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Central ANP attenuates pressor responses to central AVP in WKY and SHR
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Brain Research Bulletin, Vol. 27, pp. 247-249. 0 Pergamon Press pk. 1991. Printed in the U.S.A.
RAPID COMMUNICATION
Central ANP Attenuates Pressor Responses to Central AVP in WKY and SHR K. STEPNIAKOWSKI,* Department
A. BUDZIKOWSKI,
S. LON AND E. SZCZEPANSKA-SADOWSKA’
of Clinical and Applied Physiology and *Department of Hypertension Warsaw School of Medicine, 00-927 Warsaw, Poland
Received
29 April
and Angiology
199 I
STEPNIAKOWSKI, K., A. BUDZIKOWSKI, S. LON AND E. SZCZEPANSKA-SADOWSKA. Central ANP attenuates pressor responses to central AVP in WKY and SHR. BRAIN RES BULL 27(2) 247-249, 1991. -Blood pressure and heart rate responses to intracerebroventricular (ICV) injections of atria1 natriuretic peptide (ANP, 125 ng) arginine vasopressin (AVP, 10 ng), combination of ANP (125 ng) and AVP (10 ng) or artificial cerebrospinal fluid (acsf, 5 ~1) were compared in conscious normotensive (WKY) and spontaneously hypertensive (SHR) rats. In both strains, ICV injection of AVP elicited significant increase of mean blood pressure (MP) and heart rate (HR). Increase of MP but not of HR was significantly greater in SHR than in WKY @<0.05). Injection of acsf or ANP, as well as simultaneous administration of ANP and AVP, did not elicit significant changes of MP either in WKY or in SHR. In SHR, HR was significantly elevated by ICV injections of AVP and ANF + AVP, whereas in WKY HR was increased only after AVP. The data suggest that interaction of ANP and AVP at a central level may result in significant attenuation of central pressor effects of vasopressin. Atria1 natriuretic
peptide
Vasopressin
Central actions
Spontaneously
hypertensive
rats
h). They were fed with commercial
rat chow and had free access to water, except during the experiment. For implantation of intracerebroventricular (ICV) cannula the rats were anesthetized with chloral hydrate (3.6% solution, 0.8 ml/l00 g) 7-10 days prior the experiment. Stainless steel cannula with an outer diameter of 0.6 mm was implanted into the lateral ventricle according to the following parameters with respect to bregma: 1.5 mm posterior, 2.0 mm lateral, 5.0 mm deep from the surface of skull. The cannula was fixed in the skull with an acrylic cement. After surgery the animals were placed in individual experimental cages where they could move freely. The arterial catheter for blood pressure measurements was introduced into the femoral artery under light ether anesthesia 24-48 h before the experiment.
PRESENCE of vasopressin (AVP), atrial natriuretic peptide (ANP) and of their binding sites in the regions of the central nervous system involved in the blood pressure control (1, 3, 7, 16, 19) has drawn attention to the possibility that both peptides may participate in the central control of blood pressure. With this regard, central administration of vasopressin has been found to increase blood pressure (6,lO). On the other hand, most studies failed to demonstrate direct significant effects of centrally administered ANP on blood pressure; however, it was demonstrated that the latter peptide attenuated central pressor action of angiotensin II (2,5). The present study was aimed at elucidating whether ANP is able to affect central pressor action of AVP. Since blood pressure regulation is altered in spontaneously hypertensive animals (9) and because there are differences in density of ANP binding sites and AVP content in the central nervous system (8, 11, 14), we compared effects of central administration of ANP and of AVP in normotensive (WKY) and spontaneously hypertensive (SHR) rats.
Central Injections Central injections of vehicle or peptides were made by means of the injector introduced into the ICV cannula and connected with Hamilton microsyringe. The rate of injection was 5 $/lo s. Atria1 natriuretic peptide (rat-28 ANP, 250 ng Peninsula), vasopressin (arginine-8-vasopressin, Calbiochem 10 ng) or combination of both peptides (250 ng ANP + 10 ng AVP) freshly dissolved in 5 ~1 of artificial cerebrospinal fluid (acsf) were administered. The composition of the acsf was (in mM): 124.0 NaCl, 3.0 KCl, 1.3 CaCl,, 0.8 MgCl,, 25.0 NaHCO,, 0.5 Na,HPO,, and 0.5 NaH,PO,.
