Cholecystokinin B-type receptors mediate a G-protein-dependent depolarizing action of sulphated cholecystokinin ocatapeptide (CCK-8s) on rodent neonatal spinal ventral horn neurons.
Reports of cholecystokinin (CCK) binding and expression of CCK receptors in neonatal rodent spinal cord suggest that CCK may influence neuronal excitability. In patch-clamp recordings from 19/21 ventral horn motoneurons in neonatal (PN 5-12 days) rat spinal cord slices, we noted a slowly rising and prolonged membrane depolarization induced by bath-applied sulfated CCK octapeptide (CCK-8s; 1 microM), blockable by the CCK B receptor antagonist L-365,260 (1 microM). Responses to nonsulfated CCK-8 or CCK-4 were significantly weaker. Under voltage clamp (V H -65 mV), 22/24 motoneurons displayed a CCK-8s-induced tetrodotoxin-resistant inward current [peak: -136 +/- 28 pA] with a similar time course, mediated via reduction in a potassium conductance. In 29/31 unidentified neurons, CCK-8s induced a significantly smaller inward current (peak: -42.8 +/- 5.6 pA), and I-V plots revealed either membrane conductance decrease with net inward current reversal at 101.3 +/- 4.4 mV (n = 16), membrane conductance increase with net current reversing at 36.1 +/- 3.8 mV (n = 4), or parallel shift (n = 9). Intracellular GTP-gamma-S significantly prolonged the effect of CCK-8s (n = 6), whereas GDP-beta-S significantly reduced the CCK-8s response (n = 6). Peak inward currents were significantly reduced after 5-min perfusion with N-ethylmaleimide. In isolated neonatal mouse spinal cord preparations, CCK-8s (30-300 nM) increased the amplitude and discharge of spontaneous depolarizations recorded from lumbosacral ventral roots. These observations imply functional postsynaptic G-protein-coupled CCK B receptors are prevalent in neonatal rodent spinal cord.
Oz
Murat
M
Integrative Neuroscience Section National Institute of Drug Abuse, National Institutes of Health/Department of Health and Human Services, Intramural Research Program, Baltimore, MD 21224, USA. moz@intra.nida.nih.gov
Yang
Keun-Hang
KH
Shippenberg
Toni S
TS
Renaud
Leo P
LP
O'Donovan
Michael J
MJ
D000818:Animals; D000831:Animals, Newborn; D000870:Anterior Horn Cells / Q000187:drug effects / Q000502:physiology*; D019204:GTP-Binding Proteins / Q000502:physiology*; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D051379:Mice; D009046:Motor Neurons / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D043887:Receptor, Cholecystokinin B / Q000187:drug effects / Q000502:physiology*; D011949:Receptors, Cholecystokinin / Q000187:drug effects / Q000502:physiology; D012844:Sincalide / Q000031:analogs & derivatives* / Q000494:pharmacology; D013116:Spinal Cord / Q000187:drug effects / Q000502:physiology*; D013758:Tetragastrin / Q000494:pharmacology
C090019:8-sulfocholecystokinin octapeptide; D043887:Receptor, Cholecystokinin B; D011949:Receptors, Cholecystokinin; D013758:Tetragastrin; D019204:GTP-Binding Proteins; D012844:Sincalide