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Lordosis behavior and mounting behavior in male rats: Effects of castration and treatment with estradiol benzoate or testosterone propionate
Physiology and Behavior, Vol. 14, pp. 159-164. Brain Research Publications Inc., 1975. Printed in the U.S.A.
Lordosis Behavior and Mounting Behavior in Male Rats: Effects of Castration and Treatment with Estradiol Benzoate or Testosterone Propionate P. SODERSTEN AND K. LARSSON Department o f Psychology, University o f GOteborg, Faek, S-400 20 GOteborg 14, Sweden
(Received 8 August 1974) SODERSTEN, P. AND K. LARSSON. Lordosis behavior and mounting behavior in male rats: effects o f castration and treatment with estradiol benzoate or testosterone propionate. PHYSIOL. BEHAV. 14(2) 159-164, 1975. -Male rats were selected for showing or not showing lordosis in response to manual stimulation. They were subsequently tested for mounting behavior with receptive females and for lordosis behavior in response to manual stimulation and to male mounting. Males showing lordosis as intacts displayed this behavior more readily following castration or castration and treatment with estradioi benzoate or testosterone propionate than males which did not show lordosis before castration. No group differences in mounting behavior could be detected under any of the endocrine conditions studied. It is suggested that the neural mechanisms mediated mounting and lordosis are dissociated and that individual differences in the occurrence of lordosis in male rats are due to differences in neural sensitivity to estrogen. Lordosis
Mounting
Male rat
Castration
Estrogen
RECENT findings in our laboratory have shown that testosterone propionate (TP) may activate not only mounting behavior but also lordosis behavior in castrated male rats [ 14]. It was also found that approximately 50% of intact untreated male rats of our strain showed lordosis in response to manual stimulation without hormone treatm e n t . Additionally, treatment with the antiestrogen MER-25 inhibited lordosis behavior in intact rats and antagonized TP- and estradiol benzoate (EB)-activated lordosis behavior in castrated rats. This suggests that estrogen, secreted by the rat testis [5] or formed in the rat brain from circulating androgen [9], participates in the control of this behavior. Recent evidence also indicates that estrogen may be involved in the control of mounting behavior in male rats [ l , 4, 6, 7, 12]. Thus treatment of castrated male rats with EB in combination with 5tx-dihydrotestosterone stimulated mounting behavior as effectively as TP, and pretreatment with EB facilitated subsequent mounting behavior induced by TP. Even EB alone when given in large doses may stimulate the mounting behavior of castrated male rats [ 11 ]. These results suggest that estrogen may play a role in the control of both lordosis behavior and mounting behavior in
Testosterone
Estrogen sensitivity
male rats. In a previous study individual differences in the display of lordosis behavior by intact untreated male rats failed to correlate with either mounting behavior or with testicular secretion of estradiol or testosterone [13]. Thus individual differences in lordosis behavior between intact male rats cannot be explained by differences in testis hormone secretion. Among several possibilities, males which do or do not show lordosis behavior may differ in neural sensitivity to estrogen. In the present study observations were made of both lordosis behavior and mounting behavior of male rats which did or did not show lordosis as intacts following castration or castration and EB or TP treatment to test this hypothesis. METHOD
Animals Eighty male Wistar rats bought from M611eg~rd Breeding Laboratories, Denmark were used. The rats were maintained with continous access to food and water in an airconditioned temperature controlled colony room in which the lights were out between 12:30 and 22:30. Behavioral testing was started when the rats were 80 days old.
t Supported by the Swedish Council for Social Research. Wegratefully acknowledge the technical assistance of Mrs..Kristina Edstri~m and Miss Kristina Miintzing. Hormones were generously supplied by the Scbering Corporation.
159
160
SODERSTEN AND LARSSON RESULTS
Behavioral-Testing Procedure Lordosis behavior. The rats were first tested for lordosis behavior (concave back flexion, lateral tail deviation and neck extension) in response to manual stimulation [14]. Each rat was allowed to adapt for 30 min in a circular (50 cm dia.) Plexiglas cage and was thereafter rapidly scratched in the lumbar region with the middle and index fingers followed by combined flank-perineum palpation. Eighteen of 21 males which showed lordosis in all these tests (lordosis group) and 19 other males, randomly selected from the 39 of the remaining 59 males, which did not show lordosis in any test (no lordosis group) were selected for further study. The remaining 43 rats were not used in the subsequent tests and will not be considered further in this paper. The rats in the lordosis and no lordosis group were then given 5 daily tests for lordosis in response to male mounting. Each male was introduced to 2 cage-adapted stimulus males of known sexual vigor and the animals remained together until the test rat was mounted 10 times. If the stimulus males failed to mount, the test rat was removed and presented to 2 other males until mounted 10 times. A lordosis quotient (number of lordosis responses x 100) was 10 calculated. Tests for lordosis behavior started at least four hours after lights off. Mounting behavior. All males were given 5 tests for mounting behavior on alternate days starting the day after the final test for lordosis. The rats were allowed to adapt briefly in the cages previously used for the lordosis tests and then a sexually receptive female rat was introduced (treated with I0 ug EB 48 hr before and 0.5 mg progesterone 6 hr before testing). The following behavior patterns were measured: Mount: m o u n t with pelvic thrusting but without intromission. Intromission: mount with intromission. Ejaculation: m o u n t with a final deep intromission, slow dismounting and genital grooming. The latency to the first intromission, intromission latency, the interval from the first intromission to ejaculation, ejaculation latency, and the time from ejaculation to the following intromission, postejaculatory interval, were recorded. Tests were ended if the intromission latency was > 15 min, if the ejaculation latency was > 30 rain and if the postejaculatory intervals was > 15 min. Tests for mounting behavior started at least four hr after lights off. After completion of the above tests, all rats were castrated and thereafter tested for mounting behavior once every week for seven weeks. Immediately after each of these tests the males were tested for the display of lordosis in response to manual stimulation as described above. The males in the lordosis and no lordosis groups respectively were then randomly divided into two subgroups which received either 1 ug EB (Schering) or 200 ug TP (Schering) for 20 Days. The EB and TP was dissolved in 0.1 ml peanut oil and was injected sc. The rats were tested with receptive females for mounting behavior and with manual stimulation for lordosis behavior on Treatment Days 3, 6, 9, 14 and 19. Additionally, all males were tested for lordosis with stimulus males on Days 5, 10, 15 and 20 of hormone treatment. After the end of behavioral testing all rats were killed and weighed. The glans penis, seminal vesicles (coagulating gland included seminal fluid expressed) and ventral prostate were dissected out, dried on a filter paper and weighed. Four penises from each treatment group were sectioned 1000 um from the tip and stained with hematoxylin and eosin.
