Document Detail

Hippocampal theta state in relation to formalin nociception.
MedLine Citation:
PMID:  16480829     Owner:  NLM     Status:  MEDLINE    
In the present study using extracellular electrophysiological recording techniques, we explored the temporal characteristics of hippocampal theta activation in relation to formalin nociception. Results indicate that, compared to hind paw injection of saline, formalin injection in behaving rat evoked biphasic increase in duration of dorsal CA1 theta. Such an increase broadly paralleled animal biphasic behavioral activation, especially lick and moment-to-moment agitated behaviors. Correspondingly, theta-modulated cell firing was observed following formalin injection in anesthetized rat. The formalin-induced theta activation in behaving rat was most marked during peak of theta activation in the 2nd theta state (11-40 min post-injection) comprising 73% of the time in the 5 min block. An increase in theta peak frequency was also observed with respect to pre-injection control. However, the peak of theta in the 2nd theta state mostly preceded the peak of lick and flinch of the affected paw. In the 41-60 min, following formalin injection while the animals displayed robust nociceptive flinching and lifting, the theta activity approached control levels. Furthermore, the theta peak frequency at peak of theta was higher than the corresponding values of sustained theta observed in correlation with the nociceptive behaviors; in contrast, high frequency theta rhythm was observed during formalin-induced other moment-to-moment agitated behaviors. These findings favor the notion that in the formalin model the theta state of the hippocampus reflects a neural drive that is dissociated from the duration of nociceptive experience and is not selective to the typical nociceptive indices of lick, flinch, and lift of the injured paw.
Siew Kian Tai; Fu-De Huang; Shabbir Moochhala; Sanjay Khanna
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Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, Non-U.S. Gov't     Date:  2006-02-09
Journal Detail:
Title:  Pain     Volume:  121     ISSN:  0304-3959     ISO Abbreviation:  Pain     Publication Date:  2006 Mar 
Date Detail:
Created Date:  2006-02-27     Completed Date:  2006-06-02     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  7508686     Medline TA:  Pain     Country:  Netherlands    
Other Details:
Languages:  eng     Pagination:  29-42     Citation Subset:  IM    
Department of Physiology (MD9), National University of Singapore, 2 Medical Drive, Singapore 117597, Singapore.
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MeSH Terms
Behavior, Animal / drug effects
Dose-Response Relationship, Drug
Electroencephalography / methods
Fixatives / pharmacology*
Formaldehyde / pharmacology*
Fourier Analysis
Hippocampus / drug effects*
Pain / chemically induced,  physiopathology*
Pain Measurement / methods
Psychomotor Agitation / etiology
Rats, Sprague-Dawley
Theta Rhythm / drug effects*
Time Factors
Reg. No./Substance:
0/Fixatives; 50-00-0/Formaldehyde

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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