Effect of Pinellia ternata tuber on the efferent activity of the gastric vagus nerve in the rat

BrainResearchBulletin, Vol. 32, pp. 103-106,1993 Printed in the USA. All rights reserved.

0361-9230/93$6.00 + .OO Copyright0 1993Pergamon Press Ltd.

Effect of Pineha ternata Tuber on the Efferent Activity of the Gastric Vagus Nerve in the Rat AKIRA NIIJIMA,*’ YUKA OKUI,‘( MASAYOSHI KUBO,? MASASHI HIGUCHI,t HEIHACHIROU TAGUCHI,? HIROSHI MITSUHASHI* AND MASUO MARUNO *Department of Physiology, Niigata University School of Medicine, Niigata 951, Japan tResearch Institute for Biology & Chemistry, Tsumura & Co., 3586 Yoshiwara, Ami-machi, Inashiki-gun, Ibaraki, 300-l 1, Japan Received 28 December 1992; Accepted 1 March 1993 NIIJIMA, A., Y. OKUI, M. KUBO, M. HIGIJCHI, H. TAGUCHI, H. MITSUHASHI AND M. MARUNO. Efict ofPinellia temata tuber on the e&rent activity of the gastric vagus nerve in the rat. BRAIN RES BULL 32(2) 103-106, 1993.-Effect of intraduodenal infusion with the hot aqueous extract of Pinellia ternata tuber on the efferent discharges in the gastric branch of the vagus nerve was observed in the anesthetized rat. The infusion of the extract in doses of 2-150 mg per animal (c.a. 300 g, b.wt.) resulted in a dose-related increase in efferent activity of the vagal gastric nerve. The enhancement of the nerve activity following administration of 150 mg of this substance lasted longer than 90 min. It was observed that the suppressive effect on vagal gastric activity due to apomorphine and copper sulfate was antagonized by prior administration of the extract. From these observations it is suggested that Pine& tuber acts as a facilitatory agent on gastric function. Vagus nerve

Gastric branch

Efferent discharges

Pinellia ternata

After the laparotomy, nerve filaments were dissected from the central cut end of of the ventral gastric branch of the vagus nerve, which originates from the ventral subdiaphragmatic vagus nerve trunk. Usually dorsal subdiaphragmatic vagus was also sectioned. The efferent nerve activity was recorded with a pair of silver wire electrodes. Nerve activity was amplified by means of a condenser coupled differential amplifier and displayed on an oscilloscope and stored on magnetic tape. All analysis of nerve activity was performed after conversion of raw data to standard pulses using a window discriminator, which ditinguished nerve activity from the background noise. A rate meter with a reset time of 5 s was used to observe the time course of the nerve activity that was recorded with a pen recorder. A cannula was inserted into the duodenum to infuse the test solutions or saline. The effect of infusion of the solution of Pinellia ternata and other solutions on the efferent activity was investigated by comparing the mean number of impulses per 5 s over 50 s (i.e., mean value of 10 successive measured samples) before and after stimulations. Significance was determined by ANOVA. Commercial tubers of P. ternata, the product of Japan and China, were pulverized and then extracted with water under reflux. The hot aqueous extracts were filtered and spray dried. The extract was stored in a desiccator prior to use. For infusion into the duodenum, the pulverized material was dissolved in 2 or 4 ml warm saline (c.a. 35°C) and mixed by means of an

THE tuber of Pinellia ternata (Thunb.) Breit, (Araceae), (Hange in Japanese), which is widely distributed in China, Korea, and Japan, has been used in traditional Chinese medicine. It is known that the prescriptions containing Pinellia tuber show antiemetic (5), antitussive, sedative, antiinflammatory, and antiimplantation effects. In relation to the emetic or gastric dysfunction, it was reported that an inhibition in efferent activity of the gastric vagus nerve was observed in such condition (4). Recently it was reported that a fraction of Pinellia tuber extracts was antagonistic to the emetic action to the leopard and ranid frog (3). This report suggests that Pinellia tuber may activate efferent activity of the gastric vagus nerve and antagonize the inhibitory effect of apomorphine and copper sulfate those are known as emetic agents. This paper mainly deals with the effect of Pinellia tuber on the efferent activity of the gastric branch of the vagus nerve in the rat. METHOD

