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Multiple implants do not aggravate the tissue reaction in rat brain.

Lind G, Gällentoft L, Danielsen N, Schouenborg J, Pettersson LM - PLoS ONE (2012)

Bottom Line: This possible interaction was only seen between implants within the same hemisphere, no interaction with the contralateral hemisphere was found.More importantly, we found no aggravation of tissue reactions as a result of a larger number of implants.These results highlight the possibility of implanting multiple electrodes without aggravating the glial scar surrounding each implant.

View Article: PubMed Central - PubMed

Affiliation: Department of Experimental Medical Sciences, Neuronano Research Center, Medical Faculty, Lund University, Lund, Sweden. gustav.lind@med.lu.se

ABSTRACT
Chronically implanted microelectrodes are an invaluable tool for neuroscientific research, allowing long term recordings in awake and behaving animals. It is known that all such electrodes will evoke a tissue reaction affected by its' size, shape, surface structure, fixation mode and implantation method. However, the possible correlation between tissue reactions and the number of implanted electrodes is not clear. We implanted multiple wire bundles into the brain of rats and studied the correlation between the astrocytic and microglial reaction and the positioning of the electrode in relation to surrounding electrodes. We found that an electrode implanted in the middle of a row of implants is surrounded by a significantly smaller astrocytic scar than single ones. This possible interaction was only seen between implants within the same hemisphere, no interaction with the contralateral hemisphere was found. More importantly, we found no aggravation of tissue reactions as a result of a larger number of implants. These results highlight the possibility of implanting multiple electrodes without aggravating the glial scar surrounding each implant.

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Glial reactions surrounding implants after six weeks.Example pictures of GFAP (magenta) & ED1 (green) staining from middle (A), outer (B), contralateral (C) & solitary (D) implant locations after six weeks. Scale bar 100 µm. Quantifications of GFAP & ED1 staining after six weeks in 0–50 µm ROI (E) & 50–200 µm ROI (F). X-axes show different implant locations. Y-axes show the fraction of area in each ROI that is above the set threshold. The astrocytic scar surrounding the middle implant was significantly smaller than surrounding the contralateral implant in the inner ROI (p<0.01, K-W test with Dunn’s post hoc test). No difference was found for ED1 staining between any of the groups, n = 6 for all groups except “solitary” where n = 5.
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pone-0047509-g002: Glial reactions surrounding implants after six weeks.Example pictures of GFAP (magenta) & ED1 (green) staining from middle (A), outer (B), contralateral (C) & solitary (D) implant locations after six weeks. Scale bar 100 µm. Quantifications of GFAP & ED1 staining after six weeks in 0–50 µm ROI (E) & 50–200 µm ROI (F). X-axes show different implant locations. Y-axes show the fraction of area in each ROI that is above the set threshold. The astrocytic scar surrounding the middle implant was significantly smaller than surrounding the contralateral implant in the inner ROI (p<0.01, K-W test with Dunn’s post hoc test). No difference was found for ED1 staining between any of the groups, n = 6 for all groups except “solitary” where n = 5.

Mentions: To evaluate whether any interactions within a hemisphere were present we compared the tissue reactions towards the middle implant to that towards the contralateral implant and the outer implants (Figure 1). We found significantly less immunofluorescence for GFAP at the middle implant in the innermost ROI (0–50 µm) after six weeks when compared to the contralateral implant (Figure 2). This suggests that a large number of implants in one hemisphere do not aggravate the tissue reactions to each implant. Notably, the middle scar exhibited less GFAP staining than both the contralateral scar and the outer scars in every animal (in the inner ROI at the six week time point), even if the difference between the middle and outer scars was not statistically significant. Furthermore, there was a similar tendency after one week, where the contralateral implant exhibited higher GFAP levels than the middle implant in the inner ROI in all animals except one, and the outer implant exhibited higher levels than the middle implant in all animals (Figure 3). These differences were not statistically significant. No differences or tendencies to differences were seen between any of the groups when analysed with regards to ED1-staining (Figures 2, 3).


