NEUROPEPTIDES

active avoidance response in rats ( 2 - 4 ) , i.e. both pep-tides w e r e e f f e c t i v e in the fear-motivated learning behavior o f rats.

T h e present study w a s undertaken to determine structure-activity relationships in the e f f e c t s o f A N P , B N P and their fragments o n fear-motivated learning behavior f o l l o w i n g i.c.v. administration.

T o enable a comparison o f the effects, the peptides w e r e u s e d in equimolar concentrations.

M a t e r i a l s a n d M e t h o d s Animals

T h e experiments w e r e performed on male C F Y rats (LATI Gödöllő, H) w e i g h i n g 1 5 0 - 2 5 0 g. T h e ani-mals xvere used 6 per c a g e at room temperature ( 2 0 - 2 1 °C). T h e y were kept in artificial 12-hour light (started at 6 a.m.), 12hour dark periods. C o m -mercial food and tap water were given ad libitum.

All observations were carried out b e t w e e n 8 a.m.

and 4 p.m.

Peptides

Rat A N P ( r A N P 1-28) w a s purchased from B a c h e m ( C A , U S A ) and also synthesized by G. Tóth. All the A N P fragments and the human A N P - 1 - 2 8 were also synthesized by a solid-phase technique, utilizing B o c (fert.-Butvloxycarbonyl) chemistry. T h e fol-l o w i n g peptides were used: r A N P 1-28, r A N P 5 - 2 8 , r A N P 5 - 2 7 , rANP 7 - 2 3 (ring), rANP 17-23, h A N P 10-28, h A N P 15-28, h A N P 2 0 - 2 8 , h A N P 1-28.

Porcine B N P s ( p B N P 1-32 and p B N P 7 - 3 2 ) w e r e kindly donated by the American Peptide C o m p a n y (Santa Clara, C A , U S A ) via János Varga.

T h e peptides were diluted with 0.9% saline to equimolar concentrations before administration in a v o l u m e o f 2 pi into the lateral brain ventricle.

Surgery

The rats w e r e anesthetized with pentobarbital-Na (Nembutal, 35 mg/kg, i.p.) and a cannula w a s placed into the lateral ccrcbrovcntricle and fixed to tbc skull with dental cement. T h e stereotaxic coordinates o f Fifkova and Marsala (6) were used (AP: + 1.0, L:

1.5, V: 3.0). The operated animals were taken for the experiment after a recovery period o f 5 d. T h e correct positioning o f the cannula was c h c c k e d by

injecting methylene blue through the cannula and subsequent dissection o f the brain. A n i m a l s with incorrect placement o f the cannula were discarded and e x c l u d e d from the statistical evaluations.

Behavioral methods

Fear-motivated learning behavior w a s studied, using the f o l l o w i n g tests:

1. Passive avoidance test—one-trial learning stepthrough passive avoidance behavior w a s m e a -sured according to Ader et al (1). Briefly, rats w e r e placed o n a platform and a l l o w e d to enter a dark compartment. Since rats prefer dark to light, they normally entered within 15 s. On the f o l l o w i n g day t w o additional trials were given.

After the s e c o n d trial, unavoidable electric foot-s h o c k foot-s (0.75 m A , 2 foot-s) were delivered through the grid floor during the learning trial. H a v i n g entered the b o x , the animals could not escape the footshock. After this single learning trial, the rats w e r e immediately removed from the apparatus and w e r e treated with peptide. Consolidation o f p a s s i v e avoidance behavior w a s tested 2 4 h later:

every rat w a s placcd on the platform and the latcncy to enter the dark compartment w a s mea-sured up to a m a x i m u m o f 3 0 0 s.

2. Active avoidance test—this was performed according to the method described in detail by T e l e g d y et al (15, 16). Briefly, the experimental apparatus consisted o f a 'bench-jumping' condi-tioning box. T h e conditional stimulus w a s the light o f a 4 5 W bulb. The unconditional stimu-lus w a s an electric shock o f 1 m A A C , delivered through the grid floor. Daily experimental ses-sions w e r e performed, with a duration o f 10 min each. Every session consisted o f 10 trials with a m e a n intertrial interval o f 6 0 s (range 5 0 - 7 0 s).