Male Wistar rats, weighing about 300 g, were used. They were kept in a room at 24°C with illumination for 12 h a day (0700-1900 h). Food, but not water, was removed 12 h before the experiment. The animals were anesthetized by intraperitoneal injection of 1 g/kg urethane. A tracheal cannula was inserted.

’ Requests for reprints should be addressed to Akira Niijima, 3 1-2, Hamauracho, Niigata City, 95 1 Japan.

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104 ultrasonic cleaner for a few minutes to make a homogenized suspension. Then, the solution was slowly infused into the duodenum after control recording of stabilized efferent discharges for 30 min. Infusion time was usually 3-5 min. In some experiments solution of copper sulfate was infused into the doudenum, and in the other experiment the solution of apomorphine (Sigma) was injected in the vein through a catheter inserted into the vena cava inferior. Animal body temperature was maintained by means of a heating pad.

product of 3apan (n = 9) Total (n = 18) Product of China (n = 9) Pinellia ternata lSOmg, 4ml i.d.

RESULTS

Figure 1 shows the effect of intmdu~enal infusion of 150 mg (4 ml) solution of the extract of Pjnel~i~ tuber on the efferent discharge rate of the gastric vagus nerve filament. Upper trace shows the effect of the product of Japan. In this particular preparation dorsal subdiaphragmatic vagus trunk was kept intact. After the infusion discharge rate increased gradually and reached the plateau level about 60 min after infusion. At the plateau level the increase in discharge rate was about 116% of the control level and it lasted longer than 20 min until the end of observation. Further, it was observed that the sectioning of dorsal (left) subdiaphragmatic vagus trunk during plateau periond caused no noticeable change in discharge rate. Lower trace shows the effect of a Chinese product on efferent activity. As shown in the trace, an infusion caused a gradual increase in discharge rate which reached a plateau level as well about 100 min after adminis~ation. The increase in discharge rate at plateau in this particular preparation was about 180% of the control level. Eight other observations were made on the effect of Japanese product, and a further eight observations were made on the Chinese product. The mean discharge rate (n = 9, including observation in Fig. 1) before administrations of the Japanese product was 76.4 cf: 6.9 impulses/5 s (mean -t SEM) and that of 30 min and 60 min after administration was 114.4 f: 8.7 and 158.7 + 13.8, respectively. The mean discharge rate before infusions of the Chinese product was 77.6 + 6.3, and that of 30

The extract of Pine&o tuber (Japan)

Sectioning of the left vagos

lSOmg, 4ml i.d.

The extract of Pine&u

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I

tuber (China)

bars: bars:

IOmin 100 impulses/5

siec

FIG. I. Effectof intraduodenal administration of the extract of Pinellia on the efferent discharge rate of the vagal gastric nerve.

tuber

0;

-20

.

I

0

.

I

.

20

I

40

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I

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*

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minutes FIG. 2. Efferentdischargerate of the gastric vagus nerve before (control), 30 min aRer, and 60 min after administration of the extract of Pine&a tuber.