Behavior o f Intact Rats Lordosis behavior. During the 5 manual stimulation tests it was found that 30, 32, 36, 31 and 33 of the 80 rats showed lordosis and that 41 of the rats (51.3% showed lordosis in at least one of these tests. In the 5 male mounting tests 4, 5, 1, 3 and 1 of the males in the lordosis group displayed lordosis and 6 of these 18 rats (33.3%) showed lordosis in at least one of the tests. The lordosis quotients were low, the means (nonresponders excluded) were: 26.7, 20.0, 3.3, 5.0 and 1.7 and the overall mean + SE was 11.3 -+ 4.3. None of the rats in the no lordosis group showed lordosis in response to male mounting. Mounting behavior. Figure 1 and Table 1 show that there were no differences in any parameter of the mounting behavior between the two groups.
GROUP
A •
LORDOSIS NO LORDOSIS
MOUNT
INTROMISSION EJACULATION
50 1 2 34
51
2 34
51
2 34
5
SUCCESSIVE TESTS
FIG. 1. Percentage of 2 groups of male rats showing mounts, intromissions and ejaculation in 5 tests. The rats were selected for showing or not showing lordosis.
Behavior o f Castrated Rats Lordosis behavior. Some of the rats in the lordosis group continued to display lordosis to manual stimulation after castration (Fig. 2). Ten of the 18 males (55.6%) in the lordosis group, but none of the rats in the no lordosis group, showed this behavior at least once following castration. Mounting behavior. There was a decline of the mounting behavior in both groups of rats following castration. No group differences in either the percentage of responding rats (Fig. 2) or in the behavior pattern displayed by the ejaculating rats (Table 2) could be detected. Behavior o f Castrated Rats Treated with EB or TP Lordosis behavior. Following treatment with EB or TP the castrated males in the lordosis group showed lordosis to manual stimulation in significantly more tests than the males in the no lordosis group (p<0.05, two-tailed MannWhitney U tests, Fig. 3). When tested with stimulus males the males in the lordosis group were found to show significantly higher lordosis quotients following EB treatment than the males in the no lordosis group (Table 3). A similar nonsignificant trend was also noticed following TP treatment (Table 3). Mounting behavior. EB and TP treatment stimulated mounting behavior in both groups (Fig. 3, Tables 4 and 5). There were no statistically significant differences in the
SEX BEHAVIOR IN MALE RATS
161 TABLE 1
MOUNTING BEHAVIOR DISPLAYED BY MALE RATS WHICH DID OR DID NOT SHOW LORDOSIS. THE VALUES REPRESENT THE MEANS ± S.E. OF FIVE TESTS GIVEN ON ALTERNATE DAYS. ONLY TESTS WITH EJACULATION ARE INCLUDED.
Behavioral Parameter Mounts lntromissions
Lordosis Group (N = 18)
No Lordosis Group (N = 19)
p*
15.0 -+ 1.8
15.7 ± 2.4
NS t
9.5 ± 0.6
11.5 ± 0.7
NS
Intromission latency (min)
1.1 ± 0.3
0.7 -+ 0.2
NS
Ejaculation latency (min)
9.9 -* 0.9
8.9 ± 0.9
NS
Postejaculatory interval (min)
5.8 ± 0.2
6.1 ± 0.2
NS
Percent ejaculating
100
100
*Two-tailed Mann-Whitney U-test tNS, p>0.05 TABLE 2 MOUNTING BEHAVIOR DISPLAYED BY MALE RATS WHICH DID OR DID NOT SHOW LORDOSIS. THE VALUES REPRESENT THE MEANS ± S.E. OF SEVEN WEEKLY TESTS FOLLOWING CASTRATION. ONLY TESTS WITH EJACULATION ARE INCLUDED. Lordosis Group (N = 18)
No Lordosis Group (N = 19)
p*
17.1 ± 3.1
18.2 -+ 1.3
NS t
Intromissions
5.5 ± 0.5
5.9 ± 0.5
NS
lntromission latency (min)
1.9 -+ 0.3
1.2 ± 0.3
NS
Ejaculation latency (min)
10.2 ± 0.3
12.0 -* 1.2
NS
8.8 ± 0.6
8.2 -+ 0.6
NS
61.1
81.1
Behavioral Parameter Mounts
Postejaculatory interval (min) Percent ejaculating *Two-tailed Mann-Whitney U-test iNS, p>0.05
GROUP
MOUNT
LORDOSIS • NO LORDOSIS INTROEJACUMISSION LATION
LORDOSIS
50
1 3 5 7 1 3 5 7 1 3 5 7 1 3 5 7 SUCCESSIVE WEEKLY TESTS FIG. 2; Percentage of 2 groups of male rats showing mounts, intromissions, ejaculation and lordosis following castration. The rats were selected for showing or not showing lordosis as intacts.
r e s p o n s e t o e i t h e r EB or TP w i t h regard to t h e p e r c e n t a g e of r e s p o n d i n g a n i m a l s or t o t h e b e h a v i o r p a t t e r n displayed b y ejaculating animals. T o c o m p a r e EB- w i t h TP-activated m o u n t i n g b e h a v i o r t h e d a t a f r o m t h e lordosis and n o lordosis g r o u p s were c o m b i n e d . It was f o u n d t h a t rats t r e a t e d w i t h EB s h o w e d m o u n t s and i n t r o m i s s i o n s in as m a n y tests as T P - t r e a t e d rats b u t ejaculated in fewer tests ( p < 0.01, two-tailed M a n n W h i t n e y U tests). E B - t r e a t e d rats s h o w e d m o r e m o u n t s p r i o r to e j a c u l a t i o n ( p < 0 . 0 2 , two-tailed M a n n - W h i t n e y U (tests), h a d longer e j a c u l a t i o n latencies ( p < 0 . 0 2 , two-tailed M a n n - W h i t n e y U test) and had longer p o s t e j a c u l a t o r y intervals ( p < 0 . 0 2 , two-tailed M a n n - W h i t n e y U test) t h a n TPtreated males. N o o t h e r differences were statistically significant.
