Brain Research, 508 (1990) 325-328 Elsevier
325
BRES 23944
Gastrin-17 injected into the hypothalamic paraventricular nucleus can induce gastric acid secretion in rats M. O h t a k e t a n d T. S a k a g u c h i 2 Departments of ¢Surgery and 2physiology, Niigata University School of Medicine, Niigata (Japan) (Accepted 17 October 1989) Key words: Cholecystokinin-8;Gastrin-17; Paraventricular nucleus; Vagus nerve; Rat
Injections of picomolar quantities of gastrin-17 into the hypothalamic paraventricular nucleus increased gastric acid output in anesthetized rats. The response was dose-dependent, and it was blocked by atropin and by vagotomy. The same doses, injected intravenously, intraventriculary or into sites far from the nucleus, did not increase the output, Cholecystokinin-8 injected into the nucleus had no effect on the acid output.
Gastrin is a peptide hormone physiologically controlling gastric acid secretion, and its main source is the antrum of the stomach 3. Recent immunohistochemical and biochemical studies have revealed a peptide identical to gastrin in the hypothalamus, pituitary, and medulla oblongata of several mammals4"8'16; gastrin is a peptide common to the stomach and brain. Moreover, it has been shown that gastrin injected into the lateral hypothalamic areas (LHA) stimulates gastric acid secretion, and it has been speculated that there is a neuron receptive to gastrin in the brain, and gastrin endogenous to the hypothalamus, perhaps acting as a neurotransmitter or neurohormone, serves in neural control of gastric acid 14. However, the effect of gastrin on gastric acid secretion has not yet been examined in the hypothalamus except for the LHA. On the other hand, the paraventricular nucleus (PVN) adjacent to the L H A has been shown to contain the peptide s, and it has been presumed that there might be a neuron receptive to gastrin. The present study was designed to investigate whether gastrin injected into the PVN influences gastric acid secretion in relation to the LHA. Sixty-two male Wistar rats weighing 250-280 g were used. After anesthesia with pentobarbital sodium (45 mg/kg, i,p.), the animals were mounted in a stereotaxic apparatus. Twenty-two-gauge guide cannulas were aimed at the PVN, the L H A and the third ventricle using the coordinates of Pellegrino et al. 7. These cannulas were inserted through burr holes and anchored to the skull with dental cement and stainless steel screws. A 28-gauge needle was inserted through the 22-gauge guide cannulas
by the maneuver reported earlier ~1. After the implantation of the cannulas, the animals were fed on a standard diet with free access to tap water. Six to 9 days after the implantation, the injection experiments were carried out 6A2. The animals were deprived of food for 22 h beforehand. On the day of the experiment, the animals, anesthetized with pentobarbital sodium (45 mg/kg, i.p.), were bilaterally adrenalectomized about 30 min before the experiment to eliminate the usual variation in plasma concentrations of glucose and insulin, and to prevent the inhibition of gastric acid secretion by the adrenaline which would have been released in response to hypoglycemia 1"~3. A cannula was inserted into the trachea to provide adequate ventilation. In some animals, a catheter was placed in the right jugular vein. The evaluation of the gastric acid output was made by the method described earlier m. Briefly, a polyethylene tube was introduced into the stomach through the esophagus and was tied in position by a ligature around the esophagus in the neck. A cannula was then inserted into the pyloroduodenal junction and passed up into the stomach. The stomach was perfused with a solution of 154 mM NaCI warmed to 37 °C, and titratable acidity (end point 7.0) was determined with 0.01 N NaOH. Acid output was calculated every 3 min. The rectal temperature was maintained at about 36.5 + 0.5 °C with a heating lamp. Gastrin-17 (human) (Peptide Institute, Inc., Japan) and cholecystokinin-8 (26-33) (Peptide Institute, Inc., Japan) were used. Two forms (non-sulfated and sulfated) of cholecystokinin (CCK) were tested. A test solution
Correspondence: T. Sakaguchi, Department of Physiology, Niigata University School of Medicine, Niigata 951, Japan. 0006-8993/90/$03.50 © 1990 Elsevier Science Publishers B.V. (Biomedical Division)
