Effect of emodin on rabbit gastric electric activity and mechanisms involved

AIM: To observe the effect of emodin on rabbit gastric electric activity (GEA) by microinjecting emodin in the medial reticular formation (MRF) of the medulla oblongata (MO) and injecting emodin in external system, and to discuss the possible mechanisms responsible for the effect of emodin on gastrointestinal movement.

METHODS: Rabbits were treated by intravenously injecting emodin in external system and microinjecting emodin in the MRF of MO, and giving electrical stimulation with a gastric pacemaker. Four pairs of bipolar Ag-AgCl electrodes were positioned under the serosa along the gastric greater curve to record GEA synchronously, and one pair of Pt stimulating electrodes were used for gastric pacing. The microinjection and stimulation of MRF were carried out using a brain stereo-localizer. Tested parameters included frequency (F), phase difference (PD), ratio of negative PD (RNPD) and corresponding rate of waves (CRW).

RESULTS: The normal frequency of GEA ranged from 3.48 to 3.77 cycles per minute (cpm) two hours after surgery, which could be driven by gastric pacing. The frequency of GEA at corpus 1 (P = 0.001) and corpus 2 (P = 0.021) and the RNPD of corpus 2 (P =0 .007) were increased, and the PD of corpus 3 (P = 0.037) and the CRW of corpus 3 (P = 0.001) and corpus 4 (P = 0.046) were decreased after pacing. Intravenous injection of emodin could decrease the frequency of corpus 1 (P = 0.031) and corpus 2 (P = 0.047) and the CRW of corpus 4 (P = 0.035), but had no effect on gastric electrical stimulation-driven GEA. The effects of emodin could be partly reversed by gastric pacing. Microinjection of 7 μL emodin could decrease the frequency of corpus 2 in P7 (P = 0.026), the frequency of corpus 1 in P8.5 (P = 0.045), which could be reversed by atropine, the frequency of antrum in P9.5 (P = 0.029), and greatly increased the frequency of corpus 1 in P11 (P = 0.011). In the control group, microinjection of 0.9% saline in P8.5, P9.5 and P11 had no effect on the GEA, except the frequency of corpus 2 in P7, which was increased (pH 8.5).

CONCLUSION: Gastric pacing had notable "driven effects" on the GEA. The GEA could be greatly inhibited by intravenous injection of emodin. The frequency and PD of the GEA were decreased by microinjection of emodin in MRF of nuclei raphe magnus (P7-P9.5). But in the P11, the frequency of the GEA was increased.

[Emodin blocks voltage dependent potassium channels in rat proximal colon smooth muscle cells]

AIM

To investigate the effect of emodin on the voltage dependent potassium (K(V)) currents in rat proximal colon smooth muscle cells.

METHODS

Whole cell patch clamp technique was used to record potassium currents including fast transient outward current (I(KA)) and delayed rectifier current (I(Kdr)). Contamination of calcium-dependent potassium currents was minimized with CdCl2 in external solution and EGTA in pipette solution.

RESULTS

Emodin (1-30 micromol x L(-1)) reversibly and dose-dependently reduced the amplitude of I(Kdr) with an K(d) value of (1.9 +/- 0.1) micromol x L(-1). I(KA) was also inhibited with 30 micromol x L(-1) emodin to a lesser extent. Although acceleration of the decay rate of the K(V) currents was observed, the block by emodin was not through open block mechanism because a steady state level of inhibition of I(Kdr) was achieved during the first pulse from holding potential -70 mV to + 50 mV after the cells were holding at -70 mV for a three minutes interval in the presence of emodin. Emodin (5 micromol x L(-1)) had no effect on the steady-state activation and inactivation kinetics of K(V) currents, but 30 micromol x L(-1) of emodin produced a positive shift of the voltage dependence of activation, and an increase in the steepness of activation gating as well as shifted the voltage dependence of inactivation to positive direction.

CONCLUSION

Emodin, not through open block mechanism, markedly reduced the amplitude of I(KA) and I(Kdr) and modulated the gating properties of K(V) channels in a reversible and dose-dependent manner.

[Electroencephalogram changes of meningioma]

Electroencephalogram (EEG) was used in investigating 42 cases of meningiomas proved by operations and pathological examinations. The abnormality rate of EEG was 95.24%. Compared with the clinical findings, the accuracy rate of EEG lesion-location was 64.29%; the accuracy rate of EEG lesion-side location was 26.19%; the total accuracy rate of lesion-location and lesion-side location was 90.48%. The EEG characteristics and the value of location diagnosis of meningioma were discussed. This indicates that EEG is still an important supplementary diagnostic method of intracranial meningioma.