Corticothalamic modulation on formalin-induced change of VPM thalamic activities.
Spontaneous activities of single cells were extracellularly recorded in ventral posterior medial (VPM) thalamus of anesthetized rats to characterize the corticothalamic modulation on formalin-induced changes of spontaneous thalamic firing. Formalin injected into the peripheral receptive field, dose-dependently induced the reversible facilitation of spontaneous activities of VPM. However, when the primary somatosensory (SI) cortex was inactivated by muscimol, the pattern of formalin-induced changes of VPM firing was altered. This altered responsiveness included both first and second phase of facilitated spontaneous activities. Bicuculline infused into SI cortex did not alter the pattern of formalin-induced thalamic changes. These results suggest that the pain reactivity of VPM thalamus may be modulated by cortex via corticothalamic pathway during the generation of inflammatory pain.
Jung
Sung-Cherl
SC
Departments of Dental Pharmacology, College of Dentistry, Kyungpook National University, Daegu, 702-412, Korea.
Kim
Ji-Hyun
JH
Choi
In-Sun
IS
Cho
Jin-Hwa
JH
Bae
Yong-Chul
YC
Lee
Maan-Gee
MG
Shin
Hyung-Cheul
HC
Choi
Byung-Ju
BJ
D000818:Animals; D001640:Bicuculline / Q000494:pharmacology; D005557:Formaldehyde; D018755:GABA Agonists / Q000494:pharmacology; D018756:GABA Antagonists / Q000494:pharmacology; D008297:Male; D009118:Muscimol / Q000494:pharmacology; D009434:Neural Pathways; D009619:Nociceptors / Q000187:drug effects / Q000502:physiology; D010146:Pain / Q000503:physiopathology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013003:Somatosensory Cortex / Q000166:cytology* / Q000502:physiology*; D020651:Ventral Thalamic Nuclei / Q000166:cytology* / Q000502:physiology*; D014738:Vibrissae / Q000294:innervation / Q000502:physiology
D018755:GABA Agonists; D018756:GABA Antagonists; D005557:Formaldehyde; D009118:Muscimol; D001640:Bicuculline