326 was injected for 10 s in a volume of 500 nl with an infusion pump. The data from this study were taken from the initial response of the animals to one of the injected solutions and were analyzed by an analysis of variance and D u n c a n ' s multiple range test. Injection of 40 pM gastrin-17 into the PVN increased gastric acid output, and the time required to reach maximal response was about 9 min after the injection, and the response had disappeared within another 12 min. No significant change in the acid output was noted after saline was injected into the PVN. A N O V A revealed that differences among times and groups were Fs.t08 = 16.148, P < 0.002 and F],10 s = 264.671, P < 0.002, respectively (Fig. 1). The effect of gastrin-17 on the acid output was dose-dependent. Both non-sulfated and sulfated forms of CCK-8 injected into the PVN failed to cause the acid response. The stimulatory acid response evoked by gastrin-17 was blocked by prior section of the vagus nerve at the subdiaphragmatic level, and by atropine sulfate (100/~g/kg). It was also observed that 40 pM gastrin-17 injected into the right jugular vein or into the third ventricle produced no significant effect on the acid output. The difference in the output among groups was reliable, F9,69 = 43.572, P < 0.001 (Fig. 2). Gastrin-17 injection (40 pM) into the L H A increased gastric acid output, but, there was a difference in the magnitude of acid response; acid output was greater in the L H A injection than that in the PVN injection, and the greatest response in the acid output was observed after simultaneous injection of gastrin-17 into the PVN and L H A . The
°~
E
10._J.. b I= °~
•'o I:: 5-
I
(,~
I
II
III
IV
V
14
~tl
~11
IX
X
Fig. 2. The levels of gastric acid output 12 min after infusing saline (I), 20 pM gastrin-17 (II), 40 pM gastrin-17 (III), 80 pM gastrin-17 (IV), 40 pM CCK-8 (non-sulfated form) (V), 40 pM CCK-8 (sulfated form) (VI), 40 pM gastrin-17 with vagotomy (VII), 40 pM gastrin-17 with atropine sulfate (VIII), 40 pM gastrin-17 injection into the jugular vein (IX) and 40 pM gastrin-17 injection into the third ventricle (X). Vagotomy was done at the subdiaphragmatic level, and the dose of atropine was i00/~g/kg. There are 7 samples to each bar. Values are the mean + S.E.M. a: P < 0.05 vs I and VI; b: P < 0.01 vs II; and c: P < 0.01 vs III.
difference in the acid output among groups was A N O V A significant, F3,27 = 414.905, P < 0.05 (Fig. 3). The effective sites of the brain cannulas were in or near the PVN and L H A (Fig. 4). From the histological examinations, it was estimated that effective zones for 40 pM gastrin-17 were within 350 /xm from the tip of the cannula. The present study demonstrated that neurons receptive to gastrin in the P V N may participate in the control of gastric acid secretion; the injection of picomolar quantities of gastrin-17 into the PVN produced an increase in gastric acid output (Fig. 1). Although the gut hormones gastrin and C C K have been shown to possess a c o m m o n origin and a c o m m o n C O O H terminal, which constitute their active site 9, the acid response caused by
d i,ii v
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5
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-;
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6
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ll min
Fig. 1. Changes in gastric acid output following gastrin-17 injection into the paraventrieular nucleus. Forty pM gastrin-17 (O; n = 7) or saline (O; n = 7) was injected into the nucleus. The arrow shows the time of injection. Values are the mean + S.E.M. a: P < 0.01 vs the value just before injection; and b-g: P < 0.01 vs saline injection.
I
II
III
IV
Fig. 3. Gastric acid output after gastrin-17 injection into two different regions of the hypothalamus. Forty pM gastrin-I7 was injected into the paraventricular nucleus (II), into the Iateral hypothalamic areas (III) and into both these regions simultaaeousty (IV). Control injection of saline was injected into both regions (I). The acid output 12 min after each injection was compared. There are 7 samples to each bar. Values are the mean + S.E.M. a: P < 0.01 vs I; b: P < 0.01 vs II; and c: P < 0.01 vs III.
