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Inhibition of gastric motility induced by activation of the hypothalamic paraventricular nucleus
Brain Research, 335 (1985) 365-367 Elsevier
365
BRE 20832
Inhibition of gastric motility induced by activation of the hypothalamic paraventricular nucleus TAKEO SAKAGUCHI and MASAHIRO OHTAKE
Department of Physiology, Niigata University School of Medicine, Niigata 951 (Japan) (Accepted January 3rd, 1985)
Key words: gastric motility - - glucose - - neurohypophysis - - paraventricular nucleus - - pituitary stalk - - vagus nerve
Electrical stimulation of the paraventricular nucleus depressed the intragastric pressure of adrenalectomized male rats of which gastric movement had been induced by insulin-hypoglycemia. Electrical stimulation to the pituitary stalk produced a similar response in the pressure, but the response was abolished by bilateral lesion of the paraventricular nucleus. These findings allow us to speculate that the paraventricular nucleus is capable of modulating gastric motility, and suggest that the nucleus has a neural connection between the neurohypophysis and the system relevant to visceral function. Anatomical studies have revealed that the paraventricular nucleus (PVN) projects not only to the neurohypophysis but also to the dorsal vagal complex (DVC) 7,12-14,16. This finding has been supported by recent electrophysiological works, where the electrical properties of PVN were identified4,19. Moreover, it has been shown that electrical stimulation of the pituitary stalk causes activation of PVN antidromically6. On the other hand, it has been well documented that changes in glucose concentration in the blood vagally control gastric motility via a central mechanism receptive to glucosel,8, 9. However, reports concerning the functional correlations between PVN and D V C which would participate in autonomic functions are few in number4,18, and the relation of PVN to gastric motility has not yet been examined. We report here that electrical stimulation of PVN or the pituitary stalk stimulation influences motility of the stomach in a rat to prove that the latter activates PVN. Thirty-nine male Wistar rats weighing from 250 to 300 g were used. They were fed on standard diet with tap water. A stimulating electrode was implanted on the paraventricular nucleus (PVN) or the pituitary stalk; a side-by-side electrode of stainless steel wire implanted and fixed to the skull with dental cement 6 - 9 days prior to the gastric experiment. Electrodes for electrolytic lesion (a 10% iridium-platinum electrode
178 ktm thick coated with Teflon except for the cut tip) of PVN were also implanted at the same time. In some animals, hypophysectomy with implantation of the stainless electrode was accomplished. After the operative treatment, the animals were housed individually. Twenty-two h before the gastric experiment, they were deprived of food, but allowed free access to tap water. The animals were anesthetized with pentobarbital sodium (45 mg/kg, i.p.) following pethidine hydrochloride (0.5 mg/kg, i.m.), and the depth of anesthesia was maintained by the same agent (7.5 mg/kg, i.m.), given at 30 min intervals. The anesthetized animals were further adrenalectomized bilaterally about 30 min before gastric experiment to preclude intrinsic fluctuations in plasma concentrations of glucose and insulin 10. The motility of the stomach was evaluated by changes in intragastric pressure using the balloon method s, that is, a polyethylene tube with a small balloon at its end was introduced into the stomach through the esophagus and filled with warm water. The pressure was measured with a strain-gauze manometer and adjusted to 0.78-0.98 kPa at the beginning of recording. Regular insulin (Novo, 42 #g/kg/h) was administered through a catheter in the jugular vein. Blood for glucose estimation was drawn from the same catheter. A train of square pulses of 0.5 ms width and 0.5
Correspondence: T. Sakaguchi, Department of Physiology, Niigata University School of Medicine, Niigata 951, Japan. 0006-8993/85/$03.30 © 1985 Elsevier Science Publishers B.V. (Biomedical Division)
366
2.5 0
PS, 30Hz
PS, 60Hz
PS, PS, 90Hz120Hz
~.,-~ 3.0 ~= 4.0 1
,., o. ~: 2.0
•.-'-
1.0
-
0
'3 rain'
Fig. 1. An example of suppression of periodic gastric movements by electrical stimulation of the paraventricular nucleus (PS) with different frequencies in rats with insulin-hypoglycemia. Arrows indicate the time at which electrical stimulation was applied. Stimulus intensity was 0.5 mA. m A intensity was repeatedly given in various frequencies for 5 s. Bilateral electrolytic lesions of PVN were performed after mass potential of PVN by the stalk stimulation was oscilloscopically identified; 1 m A of anodal current was passed for 15 s. The location and extent of the lesion were later confirmed with frozen sections after cresyl violet stain. Plasma concentrations of glucose were determined by the method of Salomon and Johnson u. Statistical significance of differences between means were established by t-test. The enhanced pressure associated with insulin-hypoglycemia was effectively decreased by the paraventricular stimulations (Fig. 1). The response was characterized by the frequencies; although electrical frequencies of 5, 15, 30 and 120 Hz produced no significant change in the pressure, 60 and 90 Hz applications were effective, and the 60 Hz stimulation was most potent (Fig. 2A). Similar responses were ob-
~" "'~' 1,0 2'0 l ° 2=
0
~..