T h e conditioning stimulus w a s presented for a m a x i m u m o f 15 s. If the rat j u m p e d onto the b e n c h during the first 10 s (conditioned avoid-a n c e response ( C A R ) ) , the conditioning stimu-lus w a s terminated. Non-occurrence o f the C A R w a s associated with termination o f the uncondi-tional stimulus in the last 5 s o f the conditioning stimulus period. The learning criterion w a s 80°.o or more C A R s measured on the third day o f train-ing. After having reached the criterion o f learn-ing, the animals were treated with peptide i.c.v.

STUDIES ON THE EFFECTS OF ATRIAL AND DRAIN NATRIURETIC PEPTIDES ON RATS

63 and their effects in the extinction of the active

avoidance behavior were studied after 3, 6 and 24 h. During the extinction trials, the conditional stimulus was not followed by electric shock. The results are expressed as the sum of the 3-day measurement.

Statistical analysis

The non-parametric ranking tests of Kruskal-Wallis (KAV) (for the passive avoidance test) and Mann-Whitney (MW) (for the active avoidance) were used for the analysis of the data. A probability level of 0.05 or less was accepted as the level of significance.

Results

The structures of the different peptides are shown in Figure 1.

For the first series of experiments on the activi-ties of the compounds in the passive avoidance con-solidation of learning, a previously selected dose of

0.065 nmol, corresponding to 200 ng of ANP per rat, was used {2-A). Each analog was administered in cquimolar concentration, corresponding to this dose. It can be seen from Table, that only two analogs (hANP 20-28 and rANP 17-23) did not facilitate the consolidation of the passive avoidance response, i.e.

they were ineffective. Shortening ANP molecule of the ANP from the N-end resulted in a gradual decline in the activity of the compounds. The ring structure (rANP 7-23), however, still preserved high activity (94%). Shortening of the molecule from the same end, within the ring, further lessened the activity, and when only 7 amino acids remained (rANP 17-23) no effect was observed, i.e. the response was the same as that in the control group.

Similar results were obtained in the second series of experiments, concerning the effect of the peptides and their analogs on the extinction of the active avoidance learning behavior. Here the dose was selected to be 0.16 nmol.

Figure 2 demonstrates the overall activity of the experimental animals in the three test situations (3.

6 and 24 h following administration of the peptides).

P E P T I D E S

AMINO ACID SEQUENCE

I 1

1 2 3 A 5 S 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 2A 25-25 27 28

o< rANP.. 2Q H

₂

N-S - L-R-R-S-S-C-E-G-G-R- I - D-R - I - G - A-Q-S - G- L-G-C-N - S - F-R- -Y-COOH

rANP 0.27 H

₂

N - - - - - - - COOH

rANP^.20 H^ COCH

hANRç

₂₈

HjN - - M COOH

hANJ^g H

₂

N - - - - - - - COOH

hANP^^g HjN COOH

rirvj-rANP

₇

_

₂₃

Fyi- - - - - - - - - COOH

rANP

_r7

_

₂₃

HjN - COOH

orhANP^ HjN M COOH

pBNFJ^HjN-S-P-K-T-M-R-D-S-G-C-F-G-R-R-L-D-R- I - G-S - L-S-G-L-G-C - N-V-L-R-R-Y-COOH

pBNP7 3 2 H 2 N - - - - - - - - - - - COOH

Fig. 1 The structure of A N P and related peptides. The underlined amino acids represent the identical residue of A N P and RNP.

174

N E U R O P E P T I D E S

T a b l e

E f f e c t s o f a - r A N P 1 - 2 8 and related c o m p o u n d s o n the c o n s o l i d a t i o n o f p a s s i v e a v o i d a n c c learning.

