Prefrontal BDNF Levels After Anodal Epidural Direct Current Stimulation in Rats

Juliana C de Souza Custódio, Cleciane W Martins, Marcelo D M V Lugon, Lívia C de Melo Rodrigues, Suely G de Figueiredo, Ester M Nakamura-Palacios, Juliana C de Souza Custódio, Cleciane W Martins, Marcelo D M V Lugon, Lívia C de Melo Rodrigues, Suely G de Figueiredo, Ester M Nakamura-Palacios

Abstract

This study measured levels of brain-derived neurotrophic factor (BDNF) in the prefrontal cortex (PFC) after single (S) and repetitive (R) anodal epidural DC stimulation (eDCS) over the left medial prefrontal cortex (mPFC). Male Wistar rats (n = 4 per group) received single application of sham (S-sham) or anodal eDCS (S-eDCS) (400 μA for 11 min) and had their PFC removed 15, 30, or 60 min later. For repetitive brain stimulation, rats received sham (R-sham) or anodal eDCS (R-eDCS) once a day, five consecutive days, and their PFC were removed 24 h after the last application. BDNF isoforms levels were measured by Western blot assays. It was observed that animals receiving S-eDCS showed smaller (p < 0.01) levels of BDNF 15 min after stimulation when compared to S-sham, especially in its mature form (mBDNF p < 0.001). Levels of BDNF, including mBDNF, were almost like the S-sham at 30 and 60 min intervals after stimulation, but not proBDNF, which was significantly smaller (p < 0.05) than S-sham at these intervals. After five sessions, BDNF levels were higher in the PFC of R-eDCS animals, notably the proBDNF (p < 0.01) when compared to R-sham. This study showed that levels of BDNF in the PFC, especially the proBDNF, were lower after a single and higher after repetitive anodal eDCS applied over the left mPFC when compared to sham. Therefore, changes of prefrontal BDNF levels may disclose molecular changes underlying the plasticity induced by cortical anodal DC stimulation, which may be opposite if applied in single or multiple sessions.

Keywords: brain-derived neurotrophin – BDNF; epidural direct current stimulation; mBDNF; prefrontal cortex; proBDNF.

Figures

FIGURE 1
FIGURE 1
Western blot analysis of brain-derived neurotrophic factor (BDNF) in the prefrontal cortex (PFC) 15 (n = 4), 30 (n = 4) or 60 (n = 4) minutes after a single session of epidural direct current stimulation (S-eDCS) at 400 μA current intensity during 11 min through a 5-mm round electrode implanted over the left medial Prefrontal Cortex (mPFC) or sham procedure (S-sham). A diagram of general procedures is shown at the top. (A) Bands of the immunoreactivity related to the migration of the proBDNF and mBDNF shown in two animals – biological replicate – from each group. Densitometry analysis: (B) Total BDNF (intensity of proBDNF plus mBDNF), (C) proBDNF, and, (D) mBDNF. Densitometry analyses were normalized to GAPDH and values are presented as the mean ± SEM. ∗p < 0.05, ∗∗p < 0.01 when compared to sham control; ∗∗∗p < 0.001 when compared to sham and to 30 and 60 min; +p < 0.05 when compared to 30 and 60 min (Bonferroni’s multiple comparisons test). Randomization: animals were distributed in groups by computer-generated randomization sequence.
FIGURE 2
FIGURE 2
Western blot analysis of brain-derived neurotrophic factor (BDNF) in the prefrontal cortex (PFC) after five (once a day) consecutive sessions of sham (R-sham, n = 4) or epidural direct current stimulation (R-eDCS, n = 4) at 400 μA current intensity during 11 min through a 5-mm round electrode implanted over the left medial Prefrontal Cortex (mPFC). A diagram of general procedures is shown at the top. (A) Bands of the immunoreactivity related to the migration of the proBDNF and mBDNF shown in two animals – biological replicate – from each group; Densitometry analysis for (B) Total BDNF (intensity of proBDNF plus mBDNF), (C) proBDNF, and (D) mBDNF. Densitometry analyses were normalized to GAPDH and values are presented as the mean ± SEM. ∗∗p < 0.01 when compared to sham control (t-test for independent samples). Randomization: animals were distributed in groups by computer-generated randomization sequence.

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