Organ Weights at Autopsy T a b l e 6 s h o w s t h a t t h e E B - t r e a t e d rats in g r o u p were l i g h t e r t h a n t h e E B - t r e a t e d rats group. H o w e v e r , t h e rats in t h e n o lordosis less ( 3 5 1 . 0 + 8.8 g) t h a t t h e rats in t h e
t h e n o lordosis in t h e lordosis g r o u p weighed lordosis g r o u p
162
SODERSTEN AND LARSSON
GROUP
MOUNT
selected for showing lordosis in response to m a n u a l stimulation did n o t differ f r o m t h a t o t h e r males w h i c h failed to show lordosis [ 13]. T h e p r e s e n t results show t h a t male rats selected for showing lordosis displayed this b e h a v i o r m o r e readily following c a s t r a t i o n or c a s t r a t i o n and t r e a t m e n t w i t h EB or TP t h a n o t h e r males w h i c h failed to show lordosis as intacts. T h e s e findings suggest t h a t individual d i f f e r e n c e s in t h e display of lordosis b e h a v i o r b e t w e e n male rats are d u e t o differences in neural sensitivity to estrogen r a t h e r t h a n to d i f f e r e n c e s in testis h o r m o n e secretion. T h e reason f o r this difference in estrogen sensitivity is u n k n o w n . We have suggested elsewhere, however, t h a t such differences m a y be d u e to v a r i a t i o n s in the p e r i n a t a l e n d o crine mileau [ 13 ], since such variations are k n o w n to affect b e h a v i o r a l responses t o h o r m o n e s in a d u l t h o o d [ 2 ] . In t h e p r e s e n t e x p e r i m e n t , we also studied possible differences in t h e m o u n t i n g b e h a v i o r of male rats w h i c h did or did n o t display lordosis as intacts. However, u n d e r n o n e o f the e n d o c r i n e c o n d i t i o n s studied were any d i f f e r e n c e s in this b e h a v i o r f o u n d . T o g e t h e r w i t h previous findings [ 1 0 , 1 2 ] , these d a t a suggest t h a t t h e neural s u b s t r a t e s for lordosis and m o u n t i n g are dissociated and d i f f e r e n t l y regulated in male rats. T h e high level of m o u n t i n g b e h a v i o r f o u n d following c a s t r a t i o n and t r e a t m e n t w i t h as little as 1 tsg EB o f t h e sexually e x p e r i e n c e d males used in the present s t u d y deserves c o n s i d e r a t i o n . Despite a m i n i m u m of p e r i p h e r a l h o r m o n a l s t i m u l a t i o n , as evidenced b y the low n u m b e r of cornified papillae o n the glans penis and t h e low weights of t h e accessory sexual organs, t h e E B - t r e a t e d males in b o t h the lordosis and t h e n o lordosis g r o u p s h o w e d m o u n t s and i n t r o m i s s i o n s as f r e q u e n t l y as males w h i c h received 200 ~zg TP. However, t h e E B - t r e a t e d males did n o t ejaculate in as m a n y tests as the T P - t r e a t e d males, t h e y s h o w e d m o r e m o u n t s prior to ejaculation, had longer e j a c u l a t i o n latencies and longer p o s t e j a c u l a t o r y intervals t h a n the T P - t r e a t e d males. Such differences in b e h a v i o r are possibly d u e t o the failure o f EB to s t i m u l a t e the p e r i p h e r a l a n d r o g e n sensitive target organs [ 11 ]. In previous e x p e r i m e n t s in o u r laboratory [7, 11, 12] using p r e p u b e r a l l y castrated male rats t r e a t e d w i t h various doses o f EB we have n o t f o u n d as high
A LORDOSIS •
NO LORDOSIS
INTROMISSION
EJACU " LATION
LORDOSIS
100 z
75 50
z
25
o ,.y
100
Z
75 50
25 0 369
1419369
14 1 9 3 6 9
14 1 9 3 6 9
1419
DAYS OF EB (TOP) OR TP (BOTTOM) TREATMENT
FIG. 3. Percentage of 2 groups of castrated male rats showing mounts, intromissions, ejaculation and lordosis following treatment with 1 tsg estradiol benzoate (EB) or 200 tsg testosterone propionate (TP). The rats were selected for showing or not showing lordosis as intacts. 382.2 + 6.8 g, p < 0 . 0 5 , t test) p r i o r to EB t r e a t m e n t , a n d the d i f f e r e n c e b e t w e e n t h e t w o g r o u p s in b o d y w e i g h t loss following EB t r e a t m e n t was n o t statistically significant (11.5 + 3.7 a n d 18.3 + 3.4 g for t h e n o lordosis a n d lordosis g r o u p respectively, NS, t test). T h e glans penis o f t h e EBt r e a t e d rats in t h e n o lordosis g r o u p were heavier t h a n t h o s e o f t h e rats in t h e lordosis group. N o o t h e r s y s t e m a t i c g r o u p d i f f e r e n c e s occurred. DISCUSSION In a previous s t u d y , we f o u n d t h a t t h e testicular secretion of estradiol a n d t e s t o s t e r o n e o f male rats w h i c h were
TABLE 3 MEAN LORDOSIS QUOTIENTS DISPLAYED BY CASTRATED MALE RATS WHICH DID OR DID NOT SHOW LORDOSIS BEFORE CASTRATION. THE RATS WERE TESTED FOLLOWING TREATMENT WITH l.o.g ESTRADIOL BENZOATE (EB) OR 200 t~g TESTOSTERONE PROPIONATE (TP) FOR 20 DAYS.
Treatment Days Treatment
No. Rats
5
10
15
20
Overall Mean -+ S.E.
% Responding
Lordosis
EB
9
68.9
75.6
73.3
73.3
72.8 + 12.2
100
No lordosis
EB
10
100
Group
p*
26.0
45.0
44.0
43.0
39.2 -+ 7.3
<0.02
<0.05
<0.05
<0.02
<0.05
Lordosis
TP
9
6.6
12.2
18.9
4.4
10.6 +- 5.0
55.6
No lordosis
TP
9
2.2
2.2
4.4
0
2.2 -+ 1.4
22.2
NS
NS
NS
p.
