Previous studies have revealed an impairment in bladder sensory transduction in aged animals. To examine the contributions of electrical property changes of bladder primary afferents to this impairment, we compared the electrical properties of dorsal root ganglion (DRG) neurons innervating the bladder among young (3 months), middle-aged (12 months), and old (24 months) female rats. The DRG neurons were labeled using axonal tracing techniques. Whole-cell current-clamp recordings of small and medium-sized neurons were performed to assess their passive and active properties. Two patterns of firing were identified based on responses to super-threshold stimuli (1.5, 2.0, 2.5, and 3.0 × rheobase): tonic neurons fired more action potentials (APs), whereas phasic neurons fired only one AP at the onset of stimulus. Tonic neurons were smaller and had a slower rate of AP rise, longer AP duration, more depolarized voltage threshold, and greater rheobase than phasic neurons. In phasic neurons, there was an age-associated increase in voltage threshold and an increase of rheobase (P < 0.05), suggesting an age-related decrease in excitability. In addition, both middle-aged and old rats had longer AP durations and slower rates of AP rise than young rats (P < 0.05). In tonic neurons, old rats had a greater AP overshoot and greater rate of AP rise, but no age-associated changes were identified in any other electrical properties. Our results suggest that the electrical properties of tonic and phasic bladder afferents are differentially altered with aging. A decrease in excitability may contribute to age-related reductions in bladder sensory function.

先前的研究表明，老年动物的膀胱感觉转导存在缺陷。为了检查膀胱初级传入神经的电特性变化对这种损伤的影响，我们比较了年轻人（3个月）、中年人（12个月）和老年人中支配膀胱的背根神经节（DRG）神经元的电特性。 24个月）雌性大鼠。使用轴突追踪技术标记 DRG 神经元。对中小型神经元进行全细胞电流钳记录，以评估其被动和主动特性。根据对超阈值刺激（1.5、2.0、2.5 和 3.0 × rheobase）的反应，确定了两种放电模式：强直神经元发射更多的动作电位 (AP)，而相位神经元在刺激开始时仅发射一个 AP。与相位神经元相比，强直神经元更小，AP 上升速率更慢，AP 持续时间更长，去极化电压阈值更大，流变碱更大。在阶段性神经元中，电压阈值出现与年龄相关的增加，流变碱也增加（ P < 0.05），表明兴奋性与年龄相关。此外，中老年大鼠的AP持续时间均较年轻大鼠更长，AP上升速度更慢（ P < 0.05）。在强直神经元中，老年大鼠的 AP 超调更大，AP 上升率更高，但在任何其他电特性中没有发现与年龄相关的变化。我们的结果表明，强直性和相位性膀胱传入神经的电特性随着年龄的增长而发生差异性改变。兴奋性下降可能导致与年龄相关的膀胱感觉功能下降。