Green B G
Monell Chemical Senses Center, Philadelphia, PA 19104-3308.
Neurosci Lett. 1993 Feb 5;150(1):44-8. doi: 10.1016/0304-3940(93)90104-s.
It has previously been shown that repeated presentations of a moderate concentration of capsaicin could either sensitize or desensitize the tongue, depending upon the temporal pattern of stimulation. Only when stimulation was halted for 5 min or longer did sensitization begin to give way to desensitization. The apparent necessity of a hiatus in stimulation led to the hypothesis that desensitization involved an inability to re-excite quiescent fibers rather than a progressive suppression of stimulated fibers. This hypothesis was tested in the present study by measuring the perceptual response to a non-desensitizing irritant, zingerone, when it was presented at the rate of l/min following a series of capsaicin conditioning stimuli. After an initial, brief period of cross-hyper-sensitization, cross-desensitization developed at a rate equivalent to that observed when no stimulus was presented. Thus, the results disproved the hypothesis that desensitization cannot occur if capsaicin-sensitive fibers continue to be stimulated, and suggested that after an initial period of excitation, the removal of capsaicin accelerates the desensitization process. This seeming paradox is discussed in terms of the neural mechanisms that may underlie capsaicin desensitization.
先前的研究表明，反复给予中等浓度的辣椒素会使舌头产生敏感或脱敏反应，这取决于刺激的时间模式。只有当刺激停止5分钟或更长时间时，敏感化才开始让位于脱敏。刺激中断的明显必要性导致了这样一种假设，即脱敏涉及无法重新激发静止的纤维，而不是对受刺激纤维的逐渐抑制。在本研究中，通过测量在一系列辣椒素条件刺激后以每分钟1次的速率给予非脱敏刺激剂姜辣素时的感知反应，对这一假设进行了检验。在最初短暂的交叉超敏期之后，交叉脱敏以与未给予刺激时观察到的速率相当的速度发展。因此，结果反驳了如果辣椒素敏感纤维继续受到刺激就不会发生脱敏的假设，并表明在最初的兴奋期之后，去除辣椒素会加速脱敏过程。本文根据可能是辣椒素脱敏基础的神经机制讨论了这一看似矛盾的现象。