327
A Effective
Sites
B
Ineffective
Sites 7.2
CO
,
6.6
6.0
5.4
4.8
4.2
1.0 mm
Fig. 4. Effective sites of injections in six rats (A) were in the vicinity of the paraventricular nucleus (PVN) or in the vicinity of the lateral hypothalamic areas (LHA). Ineffective sites (B) were far from these nuclei. Numbers in upper right corner of each panel indicate distances in millimeters from the vertical zero plane. AHA, anterior hypothalamic area; ARH, arcuate nucleus; CO, chiasma opticum; DMH, hypothalamic dorsomedial nucleus; FX, fornix; ML, lateral mamillary nucleus; MM, medial mamillary nucleus; MT, mamillothalamic tract; OT, optic tract; PH, posterior hypothalamic nucleus; PMD, dorsal premamillary nucleus; PMV, ventral premamillary nucleus; RE, reuniens nucleus; V, ventricle; VMH, ventromedial hypothalamic nucleus. the peptide seemed to be specific to gastrin, because the peptide effects were dose-dependent and CCK-8 had no effect on the acid output (Fig. 2). Chemically, it has been estimated that the normal concentration of gastrin in the PVN and neural lobe of the pituitary stalk which would come from the PVN was 8-30 pmol/g tissue ~'9. In this study, 3 different doses of the peptide were applied, and the threshold concentration was 20 pM (Fig. 2). It is not easy to estimate the physiologically acting concentration of the peptide. But, if gastrin were released locally onto the PVN neurons and they acted as neurotransmitters or neuromodulators, the concentration of the peptide near the cell body might be much higher than the threshold concentration. The stimulatory response in acid output caused by the PVN injection of gastrin-17 was abolished by subdia-
phragmatic vagotomy or by atropine sulfate, suggesting that the response was mediated by vagal and cholinergic fibers to the stomach (Fig. 2). Pentagastrin has the effect of a potent secretagogue on gastric acid secretion when injected into the systemic circulation 2, and its effect has been thought to be derived from direct activation of the parietal cells of the stomach 3. However, it should be remembered that pentagastrin injected into the systemic circulation penetrated the blood-brain barrier, and activated the cells producing gastric acid secretion within the brain. In the present study, 40 pM gastrin-17 potently stimulated acid output when injected into the PVN, whereas no significant change in the acid output was noted when the same dosage of the peptide was injected into the jugular vein or into the third ventricle (Fig. 2). These results could
328 eliminate the possibility that the peptide leaking from the brain tissue into the blood-stream or cerebrospinal fluid was active in the response. A significant increase in the acid output was obtained when 10-100 times larger doses of the peptide were injected into the vein or into the third ventricle (unpublished data). It appears that the stimulatory response in the acid output was attributable to localized activation of the PVN cells by gastrin-17 (Figs. 3 and 4). Gastric acid output was increased following gastrin-17 injection into the L H A (Figs. 3 and 4). This is consistent with the previous report that pentagastrin injected into the L H A enhanced gastric acid output 14. Considering that finding together with the fact that there was an additive increase in the acid output when gastrin-17 was
injected into the PVN and L H A simultaneously (~'ig. 3), it was suggested that this type of gastric acid secretion is characteristic of the PVN and L H A , separately or together. Further work needs to be done on characterization. Since gastrin has been identified in the hypothalamus, in the medulla oblongata and in the fibers of the vagus nerve 4'5'8'~5''~ it is considered that there is a gastrinergic pathway connecting the hypothalamus and the vagal nuclei and projecting to the stomach. These observations led us to speculate that gastrin is active in the vagal secretion of gastric acid at the hypothalamic PVN level.