A voidance latency Activity

Peptide Mean ± SEM % ' Significance a - r A N P 1-28 (30) 182.4 ± 1 8 . 1 100 ^•

rANP 1-27 (11) 168.2 ± 11.0 92 ^* rANP 5-28 (12) 188.2 ± 11.5 103 ^• hANP 10-28 (8) 175.1 ± 4 . 4 96

hANP 15-28 (8) 158.9 ± 9 . 4 87 ^* hANP 20-28 (12) 113.2 ± 9.1 62 N S

rANP 7-23 (10) 172.2 ± 11.0 94 ^• rANP 17-23 (10) 120.8 ± 9 . 0 66 N S a-hANP 1-28 (12) 226.2 ± 18.0 124 ^*

pBNP 1-32 (14) 204.6 ± 9 . 5 112 ^* pBNP 7-32 (8) 207.7 ± 5 . 0 114 ^* Control (19) 101.7 ± 7.5

( ) Number of animals used. * vs Control p 0.05

The means were summarized and compared by the Mann-Whitney test. The same two fragments as pre-viously were ineffective in delaying the extinction of the avoidance response (p < 0.05, MW).

D i s c u s s i o n

In 1986 Itoh et al (7), using reverse-phase-high

per-formance liquid chromatography (RP-IIPLC) cou-pled with radioimmunoassay (RIA). reported that the predominant forms of ANP in the rat brain were a - r A N P 4 - 2 8 and a-rANP 5-28. They also suggested that the molecular form of ANP as a brain peptide differs from the circulating (hormonal) peptide form. These data promted us to investigate the actions of ANP, BNP and a number of synthetic frag-ments related to them for their behavioral effects on fear-motivated learning. What we have learned from these observations is as follows:

rANP 1-28, hANP 1-2S and BNP F-32 had sim-ilar cqtiipotential actions in the two tests. This indi-cates that presumably the same type of response is due to the identical amino acids in the same posi-tions i.e. posiposi-tions 15. 16, 19, 20, 21. 22 and 23.

Since hANP 10-28 and hANP 15-2S were also active, despite the fact that the ring structure is not present, the ring is probably not an essential struc-tural element for the biological activity measured.

Since rANP 17-23 was not effective, but rANP 15-28 was, while ANP 7-23 with the ring structure retained full biological activity, the effective bio-logical active center of the peptide in (ear-motivated behavior might be between amino acids 15 and 23.

EXTINCTION

%

1005 0

-26 ^{21 14 14} 14 17 27 15 14 15 14 15 C c4rANP rANP rANP rANP rANP hANP rANP rANP hANP pBNP pBNP

1-28 20-28 5-27 5 - 2 8 10-28 15-28 7-23 17-23 1-28 1-32 7-32

* p< 0.001 vs Control ( M - W t e s t )

Fig. 2 The effects of ANP 1-28 and related peptides on the extinction of active avoidance behavior.

STUDIES ON THE EFFECTS OF ATRIAL AND BRAIN NATRIURETIC PEPTIDES ON RATS

-65

R e f e r e n c e s

1. Ader. R.. Wcijnen. J. A. W. M. and Molcman, P. (1972).

Retention of a passive avoidance response as a Function of the intensity, and duration of electric shock. Psychosom. Sci.

26:126—128."

2. Bidzseranova. A.. Telegdy, G. and Pcnke, B. (1991). The effects of atrial natriuretic peptide on passive avoidance behavior in rats. Brain Res. Bull. 26: 177-1 SO.

3. Bidzseranova, A.. Telegdy, G. and Tóth, G.( 1991). The effects ofreceptorblockers on atrial natriuretic peptide-induced action on passive avoidancc behavior in rats. Pharm. Bioch. Behav.

40 (2) (in press).

4. Bidzseranova. A.. Gueron. J.. Pcnke, B. and Telegdy. G.

(1991). The effects of atrial natriuretic peptide on active avoidance behavior in rats. The role of the transmitter sys-tems. Pharmacol. Bioch. Behav. 40 (1): 61-64.

5. DcBold A. J., Borenstein. H. B„ Veress A. T. and Sonnenberg. H. (19SI). A rapid and potent natriuretic response to intravenous injection of atrial myocardial extract in rats. Life Sci. 2S: 83-94.

6. Fifkova. E. and Marsala. J. (1967). Stereotaxic atlases for the cat. rabbit and rat. In: Electrophysiological Methods in Biological Research (Bures, J., Petrán, M.. Zacher. J., Eds.).