and 60 min after infusions was I 15.7 + 8.0 and 158.9 Lt 11.0 (n = 9, including an observation in Fig. 1). There were significant differences in discharge rates between control values and those after administration of the Japanese and Chinese products. Mean discharge rate of the total experiments (n = 18), which includes administrations of the Japanese product (n = 9) and the Chinese product (n = 9) in control observation was 77.0 f 5.2, and those of 30 and 60 min after administration was 115.0 + 5.7 and 158.7 f 8.6, respectively. No significant difference was observed between values obtained at control periods, and at 30 min and 60 min after infusions of the Japanese and Chinese products (Fig. 2 and Table I),, suggesting no difference in facilitatory effect between the Japanese and Chinese product on the efferent activity of the gastric vagus nerve. Figure 3 shows the effect of three different doses of P~~eI~~a ternata administrated into the duodenum on the efferent activity of the gastric branch of the vagus nerve. The top trace of Fig. 3 shows the effect of 2 mg administration on the gastric nerve activity. As shown in the trace, after administration a slight increase in the discharge rate was observed. A peak was reached about 45 min after slow increase in the discharge rate, then it decreased gradually to return the control level about 80 min after administration. The middle trace shows the effect of 10 mg administration. After the administration a slow increase in the discharge rate was observed. The peak value was reached about 100 min after administration. The bottom trace presents the effect of 150 mg administration. The discharge rate markedly increased after administration, which reached the peak value about 110 min after the infusion. The discharge rates of upper (2 mg id.), middle (10 mg i.d.), and bottom f I50 mg id.) trace at 90 min after administration was 8 1.4 f 3.1 impulses/5 s (mean I SEM), 123.7 + 3.9 and 249.0 ? 5.2, respectively. The responses seem to be dose related. Figure 4 represents the effects of apomorphine and copper sulfate after administration of 150 mg Pinelliu ternata. In the upper trace an increase in the discharge rate was observed following intraduodenal administration ofthe Chinese Pinellia ter-

Pinellia ternata ON VAGAL ACTIVITY

105

TABLE 1 EFFECT OF THE EXTRACT OF PINELLIA TUBER ON THE EFFERENT ACTIVITY OF THE GASTRIC BRANCH OF THE VAGUS NERVE (I 50 m& 4 ml INTRADUODENAL INFUSION) Impulses/5 s (Mean + SEM)

Product in Japan (n = 9) Product in China (n = 9) Total (n = 18)

Control

30 min

60 min

76.4 + 6.9 77.6 f 6.3 77.0 + 5.2

114.4 f 8.7* 115.7 + 8.0* 115.0 + 5.7* p < 0.05

158.7 + 13.8* 158.9 + 1l.O* 158.7 f 8.6*

* Notes significant difference to control value. nata. Then, 1 mg (0.1 ml) apomorphine was injected into the vein 75 min after the duodenal infusion, which caused a prompt decrease in efferent activity. However, the level of suppression was a little higher than the control level. The same type of response was observed in the lower trace. An infusion of copper sulfate solution (0.08%, 5 ml) into the duodenum also resulted in a quick inhibition of the efferent discharge rate. The level of inhibition was a little higher than the level of the firing rate before Pinellia ternata administration. It was further observed that intravenous administration of apomorphine ( 1 mg, 0.1 ml) or intraduodenal in fusion of copper sulfate (0.08%, 5 ml) alone caused a suppression of discharge rate below the control level (not presented). DISCUSSION

The experimental results indicate that intraduodenal infusion of the extract of Pinellia tuber accelerates efferent activity of the The extract of Pineilia

tuber (Japan)

2mg, 2ml i.d.

of Pinellia tuber (China) 15Omg.4ml i.d.

The extract

The extract of Pinellia tuber (Japan)

lOmg, 2ml i.d.

The extract of Pinellia

Vertical

Apomorphine1mg O.lml i.v. I

The extract of Pinellia tuber (China)

tuber (China)

0.08% CuSO4 5mI i.d.

15Omg.4ml i.d.

15Omg.4ml i.d.

