Role of a voltage-sensitive calcium channel blocker on inhibition of apoptosis in sensory neurons of cultured dorsal root ganglia in adult rat

Introduction: Under pathological conditions, abnormal increase in intracellular calcium concentrations is believed to induce cell death. In the present study, a voltage-sensitive calcium channel blocker (loperamide hydrochloride) was used to investigate its role in inhibition of apoptosis in sensory neurons of cultured spinal dorsal root ganglia (DRG). Methods: L5 DRG from adult rats were dissected and divided into three groups: 1. Freshly prepared DRG; 2. Control DRG; and 3. DRG treated with voltage-sensitive calcium channel blocker (loperamide hydrochloride, 200 μM). The control and the treated DRG were incubated in a culture medium for 72 hours. The DRG were then fixed and sectioned by a cryostat. Morphological and biochemical features of apoptosis in sensory neurons were studied by fluorescent staining (Propidium iodide and Hoechst) and TUNEL methods, respectively. Results: After 72 hours in culture, sensory neurons displayed morphological features of apoptosis. Most of these neurons also appeared as TUNEL positive. At this time period, the application of loperamide hydrochloride not only inhibited both morphological and biochemical features of apoptosis in the sensory neurons but also significantly increased the mean diameter of nucleus in these neurons compared to the control. Conclusion: This study showed that elevated intracellular calcium concentration might be one of reasons for apoptosis of sensory neurons in the cultured DRG.