1 Armin, J. and Grant, R.T., Adrenaline release during insulin hypoglycaemia in the rabbit, J. Physiol. (Lond.), 149 (1959) 228-249. 2 Barrett, A.M., Specific stimulation of gastric acid secretion by a pentapeptide derivative of gastrin, J. Pharm. Pharmac., 18 (1966) 633-639. 3 Davenport, H.W., Physiology of the Digestive tract, Year Book Medical Publishers Inc., Chicago, 1977. 4 Loren, I., Alumets, J., Hhkanson, R. and Sundler, E, Distribution of gastrin and CCK-like peptides in rat brain, Histochemistry, 59 (1979) 249-257. 5 Luiten, P,G,M., Ter Horst, G.J. and Steffens, A.B., The hypothalamus, intrinsic connections and outflow pathways to the endocrine system in relation to the control of feeding and metabolism, Prog. Neurobiol., 28 (1987) 1-54. 6 Ohtake, M. and Sakaguchi, T., Inhibition of gastric acid secretion evoked by activation of the hypothalamic paraventricular nucleus, Exp. Brain Res., 66 (1987) 222-224. 7 Pellegrino, L.J., Pellegrino, A.S. and Cushman, A.J., A Stereotaxic Atlas" of the Rat Brain, Plenum, New York, 1979. 8 Rehfeld, J.E, Localization of gastrins to neuro- and adenohypophysis, Nature (Lond.), 271 (1978) 771-773. 9 Rehfeld, J.F., Hansen, H.E, Larsson, L.-I., Stengaard-Pedersen, K. and Thorn, N.A., Gastrin and cholecystokinin in
pituitary neurons, Proc, Natl. Acad. Sci. U.S.A., 81 (1984) 1902-1905. 10 Sakaguchi, T., Alterations in gastric acid secretion following hepatic portal injections of D-glucose and its anomers, 3. Auton. Nerv. Syst., 5 (1982) 337-344. 11 Sakaguchi, T. and Bray, G.A., Intrahypothalamic injection of insulin decreases firing rate of sympathetic nerves, Proc. Natl. Acad. Sci. U.S.A., 84 (1987) 2012-2014. 12 Sakaguchi, T. and Sato, Y., D-Glucose anomers in the nucleus of the tractus solitarius can reduce gastric acid secretion of rats, Exp. Neurol., 95 (1987) 525-529. 13 Sakaguchi, T. and Yamaguchi, K., Effects of vagal stimulation, vagotomy and adrenalectomy on release of insulin in the rat; J. Endocrinol., 85 (1980) 131-136. 14 Tepperman, B.L. and Evered, M.D., Gastrin injected into the lateral hypothalamus stimulates secretion of gastric acid in rats, Science, 209 (1980) 1142-1143. 15 Uvn~is-Wallensten, K., Rehfeld, J.E, Larsson, L.-I. and Uvn~is, B., Heptadecapeptide gastrin in the vagal nerve, Proc. Natl. Acad. Sci. U.S.A., 74 (1977) 5707-5710. 16 Vanderhaeghen, J.J., Lotstra, E, De Mey, J. and Gilles, C., Immunohistochemical localization of cholecystokinin- and gastrin-like peptides in the brain and hypophysis of the rat, Proc. Natl. Acad. Sci. U.S.A., 77 (1980) 1190-1194.
This study was supported by Grant 63570077 from the Ministry of Education, Science and Culture of Japan.
325
BRES 23944
Gastrin-17 injected into the hypothalamic paraventricular nucleus can induce gastric acid secretion in rats M. O h t a k e t a n d T. S a k a g u c h i 2 Departments of ¢Surgery and 2physiology, Niigata University School of Medicine, Niigata (Japan) (Accepted 17 October 1989) Key words: Cholecystokinin-8;Gastrin-17; Paraventricular nucleus; Vagus nerve; Rat
Injections of picomolar quantities of gastrin-17 into the hypothalamic paraventricular nucleus increased gastric acid output in anesthetized rats. The response was dose-dependent, and it was blocked by atropin and by vagotomy. The same doses, injected intravenously, intraventriculary or into sites far from the nucleus, did not increase the output, Cholecystokinin-8 injected into the nucleus had no effect on the acid output.
Gastrin is a peptide hormone physiologically controlling gastric acid secretion, and its main source is the antrum of the stomach 3. Recent immunohistochemical and biochemical studies have revealed a peptide identical to gastrin in the hypothalamus, pituitary, and medulla oblongata of several mammals4"8'16; gastrin is a peptide common to the stomach and brain. Moreover, it has been shown that gastrin injected into the lateral hypothalamic areas (LHA) stimulates gastric acid secretion, and it has been speculated that there is a neuron receptive to gastrin in the brain, and gastrin endogenous to the hypothalamus, perhaps acting as a neurotransmitter or neurohormone, serves in neural control of gastric acid 14. However, the effect of gastrin on gastric acid secretion has not yet been examined in the hypothalamus except for the LHA. On the other hand, the paraventricular nucleus (PVN) adjacent to the L H A has been shown to contain the peptide s, and it has been presumed that there might be a neuron receptive to gastrin. The present study was designed to investigate whether gastrin injected into the PVN influences gastric acid secretion in relation to the LHA. Sixty-two male Wistar rats weighing 250-280 g were used. After anesthesia with pentobarbital sodium (45 mg/kg, i,p.), the animals were mounted in a stereotaxic apparatus. Twenty-two-gauge guide cannulas were aimed at the PVN, the L H A and the third ventricle using the coordinates of Pellegrino et al. 7. These cannulas were inserted through burr holes and anchored to the skull with dental cement and stainless steel screws. A 28-gauge needle was inserted through the 22-gauge guide cannulas
