Concurrent acquisition of hippocampal neurochemical and electrophysiological measures from freely moving rats

The authors have recently developed surgical and recording procedures which allow them to monitor levels of select neurochemicals (via microdialysis) simultaneous with measures of neuronal excitability (evoked response measures) within the hippocampal formation of freely moving adult rats. These procedures were employed to examine changes in hippocampal neurochemistry and neuronal excitability associated with the establishment, maintenance, and decay of hippocampal long-term potentiation (LTP). Measures of hippocampal norepinephrine (NE) levels along with measures of the dentate granule cell population spike amplitude (PSA) were obtained before, during, and after tetanization of the medial perforant using two separate tetanization paradigms. Results indicated that changes in NE levels following tetanization were strongly correlated with changes in the dentate granule cell PSA measure. The results indicate that this newly developed procedure can be effectively used to directly examine the relationship between neurochemical and neurophysiological changes associated with hippocampal neuroplasticity