METHOD
Animals and Surgical Procedures Experiments were performed on 10 normotensive and 10 spontaneously hypertensive rats. The animals were maintained under conditions of 12 h/12 h light cycle (light on 0700 to 1900
‘Requests for reprints should be addressed to Ewa Szczepanska-Sadowska, Medical College of Wisconsin, town Plank Road, Milwaukee, WI 53226, c/o Professor Alan W. Cowley, Jr. 247
Department
of Physiology,
8701 Water-
STEPNIAKOWSKI
EP .41
-10 acsf
125
ng
AN’
10
ng
AVP
AFP+AW
FIG. 1, Mean blood pressure changes after intracerebroventricular injection of acsf, 125 ng ANP, 10 ng AVP and 125 ng ANP + 10 ng AVP in WKY and SHR rats. *Significant difference from control at the level of **p
Experimental Design and Measurements The experiments were performed while the animals were conscious and freely moving in the experimental cages. The arterial catheter was connected to a Gould Statham transducer (P23Db). The amplified signal was frequency modulated with analog to digital converter connected through an interface to Amstrad-Schneider CPC 6128 for calculation on line of mean (MP), systolic (SP) and diastolic (DP) blood pressures and heart rate period (HRp). Thirty min were allowed for blood pressure and heart rate equilibration. Subsequently, the animals were ICV injected with vehicle (acsf), ANP, AVP or ANP and AVP at 40-min intervals. Subsequent central injections were made when MP and HRp have returned to the resting level found at the onset of the experiment. Means 2 standard errors are presented in this study. One-way and factorial analysis of variance followed by Newman-Keuls a posteriori test were used to isolate significant differences, when appropriate. The results were considered to be significant if p
In agreement with other studies, the present investigation demonstrates significant increase of blood pressure and heart rate
acsf
125
ng
A19
10
r-q
AVP
Af-P+AW
FIG. 2. Heart rate changes after intracerebroventricular injection of acsf, 125 ng ANP, 10 ng AVP and 125 ng ANP + 10 ng AVP in WKY and SHR rats. *Significant difference from the control at the level of *p
INTERACTION OF ANP AND AVP
249
ACKNOWLEDGEMENTS The authors wish to thank Calbiochem-Behring Corp. for the generous gift of arginine’vasopressin. The generous gift of rat ANP was obtained from Peninsula Inc., thanks to the courtesy of Dr. Andrzej Januszewicz of the Department of Hypertension and Angiology (Warsaw School of Medicine).
REFERENCES 1. Buijs, R. M. Vasopressin localization and putative functions in the brain. In: Gash, M.; Boer G. J., eds. Vasopressin, principles and properties. New York: Plenum Press; 1987:91-115. 2. Casto, R.; Hilbig, J.; Schroeder, G.; Stock, G. Atria1 natriuretic factor inhibits central angiotensin II pressor responses. Hypertension 9475-477; 1987. 3. Gardner, D. G.; Vlasuk, G. P.; Baxter, J. D.; Fiddes, J. C.; Lewicki, J. A. Identification of atria1 natriuretic factor gene transcripts in the central nervous system of the rat. Proc. Natl. Acad. Sci. USA 84:2175-2179; 1987. 4. Haack, D.; Mohring, J. Vasopressin-mediated blood pressure response to intraventricular injections of angiotensin II in the rat. Pflugers Arch. 373:167-173; 1987. 5. Itoh, H.; Nakao, K.; Morii, N.; Yamadon, T.; Shiono, S.; Sakamoto, M.; Sugawara, A.; Saito, Y.; Katsuura, G.; Shiomi, T.; Eigyo, M.; Matsushita, A.; Imura, M. Central actions of atrial natriuretic polypeptide on blood pressue in conscious rats. Brain Res. Bull. 15:745-769; 1986. 6. Janiak, B.; Kasson, B. G.; Brody, M. J. Central vasopressin raises arterial pressure by sympathetic activation and vasopressin release. Hypertension 13:935-940; 1989. 7. Mantych, Ch. R.; Kruger, L.; Brecha, N. C.; Mantych, P. W. Localization of specific binding sites for atria1 natriuretic factor in the central nervous system of rat, guinea pig, cat and humans. Brain Res. 412:329-342; 1987. 8. Mohring, J.; Schoun, J.; Kintz, J.; McNeil, R. Decreased vasopressin content in the brain stem of rats with spontaneous hypertension. Naunyn Schmiedebergs Arch. Pharrnacol. 315:83-84; 1980. 9. No&a, S.; Wang, S. C. Carotid sinus baroreceptor functions in the spontaneously hypertensive rat. Am. J. Physiol. 222:1079-1098; 1972. 10. Pittman, Q. J.; Lawrence, D.; McLean, L. Central effects of arginine vasopressin on blood pressure in rats. Endocrinology 110:1058-
1060; 1982.
