title: Substance P hyperpolarizes vagal sensory neurones of the ferret.
abstract: 1. Intracellular recordings were made in intact and in acutely dissociated vagal afferent neurones (nodose ganglion cells) of the ferret to investigate the effects of substance P(SP). 2. In current-clamp recordings, SP (100 nM) applied by superfusion hyperpolarized the membrane potential (7 +/- 0.7 mV; mean +/- S.E.M.; n = 105) and decreased the input resistance in 80% of the neurones. With voltage-clamp recording, SP produced an outward current of 3 +/- 0.2 nA (n = 10). 3. The SP current was concentration dependent with an estimated EC50 of 68 nM. The SP-induced hyperpolarization or current was mimicked by the tachykinin receptor NK1 agonist Ac-[Arg6, Sar9, Met(O2)11]SP(6-11) (ASM-SP; 100 nM; n = 10) and blocked by the NK1 antagonist CP-96,345 (10 nM; n = 6), but not by the NK2 antagonist SR48968 (100 nM; n = 4). No measurable change in membrane potential or input resistance was observed with application of either [beta-Ala8]neurokinin A or senktide, selective NK2 and NK3 receptor agonists, respectively (100 nM; n = 3 for each agonist). 4. The reversal potential (Erev) for the SP outward current was -85 +/- 2.5 mV (n = 4). The Erev for the SP response shifted in a Nernstian manner with changes in extracellular potassium concentration. Alterations in extracellular sodium or chloride concentrations had no significant effect on the Erev for the SP response (n = 3 for each ion). 5. Nominally Ca(2+)-free external solution abolished the SP response. Removal of magnesium from the extracellular solution had no effect on the response. 6. Caesium (100 microM), barium (1 mM), tetraethylammonium (TEA; 5 mM), apamin (10 nM) and 4-aminopyridine (4-AP; 4 mM) each completely prevented the SP response (n > or = 3 for each). 7. These results indicate that SP, via an NK1 receptor, can induce a Ca(2+)-dependent outward potassium current which hyperpolarizes the resting membrane potential of vagal afferent somata.
authors: University of Maryland, School of Medicine, Department of Pharmacology and Experimental Therapeutics, Baltimore 21201-1559, USA.
authors: M S
authors: MS
authors: Jafri
authors: D
authors: D
authors: Weinreich
mesh_terms: D015761:4-Aminopyridine / Q000494:pharmacology; D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology; D001030:Apamin / Q000494:pharmacology; D001549:Benzamides / Q000494:pharmacology; D001713:Biphenyl Compounds / Q000494:pharmacology; D002413:Cations, Divalent / Q000494:pharmacology; D002586:Cesium / Q000494:pharmacology; D004594:Electrophysiology; D005289:Ferrets / Q000378:metabolism; D066298:In Vitro Techniques; D008297:Male; D009475:Neurons, Afferent / Q000378:metabolism*; D009620:Nodose Ganglion / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D010446:Peptide Fragments / Q000494:pharmacology; D010880:Piperidines / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D011761:Pyrrolidonecarboxylic Acid / Q000031:analogs & derivatives; D000644:Quaternary Ammonium Compounds / Q000494:pharmacology; D018039:Receptors, Tachykinin / Q000819:agonists / Q000037:antagonists & inhibitors; D013373:Substance P / Q000494:pharmacology*; D014630:Vagus Nerve / Q000378:metabolism*
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D001549:Benzamides; D001713:Biphenyl Compounds; D002413:Cations, Divalent; D010446:Peptide Fragments; D010880:Piperidines; D000644:Quaternary Ammonium Compounds; D018039:Receptors, Tachykinin; D002586:Cesium; D001030:Apamin; D013373:Substance P; C032292:substance P (6-11); C073839:SR 48968; D015761:4-Aminopyridine; C027917:tetramethylammonium; D011188:Potassium; D011761:Pyrrolidonecarboxylic Acid; C066892:CP 96345