potentials; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D010179:Pancreas / Q000294:innervation*; D010477:Perfusion; D012844:Sincalide / Q000031:analogs & derivatives / Q000494:pharmacology*; D013569:Synapses / Q000187:drug effects / Q000502:physiology; D009435:Synaptic Transmission / Q000187:drug effects* / Q000502:physiology
C090019:8-sulfocholecystokinin octapeptide; D018738:Hexamethonium; D012844:Sincalide; D000109:Acetylcholine