NS'~ *Two-tailed Mann-Whitney U-test
~NS, p>0.05
NS
SEX B E H A V I O R IN M A L E R A T S
163 TABLE 4
MOUNTING BEHAVIOR DISPLAYED BY MALE RATS WHICH DID OR DID NOT SHOW LORDOSIS. THE VALUES REPRESENT THE MEANS -* S.E. OF FIVE TESTS FOLLOWING CASTRATION AND TREATMENT WITH lbtg ESTRADIOL BENZOATE (EB) FOR 20 DAYS. THE RATS WERE TESTED ON DAYS 3, 6, 9, 14 AND t9 OF EB TREATMENT. ONLY TESTS WITH EJACULATION ARE INCLUDED. Lordosis Group (N = 9)
No Lordosis Group (N = 10)
p*
Mounts
18.5 -+ 2.0
26.4 ± 2.6
NSt
lntromissions
13.9 ± 1.3
14.5 -+ 1.3
NS
Intromission latency (min)
0.7 ± 0.2
0.9 -+0.3
NS
Ejaculation latency (min)
11.7 -+ 2.6
15.2 ± 1.6
NS
6.1 -+ 0.3
6.6 ± 0.3
NS
66.7
80
Behavioral Parameter
Postejaculatory interval (rain) Percent ejaculating *Two-tailed Mann-Whitney U-test tNS, p>0.05
TABLE 5 MOUNTING BEHAVIOR DISPLAYED BY MALE RATS WHICH DID OR DID NOT DISPLAY LORDOSIS. THE VALUES REPRESENT THE MEANS ± S.E. OF FIVE TESTS FOLLOWING CASTRATION AND TREATMENT WITH 200 ttg TESTOSTERONE PROPIONATE (TP) FOR 2 0 DAYS. THE RATS WERE TESTED ON DAYS 3, 6, 9, 14 AND 19 OF TP TREATMENT. ONLY TESTS WITH EJACULATION ARE INCLUDED. Lordosis Group (N = 9)
No Lordosis Group (N = 9)
p*
Mounts
12.9 ± 3.0
14.8 ± 2.5
NSt
Intromissions
Behavioral Parameter
13.4 -+ 0.8
14.9 -+ 1.1
NS
Intromission latency (min)
1.1 -+0.4
0.5 ± 0.1
NS
Ejaculation latency (rain)
9.9 -+ 0.8
8.9 ± 1.3
NS
Postejaculatory interval (rain)
5.2 ± 0.3
5.7 ± 1.2
NS
100
100
Percent ejaculating *Two-tailed Mann-Whitney U-test -[-NS, p>0.05
levels o f m o u n t i n g b e h a v i o r as t h o s e f o u n d in t h e p r e s e n t study. T h e s e o b s e r v a t i o n s suggest i m p o r t a n t d i f f e r e n c e s in the r e s p o n s e to h o r m o n e s in a d u l t h o o d b e t w e e n prep u b e r a l l y c a s t r a t e d males and a d u l t c a s t r a t e d sexually e x p e r i e n c e d males. It is k n o w n since very long t h a t c a s t r a t i o n o f sexually e x p e r i e n c e d male rats results in a g r a d u a l r a t h e r t h a n a b r u p t decline o f sexual b e h a v i o r [ 1 5 , 1 6 ] . This was also f o u n d in t h e p r e s e n t study. F u r t h e r m o r e it was f o u n d t h a t c a s t r a t i o n was n o t followed b y a n i m m e d i a t e a b o l i t i o n o f lordosis b e h a v i o r in t h o s e m a l e s w h i c h s h o w e d this b e h a v i o r p r i o r t o
castration. T h e reason for this g r a d u a l waning o f sexual b e h a v i o r a f t e r c a s t r a t i o n in rats is u n k n o w n . N e i t h e r p r i o r sexual e x p e r i e n c e n o r r e m o v a l o f the adrenals have b e e n f o u n d to affect t h e p o s t c a s t r a t i o n a l changes in sexual b e h a v i o r [ 3 ] . Possibly t h e persistence o f sexual b e h a v i o r following c a s t r a t i o n m a y d e p e n d u p o n long lasting effects o f testicular a n d r o g e n s o r estrogens. Such effects have previously b e e n r e p o r t e d t o affect o t h e r e s t r o g e n sensitive b e h a v i o r p a t t e r n s in t h e rat [ 8 ] . However, at t h e p r e s e n t state o f k n o w l e d g e f u r t h e r s p e c u l a t i o n seems g r a t u i t o u s .
164
S O D E R S T E N AND L A R S S O N
TABLE 6 MEAN -+ S.E. ORGAN WEIGHTS AND NUMBER OF CORNIFIED PAPILLAE ON THE GLANS PENIS OF CASTRATED MALE RATS TREATED WITH Dzg ESTRADIOL BENZOATE (EB) OR 200 #g TESTOSTERONE PROPIONATE (TP) FOR 20 DAYS. THE RATS WERE SELECTED FOR SHOWING OR NOT SHOWING LORDOSIS BEFORE CASTRATION.
Treatment
No. Rats
Body (g)
Seminal Vesicles (mg/100 g bw)
Ventral Prostate (mg/100 g bw)
Glans Penis (mg/100 g bw)
No. Cornified Papillae~
Lordosis
EB
9
365.0 ± 7.8
25.4 ± 1.4
7.5 + 0.6
30.1 *- 0.5
13.8 ± 2.8
No lordosis
EB
10
340.3 _* 7.2
28.0 ± 1.1
7.2 _+ 0.7
33.0 -+ 0.6
8.3 ~: 1.8
<0.05
NSt
NS
<0.01
NS
Group
p* Lordosis
TP
9
397.5 -+ 6.8
115.7 ± 3.4
67.3 +- 8.6
37.3 ± 1.0
66,8 _4:1.1
No lordosis
TP
9
392.7 _+ 7.2
122.8 -+ 3.2
80.3 -+ 4.1
39.2 -+ 0.9
68.0 ± 1.8
NS
NS
NS
NS
NS
p* *t-test I"NS, p>0.05 :~based on four rats in each group
REFERENCES 1. Baum, M. J. and J. T. M. Vreeburg. Copulation in castrated male rats following combined treatment with estradiol and dihydrotestosterone. Science 182: 283-285, 1973. 2. Beach, F. A. Hormonal factors controlling the differentiation, development, and display of copulatory behavior in the ramstergig and related species. In: The Biopsychology of Development, edited by E. Tobach, L. R. Aronson and E. Shaw. New York: Academic Press, 1971, pp. 249-302. 3. Bloch, G. J. and J. M. Davidson. Effects of adrenalectomy and experience on postcastration behavior in the male rat. Physiol. Behav. 3: 461-465, 1968. 4. Feder, H. H., F. Naftolin and K. J. Ryan. Male and female sexual responses in male rats given estradiol benzoate and 5c~a d r o s t a n - 1 7 ~ - o l - 3 - o n e p r o p i o n a t e . Endocrinology 94: 136-141, 1974. 5. de Jong, F. H., A. H. Hey and H. J. van der Molen. Effect of gonadotropins on the secretion of ocstradiol-17~ and testosterone by the rat testis. J. Endocr. 57: 277-284, 1973. 6. Larsson, K., P. SiSdersten and C. Beyer. Induction of male sexual behaviour by oestradiol benzoate in combination with dihydrotestosterone. J. Endrocr. 57: 563-564, 1973. 7. Larsson, K., P. Sbdersten and C. Beyer. Sexual behavior in male rats treated with estrogen in combination with dihydrotestosterone. Hormones Behav. 4: 289-299, 1973. 8. Leon, M., M. Numan and H. Moltz. Maternal behavior in the rat: Facilitation through ovariectomy. Science 179: 10181019, 1973.
