Chiocchetti Roberto, Pisoni Luciano, Joechler Monika, Cancellieri Adele, Giancola Fiorella, Galiazzo Giorgia, Salamanca Giulia, Cunha Rodrigo Zamith, Gentile Arcangelo
Department of Veterinary Medical Sciences, University of Bologna, Via Tolara di Sopra, 50, 40064 Ozzano dell'Emilia, Italy.
Animals (Basel). 2025 Jun 6;15(12):1689. doi: 10.3390/ani15121689.
The presence of dichotomizing neurons in the dorsal root ganglia (DRG) of cattle, innervating both the reticulum and the withers, may indicate a pre-spinal convergence of visceral and cutaneous sensory information, i.e., that the DRG primary sensory neurons may elaborate the sensory information coming from two different anatomical areas before reaching the secondary sensory neurons within the spinal cord. This anatomical feature could be the underlying basis for the cutaneous allodynia observed in traumatic reticuloperitonitis, also known as the "Kalchschmidt pain test". The aim of the study was to identify the DRG primary sensory neurons innervating the reticulum and the withers by using two different retrograde fluorescent tracers, Fast Blue (FB, affinity for cytoplasm) and Diamidino Yellow (DY, affinity for nucleus). In two anesthetized calves, FB and DY were injected into the reticulum and skin of the withers, respectively. At the end of the experimental period, the calves were deeply anesthetized and then euthanatized. The thoracic (T1-T8) DRG were collected and processed to obtain cryosections which were examined on a fluorescent microscope. A large number of neurons localized, especially in the T7 DRG, presented nuclei labeled with DY. On the contrary, only a few neurons localized exclusively in T6 and T7 DRG presented the cytoplasm labeled with FB. No neurons displayed FB and DY simultaneously within the cytoplasm and nucleus, respectively. The absence of double-labeled DRG neurons suggests that the convergence of visceral and somatic sensory inputs underlying the Kalchschmidt pain response likely does not occur at the level of individual DRG neurons. Rather, it may involve higher-order integrative centers, possibly including vagal pathways and brainstem nuclei which integrate the afferent information to coordinate respiratory movements of the diaphragm, intercostal muscles, and larynx. Although limited by the sample size, this case study provides a neuroanatomical basis for further investigation into central mechanisms of referred visceral pain in cattle.
牛背根神经节（DRG）中存在对网胃和肩胛部均有支配的二分神经元，这可能表明内脏和皮肤感觉信息在脊髓前发生了汇聚，即DRG初级感觉神经元可能在将来自两个不同解剖区域的感觉信息传递至脊髓内的次级感觉神经元之前，就对这些信息进行了整合。这一解剖学特征可能是创伤性网胃炎（也称为“卡尔施密特疼痛试验”）中观察到的皮肤异常性疼痛的潜在基础。本研究的目的是使用两种不同的逆行荧光示踪剂，即快蓝（FB，对细胞质有亲和力）和双脒基黄（DY，对细胞核有亲和力），来识别支配网胃和肩胛部的DRG初级感觉神经元。在两只麻醉的小牛中，分别将FB和DY注入网胃和肩胛部皮肤。实验期结束时，将小牛深度麻醉，然后实施安乐死。收集胸段（T1 - T8）DRG并进行处理以获得冰冻切片，在荧光显微镜下进行检查。大量定位的神经元，特别是在T7 DRG中，呈现出被DY标记的细胞核。相反，仅在T6和T7 DRG中定位的少数神经元呈现出被FB标记的细胞质。没有神经元在细胞质和细胞核中同时显示FB和DY。DRG神经元未出现双重标记表明，卡尔施密特疼痛反应所基于的内脏和躯体感觉输入的汇聚可能并非发生在单个DRG神经元水平。相反，它可能涉及更高阶的整合中枢，可能包括迷走神经通路和脑干核，这些中枢整合传入信息以协调膈肌、肋间肌和喉部的呼吸运动。尽管受样本量限制，但该案例研究为进一步研究牛牵涉性内脏痛的中枢机制提供了神经解剖学基础。