served following the pituitary stalk ,,timulation (Fig. 2B). The lesion of PVN (n = 5), as well as i~ypophysectomy (n = 3), precluded the changes by the stalk stimulation. Histologically, the lesion of PVN included the magnocellular regions, but spared the ventromedial nucleus and the lateral hypothalamic areas (Fig. 3). Throughout the stimulation experiments, plasma concentrations of glucose were 3.44 ± 0.12 mM (n = 118). The present results demonstrated for the first time that PVN may participate in the control of gastric motility. Electrical stimulation applied to PVN produced a decrease in intragastric pressure (Fig. 1). The optimal frequency of 60 Hz to elicit the maximum response in the gastric pressure (Fig. 2A) was in the close range to cause full activation of neurosecretory PVN cells and oxytocin release2,3,~L As iontophoretic application of oxytocin inhibited medullary neurons 5 and oxytocinergic projections to the dorsal vagal complex (DVC) have been established in many reports 7,12-16, it is assumed, in this case, that such neural projections are concerned. The pituitary stalk stimulation also suppressed intragastric pressure (Fig. 2B). It could be interpreted
OT,
O/~-~P
V
_I (mi.)
(rnln)
Fig. 2. Changes in intragastric pressure in response to the paraventricular (A) and the pituitary stalk (B) stimulations. Thirty (C), n = 12), 60 (11, n = 12) and 90 (O, n = 14) Hz stimulations were applied for 5 s. Values are means + S.E.M. *P < 0.01 and **P < 0.002: significantly different from the value immediately before stimulation.
Fig. 3. Composite diagrams of lesions in the paraventricular nucleus (PV) from 5 rats shown in the frontal plane of the hypothalamus. DM, dorsomedial nucleus; FX, fornix; OT, optic tract; RE, nucleus reuniens thalami; SO, supraoptic nucleus; VM, ventromedial nucleus; VIII, third ventricle.
367 that the stalk stimulation affected D V C directly
cleus in the neighboring regions have been known to
through axonal branches, especially since magnocellular PVN cells have b e e n shown to have divergent
activate PVN antidromically15,'8.
axons to both the neurohypophysis and the medulla by either double-labeling methods 14 or antidromic
ist in PVN, definite relation between gastric motility
activation techniques4.19. The abolition of the effect in the PVN-lesioned or the hypophysectomized animals indicated that there was not the current spread to other areas of the hypo-
Although several peptides have been shown to exand the peptides needs further research. The authors are deeply grateful to Dr. Y. Sakuma and Dr. T. Akaishi for their valuable suggestions and to Mr. K. Kunihara for his assistance.
