Postnatal decrease of sodium current density in rat pituitary melanotropes following the onset of dopaminergic innervation.
Peptide secretion from rat melanotropes is tonically inhibited by a dopaminergic synaptic input that develops after birth and acts through D2 dopamine receptors. In this study, whole-cell Na(+) currents were recorded from melanotropes that were isolated from rat pituitary intermediate lobes at postnatal days 1-20 (P1-P20) and maintained in culture for 5-24 h. Coincident with the development of innervation, melanotropes exhibited a progressive decrease in peak Na(+) current density from P3 to P14. The decrease involved a 50% reduction in maximal Na(+) conductance with no detectable changes in channel gating. Subcutaneous injections of the D2 antagonist sulpiride, applied from P11 to P13, restored melanotrope Na(+) channel activity to pre-innervation levels. Thus, the activation of D2 receptors by the dopaminergic input reduces the functional expression of Na(+) channels in melanotropes.
López-Santiago
L F
LF
Department of Physiology, Biophysics and Neuroscience, Cinvestav-IPN, AP 14-740 Mexico City, DF 07000, Mexico.
Gómora
J C
JC
Cota
G
G
D000375:Aging / Q000502:physiology; D000818:Animals; D000831:Animals, Newborn / Q000235:genetics / Q000378:metabolism*; D002478:Cells, Cultured; D004298:Dopamine / Q000502:physiology*; D004553:Electric Conductivity; D009074:Melanocyte-Stimulating Hormones / Q000378:metabolism*; D010902:Pituitary Gland / Q000254:growth & development / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D015222:Sodium Channels / Q000502:physiology*
D015222:Sodium Channels; D009074:Melanocyte-Stimulating Hormones; D004298:Dopamine