Multiple implants do not aggravate the tissue reaction in rat brain.

Lind G, Gällentoft L, Danielsen N, Schouenborg J, Pettersson LM - PLoS ONE (2012)

Glial reactions surrounding implants after six weeks.Example pictures of GFAP (magenta) & ED1 (green) staining from middle (A), outer (B), contralateral (C) & solitary (D) implant locations after six weeks. Scale bar 100 µm. Quantifications of GFAP & ED1 staining after six weeks in 0–50 µm ROI (E) & 50–200 µm ROI (F). X-axes show different implant locations. Y-axes show the fraction of area in each ROI that is above the set threshold. The astrocytic scar surrounding the middle implant was significantly smaller than surrounding the contralateral implant in the inner ROI (p<0.01, K-W test with Dunn’s post hoc test). No difference was found for ED1 staining between any of the groups, n = 6 for all groups except “solitary” where n = 5.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3472973&req=5

pone-0047509-g002: Glial reactions surrounding implants after six weeks.Example pictures of GFAP (magenta) & ED1 (green) staining from middle (A), outer (B), contralateral (C) & solitary (D) implant locations after six weeks. Scale bar 100 µm. Quantifications of GFAP & ED1 staining after six weeks in 0–50 µm ROI (E) & 50–200 µm ROI (F). X-axes show different implant locations. Y-axes show the fraction of area in each ROI that is above the set threshold. The astrocytic scar surrounding the middle implant was significantly smaller than surrounding the contralateral implant in the inner ROI (p<0.01, K-W test with Dunn’s post hoc test). No difference was found for ED1 staining between any of the groups, n = 6 for all groups except “solitary” where n = 5.
Mentions: To evaluate whether any interactions within a hemisphere were present we compared the tissue reactions towards the middle implant to that towards the contralateral implant and the outer implants (Figure 1). We found significantly less immunofluorescence for GFAP at the middle implant in the innermost ROI (0–50 µm) after six weeks when compared to the contralateral implant (Figure 2). This suggests that a large number of implants in one hemisphere do not aggravate the tissue reactions to each implant. Notably, the middle scar exhibited less GFAP staining than both the contralateral scar and the outer scars in every animal (in the inner ROI at the six week time point), even if the difference between the middle and outer scars was not statistically significant. Furthermore, there was a similar tendency after one week, where the contralateral implant exhibited higher GFAP levels than the middle implant in the inner ROI in all animals except one, and the outer implant exhibited higher levels than the middle implant in all animals (Figure 3). These differences were not statistically significant. No differences or tendencies to differences were seen between any of the groups when analysed with regards to ED1-staining (Figures 2, 3).

Bottom Line: This possible interaction was only seen between implants within the same hemisphere, no interaction with the contralateral hemisphere was found.More importantly, we found no aggravation of tissue reactions as a result of a larger number of implants.These results highlight the possibility of implanting multiple electrodes without aggravating the glial scar surrounding each implant.

View Article: PubMed Central - PubMed

Affiliation: Department of Experimental Medical Sciences, Neuronano Research Center, Medical Faculty, Lund University, Lund, Sweden. gustav.lind@med.lu.se

ABSTRACT
Chronically implanted microelectrodes are an invaluable tool for neuroscientific research, allowing long term recordings in awake and behaving animals. It is known that all such electrodes will evoke a tissue reaction affected by its' size, shape, surface structure, fixation mode and implantation method. However, the possible correlation between tissue reactions and the number of implanted electrodes is not clear. We implanted multiple wire bundles into the brain of rats and studied the correlation between the astrocytic and microglial reaction and the positioning of the electrode in relation to surrounding electrodes. We found that an electrode implanted in the middle of a row of implants is surrounded by a significantly smaller astrocytic scar than single ones. This possible interaction was only seen between implants within the same hemisphere, no interaction with the contralateral hemisphere was found. More importantly, we found no aggravation of tissue reactions as a result of a larger number of implants. These results highlight the possibility of implanting multiple electrodes without aggravating the glial scar surrounding each implant.

Show MeSH
Related in: MedlinePlus