Frequency-dependent changes in the paired-pulse index in the hippocampus of the freely moving adult male rat.
The paired-pulse index (PPI) has been widely used as a measure of modulation of cellular excitability in the hippocampal trisynaptic circuit. This paper presents a quantification of the changes in this measure of neuronal modulation as a result of the application of pulse trains having six different train frequencies (0.1, 1, 5, 8, 15, and 30 Hz) to one of the major efferent pathways to the dentate gyrus, the medial perforant path (MPP). Our findings indicate that the modulation of the first leg of the hippocampal trisynaptic circuit is dependent on the frequency of the "burst train" applied to the perforant pathway. This methodological finding is of importance to all investigators studying hippocampal plasticity via LTP or LTD approaches. The different synaptic mechanisms implicated in being responsible for the changes in the PPI are also discussed.
Department of Engineering, Trinity College, Hartford, CT 006106-3100, USA. william.yorns@trincol.edu
W R
WR
Yorns
J H
JH
Blaise
J D
JD
Bronzino
D000344:Afferent Pathways / Q000187:drug effects / Q000502:physiology; D000818:Animals; D004558:Electric Stimulation / Q000379:methods*; D019706:Excitatory Postsynaptic Potentials / Q000502:physiology / Q000528:radiation effects; D006624:Hippocampus / Q000033:anatomy & histology / Q000502:physiology / Q000528:radiation effects*; D017774:Long-Term Potentiation / Q000502:physiology / Q000528:radiation effects; D008297:Male; D008474:Medial Forebrain Bundle / Q000528:radiation effects; D009068:Movement; D009433:Neural Inhibition / Q000528:radiation effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D013569:Synapses / Q000502:physiology / Q000528:radiation effects*