Optimizing GABAA receptor antagonism for the induction of long-term potentiation in the mouse and rat dentate gyrus in vitro

The reliable induction of long-term potentiation (LTP) in the dentate gyrus (DG) in vitro requires the blockade of the gamma-aminobutyric acid A (GABA(A)) receptor. In these studies we examined the effectiveness of the specific GABA(A) receptor antagonist bicuculline methiodide (BMI) in facilitating LTP in the DG from hippocampal slices obtained from either C57Bl/6 mice or Sprague-Dawley rats, two species commonly used for electrophysiology. In the C57Bl/6 mice, maximal short-term potentiation and LTP in the DG were produced with a concentration of 5 mu M BMI. In contrast, a concentration of 10 mu M BMI was required to produce maximal short-term potentiation and LTP in the DG of Sprague-Dawley rats. These results reveal that there are species differences in the optimal amount of BMI required to produce robust and reliable LTP in the rodent DG in vitro and highlight the need to take consideration of the species being used when choosing concentrations of pharmacological agents to employ for electrophysiological use.