thalamus since the median e m i n e n c e or arcuate nu-
1 Bachrach, W. H., Action of insulin hypoglycemia on motor and secretory functions of the digestive tract, Physiol. Rev., 33 (1953) 566-592. 2 Dyball, R. E. J., Oxytocin and ADH secretion in relation to electrical activity in antidromically identified supraoptic and paraventricular units, J. Physiol. (Lond.), 214 (1971) 245-256. 3 Jones, P. M., Robinson, I. C. A. F. and Harris, M. C., Release of oxytocin into blood and cerebrospinal fluid by electrical stimulation of the hypothalamus or neural lobe in the rat, Neuroendocrinology, 37 (1983) 454-458. 4 Kannan, H. and Yamashita, H., Electrophysiological study of paraventricular nucleus neurons projecting to the dorsomedial medulla and their response to baroreceptor stimulation in rats, Brain Research, 279 (1983) 31-40. 5 Morris, R., Salt, T. E., Sofroniew, M. V. and Hill, R. G., Actions of microiontophoretically applied oxytocin, and immunohistochemical localization of oxytocin, vasopressin and neurophysin in the rat caudal medulla, Neurosci. Lett., 18 (1980) 163-168. 6 Negoro, H. and Akaishi, T., Interaction of hypertonic NaC1, hemorrhage and angiotensin II in stimulating paraventricular neurosecretory cells in the rat, Exp. Brain Res., 48 (1982) 121-126. 7 Nilaver, G., Zimmerman, E. A., Wilkins, J., Michaels, J., Hoffman, D. and Silverman, A.-J., Magnocellular hypothalamic projections to the lower brain stem and spinal cord of the rat, Neuroendocrinology, 30 (1980) 150-158. 8 Sakaguchi, T. and Shimojo, E., Inhibition of gastric motility induced by hepatic portal injections of D-glucose and its anomers, J. Physiol. (Lond.), 351 (1984) 573-581. 9 Sakaguchi, T., Taguchi, T. and Okuda, J., Different effects of D-glucose anomers on enhanced motility of the stomach, Biochem. Int., 7 (1983) 299-305. 10 Sakaguchi, T. and Yamaguchi, K., Effects of vagal stimulation, vagotomy and adrenalectomy on release of insulin in the rat, J. Endocr., 85 (1980) 131-136.
11 Salomon, L. L. and Johnson, J. E., Enzymatic microdeterruination of glucose in blood and urine, Analyt. Chem., 31 (1959) 453-456. 12 Saper, C. B., Loewy, A. D., Swanson, L. W. ancl Cowan, W. M., Direct hypothalamo-autonomic connections, Brain Research, 117 (1976) 305-312. 13 Sawchenko, P. E. and Swanson, L. W., Central noradrenergic pathways for the integration of hypothalamic neuroendocrine and autonomic responses, Science, 214 (1981) 685-687. 14 Swanson, L. W. and Kuypers, H. G. J. M., The paraventricular nucleus of the hypothalamus: cytoarchitectonic subdivisions and organization of projections to the pituitary, dorsal vagal complex, and spinal cord as demonstrated by retrograde fluorescence double-labeling methods, J. comp. Neurol., 194 (1980) 555-570. 15 Swanson, L. W. and Sawchenko, P. E., Hypothalamic integration: organization of the paraventricular and supraoptic nuclei, Ann. Rev. Neurosci., 6 (1983)269-324. 16 Sofroniew, M. V., Morphology of vasopressin and oxytocin neurones and their central and vascular projections, Progr. Brain Res., 60 (1983) 101-114. 17 Sofroniew, M. V. and Schrell, U., Evidence for a direct projection from oxytocin and vasopressin neurons in the hypothalamic paraventricular nucleus to the medulla oblongata: Immunohistochemical visualization of both the horseradish peroxidase transported and the peptide produced by the same neurons, Neurosci. Lett., 22 (1981) 211-217. 18 Yamashita, H., Kannan, H., Inenaga, K. and Koizumi. K.. Role of neurones in the supraoptic and paraventricular nuclei in cardiovascular control, Progr. Brain Res., 60 (1983) 459-468. 19 Zerihun, L. and Harris, M., An electrophysiological analysis of caudally-projecting neurones from the hypothalamic paraventricular nucleus in the rat, Brain Research, 261 (1983) 13-20.