Publishine House of the Czechoslovak Academy of Sciences, Prague. 653-731.

7. ltoh. H.. Nakao. K.. Katsura. G. et al (I9S6). Atrial natri-uretic polypeptides: Structure-activity relationship in the central action—a comparison of their antidipsogenic action.

Ncurosc. Lett. 74: 102-106.

8. Kawata. M. K.. Nakao. K.. Morii, N.. Kiso. J.. Jamashita.

H.. Itnura. II. and Sano. J. (1985). Atrial natriurcticpolypcp-lidtf: Topographical distribution in the rat brain by

radio-immunoassay and immunohistochemistry. Neuroscicnce 16:

521-546.

9. Morii. N., Nakao. K., Sugawara. A., Sakamoto, M., Suda.

M., Sltimokura, M.. Kiso, J.. Jamori. J. and Inutra. H.

(1985). Occurrence of atrial natriuretic polypeptide in brain.

Biocltem: Biophys. Res. Common. 127: 413—119.

10. Quirion, R.. Dalpe, H., DcLcnn. A.. Gulkowska. J.. Cnotio, M.

and Gcnest, J. (1984). Atrial natriuretic factor (ANF) binding sites in brain and related structures. Peptides 5: 1167—1172.

11. Quinon, R. (I9SS). Atrial natriuretic factors and die brain:

an update. TINS. 11.2: 58-62.

12. Sudoli, T„ Kangawa, K„ Minamino. N. and Matstio. 11.(19SS)..

A new natriuretic peptide in porcine brain. Nature 332:7S-81.

13. Sudoli. T., Minamino, N., Kaneasva, K. and Matstio, H.

(1990). C-type natriuretic peptide (CNP): a new member of natriuretic peptide family identified in porcine brain.

Biochem. Biophys. Res. Commun. 168: 863-870.

' 14. Tanaka. 1., Mlsono, K. S. and Inagami, T. (I9S4). Atrial natriuretic factor in rat hypothalamus, atria and plasma:

Determination of specific radioimmunoassay. Biochem.

Biophys. Res. Commun. 124: 663-668.

15. Telegdy, G.. Hadnagy, J. and Lissak. K. (1968). The efTcct of gonads on conditioned avoidance behavior of rats. Acta Physiol. Acad. Sci. Hung. 37: 439-144.

16. Telegdy, G. (1987). In: Neuropeptides and Brain Function.

Karger. Basel, pp. 1-332.

17. Skofitsch. G. and Jacobowitz. D. (I98S). Atrial natriuretic peptide in the ccntral nervous system of the rat. Cell. Moll.

Ncurobiol. 4; 339-391.

18. Zatnir, N.. Skofitsch. G.. Eskay. R. L. and Jacobowitz. D. M.

(I9S6). Distribution of iintminoreactivc atrial natriuretic pep-tides in the ccntral nervous svstcin of the rat. Drain Res. 365:

105-111.

lírain Research Hullern. Vol. 28. pp. 767-768. 1992 Prímed in the USA. All rights reserved.

2.7

0361-9230/92 $5.00 + .00 Copyright 0 1992 Peigamon Press Ltd.

Effect of Atrial Natriuretic Peptide on DOPA Potentiation in Mice

A M E L I A B I D Z S E R A N O V A , * J O N Y G U E R O N , * G Á B O R T Ó T H . t B O T O N D P E N K E f A N D G Y U L A T E L E G D Y *¹

*Institttie of Pathophysiology and f Institute of Medical Chemistry, Albert Szent-Györgyi Medical University, Szeged, Hungary

• Received 6 M a y 1991

BIDZSERANOVA. A., J. GUERON. G. TÓTI I, B. PENKE AND G. TELEGDY. Effect of atrial natriuretic peptide on DOPA potentiation in mice. BRAIN RES BULL 28(5) 767-768. 1992.—The effect of rat atrial natriuretic peptide (ANP,_:|) on the pargyline-DOPA potentiation test was studied following its administration into the lateral brain ventricle in mice. Thirty minutes after pargyline pretreatment, three doses of ANP (200, 500, or 1,000 ng/mouse) were administered simultaneously with DOPA and animals were then observed for 2 h. ANP in doses of 500 and 1,000 ng markedly enhanced the effect of DOPA. The maximum intensity of the effect was registered 30-45 min following administration of the peptide. The data suggest that ANP might be regarded as a dopaminergic-modulating agent in the CNS.