by the maneuver reported earlier ~1. After the implantation of the cannulas, the animals were fed on a standard diet with free access to tap water. Six to 9 days after the implantation, the injection experiments were carried out 6A2. The animals were deprived of food for 22 h beforehand. On the day of the experiment, the animals, anesthetized with pentobarbital sodium (45 mg/kg, i.p.), were bilaterally adrenalectomized about 30 min before the experiment to eliminate the usual variation in plasma concentrations of glucose and insulin, and to prevent the inhibition of gastric acid secretion by the adrenaline which would have been released in response to hypoglycemia 1"~3. A cannula was inserted into the trachea to provide adequate ventilation. In some animals, a catheter was placed in the right jugular vein. The evaluation of the gastric acid output was made by the method described earlier m. Briefly, a polyethylene tube was introduced into the stomach through the esophagus and was tied in position by a ligature around the esophagus in the neck. A cannula was then inserted into the pyloroduodenal junction and passed up into the stomach. The stomach was perfused with a solution of 154 mM NaCI warmed to 37 °C, and titratable acidity (end point 7.0) was determined with 0.01 N NaOH. Acid output was calculated every 3 min. The rectal temperature was maintained at about 36.5 + 0.5 °C with a heating lamp. Gastrin-17 (human) (Peptide Institute, Inc., Japan) and cholecystokinin-8 (26-33) (Peptide Institute, Inc., Japan) were used. Two forms (non-sulfated and sulfated) of cholecystokinin (CCK) were tested. A test solution
Correspondence: T. Sakaguchi, Department of Physiology, Niigata University School of Medicine, Niigata 951, Japan. 0006-8993/90/$03.50 © 1990 Elsevier Science Publishers B.V. (Biomedical Division)
326 was injected for 10 s in a volume of 500 nl with an infusion pump. The data from this study were taken from the initial response of the animals to one of the injected solutions and were analyzed by an analysis of variance and D u n c a n ' s multiple range test. Injection of 40 pM gastrin-17 into the PVN increased gastric acid output, and the time required to reach maximal response was about 9 min after the injection, and the response had disappeared within another 12 min. No significant change in the acid output was noted after saline was injected into the PVN. A N O V A revealed that differences among times and groups were Fs.t08 = 16.148, P < 0.002 and F],10 s = 264.671, P < 0.002, respectively (Fig. 1). The effect of gastrin-17 on the acid output was dose-dependent. Both non-sulfated and sulfated forms of CCK-8 injected into the PVN failed to cause the acid response. The stimulatory acid response evoked by gastrin-17 was blocked by prior section of the vagus nerve at the subdiaphragmatic level, and by atropine sulfate (100/~g/kg). It was also observed that 40 pM gastrin-17 injected into the right jugular vein or into the third ventricle produced no significant effect on the acid output. The difference in the output among groups was reliable, F9,69 = 43.572, P < 0.001 (Fig. 2). Gastrin-17 injection (40 pM) into the L H A increased gastric acid output, but, there was a difference in the magnitude of acid response; acid output was greater in the L H A injection than that in the PVN injection, and the greatest response in the acid output was observed after simultaneous injection of gastrin-17 into the PVN and L H A . The
°~
E
10._J.. b I= °~
•'o I:: 5-
I
(,~
I
II
III
IV
V
14
~tl
~11
IX
X
Fig. 2. The levels of gastric acid output 12 min after infusing saline (I), 20 pM gastrin-17 (II), 40 pM gastrin-17 (III), 80 pM gastrin-17 (IV), 40 pM CCK-8 (non-sulfated form) (V), 40 pM CCK-8 (sulfated form) (VI), 40 pM gastrin-17 with vagotomy (VII), 40 pM gastrin-17 with atropine sulfate (VIII), 40 pM gastrin-17 injection into the jugular vein (IX) and 40 pM gastrin-17 injection into the third ventricle (X). Vagotomy was done at the subdiaphragmatic level, and the dose of atropine was i00/~g/kg. There are 7 samples to each bar. Values are the mean + S.E.M. a: P < 0.05 vs I and VI; b: P < 0.01 vs II; and c: P < 0.01 vs III.
difference in the acid output among groups was A N O V A significant, F3,27 = 414.905, P < 0.05 (Fig. 3). The effective sites of the brain cannulas were in or near the PVN and L H A (Fig. 4). From the histological examinations, it was estimated that effective zones for 40 pM gastrin-17 were within 350 /xm from the tip of the cannula. The present study demonstrated that neurons receptive to gastrin in the P V N may participate in the control of gastric acid secretion; the injection of picomolar quantities of gastrin-17 into the PVN produced an increase in gastric acid output (Fig. 1). Although the gut hormones gastrin and C C K have been shown to possess a c o m m o n origin and a c o m m o n C O O H terminal, which constitute their active site 9, the acid response caused by
d i,ii v
=.
