[Rat orbital frontal (orbital frontal cortex, OFC) GABA B receptor mechanisms in stress and depression].

Stress-induced depression is a kind of functional and structural disability of the brain and involves many neurotransmitters and regions of the brain. A number of studies suggest involvement of γ-Aminobutyric acid (GABA) in the orbital frontal cortex (OFC) in the mechanism of stress-associated depression-like behavior in rodents. However, little work has been done on the relationship between GABA and neural plasticity of the OFC under stress. Here we examine the effect of the GABA in the OFC during acute forced swim stress (FSS). We found remarkable depression-like behavior in FSS and an open field test (OFT), and we observed a marked decrease in Kalirin-7 expression and the basal dendritic spine density of layer V pyramidal neurons in OFC after FSS. GABA administration reversed these changes, which were inhibited by CGP35348, an antagonist of GABA-B receptors. These results suggest an anti-depression effect of GABA in the OFC, which may be mediated by GABA-B receptor. The anti-depression effect of GABA is related to the plasticity of the dendritic spine density. This discovery may be helpful in the development of new therapies to treat depression.

[Effect and mechnaisim of GLU and GABA in OFC on gastric motility].

AIM: To Investigate the effect of glutamate (Glu) and gamma-aminobutyric acid(GABA) in orbitofrontal cortex (OFC) on regulation of gastric motility. METHODS: Using microinjection in OFC,together with lesion of related nucleus,and recording the intragastric pressure(IGP). RESULTS: (1) Microinjection of Glu in OFC caused a significant reduce of the amplitude of gastric motility, this effect could be reverse by lesion of amygdala, while lesion of LC had no influence on the effect of Glu. (2) microinjection of GABA in OFC could increase the amplitude of gastric motility significantly,and lesion of LC could abolish this effect,while lesion of amygdala could enhance the effect of GABA more. CONCLUSION: Microinjection of Glu in OFC may enhance the normal inhibitory effect of amygdale on gastric motility, and the effect of microinjection of GABA in OFC on gastric motility is closely related with LC.

[Effects and mechanism of hypothalamic TRH on cardiac function in rats].

AIM: To investigate the effect of hypothalamic thyrotropin-releasing hormone (TRH) on cardiac function and its mechanism. METHODS: The Sprague-Dawley rats were mounted in a stereotaxic apparatus and a guide cannula placed in the left hypophysiotropic area, through which TRH were microinjected in presence or absence of L-NAME and atropine. The left ventricular systolic pressure (LVSP), heart rate (HR) and the maximum velocity of ascending or descending in intraventricular pressure (+/- dp/dt(max)) were recorded. RESULTS: (1) TRH microinjected into the hypophysiotropic area induced a significant increase of LVSP, HR, dp/dt and-dp/dt(max) (P < 0.05, P < 0.01). (2) L-NAME significant increased LVSP and pretreatment with L-NAME inhibited the positive effects induced by TRH. (3) Atropine increased LVSP and dp/dt(max) (P < 0.05), but it significantly descended heart rate (P < 0.05). Pretreatment with atropine weakened the tachycardiac response induced by TRH. CONCLUSION: (1) Hypothalamic TRH can produce positive inotropic and chronotropic response to myocardium. (2) Hypothalamic endogenous NO can descend LVSP, but has no effects on HR, dp/dt(max), and-dp/dt(max). The effect of TRH is through nitric oxide-dependent pathway. (3) Hypothalamic endogenous cholinergic transmitter can produce negative chronotropic and positive inotropic response to myocardium. Hypothalamic TRH mediates cardiac function maybe partly through cholinergic M receptor.