11. Rascher, W.; Lang, R. E.; Unger, T.; Ganten, D.; Gross, F. Vaso12.
13.
14.
15. 16.
17. 18.
19.
pressin in brain of spontaneously hypertensive rats. Am. J. Physiol. 242:H496-H499; 1982. Riphagen, C. L.; Pittman, Q. J. Mechanisms underlying the cardiovascular responses to intrathecal vasopressin administration in the rat. Can. J. Physiol. Pharmacol. 67:269-275; 1989. Rohmeiss, P.; Becker, H.; Dietrich, R.; Luft, F.; Unger, T. Vasopressin: Mechanism of central cardiovascular action in conscious rats. J. Cardiovasc. Pharmacol. 8:689496; 1986. Saavedra, J. M.; Israel, A.; Kurihara, M.; Fuchs, E. Decreased number and affinity of atrial natriuretic peptide (6-33) binding sites in the subfomical organ of spontaneously hypertensive rats. Circ. Res. 58:389-392; 1986. Samson, W. K. Central nervous system actions of atria1 natriuretic factor Brain Res. Bull. 20:831-837; 1988. Saper, C. B.; Standaert, D. G.; Currtie, M. G.; Schwartz, D.; Geller, D. M.; Needleman, P. Atriopeptin-immunoreactive neurons in the brain: presence in cardiovascular regulatory areas. Science 227:1047-1049; 1985. Severs, W. B.; Daniels-Severs, A. E. Effects of angiotensin on the central nervous system. Pharmacol. Rev. 24:41549; 1973. Szczepanska-Sadowska, E.; Wocial, B.; Sobocinska, J.; KowalikBorowka, E. Central effects of atria1 natriuretic peptide on plasma catecholamines, vasopressin, renin and beta-endorphin and on renal excretory functions in the dog. Horm. Metab. Res. 22:323-328; 1990. Tribollet, E.; Barberise, C.; Jard, S.; Dubois-Dauphin, M.; Dreifuss, J. J. Localization and pharmacological characterization of high affinity binding sites for vasopressin and oxytocin in the rat brain by light microscopic autoradiography. Brain Res. 442: 105118: 1988.
Brain Research Bulletin, Vol. 27, pp. 247-249. 0 Pergamon Press pk. 1991. Printed in the U.S.A.
RAPID COMMUNICATION
Central ANP Attenuates Pressor Responses to Central AVP in WKY and SHR K. STEPNIAKOWSKI,* Department
A. BUDZIKOWSKI,
S. LON AND E. SZCZEPANSKA-SADOWSKA’
of Clinical and Applied Physiology and *Department of Hypertension Warsaw School of Medicine, 00-927 Warsaw, Poland
Received
29 April
and Angiology
199 I
STEPNIAKOWSKI, K., A. BUDZIKOWSKI, S. LON AND E. SZCZEPANSKA-SADOWSKA. Central ANP attenuates pressor responses to central AVP in WKY and SHR. BRAIN RES BULL 27(2) 247-249, 1991. -Blood pressure and heart rate responses to intracerebroventricular (ICV) injections of atria1 natriuretic peptide (ANP, 125 ng) arginine vasopressin (AVP, 10 ng), combination of ANP (125 ng) and AVP (10 ng) or artificial cerebrospinal fluid (acsf, 5 ~1) were compared in conscious normotensive (WKY) and spontaneously hypertensive (SHR) rats. In both strains, ICV injection of AVP elicited significant increase of mean blood pressure (MP) and heart rate (HR). Increase of MP but not of HR was significantly greater in SHR than in WKY @<0.05). Injection of acsf or ANP, as well as simultaneous administration of ANP and AVP, did not elicit significant changes of MP either in WKY or in SHR. In SHR, HR was significantly elevated by ICV injections of AVP and ANF + AVP, whereas in WKY HR was increased only after AVP. The data suggest that interaction of ANP and AVP at a central level may result in significant attenuation of central pressor effects of vasopressin. Atria1 natriuretic
peptide
Vasopressin
Central actions
Spontaneously
hypertensive
rats
h). They were fed with commercial
rat chow and had free access to water, except during the experiment. For implantation of intracerebroventricular (ICV) cannula the rats were anesthetized with chloral hydrate (3.6% solution, 0.8 ml/l00 g) 7-10 days prior the experiment. Stainless steel cannula with an outer diameter of 0.6 mm was implanted into the lateral ventricle according to the following parameters with respect to bregma: 1.5 mm posterior, 2.0 mm lateral, 5.0 mm deep from the surface of skull. The cannula was fixed in the skull with an acrylic cement. After surgery the animals were placed in individual experimental cages where they could move freely. The arterial catheter for blood pressure measurements was introduced into the femoral artery under light ether anesthesia 24-48 h before the experiment.
