Background: Changes in microbiota alter the modulation of the hypothalamic-pituitary-adrenal (HPA) axis sensitivity, to the effect of stress, an effect that may involve the inhibitory neurotransmitter GABA, one of the neurotransmitters known to modulate of emotional states. In our laboratory we studied in adult rats the effect of long-lasting effect of a 1-2 months chronic treatment with a preparation of three different Bifidobacterium (Longum, Breve, Infantis) on GABAA receptor gene expression and GABAergic function and structure in the hippocampus as well as the HPA axis sensitivity to acute foot-shock stress. Methods: Were used adult male rats of Sprague Dawley strain. Rats were treated for 1 or 2 month per os, once a day, with a mixture of different three different Bifidobacterium: longum (BB536 strain, final concentration of 3*109 CFU), brevis (M-16 strain, final concentration of 1*109 CFU) and infantis (M-63 strain, final concentration of 1*109 CFU). In these rats were carried out the following studies in hippocampus: Western blot to assess the changes in ?1, ?4, ? and ? 2, GABAA receptor subunit and BDNF protein expression. We used a specific antibody against ?1, ?4, ? and ?2 (1:250; Phosphosolution) and BDNF (1:500; Santa Cruz Biotecnology). A specific antibody against GAPDH (1:1000; Millipore, USA) was used as standard; immunoistochemistry to assess the changes in ?1, ?4, ? and ? 2 GABAA receptor subunit in specific subareas of hippocampus. We used the same antibodies used for western blot experiments; electrophysiology, to assess the GABAergic tonic current and spontaneous GABAA receptor-mediated ISPCs (sIPSCs) current; Golgi impregnation, to assess the dendritic spines density; ELISA to assess the amount of corticosterone on plasma and allopregnanolone in the brain Results: Plasma corticosterone (CTS) levels were measured in basal condition and after foot-shock stress in animals previously treated with bifidobacterium. This treatment failed to change the basal content as well as the increase of CTS levels elicited by acute footshock stress when compared to vehicle treated group. In contrast, western blot and immunohistochemistry analysis showed that two months of bifidobacterium treatment reduced ?1, ?4, and ? GABAAR subunits expression while increasing ?2 subunit. Moreover, this treatment significantly reduced plasma content of allopregnanolone, an agonist ligand for GABAA receptor containing ?4 and ? subunits. Patch-clamp experiments performed in dentate gyrus granule cells showed no changes in synaptic currents while the tonic component of GABAergic inhibition was significantly decreased. The latter data are consistent with an observed increase of neuronal excitability measured in the same neurons of the dentate gyrus as well as with the parallel reduction of ? subunit and AP plasma content. Moreover, more recently we found that the same chronic treatment with bifidobacterium increased the number of dendritic spines in CA1 pyramidal neurons and in the granule cells of dentate gyrus. Conclusions: Altogether our data show that this mixture of three (Longum, Brevis and Infantis) bifidobacterium given chronically to rats is able to modify the gene expression of specific GABAA receptor subunits in the rat hippocampus, an affect associate to functional and morphological changes of specific neuronal populations of dentate gyrus and CA1 and further support the crucial role of specific gut bacteria in the modulation of accordingly brain function. Accordingly, the concept of psychobiotics as new tools to be used in mental health has been recently suggested
Chronic treatment with Bifidobacterium (Longum, breve, Infantis) modulates GABAA receptor gene expression neuronal function and structure in rat hippocampus
2018
Abstract
Background: Changes in microbiota alter the modulation of the hypothalamic-pituitary-adrenal (HPA) axis sensitivity, to the effect of stress, an effect that may involve the inhibitory neurotransmitter GABA, one of the neurotransmitters known to modulate of emotional states. In our laboratory we studied in adult rats the effect of long-lasting effect of a 1-2 months chronic treatment with a preparation of three different Bifidobacterium (Longum, Breve, Infantis) on GABAA receptor gene expression and GABAergic function and structure in the hippocampus as well as the HPA axis sensitivity to acute foot-shock stress. Methods: Were used adult male rats of Sprague Dawley strain. Rats were treated for 1 or 2 month per os, once a day, with a mixture of different three different Bifidobacterium: longum (BB536 strain, final concentration of 3*109 CFU), brevis (M-16 strain, final concentration of 1*109 CFU) and infantis (M-63 strain, final concentration of 1*109 CFU). In these rats were carried out the following studies in hippocampus: Western blot to assess the changes in ?1, ?4, ? and ? 2, GABAA receptor subunit and BDNF protein expression. We used a specific antibody against ?1, ?4, ? and ?2 (1:250; Phosphosolution) and BDNF (1:500; Santa Cruz Biotecnology). A specific antibody against GAPDH (1:1000; Millipore, USA) was used as standard; immunoistochemistry to assess the changes in ?1, ?4, ? and ? 2 GABAA receptor subunit in specific subareas of hippocampus. We used the same antibodies used for western blot experiments; electrophysiology, to assess the GABAergic tonic current and spontaneous GABAA receptor-mediated ISPCs (sIPSCs) current; Golgi impregnation, to assess the dendritic spines density; ELISA to assess the amount of corticosterone on plasma and allopregnanolone in the brain Results: Plasma corticosterone (CTS) levels were measured in basal condition and after foot-shock stress in animals previously treated with bifidobacterium. This treatment failed to change the basal content as well as the increase of CTS levels elicited by acute footshock stress when compared to vehicle treated group. In contrast, western blot and immunohistochemistry analysis showed that two months of bifidobacterium treatment reduced ?1, ?4, and ? GABAAR subunits expression while increasing ?2 subunit. Moreover, this treatment significantly reduced plasma content of allopregnanolone, an agonist ligand for GABAA receptor containing ?4 and ? subunits. Patch-clamp experiments performed in dentate gyrus granule cells showed no changes in synaptic currents while the tonic component of GABAergic inhibition was significantly decreased. The latter data are consistent with an observed increase of neuronal excitability measured in the same neurons of the dentate gyrus as well as with the parallel reduction of ? subunit and AP plasma content. Moreover, more recently we found that the same chronic treatment with bifidobacterium increased the number of dendritic spines in CA1 pyramidal neurons and in the granule cells of dentate gyrus. Conclusions: Altogether our data show that this mixture of three (Longum, Brevis and Infantis) bifidobacterium given chronically to rats is able to modify the gene expression of specific GABAA receptor subunits in the rat hippocampus, an affect associate to functional and morphological changes of specific neuronal populations of dentate gyrus and CA1 and further support the crucial role of specific gut bacteria in the modulation of accordingly brain function. Accordingly, the concept of psychobiotics as new tools to be used in mental health has been recently suggestedI documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
