L-type Ca2+ channels in the enteric nervous system mediate oscillatory Cl- secretion in guinea pig colon

Preclinical Studies to Evaluate the Gut Stimulatory Activity of Aloe Musabbar

Background

Constipation is a common functional gastrointestinal disorder. Medicines derived from nature are routinely used to treat it. The present study evaluates the gut stimulatory activity of Aloe musabbar (processed powder of Aloe vera) using in vitro and in vivo models for gut stimulatory activity.

Materials and Methods

In vitro tests were conducted on isolated rat colon, guinea pig ileum, and rabbit jejunum, while in vivo study was performed using mice intestinal transit time. Aloe musabbar (A. musabbar) was tested at doses 0.2–200 mg/mL (in-vitro study) and 86.6 mg/kg (in vivo study). In vitro studies were done in the presence and absence of atropine sulphate (1 ng/ml). The results were statistically analyzed, and p < 0.05 was considered to indicate the significance.

Results

A. musabbar exhibited dose-dependent increase in the smooth muscle contraction of isolated gut tissues. Presence of atropine minimized the contractile responses and shifted the dose-response curves towards the right-hand side. The intestinal transit time in mice was observed to be increased significantly (p < 0.01) in A. musabbar-treated animals, when compared with normal animals.

Conclusion

A mild smooth muscle contraction induced by A. musabbar suggests that it can stimulate intestinal bowel movement without causing spasms. The diminished responses in the presence of atropine indicated that the gut stimulatory activity could be mediated partially through parasympathetic innervations. More studies are needed to determine the precise mechanism of action including the specific active ingredient responsible for the gut stimulatory activity.

R-type calcium channels are crucial for semaphorin 3A-induced DRG axon growth cone collapse

Semaphorin 3A (Sema3A) is a secreted protein involved in axon path-finding during nervous system development. Calcium signaling plays an important role during axonal growth in response to different guidance cues; however it remains unclear whether this is also the case for Sema3A. In this study we used intracellular calcium imaging to figure out whether Sema3A-induced growth cone collapse is a Ca²⁺ dependent process. Intracellular Ca²⁺ imaging results using Fura-2 AM showed Ca²⁺ increase in E15 mice dorsal root ganglia neurons upon Sema3A treatment. Consequently we analyzed Sema3A effect on growth cones after blocking or modifying intracellular and extracellular Ca²⁺ channels that are expressed in E15 mouse embryos. Our results demonstrate that Sema3A increased growth cone collapse rate is blocked by the non-selective R- and T- type Ca²⁺ channel blocker NiCl₂ and by the selective R-type Ca²⁺ channel blocker SNX482_. These Ca²⁺ channel blockers consistently decreased the Sema3A-induced intracellular Ca²⁺ concentration elevation. Overall, our results demonstrate that Sema3A-induced growth cone collapses are intimately related with increase in intracellular calcium concentration mediated by R-type calcium channels.