9. Naftolin, F., K. J. Ryan and Z. Petro. Aromatization of androstenedione by the anterior hypothalamus of adult male and female rats. Endocrinology 90:. 295 - 2 9 8 , 1972. 10. Pfaff, D. W. Nature of sex hormone effects on rat sex behavior: Specificity of effects and individual patterns of response. J. comp. physiol. Psychol. 73: 349-358, 1970. 11. Sbdersten, P. Estrogen-activated sexual behavior in male rats. HormonesBehav. 4: 247-256, 1973. 12. SiSdersten, P. Male and female sexual behavior in castrated male rats treated with testosterone ptopionate, or with estradiol benzoate or dihydrotestosterone in combination with testosterone propionate. Hormones Behav. in press. 13. SiSdersten, P., F. H. de Jong, J. T. M. Vreeburg and M. J. Baum. Lordosis behavior in intact male rats: absence of correlation with mounting behavior or testicular secretion of estradiol-17~ or testosterone. Physiol. Behav. in press. 14. S~Sdersten, P. and K. Larsson. Lordosis behavior in castrated male rats treated with estradiol benzoate or testosterone propionate in combination with an estrogen antagonist, MER-25, and in intact male rats. Hormones Behav. 5: 13-18, 1974. 15. Steinach, E. Untersuchungen zur vergleichenden Physiologic der miinnlichen Geschlechtsorgane inbesondere der accessorischen Geschlechtsdriisen. Pfliigers Arch. ges. Physiol. 56: 304-338, 1894. 16. Stone, C. P. The retention of copulatory activity in male rats following castration. J. comp. Psychol. 7: 269-287, 1927.
Lordosis Behavior and Mounting Behavior in Male Rats: Effects of Castration and Treatment with Estradiol Benzoate or Testosterone Propionate P. SODERSTEN AND K. LARSSON Department o f Psychology, University o f GOteborg, Faek, S-400 20 GOteborg 14, Sweden
(Received 8 August 1974) SODERSTEN, P. AND K. LARSSON. Lordosis behavior and mounting behavior in male rats: effects o f castration and treatment with estradiol benzoate or testosterone propionate. PHYSIOL. BEHAV. 14(2) 159-164, 1975. -Male rats were selected for showing or not showing lordosis in response to manual stimulation. They were subsequently tested for mounting behavior with receptive females and for lordosis behavior in response to manual stimulation and to male mounting. Males showing lordosis as intacts displayed this behavior more readily following castration or castration and treatment with estradioi benzoate or testosterone propionate than males which did not show lordosis before castration. No group differences in mounting behavior could be detected under any of the endocrine conditions studied. It is suggested that the neural mechanisms mediated mounting and lordosis are dissociated and that individual differences in the occurrence of lordosis in male rats are due to differences in neural sensitivity to estrogen. Lordosis
Mounting
Male rat
Castration
Estrogen
RECENT findings in our laboratory have shown that testosterone propionate (TP) may activate not only mounting behavior but also lordosis behavior in castrated male rats [ 14]. It was also found that approximately 50% of intact untreated male rats of our strain showed lordosis in response to manual stimulation without hormone treatm e n t . Additionally, treatment with the antiestrogen MER-25 inhibited lordosis behavior in intact rats and antagonized TP- and estradiol benzoate (EB)-activated lordosis behavior in castrated rats. This suggests that estrogen, secreted by the rat testis [5] or formed in the rat brain from circulating androgen [9], participates in the control of this behavior. Recent evidence also indicates that estrogen may be involved in the control of mounting behavior in male rats [ l , 4, 6, 7, 12]. Thus treatment of castrated male rats with EB in combination with 5tx-dihydrotestosterone stimulated mounting behavior as effectively as TP, and pretreatment with EB facilitated subsequent mounting behavior induced by TP. Even EB alone when given in large doses may stimulate the mounting behavior of castrated male rats [ 11 ]. These results suggest that estrogen may play a role in the control of both lordosis behavior and mounting behavior in
Testosterone
Estrogen sensitivity
male rats. In a previous study individual differences in the display of lordosis behavior by intact untreated male rats failed to correlate with either mounting behavior or with testicular secretion of estradiol or testosterone [13]. Thus individual differences in lordosis behavior between intact male rats cannot be explained by differences in testis hormone secretion. Among several possibilities, males which do or do not show lordosis behavior may differ in neural sensitivity to estrogen. In the present study observations were made of both lordosis behavior and mounting behavior of male rats which did or did not show lordosis as intacts following castration or castration and EB or TP treatment to test this hypothesis. METHOD
Animals Eighty male Wistar rats bought from M611eg~rd Breeding Laboratories, Denmark were used. The rats were maintained with continous access to food and water in an airconditioned temperature controlled colony room in which the lights were out between 12:30 and 22:30. Behavioral testing was started when the rats were 80 days old.
t Supported by the Swedish Council for Social Research. Wegratefully acknowledge the technical assistance of Mrs..Kristina Edstri~m and Miss Kristina Miintzing. Hormones were generously supplied by the Scbering Corporation.
