This paper describes surgical and recording procedures that have been devel
oped which permit the simultaneous monitoring of levels of select neurochem
icals (via microdialysis) and measures of dentate-evoked held potentials wi
thin the hippocampal formation of freely moving adult rats. To test and eva
luate these procedures, they were employed to examine changes in hippocampa
l neurochemistry and neuronal excitability associated with the establishmen
t and maintenance of hippocampal long-term potentiation (LTP), Measures of
hippocampal norepinephrine (NE) and glutamate levels along with measures of
the dentate granule cell population spike amplitude (PSA) mere obtained be
fore, during, and after tetanization of the medial perforant path using two
separate tetanization paradigms. Results obtained using these new procedur
es in several animals indicated that changes in NE and glutamate levels wer
e strongly correlated with increases in the dentate granule cell PSA measur
e obtained following tetanization. The results indicate that this newly dev
eloped procedure can be effectively used to directly examine the relationsh
ip between neurochemical and neurophysiological changes associated with hip
pocampal neuroplasticity, (C) 1999 Academic Press.