365
BRE 20832
Inhibition of gastric motility induced by activation of the hypothalamic paraventricular nucleus TAKEO SAKAGUCHI and MASAHIRO OHTAKE
Department of Physiology, Niigata University School of Medicine, Niigata 951 (Japan) (Accepted January 3rd, 1985)
Key words: gastric motility - - glucose - - neurohypophysis - - paraventricular nucleus - - pituitary stalk - - vagus nerve
Electrical stimulation of the paraventricular nucleus depressed the intragastric pressure of adrenalectomized male rats of which gastric movement had been induced by insulin-hypoglycemia. Electrical stimulation to the pituitary stalk produced a similar response in the pressure, but the response was abolished by bilateral lesion of the paraventricular nucleus. These findings allow us to speculate that the paraventricular nucleus is capable of modulating gastric motility, and suggest that the nucleus has a neural connection between the neurohypophysis and the system relevant to visceral function. Anatomical studies have revealed that the paraventricular nucleus (PVN) projects not only to the neurohypophysis but also to the dorsal vagal complex (DVC) 7,12-14,16. This finding has been supported by recent electrophysiological works, where the electrical properties of PVN were identified4,19. Moreover, it has been shown that electrical stimulation of the pituitary stalk causes activation of PVN antidromically6. On the other hand, it has been well documented that changes in glucose concentration in the blood vagally control gastric motility via a central mechanism receptive to glucosel,8, 9. However, reports concerning the functional correlations between PVN and D V C which would participate in autonomic functions are few in number4,18, and the relation of PVN to gastric motility has not yet been examined. We report here that electrical stimulation of PVN or the pituitary stalk stimulation influences motility of the stomach in a rat to prove that the latter activates PVN. Thirty-nine male Wistar rats weighing from 250 to 300 g were used. They were fed on standard diet with tap water. A stimulating electrode was implanted on the paraventricular nucleus (PVN) or the pituitary stalk; a side-by-side electrode of stainless steel wire implanted and fixed to the skull with dental cement 6 - 9 days prior to the gastric experiment. Electrodes for electrolytic lesion (a 10% iridium-platinum electrode
178 ktm thick coated with Teflon except for the cut tip) of PVN were also implanted at the same time. In some animals, hypophysectomy with implantation of the stainless electrode was accomplished. After the operative treatment, the animals were housed individually. Twenty-two h before the gastric experiment, they were deprived of food, but allowed free access to tap water. The animals were anesthetized with pentobarbital sodium (45 mg/kg, i.p.) following pethidine hydrochloride (0.5 mg/kg, i.m.), and the depth of anesthesia was maintained by the same agent (7.5 mg/kg, i.m.), given at 30 min intervals. The anesthetized animals were further adrenalectomized bilaterally about 30 min before gastric experiment to preclude intrinsic fluctuations in plasma concentrations of glucose and insulin 10. The motility of the stomach was evaluated by changes in intragastric pressure using the balloon method s, that is, a polyethylene tube with a small balloon at its end was introduced into the stomach through the esophagus and filled with warm water. The pressure was measured with a strain-gauze manometer and adjusted to 0.78-0.98 kPa at the beginning of recording. Regular insulin (Novo, 42 #g/kg/h) was administered through a catheter in the jugular vein. Blood for glucose estimation was drawn from the same catheter. A train of square pulses of 0.5 ms width and 0.5
Correspondence: T. Sakaguchi, Department of Physiology, Niigata University School of Medicine, Niigata 951, Japan. 0006-8993/85/$03.30 © 1985 Elsevier Science Publishers B.V. (Biomedical Division)
366
2.5 0
PS, 30Hz
PS, 60Hz
PS, PS, 90Hz120Hz
~.,-~ 3.0 ~= 4.0 1
,., o. ~: 2.0
•.-'-
1.0
-
0
'3 rain'
Fig. 1. An example of suppression of periodic gastric movements by electrical stimulation of the paraventricular nucleus (PS) with different frequencies in rats with insulin-hypoglycemia. Arrows indicate the time at which electrical stimulation was applied. Stimulus intensity was 0.5 mA. m A intensity was repeatedly given in various frequencies for 5 s. Bilateral electrolytic lesions of PVN were performed after mass potential of PVN by the stalk stimulation was oscilloscopically identified; 1 m A of anodal current was passed for 15 s. The location and extent of the lesion were later confirmed with frozen sections after cresyl violet stain. Plasma concentrations of glucose were determined by the method of Salomon and Johnson u. Statistical significance of differences between means were established by t-test. The enhanced pressure associated with insulin-hypoglycemia was effectively decreased by the paraventricular stimulations (Fig. 1). The response was characterized by the frequencies; although electrical frequencies of 5, 15, 30 and 120 Hz produced no significant change in the pressure, 60 and 90 Hz applications were effective, and the 60 Hz stimulation was most potent (Fig. 2A). Similar responses were ob-
~" "'~' 1,0 2'0 l ° 2=
0
~..