159
160
SODERSTEN AND LARSSON RESULTS
Behavioral-Testing Procedure Lordosis behavior. The rats were first tested for lordosis behavior (concave back flexion, lateral tail deviation and neck extension) in response to manual stimulation [14]. Each rat was allowed to adapt for 30 min in a circular (50 cm dia.) Plexiglas cage and was thereafter rapidly scratched in the lumbar region with the middle and index fingers followed by combined flank-perineum palpation. Eighteen of 21 males which showed lordosis in all these tests (lordosis group) and 19 other males, randomly selected from the 39 of the remaining 59 males, which did not show lordosis in any test (no lordosis group) were selected for further study. The remaining 43 rats were not used in the subsequent tests and will not be considered further in this paper. The rats in the lordosis and no lordosis group were then given 5 daily tests for lordosis in response to male mounting. Each male was introduced to 2 cage-adapted stimulus males of known sexual vigor and the animals remained together until the test rat was mounted 10 times. If the stimulus males failed to mount, the test rat was removed and presented to 2 other males until mounted 10 times. A lordosis quotient (number of lordosis responses x 100) was 10 calculated. Tests for lordosis behavior started at least four hours after lights off. Mounting behavior. All males were given 5 tests for mounting behavior on alternate days starting the day after the final test for lordosis. The rats were allowed to adapt briefly in the cages previously used for the lordosis tests and then a sexually receptive female rat was introduced (treated with I0 ug EB 48 hr before and 0.5 mg progesterone 6 hr before testing). The following behavior patterns were measured: Mount: m o u n t with pelvic thrusting but without intromission. Intromission: mount with intromission. Ejaculation: m o u n t with a final deep intromission, slow dismounting and genital grooming. The latency to the first intromission, intromission latency, the interval from the first intromission to ejaculation, ejaculation latency, and the time from ejaculation to the following intromission, postejaculatory interval, were recorded. Tests were ended if the intromission latency was > 15 min, if the ejaculation latency was > 30 rain and if the postejaculatory intervals was > 15 min. Tests for mounting behavior started at least four hr after lights off. After completion of the above tests, all rats were castrated and thereafter tested for mounting behavior once every week for seven weeks. Immediately after each of these tests the males were tested for the display of lordosis in response to manual stimulation as described above. The males in the lordosis and no lordosis groups respectively were then randomly divided into two subgroups which received either 1 ug EB (Schering) or 200 ug TP (Schering) for 20 Days. The EB and TP was dissolved in 0.1 ml peanut oil and was injected sc. The rats were tested with receptive females for mounting behavior and with manual stimulation for lordosis behavior on Treatment Days 3, 6, 9, 14 and 19. Additionally, all males were tested for lordosis with stimulus males on Days 5, 10, 15 and 20 of hormone treatment. After the end of behavioral testing all rats were killed and weighed. The glans penis, seminal vesicles (coagulating gland included seminal fluid expressed) and ventral prostate were dissected out, dried on a filter paper and weighed. Four penises from each treatment group were sectioned 1000 um from the tip and stained with hematoxylin and eosin.
Behavior o f Intact Rats Lordosis behavior. During the 5 manual stimulation tests it was found that 30, 32, 36, 31 and 33 of the 80 rats showed lordosis and that 41 of the rats (51.3% showed lordosis in at least one of these tests. In the 5 male mounting tests 4, 5, 1, 3 and 1 of the males in the lordosis group displayed lordosis and 6 of these 18 rats (33.3%) showed lordosis in at least one of the tests. The lordosis quotients were low, the means (nonresponders excluded) were: 26.7, 20.0, 3.3, 5.0 and 1.7 and the overall mean + SE was 11.3 -+ 4.3. None of the rats in the no lordosis group showed lordosis in response to male mounting. Mounting behavior. Figure 1 and Table 1 show that there were no differences in any parameter of the mounting behavior between the two groups.
GROUP
A •
LORDOSIS NO LORDOSIS
MOUNT
INTROMISSION EJACULATION
50 1 2 34
51
2 34
51
2 34
5
SUCCESSIVE TESTS
FIG. 1. Percentage of 2 groups of male rats showing mounts, intromissions and ejaculation in 5 tests. The rats were selected for showing or not showing lordosis.
Behavior o f Castrated Rats Lordosis behavior. Some of the rats in the lordosis group continued to display lordosis to manual stimulation after castration (Fig. 2). Ten of the 18 males (55.6%) in the lordosis group, but none of the rats in the no lordosis group, showed this behavior at least once following castration. Mounting behavior. There was a decline of the mounting behavior in both groups of rats following castration. No group differences in either the percentage of responding rats (Fig. 2) or in the behavior pattern displayed by the ejaculating rats (Table 2) could be detected. Behavior o f Castrated Rats Treated with EB or TP Lordosis behavior. Following treatment with EB or TP the castrated males in the lordosis group showed lordosis to manual stimulation in significantly more tests than the males in the no lordosis group (p<0.05, two-tailed MannWhitney U tests, Fig. 3). When tested with stimulus males the males in the lordosis group were found to show significantly higher lordosis quotients following EB treatment than the males in the no lordosis group (Table 3). A similar nonsignificant trend was also noticed following TP treatment (Table 3). Mounting behavior. EB and TP treatment stimulated mounting behavior in both groups (Fig. 3, Tables 4 and 5). There were no statistically significant differences in the
SEX BEHAVIOR IN MALE RATS
161 TABLE 1
MOUNTING BEHAVIOR DISPLAYED BY MALE RATS WHICH DID OR DID NOT SHOW LORDOSIS. THE VALUES REPRESENT THE MEANS ± S.E. OF FIVE TESTS GIVEN ON ALTERNATE DAYS. ONLY TESTS WITH EJACULATION ARE INCLUDED.
Behavioral Parameter Mounts lntromissions
Lordosis Group (N = 18)
No Lordosis Group (N = 19)
p*
15.0 -+ 1.8
15.7 ± 2.4
NS t
9.5 ± 0.6
11.5 ± 0.7
NS
Intromission latency (min)
1.1 ± 0.3
0.7 -+ 0.2
NS
Ejaculation latency (min)
9.9 -* 0.9
8.9 ± 0.9
NS
Postejaculatory interval (min)
5.8 ± 0.2
6.1 ± 0.2
NS
Percent ejaculating
100
100
*Two-tailed Mann-Whitney U-test tNS, p>0.05 TABLE 2 MOUNTING BEHAVIOR DISPLAYED BY MALE RATS WHICH DID OR DID NOT SHOW LORDOSIS. THE VALUES REPRESENT THE MEANS ± S.E. OF SEVEN WEEKLY TESTS FOLLOWING CASTRATION. ONLY TESTS WITH EJACULATION ARE INCLUDED. Lordosis Group (N = 18)
No Lordosis Group (N = 19)
p*
17.1 ± 3.1
18.2 -+ 1.3
NS t
Intromissions
5.5 ± 0.5
5.9 ± 0.5
NS
lntromission latency (min)
1.9 -+ 0.3
1.2 ± 0.3
NS
Ejaculation latency (min)
10.2 ± 0.3
12.0 -* 1.2
NS
8.8 ± 0.6
8.2 -+ 0.6
NS
61.1
81.1
Behavioral Parameter Mounts
Postejaculatory interval (min) Percent ejaculating *Two-tailed Mann-Whitney U-test iNS, p>0.05
GROUP
MOUNT
LORDOSIS • NO LORDOSIS INTROEJACUMISSION LATION
LORDOSIS
50
1 3 5 7 1 3 5 7 1 3 5 7 1 3 5 7 SUCCESSIVE WEEKLY TESTS FIG. 2; Percentage of 2 groups of male rats showing mounts, intromissions, ejaculation and lordosis following castration. The rats were selected for showing or not showing lordosis as intacts.