Horizontal

gastric branch of the vagus nerve. This acceleration could not be blocked by bilateral subdiaphragmatic vagotomy, suggesting the excitatory effect of the extract of Pinellia tuber infused into the duodenum is not due to the vagal afferent signals from the digestive canal. Further, it was observed that the plateau of the discharge rate after gradual increase was reached at least 60 min after the infusion. This time delay suggests that the excitatory effect is due to the blood-borne Pinellia ternata or its derivatives after absorption from the intestinal wall, and not to the afferent signals through the splanchnic afferents. Figure 3 shows that the infusion of a small amount of Pinellia ternata caused a small and short response, and that of large amount resulted in larger and longer response. It is likely that the response is a dose-related type and the least effective dose seems to be 1 - 2 mg per animal. It was demonstrated in Fig. 4 that administrations of emetic agents such as apomorphine and copper sulfate suppresses efferent activity of the vagus nerve. Borrison and Wang (1)reported that emetic effect of apomorphine is due to the action of this substance to fasciculus solitarius and area postrema in the medulla oblongata. They also reported (6) that the emetic action

bars: bars:

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FIG. 3. Effects of intraduodenal administration of 2 mg, 10 mg, and 150 mg of the extract of Pinelliatuber on the efferent activity of the gastric branch of the vagus nerve.

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min impulses/5

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FIG. 4. Suppressive effect of apomorphine and copper sulfate on the efferent vagal gastric nerve activity after administration of the extract of Pinelliatuber.

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of copper sulfate is twofold, involving a central as well as a peripheral effect. It has been mentioned that intraduodenal infusion of copper sulfate inhibits efferent activity of the gastric vagus nerve. It was also reported (4) that intragastric administration of this substance demonstrates the similar response on the vagal gastric efferents. The inhibitory effect on vagai gastric efferent activity by emetic agents such as apomorphine and copper sulfate (Fig. 4) indicates the suppressive effect on gastric function even though the rat cannot vomit. As shown in Fig. 4, a prior administration of the extract of Pinellia tuber reduced the suppressive effect of emetic agents on vagal gastric nerve activity which kept nerve activity above the control level. The antiemetic effect of the extrtact of Pinellia tuber in human subjects can be explained in this light. It is generally recognized that the acceleration of vagal efferent activity facilitates gastric secretion and movement. In this sense

the extract of Pinelfia tuber acts as a facilitatory agent on gastric function. Several years ago, a new assay method for the emetic action of toxic mushrooms using frogs as the test animal was reported (2). This method was employed to study the antiemetic action of the extract of Pinellia tuber and it was reported (3) recently that a polysaccharide fraction isolated from the aqueous extracts of the tuber of Pinellia tuber demonstrated antagonistic effect to the emetic action induced by apomorphine by the oral administration to leopard and ranid frogs. The present study indicates that the observation of the vagal gastric nerve activity can be a new assay method to study the antiemetic as well as facilitatory effect on gastric function. This method can be employed to find out the effective fractions isolated from the extract of Pineliia tuber.

REFERENCES

Borrison, H. L.; Wang, S. C. Physiologyand pharmacology of vomiting. Pharmacol. Rev. 5: 193-230; 1953. Maki, T.; Takahashi, K.; Shibata, S. Isolation of vomiting principles from the mushroom Rhodophyllus rhodopolius. J. Agr. Fd. Chem. 33:1204-1205; 1985. Maki, T.; Takahashi, K.; Shibata, S. An anti-emetic principle of Pinellia ternata Tuber. Planta Med. 53:410-414, 1987. Niijima, A.; Jiang, Z. Y.; Daunton, N. G.; Fox, R. A. Experimental studies of gastric dysfunction in motion sickness: The effect of gastric

and vestibular stimulation on the vagal and splanchnic gastric efferents. In: Hwang. J. C.: Daunton, N. G.; Wilson, V. J., eds. Basic and applied aspects of vestibular function. Hong Kong: Hong Kong University Press; 1988. 5. Takabe. N. On the aitiemetic action of Pine/ha. Acta Schol. Med. Universit. Gifu 6:243-250; 1958. 6. Wang, S. C.; Borrison, H. L. Copper sulphate emesis: A study of afferent pathways from the gastrointestinal tract. Am. J. Physiol 1265: 520-526: 1951.