Atrial natriuretic peptide Pargyline DOPA potentiation

IN previous experiments, we demonstrated that atrial natriuretic peptide (ANP) participates in fear-induced learning processes via dopaminergic and cholinergic mediation (1,4,5). We con-firmed the supposition that ANP might be considered a mod-ulatory peptide of dopamine (DA) mediation by describing its effect on apomorphine-induced stereotyped cage-climbing be-havior in rats (2). The present work provides more experimental data in this respect. The effect of ANP on pargyline-DOPA po-tentiation in mice was studied following its administration into the lateral brain ventricle. The pargyline-DOPA mouse test of Plotnikoff et al. (9), which has been used to screen new substances for antidepressant action-, was explored to demonstrate the effect of ANP on DA mediation.

M E T H O D

Adult CFLP mice of an inbred strain were used. Animals weighed 2 5 - 3 0 g and were housed 10 per cage. They had access to commercial food and tapwater ad lib and were kept on a standard 12 L: 12 D cycle (lights on at 6:00 a.m.).

Experiments were carried out daily between 8:00 a.m. and noon.

Micc were anesthetized with pentobarbital-Na (nembutal, 35 mg/kg, IP) and a cannula was placed into the right lateral cere-brovcntricle and fixed to' the skull with dental ccment. Animals were used 5 days following operation. The correct positioning of the cannula was checked individually by injection of meth-ylene blue after experiments had been completed. Only those with right positioning of the cannula were included in the sta-tistical evaluation.

The DOPA response potentiation test in mice, as developed and described by Plotnikoff et al. (10), was used with modification to have a quantitative evaluation for statistical analysis. The method consists of pretreating animals with pargyline HCI (40 mg/kg, IP) (6.10) 30 min before DOPA and then observing them for 1-2 h. Observation was done in a double-blind manner and the behavior was scored every 15 min. Potentiation of the DOPA-induced response was scored by means of the changes in the expression of five different indexes—piloerection, salivation, jumping, squeaking, and aggressive fightings—using a four-de-gree scoring scale for each of them (0 stands for no DOPA effect,

1 for slight DOPA effect, 2 for moderate one, and 3 for marked

TABLE 1

SCHEME OF TREATMENTS FOR MEASURING DOPA POTENTIATION IN MICE

Groups

Treatment (min)

Groups 0 30 30-150

Control Paragyline* DOPAf + saline Testing

200 ng ANP Paragyline DOPA + ANP Testing

500 ng ANP Paragyline DOPA + ANP Testing

1,000 ng ANP * Paragyline DOPA + ANP Testing

* Paragyline 40 mg/kg IP,*,, t l.-DOPA 100 mg/kg IP.' -.

1 Requests for reprints should be addressed to Gyula Telegdv, Institute of Pathophysiology, A. Szem-Györgyi Medical University, Semmelweis u.

I, POB 531, Szeged 6701, Hungary.

767

7 6 8 BIDZSERANOVA ET AL.

TABLE 2

EFFECT OF ANP ON DOPA POTENTIATION IN MICE Test Periods (min) rANPi.j!

(ng/mouse. ICV)

n

⁴⁵ 60 75 90 120 ISO

Control 24 0.63 ±0.16 0.79 + 0.16 1.46 ±0.23 1.41 ±0.23 0.63 ±0.13 0 . 0 0 ± 0 . 0 0

200 16 0.75 ±0.18 1.00 ±0.16 1.69 ±0.24 1.43 ±0.20 0.94 + 0.14 0 . 0 0 ± 0 . 0 0

500 16 0.94 ±0.17* 1.88 ±0.20* 2.75 ±0.11* 2.25 ±0.17* 1.19 ±0.16* 0.38 ±0.18*

1000 16 1.70 ±0.15* 2.75 ±0.11* 2.81 ±0.10* 2.13 ±0.18* 1.75 ±0.17* 0.75 ±0.14*

Data are means ± SEM of individual scores.