PRESENCE of vasopressin (AVP), atrial natriuretic peptide (ANP) and of their binding sites in the regions of the central nervous system involved in the blood pressure control (1, 3, 7, 16, 19) has drawn attention to the possibility that both peptides may participate in the central control of blood pressure. With this regard, central administration of vasopressin has been found to increase blood pressure (6,lO). On the other hand, most studies failed to demonstrate direct significant effects of centrally administered ANP on blood pressure; however, it was demonstrated that the latter peptide attenuated central pressor action of angiotensin II (2,5). The present study was aimed at elucidating whether ANP is able to affect central pressor action of AVP. Since blood pressure regulation is altered in spontaneously hypertensive animals (9) and because there are differences in density of ANP binding sites and AVP content in the central nervous system (8, 11, 14), we compared effects of central administration of ANP and of AVP in normotensive (WKY) and spontaneously hypertensive (SHR) rats.
Central Injections Central injections of vehicle or peptides were made by means of the injector introduced into the ICV cannula and connected with Hamilton microsyringe. The rate of injection was 5 $/lo s. Atria1 natriuretic peptide (rat-28 ANP, 250 ng Peninsula), vasopressin (arginine-8-vasopressin, Calbiochem 10 ng) or combination of both peptides (250 ng ANP + 10 ng AVP) freshly dissolved in 5 ~1 of artificial cerebrospinal fluid (acsf) were administered. The composition of the acsf was (in mM): 124.0 NaCl, 3.0 KCl, 1.3 CaCl,, 0.8 MgCl,, 25.0 NaHCO,, 0.5 Na,HPO,, and 0.5 NaH,PO,.
METHOD
Animals and Surgical Procedures Experiments were performed on 10 normotensive and 10 spontaneously hypertensive rats. The animals were maintained under conditions of 12 h/12 h light cycle (light on 0700 to 1900
‘Requests for reprints should be addressed to Ewa Szczepanska-Sadowska, Medical College of Wisconsin, town Plank Road, Milwaukee, WI 53226, c/o Professor Alan W. Cowley, Jr. 247
Department
of Physiology,
8701 Water-
STEPNIAKOWSKI
EP .41
-10 acsf
125
ng
AN’
10
ng
AVP
AFP+AW
FIG. 1, Mean blood pressure changes after intracerebroventricular injection of acsf, 125 ng ANP, 10 ng AVP and 125 ng ANP + 10 ng AVP in WKY and SHR rats. *Significant difference from control at the level of **p
Experimental Design and Measurements The experiments were performed while the animals were conscious and freely moving in the experimental cages. The arterial catheter was connected to a Gould Statham transducer (P23Db). The amplified signal was frequency modulated with analog to digital converter connected through an interface to Amstrad-Schneider CPC 6128 for calculation on line of mean (MP), systolic (SP) and diastolic (DP) blood pressures and heart rate period (HRp). Thirty min were allowed for blood pressure and heart rate equilibration. Subsequently, the animals were ICV injected with vehicle (acsf), ANP, AVP or ANP and AVP at 40-min intervals. Subsequent central injections were made when MP and HRp have returned to the resting level found at the onset of the experiment. Means 2 standard errors are presented in this study. One-way and factorial analysis of variance followed by Newman-Keuls a posteriori test were used to isolate significant differences, when appropriate. The results were considered to be significant if p
In agreement with other studies, the present investigation demonstrates significant increase of blood pressure and heart rate
acsf
125
ng
A19
10
r-q
AVP
Af-P+AW
FIG. 2. Heart rate changes after intracerebroventricular injection of acsf, 125 ng ANP, 10 ng AVP and 125 ng ANP + 10 ng AVP in WKY and SHR rats. *Significant difference from the control at the level of *p
INTERACTION OF ANP AND AVP
249
ACKNOWLEDGEMENTS The authors wish to thank Calbiochem-Behring Corp. for the generous gift of arginine’vasopressin. The generous gift of rat ANP was obtained from Peninsula Inc., thanks to the courtesy of Dr. Andrzej Januszewicz of the Department of Hypertension and Angiology (Warsaw School of Medicine).
