Transcranial direct current stimulation (tDCS) is increasingly being used in human studies as an adjuvant tool to promote recovery of function after stroke. However, its neurobiological effects are still largely unknown. Electric fields are known to influence the migration of various cell types in vitro, but effects in vivo remain to be shown. Hypothesizing that tDCS might elicit the recruitment of cells to the cortex, we here studied the effects of tDCS in the rat brain in vivo. Adult Wistar rats (n = 16) were randomized to either anodal or cathodal stimulation for either 5 or 10 consecutive days (500 µA, 15 min). Bromodeoxyuridine (BrdU) was given systemically to label dividing cells throughout the experiment. Immunohistochemical analyses ex vivo included stainings for activated microglia and endogenous neural stem cells (NSC). Multi-session tDCS with the chosen parameters did not cause a cortical lesion. An innate immune response with early upregulation of Iba1-positive activated microglia occurred after both cathodal and anodal tDCS. The involvement of adaptive immunity as assessed by ICAM1-immunoreactivity was less pronounced. Most interestingly, only cathodal tDCS increased the number of endogenous NSC in the stimulated cortex. After 10 days of cathodal stimulation, proliferating NSC increased by ∼60%, with a significant effect of both polarity and number of tDCS sessions on the recruitment of NSC. We demonstrate a pro-inflammatory effect of both cathodal and anodal tDCS, and a polarity-specific migratory effect on endogenous NSC in vivo. Our data suggest that tDCS in human stroke patients might also elicit NSC activation and modulate neuroinflammation.

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In biomedical research the pig is widely used as an animal model for experimental surgery. Feasible monitoring tools during anaesthesia are pivotal for successful and reliable research outcome. Blood lactate values are a monitoring tool and prognostic indicator during surgery both in humans and animals. Lactate levels in pigs might be influenced by various parameters including stressful handling, breed and weight differences. To determine blood lactate levels present prior to experimental surgery, values of 124 female farm pigs were measured in venous blood samples. Pigs presented with blood lactate concentrations ranging from 0.5 to 5.5 mmol/L (median, 1.2 mmol/L; interquartile range [IQR] 1.2). Considering genetic background, Rheinhybrid/Pietrain pigs (n ¼ 51; median, 1.4 mmol/L; IQR, 1) had significantly higher blood lactate levels compared with Landrace/Pietrain crossbred animals (n ¼ 73; median, 1.1 mmol/L; IQR, 1; P , 0.05). Body weight had no significant effect on blood lactate levels within the evaluated range. This report can benefit research projects monitoring blood lactate values in farm pigs during experimental surgery.