Premium
Manipulation of pyramidal cell firing in the hippocampus of freely behaving rats by local application of K+ via microdialysis
Author(s) -
Ludvig Nandor,
Chao Kenneth,
Altura Bella T.,
Altura Burton M.,
Fox Steven E.
Publication year - 1996
Publication title -
hippocampus
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.767
H-Index - 155
eISSN - 1098-1063
pISSN - 1050-9631
DOI - 10.1002/(sici)1098-1063(1996)6:2<97::aid-hipo1>3.0.co;2-4
Subject(s) - microdialysis , hippocampus , neuroscience , pyramidal cell , chemistry , central nervous system , psychology
In this study, microdialysis was performed in the hippocampus of freely behaving rats, and the firing of pyramidal cells, including place cells, was recorded at the site of the microdialysis probe. For 10‐min periods, the artificial cerebrospinal fluid (ACSF) in the microdialysis system was replaced with ACSF containing 50 mM K+(high K+ solution). Complementary in vitro tests determined that microdialysis with such high K+ solution produced an outflow of 5% of the perfused K+ from the microdialysis probe. Application of K+ with this method into the CA1 region significantly increased the firing of the local pyramidal cells, including place cells, during both movement and sleep. On average, K+ exposures increased the firing rate of the neurons to 306% and 448% of the control firing rate during movement and sleep, respectively. After the termination of the K+ outflow, the cells continued to discharge for 5–30 min with a significantly higher frequency than before the K+ challenge. This phenomenon also occurred in both behavioral states. During the period of enhanced firing, the out‐of‐field firing rate of the recorded place cells was dramatically increased. It was also found that during the K+ applications, otherwise silent pyramidal cells often became electrically active. The K+ ‐induced firing modifications were usually not accompanied by behavioral or EEG changes. The data raise the possibility that transient elevations in the extracellular K+ concentration contribute to the ionic/molecular processes which are responsible for plastic firing pattern modifications in hippocampus. Pharmacological manipulation of place cells with the described method offers a new strategy to understand the molecular bases of spatial memory. © 1996 Wiley‐Liss, Inc.