Contribution of the anterior cingulate cortex to laser-pain conditioning in rats.
The emotional component of nociception is seldom distinguished from pain behavioral testing. The aim of the present study was to develop a behavioral test that indicates the emotional pain responses using the classical conditioning paradigm. The role of the anterior cingulate cortex (ACC) in the process of this pain conditioning response was also evaluated. In laser-pain conditioning, free moving rats were trained to associate a tone (conditioned stimulus, CS) and short CO(2) laser pulsation (unconditioned stimulus, US). Monotonous tone (800 Hz, 0.6 s) was delivered through a loud-speaker as CS. CO(2) laser pulses (5 W at 50 or 100 ms in duration) applied to the hind paw was adopted as US. The CS-US interval was 0.5 s. Laser-pain conditioning was developed during 40 CS-US pairings. CS and US pairing with 100-ms laser pulse stimuli was more effective in establishing conditioning responses than that of 50-ms stimuli. The conditioning responses remained, tested by presenting CS alone, immediate to and 24 h subsequent to training. The performance of laser-pain conditioning was significantly reduced after bilateral lesioning of the ACC. Similar results were also obtained by bilateral lesions of the amygdala. The conditioning responses were also diminished following morphine treatment. The association between a neutral stimulus and a noxious stimulus could be demonstrated in a Pavlovian conditioning test in free moving rats. Thus, the conditioned response may be employed as a measure of the emotional component of the nociception. It is also suggested that the ACC may play an important role in mediating this conditioning effect.
Kung
Jen-Chuang
JC
Institute of Biomedical Sciences, Academia Sinica, Taipei 115, Taiwan, ROC.
Su
Ning-Miao
NM
Fan
Ruey-Jane
RJ
Chai
Sin-Chee
SC
Shyu
Bai-Chuang
BC
D000161:Acoustic Stimulation / Q000379:methods; D000818:Animals; D002540:Cerebral Cortex / Q000187:drug effects / Q000502:physiology; D003213:Conditioning, Psychological / Q000187:drug effects / Q000502:physiology*; D006179:Gyrus Cinguli / Q000187:drug effects / Q000502:physiology*; D007834:Lasers / Q000009:adverse effects; D009020:Morphine / Q000494:pharmacology; D017288:Pain Threshold / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley
D009020:Morphine