* p < 0.05 vs. control (ANOVA, Dunnett).

one). The response of animals from the control group (treated with pargyline, DOPA, and saline), consisting of piloerection and slight salivation, was scored as a behavioral rating of 1.

Moderate and marked increase in the above-mentioned activities were scored with 2 and 3, respectively. When there was no DOPA effect observed or it disappeared, the score was 0. For conve-nience in the statistical evaluation, the individual data are given as mean of all five index scores.

Rat A N P, . , j was purchased from Bachem (Bubendorf, Swit-zerland) and also synthesized by two of us (G.T. and B.P.). The peptide was dissolved in 0.9% saline and administered in doses of 200, 500, or 1,000 ng per animal in a volume of 2 pi ICV to freely moving animals simultaneously with L-DOPA (EGYS, Budapest) (100 mg/kg, IP). The control group received the same amount of 2 M! ICV saline and L-DOPA (10).

Statistical analysis of the results was performed by analysis of variance (ANOVA), followed by Dunnett's test.

RESULTS

Table 1 shows the scheme of treatment in the different groups.

The entire experiment lasted 150 min. Animals were observed for 120 min in their home cages.

The effect of three doses of ANP on the DOPA potentiation test is demonstrated in Table 2. The dose of 200 ng had almost no influence on the behavior of mice. The doses of 500 and 1.000 ng A N P effectively potentiated the DOPA response, with maximal intensity of the increase 30-45 min following admin-istration of the peptide [ANOVA, F[3, 7) = 26.7 and F[3, 7) =

13.3, p = 0.0001, Dunnett test, p < 0.05 vs. control). Forty-five minutes after administration of ANP, the effect gradually

de-clined and at the end of the first hour of observation only a slight (500 ng) or moderate-slight (1.000 ng) increase remained. At the end of the second hour, there was still a slight degree of DOPA potentiation at the highest dose.

DISCUSSION

In the present study, ANP administered intracerebroventric-ularly in doses of 500 or 1.000 ng/mouse was found active in the DOPA potentiation test. Our earlier studies suggested ANP might exert a modulatory effect in the processes of fear-induced learning via dopaminergic mediation (1,4,5). This peptide po-tentiated the effect of apomorphine (a DA agonist) in inducing stereotyped cage-climbing behavior in mice (2). All effects of ANP studied by us could be blocked by haloperidol (a DA blocking agent) (1,3.5). Others also reported a DA blockade on central and peripheral effects of the peptide (7,8).

Little is known about the mechanism in which ANP interacts with the dopaminergic neurotransmission. ANP may act pre-or postsynaptically on dopaminergic neurons in the hypothal-amus or other brain structures to augment the combined effects of pargyline-DOPA. It may interact with dopaminergic receptors in appropriate brain structures involved in the performance of the DOPA potentiation test. There is no literature available an-swering this question at present time. Our data confirm our ear-lier observations that the action of ANP on active and passive avoidance behavior is mediated via dopaminergic transmission (1,3,5); however, the actual site of its action, that is, whether it is acting'pre- or postsynaptically or at receptor site, remains to be clarified.

R E F E R E N C E S 1. Bidzseranova, A.; Gueron, J.; Penke, B.: Telegdy. G. The effects of

atrial natriuretic peptide on active avoidance behavior in rats. The role of the transmitter systems. Pharmacol. Biochem. Behav. 40:

61-64; 1991.

2. Bidzseranova, A.; Gueron, J.; Töth, G.; Penke, B.; Telegdy, G. Effect of atrial natriuretic peptide on apomorphine-induced stereotyped cage-climbing behavior in mice. Eur. J. Pharmacol, (in press).

3. Bidzseranova, A.; Penke, B.; Telegdy, G. The effects of atrial natri-uretic peptide on electroconvulsive shock-induced amnesia inrats:

Transmitter mediated action. Neuropeptides 19:103-106:1990.

4. Bidzseranova, A.; Telegdy, G.: Penke, B. The effects of atrial natri-uretic peptide on passive avoidance behavior in rats. Brain Res.

Bull. 26:177-180; 1991.