r e s p o n s e t o e i t h e r EB or TP w i t h regard to t h e p e r c e n t a g e of r e s p o n d i n g a n i m a l s or t o t h e b e h a v i o r p a t t e r n displayed b y ejaculating animals. T o c o m p a r e EB- w i t h TP-activated m o u n t i n g b e h a v i o r t h e d a t a f r o m t h e lordosis and n o lordosis g r o u p s were c o m b i n e d . It was f o u n d t h a t rats t r e a t e d w i t h EB s h o w e d m o u n t s and i n t r o m i s s i o n s in as m a n y tests as T P - t r e a t e d rats b u t ejaculated in fewer tests ( p < 0.01, two-tailed M a n n W h i t n e y U tests). E B - t r e a t e d rats s h o w e d m o r e m o u n t s p r i o r to e j a c u l a t i o n ( p < 0 . 0 2 , two-tailed M a n n - W h i t n e y U (tests), h a d longer e j a c u l a t i o n latencies ( p < 0 . 0 2 , two-tailed M a n n - W h i t n e y U test) and had longer p o s t e j a c u l a t o r y intervals ( p < 0 . 0 2 , two-tailed M a n n - W h i t n e y U test) t h a n TPtreated males. N o o t h e r differences were statistically significant.
Organ Weights at Autopsy T a b l e 6 s h o w s t h a t t h e E B - t r e a t e d rats in g r o u p were l i g h t e r t h a n t h e E B - t r e a t e d rats group. H o w e v e r , t h e rats in t h e n o lordosis less ( 3 5 1 . 0 + 8.8 g) t h a t t h e rats in t h e
t h e n o lordosis in t h e lordosis g r o u p weighed lordosis g r o u p
162
SODERSTEN AND LARSSON
GROUP
MOUNT
selected for showing lordosis in response to m a n u a l stimulation did n o t differ f r o m t h a t o t h e r males w h i c h failed to show lordosis [ 13]. T h e p r e s e n t results show t h a t male rats selected for showing lordosis displayed this b e h a v i o r m o r e readily following c a s t r a t i o n or c a s t r a t i o n and t r e a t m e n t w i t h EB or TP t h a n o t h e r males w h i c h failed to show lordosis as intacts. T h e s e findings suggest t h a t individual d i f f e r e n c e s in t h e display of lordosis b e h a v i o r b e t w e e n male rats are d u e t o differences in neural sensitivity to estrogen r a t h e r t h a n to d i f f e r e n c e s in testis h o r m o n e secretion. T h e reason f o r this difference in estrogen sensitivity is u n k n o w n . We have suggested elsewhere, however, t h a t such differences m a y be d u e to v a r i a t i o n s in the p e r i n a t a l e n d o crine mileau [ 13 ], since such variations are k n o w n to affect b e h a v i o r a l responses t o h o r m o n e s in a d u l t h o o d [ 2 ] . In t h e p r e s e n t e x p e r i m e n t , we also studied possible differences in t h e m o u n t i n g b e h a v i o r of male rats w h i c h did or did n o t display lordosis as intacts. However, u n d e r n o n e o f the e n d o c r i n e c o n d i t i o n s studied were any d i f f e r e n c e s in this b e h a v i o r f o u n d . T o g e t h e r w i t h previous findings [ 1 0 , 1 2 ] , these d a t a suggest t h a t t h e neural s u b s t r a t e s for lordosis and m o u n t i n g are dissociated and d i f f e r e n t l y regulated in male rats. T h e high level of m o u n t i n g b e h a v i o r f o u n d following c a s t r a t i o n and t r e a t m e n t w i t h as little as 1 tsg EB o f t h e sexually e x p e r i e n c e d males used in the present s t u d y deserves c o n s i d e r a t i o n . Despite a m i n i m u m of p e r i p h e r a l h o r m o n a l s t i m u l a t i o n , as evidenced b y the low n u m b e r of cornified papillae o n the glans penis and t h e low weights of t h e accessory sexual organs, t h e E B - t r e a t e d males in b o t h the lordosis and t h e n o lordosis g r o u p s h o w e d m o u n t s and i n t r o m i s s i o n s as f r e q u e n t l y as males w h i c h received 200 ~zg TP. However, t h e E B - t r e a t e d males did n o t ejaculate in as m a n y tests as the T P - t r e a t e d males, t h e y s h o w e d m o r e m o u n t s prior to ejaculation, had longer e j a c u l a t i o n latencies and longer p o s t e j a c u l a t o r y intervals t h a n the T P - t r e a t e d males. Such differences in b e h a v i o r are possibly d u e t o the failure o f EB to s t i m u l a t e the p e r i p h e r a l a n d r o g e n sensitive target organs [ 11 ]. In previous e x p e r i m e n t s in o u r laboratory [7, 11, 12] using p r e p u b e r a l l y castrated male rats t r e a t e d w i t h various doses o f EB we have n o t f o u n d as high
A LORDOSIS •
NO LORDOSIS
INTROMISSION
EJACU " LATION
LORDOSIS
100 z
75 50
z
25
o ,.y
100
Z
75 50
25 0 369
1419369
14 1 9 3 6 9
14 1 9 3 6 9
1419
DAYS OF EB (TOP) OR TP (BOTTOM) TREATMENT
FIG. 3. Percentage of 2 groups of castrated male rats showing mounts, intromissions, ejaculation and lordosis following treatment with 1 tsg estradiol benzoate (EB) or 200 tsg testosterone propionate (TP). The rats were selected for showing or not showing lordosis as intacts. 382.2 + 6.8 g, p < 0 . 0 5 , t test) p r i o r to EB t r e a t m e n t , a n d the d i f f e r e n c e b e t w e e n t h e t w o g r o u p s in b o d y w e i g h t loss following EB t r e a t m e n t was n o t statistically significant (11.5 + 3.7 a n d 18.3 + 3.4 g for t h e n o lordosis a n d lordosis g r o u p respectively, NS, t test). T h e glans penis o f t h e EBt r e a t e d rats in t h e n o lordosis g r o u p were heavier t h a n t h o s e o f t h e rats in t h e lordosis group. N o o t h e r s y s t e m a t i c g r o u p d i f f e r e n c e s occurred. DISCUSSION In a previous s t u d y , we f o u n d t h a t t h e testicular secretion of estradiol a n d t e s t o s t e r o n e o f male rats w h i c h were
TABLE 3 MEAN LORDOSIS QUOTIENTS DISPLAYED BY CASTRATED MALE RATS WHICH DID OR DID NOT SHOW LORDOSIS BEFORE CASTRATION. THE RATS WERE TESTED FOLLOWING TREATMENT WITH l.o.g ESTRADIOL BENZOATE (EB) OR 200 t~g TESTOSTERONE PROPIONATE (TP) FOR 20 DAYS.
Treatment Days Treatment
No. Rats
5
10
15
20
Overall Mean -+ S.E.
