Abstract
The effect of stresscopin (SCP) on oxytocin (OT) mRNA expressing neurons in the rat paraventricular nucleus (PVN) was examined using whole-cell patch-clamp recordings and single-cell reverse transcription-polymerase chain reaction (SC-RT-PCR) technique. Under current-clamp, SCP (10 nM to 600 nM) resulted in decreased basal firing rate and hyperpolarization in a dose-dependent manner. SCP -induced hyperpolarization was unaffected by co-perfusion with 0.5 μM tetrodotoxin (TTX) + 10 μM CNQX + 10 μM bicuculline. Under voltage-clamp, 300 nM SCP increased the inwardly rectifying K+ current. Extracellular application of 200 μM Ba2+, a blocker of G protein-activated, inwardly rectifying potassium (GIRK) channels, completely blocked the effects of SCP on OT mRNA expressing neurons in voltage-clamp. Extracellular application of 1 μM α-helical CRF-(9-14) (α-h CRF), a corticotrophin-releasing factor (CRF) receptors antagonist, completely blocked the SCP-induced effects in both current- and voltage-clamp. And the SC-RT-PCR analysis indicated that all OT mRNA-expressing neurons co-expressed CRF receptor 1 and receptor 2 mRNA. These results suggest that OT neurons co-express CRF receptors, and SCP inhibits to OT neurons through activation of GIRK current activities. [Jpn J Physiol 54 Suppl:S199 (2004)]