5. Bidzseranova, A.; Telegdy, G.; T6th, G. The effects of receptor blockers on atrial natriuretic peptide-induced action on passive avoidance behavior in rats. Pharmacol. Biochem. Behav. 40:237-239; 1991.

6. Fekete, M.; Telegdy, G.; Schaily, A. V.: Coy, D. Effects of/J-/TYR'/

melanotropin-/9-l8/ decapeptide on catecholamine disappearance and serotonin accumulation in discrete brain regions of rats. Neu-ropeptides 1:377-382; 1981.

7. Israel, A.; Torres, M.; Barbella. Y. Evidence for a dopaminergic mechanism for the diuretic and natriuretic action of centrally ad-ministered atrial natriuretic factor. Cell Mol. Neurobiol. 9(3):365-378; 1989.

8. Marin-Grez, M.; Briggs, I. P.; Schubert, G.; Schnermann, J. Do-pamine receptor antagonists inhibit the natriuretic response to atrial natriuretic factor (ANF). Life Sei. 36:2171-2176; 1985.

9. PlotnikolV. N. P.; Kastin. A.; Anderson. M.: Schaily, A. DOPA po-tentiation bv a hypothalamic factor, MSH release-inhibiting hormone (MIF). Life Sei. I0:l279-f283: 1971.

10. Plotnikoff. N. P.; Prange, A.; Breese. G.; Wilson. I. Thyrotropin releasing hormone: Enhancement <jf DOPA activity in thyroidec-tomized rats. Life Sei. 14:1271-1278: 1974.

2.8.

L e a r n i n g a n d M e m o r y ¡ l e u m & e i v r t

NeuroRcport 3, 283-285 (1992)

'I'm effects of ¡nlraccrchrovcntriciilar administration of rai atrial natriuretic peptide (rANP-1-28) and porcine brain natriuretic pcplule-32 (pBNP-32) on passive and active avoidance behavior and on electroconvulsive .sliocli-induccd amnesia were studied in rats. The dose range for lu.lh peptides was selected to lie between 0.016 and C.32 nmol. The two peptides were found to facilitate consolidation of the passive avoidance response, to delay extinction of the active avoidance response, and to prevent electi oconvulsive shock-induced amnesia in a similar way.

It is suggested that some m o d u l a t o r y functions in the central nervous system of the rat, so far attributed to AN I', may in fact involve a dual control by both A N P and liNP, and there is no difference in the biological activity of tile two peptides as far as fear-motivated learning be-havior is concerned.

Key words: Atrial natriuretic peptide; Brain natriuretic pep-tide; Avoidance- bebavior

Introduction

Atrial natriuretic peptide ( A N P ) is a peptide of 28 amino acid residues which was identified in mam-malian atria 10 years ago,¹ and later in mammalian brains.-' Brain natriuretic peptide ( B N P ) is a peptide ol 2(> amino acid residues, recently identified in porcine brain.' A form extended by six amino acids at the N -tcrmin.il was also discovered in porcine brain.' The six additional amino acids are reported not to change the intrinsic hioaetivity of B N P . ' T h e peptides A N P , B N P 2 6 and B N P 3 2 share substantial sequence h o m -o l -o g y and have similar p-otency in their natriuretic, diuretic and vasorelaxant activities.⁴

Despite the fact that these peptides are generally considered to participate in a control mechanism for maintaining the homeostatie balance ol b o d y fluids and electrolytes in mammals, their roles in the func-tions ot the central nervous system still remain uncer-tain. In order to clarity the existence ot physiological luneiions of the natriuretic peptide family, related to learning and memory processes, we compared the effects of rat A N P ( r A N P - 1 - 2 8 ) ami of porcine B N P ( p B N P - 3 2 ) on three diflerent lo.ir-inoiiv.ucd learning tasks in rats, following their intraccrchroventricular (i.e.v.) administration. The tests were as billows: pass-ive avoidancc, actpass-ive avoidance behavior, and eleetro-eoiivulsive shock (liCS)-indticcd amnesia.

In document Application of Polyacrylamide Gel Electrophoresis for Analysis of Oligopeptide Phosphorylation In Vitro (Pldal 95-101)