Expression Of GABA Receptors In Neurons Involved In Immuno-stimulating Stress Induced By Lipopolysaccharide

Background:The amygdaloid nucleus and hypothalamus are the important structures of limbic system and play the important roles in the regulation of cardiovascular,respiratory,visceral activities and pain,endocrine,immunization, either in physiological or stress situations,by associated with brainstem.The gamma aminobutyric acid(GABA) is the crucial inhibitor neurotransmitter in the central nervous system and the researches on GABA receptors are the hottest area in neuronscience.It has been found in our previous studies that the GABAergic projection is the major portion from the amygdaloid nucleus to the nucleus of solitary tract and parabrachial nucleus.On account of procerebrum limbic system regulate the visceral activities,pain,immunization and stress through a series of nuclei in the brainstem,the role of GABA involved in above mentioned functions and which GABA receptor subtypes and which sites do the GABA carries out inhibitory function has not been clarified.Lipopolysaccharide(LPS) is a component of gram-negative bacteria cell wall. LPS administration is known to induce a marked increase in the plasma levels of inflammatory cytokines such as interleukin-1β(IL-1β),IL-6 and tumor necrosis factor-(TNF-) and is commonly used experimentally as a model of peripheral immuno-stimulating.The proto-oncogene Fos is one of the immediate early genes that can be rapidly induced in multiple regions of the brain following various forms of stimulation.Fos epression has been used as a marker to identify neurons activated in the brain.GABA carries out inhibitory function by binding to GABA type A receptor(GABA_AR),GABA _BR and GABA_CR. GABA_AR are related with a variety of events in the brain and the subunitα1 (GABA_ARα1) has significant relation to the function of GABA_AR.GABA_BR is consisting of GABA_BR1 and GABA_BR2 subunits.GABA_BR1 is the major of two subunits of the GABA_BR.Therefore we were interested in determining if the GABA receptors in rat that are activated during immuno-stimulating stress induced by LPS.Objective:To investigate the role of GABA receptors in immuno-stimulating stress induced by LPS in rat brain.Method:The adult rats were randomly divided into two groups.LPS dissolved in saline 300μl,was given by intraperitoneal injections to stimulate the immune system and same volume saline was injected into control animals as well.Using double immunofluorescence staining and laser scanning confocal microscopy methods to observe expression of Fos, GABA_ARα1 as well as the relationship between the two labling in hypothalamus paraventricular ncleus(PVN),medial amygdaloid nucleus(Me),lateral parabrachial nucleus(LPB) and nucleus of the solitary tract(NTS) on LPS administration.In addition, investigated the changes in the expression of Fos,GABA_BR1 as well as the relationship between the two labling in PVN and hypothalamus supraoptic nucleus(SON).Results:1.In the first part,we observed that in PVN,Me,LPB andNTS,It was found a large number of Fos and GABA_ARα1 positive neurons in these sittes.The number of Fos positive neurons was increased significantly after the LPS immuno-stimulating in contrast to control group with saline.The coexistence of Fos and GABA_ARα1 positive neurons were observed in part of the neurons in these sites.In PVN,the proportion of Fos/GABA_ARα1 double-labeled neurons vs single Fos and GABA_ARα1 positive neurons were 27 %and 32%respectively.In Me,the proportion of Fos/GABA_ARα1 double-labeled neurons vs single Fos and GABA_ARα1 positive neurons were 28 %and23%respectively.In LPB,the proportion of Fos/GABA_ARα1 double-labeled neurons vs single Fos and GABA_ARα1 positive neurons were 12 %and 10%respectively.In NTS,the proportion of Fos/GABA_ARα1 double-labeled neurons vs single Fos and GABA_ARα1 positive neurons were 31 %and 56%respectively.2.In the second part,We observed that in PVN andSON,It was found a large number of Fos and GABA_BR1 positive neurons in these sittes.The number of Fos positive neurons was increased significantly after the LPS immuno-stimulating in contrast to control group with saline.The coexistence of Fos and GABA_BR1 positive neurons were observed in part of the neurons in these sites.In PVN,the proportion of Fos/GABA_BR1double-labeled neurons vs single Fos and GABA_BR1 positive neurons were 30%and 24% respectively.In SON,the proportion of Fos/GABA_BR1 double-labeled neurons vs single Fos and GABA_BR1 positive neurons were 90%and 38%respectively.Conclusion:1.The present result suggest that the GABA_ARα1 neurons in the PVN Me,LPB and NTS participate in the immuno-stimulating stress induced by LPS and GABA carries out its inhibitory function by binding to GABA_AR in peripheral immune activation.It may provide the morphological basis for understanding the function of GABA_AR in rat brain during this process.2.The present result suggest that the GABA_BR1 neurons in the PVNand SON participate in the immuno-stimulating stress induced by LPS and GABA carries out its inhibitory function by binding to GABA_BR in peripheral immune activation.It may provide the morphological basis for understanding the function of GABA_BR in rat brain during this process.