served following the pituitary stalk ,,timulation (Fig. 2B). The lesion of PVN (n = 5), as well as i~ypophysectomy (n = 3), precluded the changes by the stalk stimulation. Histologically, the lesion of PVN included the magnocellular regions, but spared the ventromedial nucleus and the lateral hypothalamic areas (Fig. 3). Throughout the stimulation experiments, plasma concentrations of glucose were 3.44 ± 0.12 mM (n = 118). The present results demonstrated for the first time that PVN may participate in the control of gastric motility. Electrical stimulation applied to PVN produced a decrease in intragastric pressure (Fig. 1). The optimal frequency of 60 Hz to elicit the maximum response in the gastric pressure (Fig. 2A) was in the close range to cause full activation of neurosecretory PVN cells and oxytocin release2,3,~L As iontophoretic application of oxytocin inhibited medullary neurons 5 and oxytocinergic projections to the dorsal vagal complex (DVC) have been established in many reports 7,12-16, it is assumed, in this case, that such neural projections are concerned. The pituitary stalk stimulation also suppressed intragastric pressure (Fig. 2B). It could be interpreted
OT,
O/~-~P
V
_I (mi.)
(rnln)
Fig. 2. Changes in intragastric pressure in response to the paraventricular (A) and the pituitary stalk (B) stimulations. Thirty (C), n = 12), 60 (11, n = 12) and 90 (O, n = 14) Hz stimulations were applied for 5 s. Values are means + S.E.M. *P < 0.01 and **P < 0.002: significantly different from the value immediately before stimulation.
Fig. 3. Composite diagrams of lesions in the paraventricular nucleus (PV) from 5 rats shown in the frontal plane of the hypothalamus. DM, dorsomedial nucleus; FX, fornix; OT, optic tract; RE, nucleus reuniens thalami; SO, supraoptic nucleus; VM, ventromedial nucleus; VIII, third ventricle.
367 that the stalk stimulation affected D V C directly
cleus in the neighboring regions have been known to
through axonal branches, especially since magnocellular PVN cells have b e e n shown to have divergent
activate PVN antidromically15,'8.
axons to both the neurohypophysis and the medulla by either double-labeling methods 14 or antidromic
ist in PVN, definite relation between gastric motility
activation techniques4.19. The abolition of the effect in the PVN-lesioned or the hypophysectomized animals indicated that there was not the current spread to other areas of the hypo-
Although several peptides have been shown to exand the peptides needs further research. The authors are deeply grateful to Dr. Y. Sakuma and Dr. T. Akaishi for their valuable suggestions and to Mr. K. Kunihara for his assistance.