2 15 Q.
0 •- U
.oE
b
10
1
._~ ~
IJ .w
5
,,i,a
0
¢I
0
-;
o
3
6
g
l'z
1'5
l'a
ll min
Fig. 1. Changes in gastric acid output following gastrin-17 injection into the paraventrieular nucleus. Forty pM gastrin-17 (O; n = 7) or saline (O; n = 7) was injected into the nucleus. The arrow shows the time of injection. Values are the mean + S.E.M. a: P < 0.01 vs the value just before injection; and b-g: P < 0.01 vs saline injection.
I
II
III
IV
Fig. 3. Gastric acid output after gastrin-17 injection into two different regions of the hypothalamus. Forty pM gastrin-I7 was injected into the paraventricular nucleus (II), into the Iateral hypothalamic areas (III) and into both these regions simultaaeousty (IV). Control injection of saline was injected into both regions (I). The acid output 12 min after each injection was compared. There are 7 samples to each bar. Values are the mean + S.E.M. a: P < 0.01 vs I; b: P < 0.01 vs II; and c: P < 0.01 vs III.
327
A Effective
Sites
B
Ineffective
Sites 7.2
CO
,
6.6
6.0
5.4
4.8
4.2
1.0 mm
Fig. 4. Effective sites of injections in six rats (A) were in the vicinity of the paraventricular nucleus (PVN) or in the vicinity of the lateral hypothalamic areas (LHA). Ineffective sites (B) were far from these nuclei. Numbers in upper right corner of each panel indicate distances in millimeters from the vertical zero plane. AHA, anterior hypothalamic area; ARH, arcuate nucleus; CO, chiasma opticum; DMH, hypothalamic dorsomedial nucleus; FX, fornix; ML, lateral mamillary nucleus; MM, medial mamillary nucleus; MT, mamillothalamic tract; OT, optic tract; PH, posterior hypothalamic nucleus; PMD, dorsal premamillary nucleus; PMV, ventral premamillary nucleus; RE, reuniens nucleus; V, ventricle; VMH, ventromedial hypothalamic nucleus. the peptide seemed to be specific to gastrin, because the peptide effects were dose-dependent and CCK-8 had no effect on the acid output (Fig. 2). Chemically, it has been estimated that the normal concentration of gastrin in the PVN and neural lobe of the pituitary stalk which would come from the PVN was 8-30 pmol/g tissue ~'9. In this study, 3 different doses of the peptide were applied, and the threshold concentration was 20 pM (Fig. 2). It is not easy to estimate the physiologically acting concentration of the peptide. But, if gastrin were released locally onto the PVN neurons and they acted as neurotransmitters or neuromodulators, the concentration of the peptide near the cell body might be much higher than the threshold concentration. The stimulatory response in acid output caused by the PVN injection of gastrin-17 was abolished by subdia-
phragmatic vagotomy or by atropine sulfate, suggesting that the response was mediated by vagal and cholinergic fibers to the stomach (Fig. 2). Pentagastrin has the effect of a potent secretagogue on gastric acid secretion when injected into the systemic circulation 2, and its effect has been thought to be derived from direct activation of the parietal cells of the stomach 3. However, it should be remembered that pentagastrin injected into the systemic circulation penetrated the blood-brain barrier, and activated the cells producing gastric acid secretion within the brain. In the present study, 40 pM gastrin-17 potently stimulated acid output when injected into the PVN, whereas no significant change in the acid output was noted when the same dosage of the peptide was injected into the jugular vein or into the third ventricle (Fig. 2). These results could
328 eliminate the possibility that the peptide leaking from the brain tissue into the blood-stream or cerebrospinal fluid was active in the response. A significant increase in the acid output was obtained when 10-100 times larger doses of the peptide were injected into the vein or into the third ventricle (unpublished data). It appears that the stimulatory response in the acid output was attributable to localized activation of the PVN cells by gastrin-17 (Figs. 3 and 4). Gastric acid output was increased following gastrin-17 injection into the L H A (Figs. 3 and 4). This is consistent with the previous report that pentagastrin injected into the L H A enhanced gastric acid output 14. Considering that finding together with the fact that there was an additive increase in the acid output when gastrin-17 was
injected into the PVN and L H A simultaneously (~'ig. 3), it was suggested that this type of gastric acid secretion is characteristic of the PVN and L H A , separately or together. Further work needs to be done on characterization. Since gastrin has been identified in the hypothalamus, in the medulla oblongata and in the fibers of the vagus nerve 4'5'8'~5''~ it is considered that there is a gastrinergic pathway connecting the hypothalamus and the vagal nuclei and projecting to the stomach. These observations led us to speculate that gastrin is active in the vagal secretion of gastric acid at the hypothalamic PVN level.