REFERENCES 1. Buijs, R. M. Vasopressin localization and putative functions in the brain. In: Gash, M.; Boer G. J., eds. Vasopressin, principles and properties. New York: Plenum Press; 1987:91-115. 2. Casto, R.; Hilbig, J.; Schroeder, G.; Stock, G. Atria1 natriuretic factor inhibits central angiotensin II pressor responses. Hypertension 9475-477; 1987. 3. Gardner, D. G.; Vlasuk, G. P.; Baxter, J. D.; Fiddes, J. C.; Lewicki, J. A. Identification of atria1 natriuretic factor gene transcripts in the central nervous system of the rat. Proc. Natl. Acad. Sci. USA 84:2175-2179; 1987. 4. Haack, D.; Mohring, J. Vasopressin-mediated blood pressure response to intraventricular injections of angiotensin II in the rat. Pflugers Arch. 373:167-173; 1987. 5. Itoh, H.; Nakao, K.; Morii, N.; Yamadon, T.; Shiono, S.; Sakamoto, M.; Sugawara, A.; Saito, Y.; Katsuura, G.; Shiomi, T.; Eigyo, M.; Matsushita, A.; Imura, M. Central actions of atrial natriuretic polypeptide on blood pressue in conscious rats. Brain Res. Bull. 15:745-769; 1986. 6. Janiak, B.; Kasson, B. G.; Brody, M. J. Central vasopressin raises arterial pressure by sympathetic activation and vasopressin release. Hypertension 13:935-940; 1989. 7. Mantych, Ch. R.; Kruger, L.; Brecha, N. C.; Mantych, P. W. Localization of specific binding sites for atria1 natriuretic factor in the central nervous system of rat, guinea pig, cat and humans. Brain Res. 412:329-342; 1987. 8. Mohring, J.; Schoun, J.; Kintz, J.; McNeil, R. Decreased vasopressin content in the brain stem of rats with spontaneous hypertension. Naunyn Schmiedebergs Arch. Pharrnacol. 315:83-84; 1980. 9. No&a, S.; Wang, S. C. Carotid sinus baroreceptor functions in the spontaneously hypertensive rat. Am. J. Physiol. 222:1079-1098; 1972. 10. Pittman, Q. J.; Lawrence, D.; McLean, L. Central effects of arginine vasopressin on blood pressure in rats. Endocrinology 110:1058-
1060; 1982.
11. Rascher, W.; Lang, R. E.; Unger, T.; Ganten, D.; Gross, F. Vaso12.
13.
14.
15. 16.
17. 18.
19.
pressin in brain of spontaneously hypertensive rats. Am. J. Physiol. 242:H496-H499; 1982. Riphagen, C. L.; Pittman, Q. J. Mechanisms underlying the cardiovascular responses to intrathecal vasopressin administration in the rat. Can. J. Physiol. Pharmacol. 67:269-275; 1989. Rohmeiss, P.; Becker, H.; Dietrich, R.; Luft, F.; Unger, T. Vasopressin: Mechanism of central cardiovascular action in conscious rats. J. Cardiovasc. Pharmacol. 8:689496; 1986. Saavedra, J. M.; Israel, A.; Kurihara, M.; Fuchs, E. Decreased number and affinity of atrial natriuretic peptide (6-33) binding sites in the subfomical organ of spontaneously hypertensive rats. Circ. Res. 58:389-392; 1986. Samson, W. K. Central nervous system actions of atria1 natriuretic factor Brain Res. Bull. 20:831-837; 1988. Saper, C. B.; Standaert, D. G.; Currtie, M. G.; Schwartz, D.; Geller, D. M.; Needleman, P. Atriopeptin-immunoreactive neurons in the brain: presence in cardiovascular regulatory areas. Science 227:1047-1049; 1985. Severs, W. B.; Daniels-Severs, A. E. Effects of angiotensin on the central nervous system. Pharmacol. Rev. 24:41549; 1973. Szczepanska-Sadowska, E.; Wocial, B.; Sobocinska, J.; KowalikBorowka, E. Central effects of atria1 natriuretic peptide on plasma catecholamines, vasopressin, renin and beta-endorphin and on renal excretory functions in the dog. Horm. Metab. Res. 22:323-328; 1990. Tribollet, E.; Barberise, C.; Jard, S.; Dubois-Dauphin, M.; Dreifuss, J. J. Localization and pharmacological characterization of high affinity binding sites for vasopressin and oxytocin in the rat brain by light microscopic autoradiography. Brain Res. 442: 105118: 1988.