TY - JOUR
T1 - Estrogen upregulates T-type calcium channels in the hypothalamus and pituitary
AU - Qiu, Jian
AU - Bosch, Martha A.
AU - Jamali, Khalid
AU - Xue, Changhui
AU - Kelly, Martin J.
AU - Rønnekleiv, Oline K.
PY - 2006/10/25
Y1 - 2006/10/25
N2 - Low voltage-activated (T-type) Ca2+ channels are responsible for generating low-threshold spikes (LTS) that facilitate burst firing and transmitter release in neurons. The T-type Ca2+ channels contain a regulatory α1 subunit, and several isoforms of the α1 subunit (Cav3.1, 3.2, 3.3) have been cloned. The Cav 3.1 α1 subunit is abundantly expressed in the hypothalamus. Previously, we found that 17 β-estradiol (E2) increased the number of arcuate neurons expressing LTS. Therefore, we used an ovariectomized female guinea pig model to measure the distribution and regulation of Cav3.1 mRNA expression by E2. Guinea pig Cav3.1 α1 subunit sequences, which were cloned by PCR, were used in ribonuclease protection (RPA) and in situ hybridization assays to evaluate mRNA expression. Based on a RPA, E2 significantly increased the mRNA expression of Cav3.1 α1 subunit in the mediobasal hypothalamus and the pituitary. In situ hybridization analysis revealed that E2 significantly increased Cav 3.1 mRNA expression in medial preoptic nuclei, bed nuclei stria terminalis, and the arcuate nucleus. Whole-cell patch recordings in arcuate neurons revealed that E2 treatment significantly increased the peak T-type Ca2+ current density by twofold without affecting the activation/inactivation characteristics and augmented the rebound excitation by threefold to fourfold. These results suggest that estrogen regulates the mRNA expression of T-type calcium channels, which leads to increased functional expression of the channel. Increased expression of T-type channels could be one mechanism by which estrogen augments burst firing and transmitter release in hypothalamic neurons.
AB - Low voltage-activated (T-type) Ca2+ channels are responsible for generating low-threshold spikes (LTS) that facilitate burst firing and transmitter release in neurons. The T-type Ca2+ channels contain a regulatory α1 subunit, and several isoforms of the α1 subunit (Cav3.1, 3.2, 3.3) have been cloned. The Cav 3.1 α1 subunit is abundantly expressed in the hypothalamus. Previously, we found that 17 β-estradiol (E2) increased the number of arcuate neurons expressing LTS. Therefore, we used an ovariectomized female guinea pig model to measure the distribution and regulation of Cav3.1 mRNA expression by E2. Guinea pig Cav3.1 α1 subunit sequences, which were cloned by PCR, were used in ribonuclease protection (RPA) and in situ hybridization assays to evaluate mRNA expression. Based on a RPA, E2 significantly increased the mRNA expression of Cav3.1 α1 subunit in the mediobasal hypothalamus and the pituitary. In situ hybridization analysis revealed that E2 significantly increased Cav 3.1 mRNA expression in medial preoptic nuclei, bed nuclei stria terminalis, and the arcuate nucleus. Whole-cell patch recordings in arcuate neurons revealed that E2 treatment significantly increased the peak T-type Ca2+ current density by twofold without affecting the activation/inactivation characteristics and augmented the rebound excitation by threefold to fourfold. These results suggest that estrogen regulates the mRNA expression of T-type calcium channels, which leads to increased functional expression of the channel. Increased expression of T-type channels could be one mechanism by which estrogen augments burst firing and transmitter release in hypothalamic neurons.
KW - Cav3.1 mRNA
KW - Dopamine
KW - Estrogen regulation
KW - Neurons
KW - POMC
KW - Rebound burst firing
KW - T-current amplitude
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U2 - 10.1523/JNEUROSCI.3229-06.2006
DO - 10.1523/JNEUROSCI.3229-06.2006
M3 - Article
C2 - 17065449
AN - SCOPUS:33751104724
SN - 0270-6474
VL - 26
SP - 11072
EP - 11082
JO - Journal of Neuroscience
JF - Journal of Neuroscience
IS - 43
ER -