1 Armin, J. and Grant, R.T., Adrenaline release during insulin hypoglycaemia in the rabbit, J. Physiol. (Lond.), 149 (1959) 228-249. 2 Barrett, A.M., Specific stimulation of gastric acid secretion by a pentapeptide derivative of gastrin, J. Pharm. Pharmac., 18 (1966) 633-639. 3 Davenport, H.W., Physiology of the Digestive tract, Year Book Medical Publishers Inc., Chicago, 1977. 4 Loren, I., Alumets, J., Hhkanson, R. and Sundler, E, Distribution of gastrin and CCK-like peptides in rat brain, Histochemistry, 59 (1979) 249-257. 5 Luiten, P,G,M., Ter Horst, G.J. and Steffens, A.B., The hypothalamus, intrinsic connections and outflow pathways to the endocrine system in relation to the control of feeding and metabolism, Prog. Neurobiol., 28 (1987) 1-54. 6 Ohtake, M. and Sakaguchi, T., Inhibition of gastric acid secretion evoked by activation of the hypothalamic paraventricular nucleus, Exp. Brain Res., 66 (1987) 222-224. 7 Pellegrino, L.J., Pellegrino, A.S. and Cushman, A.J., A Stereotaxic Atlas" of the Rat Brain, Plenum, New York, 1979. 8 Rehfeld, J.E, Localization of gastrins to neuro- and adenohypophysis, Nature (Lond.), 271 (1978) 771-773. 9 Rehfeld, J.F., Hansen, H.E, Larsson, L.-I., Stengaard-Pedersen, K. and Thorn, N.A., Gastrin and cholecystokinin in
pituitary neurons, Proc, Natl. Acad. Sci. U.S.A., 81 (1984) 1902-1905. 10 Sakaguchi, T., Alterations in gastric acid secretion following hepatic portal injections of D-glucose and its anomers, 3. Auton. Nerv. Syst., 5 (1982) 337-344. 11 Sakaguchi, T. and Bray, G.A., Intrahypothalamic injection of insulin decreases firing rate of sympathetic nerves, Proc. Natl. Acad. Sci. U.S.A., 84 (1987) 2012-2014. 12 Sakaguchi, T. and Sato, Y., D-Glucose anomers in the nucleus of the tractus solitarius can reduce gastric acid secretion of rats, Exp. Neurol., 95 (1987) 525-529. 13 Sakaguchi, T. and Yamaguchi, K., Effects of vagal stimulation, vagotomy and adrenalectomy on release of insulin in the rat; J. Endocrinol., 85 (1980) 131-136. 14 Tepperman, B.L. and Evered, M.D., Gastrin injected into the lateral hypothalamus stimulates secretion of gastric acid in rats, Science, 209 (1980) 1142-1143. 15 Uvn~is-Wallensten, K., Rehfeld, J.E, Larsson, L.-I. and Uvn~is, B., Heptadecapeptide gastrin in the vagal nerve, Proc. Natl. Acad. Sci. U.S.A., 74 (1977) 5707-5710. 16 Vanderhaeghen, J.J., Lotstra, E, De Mey, J. and Gilles, C., Immunohistochemical localization of cholecystokinin- and gastrin-like peptides in the brain and hypophysis of the rat, Proc. Natl. Acad. Sci. U.S.A., 77 (1980) 1190-1194.
This study was supported by Grant 63570077 from the Ministry of Education, Science and Culture of Japan.
