Behavioural and cardiovascular responses during latent inhibition of conditioned fear: Measurement by telemetry and conditioned freezing

Wei Ning Zhang, Carol A. Murphy, Joram Feldon*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


This study assessed freezing behaviour and cardiovascular responses during the expression of latent inhibition of conditioned fear. Animals that were either repeatedly preexposed (PE) to a tone conditioned stimulus (CS) or naive to the tone (non-preexposed; NPE) subsequently experienced three presentations of the tone paired with footshock. Animals were tested 24 h later in the context of the footshock chamber, and on the following day, in the presence of the tone CS. Changes in heart rate and blood pressure were recorded by radio-telemetry. The PE rats spent more time freezing to the conditioned contextual cues and exhibited higher blood pressures during the last half of the context test session than did the NPE animals. During the tone test, the PE rats exhibited less conditioned freezing to the tone CS compared with the NPE animals, i.e. expression of the latent inhibition. This behavioural effect was associated with a significant increase in heart rate, but not blood pressure, in the PE but not the NPE animals. Our results suggest that the increased blood pressures of the PE rats during the context test directly reflect their greater fear of the conditioning context. In contrast, the increased heart rate response but decreased freezing shown by PE rats in response to the tone CS may be due to the fact that lower stress levels (e.g. PE condition) elicit sympathetically- mediated increases in heart rate, whereas higher stress levels (e.g. NPE condition) activate both sympathetic and parasympathetic systems, thus eliminating any CS-induced increase in heart rate in the NPE rats.

Original languageEnglish
Pages (from-to)199-209
Number of pages11
JournalBehavioural Brain Research
Issue number1
StatePublished - 23 Sep 2004
Externally publishedYes


  • BP
  • Blood pressure
  • CS
  • Conditioned fear
  • Freezing
  • HR
  • Heart rate
  • LI
  • Latent inhibition
  • NPE
  • PE
  • SP
  • Telemetry
  • conditioned stimulus
  • heart rate
  • latent inhibition
  • mean blood pressure
  • non-preexposed
  • preexposed
  • systolic blood pressure


Dive into the research topics of 'Behavioural and cardiovascular responses during latent inhibition of conditioned fear: Measurement by telemetry and conditioned freezing'. Together they form a unique fingerprint.

Cite this