Study on nitric oxide and GABA in the hypothalamic paraventricular nucleus and prefrontal cortex under stress

我们之前提出，腹腔注射白细胞介素-1β (IL-1β)可增加下丘脑室旁核（PVN）中的一氧化氮（NO）水平。利用体内脑微透析技术，我们通过微透析探针将选择性γ-氨基丁酸（GABA）受体拮抗剂和激动剂灌注到内侧前额叶皮层（mPFC）后，测量了下丘脑PVN中NO代谢物（Nox^-）的细胞外水平。我们研究了选择性GABAA受体拮抗剂和激动剂对il -1β诱导的PVN一氧化氮释放的影响。采用双免疫染色法检测Fos和神经元一氧化氮合酶（neuronal nitric oxide synthase, nNOS），观察IL-Iβ在大鼠PVN中是否激活nNOS免疫反应性神经元表达Fos免疫反应性。通过向mPFC灌注GABAA受体激动剂muscimol (50 μM)，降低IL-1β (4μg/kg)后PVN中Nox^-升高的水平。我们还研究了GABAB受体拮抗剂和激动剂对il -1β诱导的PVN一氧化氮释放的影响。向mPFC灌注GABAB受体激动剂巴氯芬（250 μM）对IL-1β(4 μg/kg)后PVN内Nox^-水平升高无影响。在mPFC中灌注GABAB受体拮抗剂saclofen （50 μM）对IL-1β(4 μg/kg)后PVN中Nox^-水平升高无影响。定量分析显示，IL-1β(4 μg/kg, ig)可激活部分nnos阳性PVN神经元。这些发现可能为我们理解mPFC中GABAA和GABAB受体对il -1β诱导的PVN中NO代谢物释放的抑制调节提供有用的线索。

We have suggested previously that intraperitoneal (I.p.) administration of interleukin-1β (IL-1β) increases nitric oxide (NO) levels in the hypothalamic paraventricular nucleus (PVN). Using an in vivo brain microdialysis technique, we measured extracellular levels of NO metabolites (Nox^-) in the hypothalamic PVN upon perfusion of selective γ-aminobutyric acid (GABA) receptor antagonist as well as agonist into the medial prefrontal cortex (mPFC) through a microdialysis probe. We examined the effects of selective GABAA receptor antagonist and agonist on IL-1β-induced NO releases in the PVN in conscious rats. Double immunostaining for Fos and neuronal nitric oxide synthase (nNOS) was also used to examine whether nNOS-immunoreactive neurons in the PVN are activated to express Fos immunoreactivity by I.p. injection of IL-Iβ in the rat. The elevated levels of Nox^- in the PVN after I.p. administration IL-1β (4μg/kg) were attenuated by perfusion of muscimol (50 μM), a GABAA receptor agonist, into the mPFC. We also examined the effect of GABAB receptor antagonist and agonist on IL-1β-induced NO releases in the PVN in conscious rats. Perfusion of baclofen (250 μM), a GABAB receptor agonist, into the mPFC had no effect on the elevated levels of Nox^- in the PVN after I.p administration IL-1β(4 μg/kg). Perfusion of saclofen (50 μM), a GABAB receptor antagonist, into the mPFC had no effect on the elevated levels of Nox^- in the PVN after I.p. administration IL-1β(4 μg/kg). Quantitative analysis revealed that some nNOS-positive PVN neurons are activated by IL-1β(4 μg/kg, I.p.) administration. These findings are likely to provide helpful clues to our understanding of the inhibitory modulation of IL-1β-induced NO metabolites releases in the PVN by GABAA and GABAB receptors in the mPFC.