Distributions of different types of nociceptive neurons in thalamic mediodorsal nuclei of anesthetized rats

• Published in: The journal of physiological sciences Vol. 69; no. 2; pp. 387 - 397
• Main Authors: Lu, Pen-Li, Tsai, Meng-Li, Jaw, Fu-Shan, Yen, Chen-Tung
• Format: Journal Article
• Language: English
• Published: Japan Springer 01.03.2019; BioMed Central; Springer Japan
• Subjects: Anesthesia; Animals; Blood pressure; Electrodes; Experiments; Heart rate; Heat; Isoflurane; Laboratory animals; Male; Mechanical stimuli; Mediodorsal Thalamic Nucleus - physiology; Neurons; Neurons - physiology; Nociception - physiology; Nociceptors - physiology; Original Paper; Pain perception; Rats; Rats, Wistar; Rodents; Skin; Thalamus; Thermal stimuli; France; United States > US; Michigan; Intralaminar thalamic nuclei; Multiple single-unit recording; Stimulus–response function; Mediodorsal thalamic nucleus
• ISSN: 1880-6546; 1880-6562
• DOI: 10.1007/s12576-018-00656-3

Mediodorsal thalamic nucleus (MD) is a critical relay of nociception. This study recorded responses of MD neurons to noxious mechanical and thermal stimuli in isoflurane anesthetized rats. We found the threshold of noxious mechanical stimulation was 141 gw and that of noxious heat stimulation was 46 °C. A significantly higher percentage of noxious inhibitory neurons were found in the medial and central part of the MD, whereas a higher percentage of noxious excitatory neurons were found in the lateral part of the MD and adjacent intralaminar nuclei. The differential distribution of excitatory and inhibitory neurons implies functional differentiation between the medial and lateral part of the MD in nociception processing. Furthermore, by an analysis of the stimulus-response function (SRF), we found 80% of these excitatory neurons had a step-function or hat-shape-like SRF. This suggests that most of the MD neurons may serve as a system to distinguish innocuous versus noxious stimuli.