thalamus since the median e m i n e n c e or arcuate nu-
1 Bachrach, W. H., Action of insulin hypoglycemia on motor and secretory functions of the digestive tract, Physiol. Rev., 33 (1953) 566-592. 2 Dyball, R. E. J., Oxytocin and ADH secretion in relation to electrical activity in antidromically identified supraoptic and paraventricular units, J. Physiol. (Lond.), 214 (1971) 245-256. 3 Jones, P. M., Robinson, I. C. A. F. and Harris, M. C., Release of oxytocin into blood and cerebrospinal fluid by electrical stimulation of the hypothalamus or neural lobe in the rat, Neuroendocrinology, 37 (1983) 454-458. 4 Kannan, H. and Yamashita, H., Electrophysiological study of paraventricular nucleus neurons projecting to the dorsomedial medulla and their response to baroreceptor stimulation in rats, Brain Research, 279 (1983) 31-40. 5 Morris, R., Salt, T. E., Sofroniew, M. V. and Hill, R. G., Actions of microiontophoretically applied oxytocin, and immunohistochemical localization of oxytocin, vasopressin and neurophysin in the rat caudal medulla, Neurosci. Lett., 18 (1980) 163-168. 6 Negoro, H. and Akaishi, T., Interaction of hypertonic NaC1, hemorrhage and angiotensin II in stimulating paraventricular neurosecretory cells in the rat, Exp. Brain Res., 48 (1982) 121-126. 7 Nilaver, G., Zimmerman, E. A., Wilkins, J., Michaels, J., Hoffman, D. and Silverman, A.-J., Magnocellular hypothalamic projections to the lower brain stem and spinal cord of the rat, Neuroendocrinology, 30 (1980) 150-158. 8 Sakaguchi, T. and Shimojo, E., Inhibition of gastric motility induced by hepatic portal injections of D-glucose and its anomers, J. Physiol. (Lond.), 351 (1984) 573-581. 9 Sakaguchi, T., Taguchi, T. and Okuda, J., Different effects of D-glucose anomers on enhanced motility of the stomach, Biochem. Int., 7 (1983) 299-305. 10 Sakaguchi, T. and Yamaguchi, K., Effects of vagal stimulation, vagotomy and adrenalectomy on release of insulin in the rat, J. Endocr., 85 (1980) 131-136.
11 Salomon, L. L. and Johnson, J. E., Enzymatic microdeterruination of glucose in blood and urine, Analyt. Chem., 31 (1959) 453-456. 12 Saper, C. B., Loewy, A. D., Swanson, L. W. ancl Cowan, W. M., Direct hypothalamo-autonomic connections, Brain Research, 117 (1976) 305-312. 13 Sawchenko, P. E. and Swanson, L. W., Central noradrenergic pathways for the integration of hypothalamic neuroendocrine and autonomic responses, Science, 214 (1981) 685-687. 14 Swanson, L. W. and Kuypers, H. G. J. M., The paraventricular nucleus of the hypothalamus: cytoarchitectonic subdivisions and organization of projections to the pituitary, dorsal vagal complex, and spinal cord as demonstrated by retrograde fluorescence double-labeling methods, J. comp. Neurol., 194 (1980) 555-570. 15 Swanson, L. W. and Sawchenko, P. E., Hypothalamic integration: organization of the paraventricular and supraoptic nuclei, Ann. Rev. Neurosci., 6 (1983)269-324. 16 Sofroniew, M. V., Morphology of vasopressin and oxytocin neurones and their central and vascular projections, Progr. Brain Res., 60 (1983) 101-114. 17 Sofroniew, M. V. and Schrell, U., Evidence for a direct projection from oxytocin and vasopressin neurons in the hypothalamic paraventricular nucleus to the medulla oblongata: Immunohistochemical visualization of both the horseradish peroxidase transported and the peptide produced by the same neurons, Neurosci. Lett., 22 (1981) 211-217. 18 Yamashita, H., Kannan, H., Inenaga, K. and Koizumi. K.. Role of neurones in the supraoptic and paraventricular nuclei in cardiovascular control, Progr. Brain Res., 60 (1983) 459-468. 19 Zerihun, L. and Harris, M., An electrophysiological analysis of caudally-projecting neurones from the hypothalamic paraventricular nucleus in the rat, Brain Research, 261 (1983) 13-20.