Suchergebnisse

The hypothalamic paraventricular nucleus (PVN) is composed of functionally heterogeneous cell groups, possessing distinct electrophysiological properties depending on their functional roles. Previously, T-type Ca2+ dependent low-threshold spikes (LTS) have been demonstrated in various PVN neuronal types, including preautonomic cells. However, the molecular composition and functional properties of the underlying T-type Ca2+ channels have not been characterized. In the present study, we combined single cell reverse transcription–polymerase chain reaction (RT-PCR), immunohistochemistry and patch-clamp recordings to identify subtypes of T-type Ca2+ channels expressed in PVN cells displaying LTS (PVN-LTS), including identified preautonomic neurons. LTS appeared at the end of hyperpolarizing pulses either as long-lasting plateaus or as short-lasting depolarizing humps. LTS were mediated by rapidly activating and inactivating T-type Ca2+ currents and were blocked by Ni2+. Single cell RT-PCR and immunohistochemical studies revealed Cav3.1 (voltage-gated Ca2+ channel) as the main channel subunit detected in PVN-LTS neurons. In conclusion, these data indicate that Cav3.1 is the major subtype of T-type Ca2+ channel subunit that mediates T-type Ca2+ dependent LTS in PVN neurons. ; This work was supported by a Korea Research Foundation Grant funded by the Korean government (MOEHRD, Basic Research Promotion Fund) (KRF-2006-331-E00349) to S.Y.L. and by NIH RO1 HL 68725 to J.E.S.

GABA is a major neurotransmitter in the hypothalamus. In particular, neurons in the paraventricular nucleus (PVN) of the hypothalamus receive dense GABAergic inputs from peri-PVN regions. The noradrenergic system has been reported as a modulator of GABAergic transmission to the PVN. Previous electrophysiological and morphological studies support the presence of adrenoceptors on GABAergic neurons innervating the PVN. In this study, we identified three adrenoceptors on GABAergic neurons in the peri-PVN region, focusing on the anterior hypothalamic area (AHA) and rostral zona incerta (ZIr). GABAergic neurons were identified using enhanced green fluorescent protein (eGFP), followed by single cell RT-PCR analysis of the GABA synthetic enzymes, glutamic acid decarboxylase (GAD)65 and/or GAD67. Single cell RT-PCR data revealed the expression of α1A-, α1B- and α2A-adrenoceptor mRNA on GABAergic neurons in AHA and ZIr. Additionally, immunohistochemical studies showed that the immunoreactivities of α1A-, α1B- and α2A-adrenoceptor were colocalized with eGFP-expressing neurons in AHA and ZIr. The present findings suggest the contribution of adrenoceptors to the modulation of GABAergic neurons in AHA and ZIr. ; This work was supported by the Korea Research Foundation Grant (KRF-2003-015-E00033) funded by the Korean Government to P.D.R.