Regulatory effects of corticotropin release hormone on hypothalamic neuronal calcium signals and CREB

Yundong ZHANG; Xiaohong GU; Peifang ZHU; Zhengguo WANG; Jizong ZHAO; Jihong ZHOU; Minhui XU; Yongwen ZOU

ABSTRACT

BACKGROUND:

Through what signal pathway does corticotropin release hormone (CRH) regulate hypothalamic neuronal neuroendocrine activity during acute stress?

OBJECTIVE:

To probe into the regulatory effects of CRH on CREB secretion in hypothalamic neurons.

DESIGN:

Repetitive measurement design.

SETTING:

At Field Surgery Research Institute of Daping Hospital, Third Military Medical University of Chinese PLA; Neurosurgery Department,Tiantan Hospital Affiliated to the Capital University of Medical Sciences.MATERIALS This experiment was carried out in Daping Hospital of Third Military Medical University of Chinese PLA between December 1999and March 2002. Rat fetuses were selected from Wister rats of 17-day gestation.

METHODS:

In vitro cultured cells were divided into the following groups① CRH (10-12, 10-10, 10-8 and 10-6 mol/L) stimulation groups. ② Pretreated with nimodipine (5 μmol/L) or CP-154526 (500 μmol/L) followed by CRH (10-12, 10-10, 10-8 and 10-6 mol/L ) stimulation groups. ③ Corresponding control groups stimulated with isotonic physiological saline. PTI fluorescence imaging system was used to detect the changes of neuronal cytoplasmic free calcium concentration; meanwhile, Western blot technique was used to determine the changes of neuronal P-CREB content.MAIN OUTCOME

MEASURES:

① Changes of neuronal cytoplasmic free calcium concentration. ② Changes of neuronal P-CREB content.

RESULTS:

The content of cytoplasmic free calcium in hypothalamic neurons was lower in normal control group, and it increased immediately after exogenous CRH stimulation. However, such increase could be suppressed by pretreatment with nimodipine or CP-154526 before CRH stimulation,and the increase of neuronal P-CREB content was also obviously suppressed.

CONCLUSION:

During acute stress, the combination of CRH with hypothalamic neuronal CRH 1 receptor leads to the opening of membrane Ltype calcium ions channels, thus enhancing the influx of calcium ions and increasing cytoplasmic free calcium ions content, which would further activate P-CREB signal transduction pathway in neurons. It suggests that CRH may play a vital role in hypothalamic neuronal activation.