% Responding
Lordosis
EB
9
68.9
75.6
73.3
73.3
72.8 + 12.2
100
No lordosis
EB
10
100
Group
p*
26.0
45.0
44.0
43.0
39.2 -+ 7.3
<0.02
<0.05
<0.05
<0.02
<0.05
Lordosis
TP
9
6.6
12.2
18.9
4.4
10.6 +- 5.0
55.6
No lordosis
TP
9
2.2
2.2
4.4
0
2.2 -+ 1.4
22.2
NS
NS
NS
p.
NS'~ *Two-tailed Mann-Whitney U-test
~NS, p>0.05
NS
SEX B E H A V I O R IN M A L E R A T S
163 TABLE 4
MOUNTING BEHAVIOR DISPLAYED BY MALE RATS WHICH DID OR DID NOT SHOW LORDOSIS. THE VALUES REPRESENT THE MEANS -* S.E. OF FIVE TESTS FOLLOWING CASTRATION AND TREATMENT WITH lbtg ESTRADIOL BENZOATE (EB) FOR 20 DAYS. THE RATS WERE TESTED ON DAYS 3, 6, 9, 14 AND t9 OF EB TREATMENT. ONLY TESTS WITH EJACULATION ARE INCLUDED. Lordosis Group (N = 9)
No Lordosis Group (N = 10)
p*
Mounts
18.5 -+ 2.0
26.4 ± 2.6
NSt
lntromissions
13.9 ± 1.3
14.5 -+ 1.3
NS
Intromission latency (min)
0.7 ± 0.2
0.9 -+0.3
NS
Ejaculation latency (min)
11.7 -+ 2.6
15.2 ± 1.6
NS
6.1 -+ 0.3
6.6 ± 0.3
NS
66.7
80
Behavioral Parameter
Postejaculatory interval (rain) Percent ejaculating *Two-tailed Mann-Whitney U-test tNS, p>0.05
TABLE 5 MOUNTING BEHAVIOR DISPLAYED BY MALE RATS WHICH DID OR DID NOT DISPLAY LORDOSIS. THE VALUES REPRESENT THE MEANS ± S.E. OF FIVE TESTS FOLLOWING CASTRATION AND TREATMENT WITH 200 ttg TESTOSTERONE PROPIONATE (TP) FOR 2 0 DAYS. THE RATS WERE TESTED ON DAYS 3, 6, 9, 14 AND 19 OF TP TREATMENT. ONLY TESTS WITH EJACULATION ARE INCLUDED. Lordosis Group (N = 9)
No Lordosis Group (N = 9)
p*
Mounts
12.9 ± 3.0
14.8 ± 2.5
NSt
Intromissions
Behavioral Parameter
13.4 -+ 0.8
14.9 -+ 1.1
NS
Intromission latency (min)
1.1 -+0.4
0.5 ± 0.1
NS
Ejaculation latency (rain)
9.9 -+ 0.8
8.9 ± 1.3
NS
Postejaculatory interval (rain)
5.2 ± 0.3
5.7 ± 1.2
NS
100
100
Percent ejaculating *Two-tailed Mann-Whitney U-test -[-NS, p>0.05
levels o f m o u n t i n g b e h a v i o r as t h o s e f o u n d in t h e p r e s e n t study. T h e s e o b s e r v a t i o n s suggest i m p o r t a n t d i f f e r e n c e s in the r e s p o n s e to h o r m o n e s in a d u l t h o o d b e t w e e n prep u b e r a l l y c a s t r a t e d males and a d u l t c a s t r a t e d sexually e x p e r i e n c e d males. It is k n o w n since very long t h a t c a s t r a t i o n o f sexually e x p e r i e n c e d male rats results in a g r a d u a l r a t h e r t h a n a b r u p t decline o f sexual b e h a v i o r [ 1 5 , 1 6 ] . This was also f o u n d in t h e p r e s e n t study. F u r t h e r m o r e it was f o u n d t h a t c a s t r a t i o n was n o t followed b y a n i m m e d i a t e a b o l i t i o n o f lordosis b e h a v i o r in t h o s e m a l e s w h i c h s h o w e d this b e h a v i o r p r i o r t o
castration. T h e reason for this g r a d u a l waning o f sexual b e h a v i o r a f t e r c a s t r a t i o n in rats is u n k n o w n . N e i t h e r p r i o r sexual e x p e r i e n c e n o r r e m o v a l o f the adrenals have b e e n f o u n d to affect t h e p o s t c a s t r a t i o n a l changes in sexual b e h a v i o r [ 3 ] . Possibly t h e persistence o f sexual b e h a v i o r following c a s t r a t i o n m a y d e p e n d u p o n long lasting effects o f testicular a n d r o g e n s o r estrogens. Such effects have previously b e e n r e p o r t e d t o affect o t h e r e s t r o g e n sensitive b e h a v i o r p a t t e r n s in t h e rat [ 8 ] . However, at t h e p r e s e n t state o f k n o w l e d g e f u r t h e r s p e c u l a t i o n seems g r a t u i t o u s .
164
S O D E R S T E N AND L A R S S O N
TABLE 6 MEAN -+ S.E. ORGAN WEIGHTS AND NUMBER OF CORNIFIED PAPILLAE ON THE GLANS PENIS OF CASTRATED MALE RATS TREATED WITH Dzg ESTRADIOL BENZOATE (EB) OR 200 #g TESTOSTERONE PROPIONATE (TP) FOR 20 DAYS. THE RATS WERE SELECTED FOR SHOWING OR NOT SHOWING LORDOSIS BEFORE CASTRATION.
Treatment
No. Rats
Body (g)
Seminal Vesicles (mg/100 g bw)
Ventral Prostate (mg/100 g bw)
Glans Penis (mg/100 g bw)
No. Cornified Papillae~
Lordosis
EB
9
365.0 ± 7.8
25.4 ± 1.4
7.5 + 0.6
30.1 *- 0.5
13.8 ± 2.8
No lordosis
EB
10
340.3 _* 7.2
28.0 ± 1.1
7.2 _+ 0.7
33.0 -+ 0.6
8.3 ~: 1.8
<0.05
NSt
NS
<0.01
NS
Group
p* Lordosis
TP
9
397.5 -+ 6.8
115.7 ± 3.4
67.3 +- 8.6
37.3 ± 1.0
66,8 _4:1.1
No lordosis
TP
9
392.7 _+ 7.2
122.8 -+ 3.2
80.3 -+ 4.1
39.2 -+ 0.9
68.0 ± 1.8
NS
NS
NS
NS
NS
p* *t-test I"NS, p>0.05 :~based on four rats in each group
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