大鼠視丘腹尾外側核神經元在清醒與麻醉下對於觸覺與痛刺激反應之比較

Abstract

大鼠視丘腹尾外側核（VPL）主要接收來自於mediolemniscus (ML)和脊髓丘腦束（STT tract）的訊息並將體感覺忠實的傳遞至大腦體感覺皮質區。之前研究已在麻醉下的動物(大鼠，貓和猴子)中分辨出低閾值機械性受體（LTM）、廣動力型神經元（WDR）和疼痛傳導特定型神經元（NS）。然而痛覺只有在清醒的狀態下才可以被辨別的，因此，本篇研究的主要目的在比較這些在麻醉下所定義出的VPL神經元在清醒時對於觸覺及痛覺刺激的反應為何。此實驗經由長期記錄單一神經元（SU）的方法並使用不同強度的機械性von Frey filaments和雷射熱痛刺激，在不同的腦狀態下去測試同一神經元的反應。SR slope結果顯示，VPL中的神經元在麻醉下具有顯著性較差的反應。除此之外，LTM，WDR和NS神經元在清醒的狀態下會有功能性相似的表現。因此，我們認為在麻醉的狀態下，視丘對於感覺訊息的傳遞會有所改變。

Ventroposterior lateral nucleus (VPL) is a first-order thalamic nucleus which receives somatosensory information from mediolemniscus and spinothalamic tract, and relays inputs of the body to somatosensory cortex. Previous studies identify low-threshold (LTM), wide-dynamic range (WDR), and noxious-specific (NS) neurons in anesthetized rat, cat and monkey. However, pain sensation can only be discriminated under conscious state. Thus, the main purpose of the present study was to compare the somatosensory response of the different types of VPL neurons under conscious and anesthetized states in the rat. VPL single-unit activities were recorded by chronically implanted microwire electrodes. Mechanical von Frey filaments and laser heat stimulations applied to the paws were used for quantitative stimulations. Stimulus-response slope results showed that VPL neurons had significantly lower response under anesthetized state. In addition, LTM, WDR and NS neurons became functionally alike neurons in the conscious state. Therefore, we concluded that anesthesia altered sensory transmission in the thalamus.