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Stimulus and experiential factors controlling mounting behavior in the female rat
Physiology and Behavior, Vol. 9, pp. 263-267, Brain Research Publications Inc., 1972. Printed in Great Britain.
BRIEF COMMUNICATION Stimulus and Experiential Factors Controlling Mounting Behavior in the Female Rat' L. C O N I G L I O A N D L. G. C L E M E N S
Department of Zoology, Michigan State University, East Lansing, Michigan 48823, U.S.A. (Received 30 A u g u s t 1971) L. ANDL. G. CLEMENS. Stimulusandexperientialfactors controllingmountingbehaviorin thefemale rat. PHYSIOL. BEHAV. 9 (2) 263-267, 1972.--Spayed adult female rats treated with testosterone propionate were tested for mounting behavior under four incentive female conditions; (a) sexually receptive active, (b) non-receptive active, (c) sexually receptive inactive, (d) non-receptive inactive. Experimental females were given mounting experience subsequent to which they were divided into two groups. One group received olfactory bulb lesions and the other was sham operated. Females with olfactory impairment mounted sexually receptive active incentive females as frequently as did females without impairment. Active incentive females were mounted more often than inactive incentive females. However, the sexually receptive active females elicited a higher frequency of mounting than did the non-receptive active females. When experimental females were given no pre-operative mounting experience, similar results were obtained indicating that movement, particularly the movement of the sexually receptive female, is of primary importance in elieiting mounting behavior in female rats. CON|GLIO,
Female rat
Mounting behavior
Olfactory bulb lesion
FOLLOWINGexogenous treatment with testosterone propionate female rats show high frequencies of mounting behavior when placed with a sexually receptive female [7, 16]. While mounting is typically referred to as a masculine behavior pattern, studies of its frequency of occurrence, hormonal regulation, or neural control often do not support the frequent assumption of mounting being a sexually dimorphic character in the rat. In fact, as pointed out in a recent review, it might be suggested that the factors regulating mounting in the male are not different from those regulating mounting in the female [3]. However, in order to adequately assess the validity of this hypothesis, further investigation of the role of sensory and environmental stimuli is required. Using sexually experienced male rats, Beach [1] and Heimer and Larsson [11] found that ejaculation frequency decreased following olfactory bulb lesions. Olfactory bulb lesions in inexperienced males appear to have even greater effects on the level of sexual behavior [1, 5]. In addition to the olfactory and experiential factors influencing mounting behavior in male rats, Stone [15] proposed that movements of the sexually receptive female supply stimuli which initiate mounting in the male. In order to determine whether the factors which influence mounting in the female are similar to those reported to influence mounting in the male, experiments are reported here in which mounting experience and the condition of the incentive female were varied.
Heterotypical behavior
I~THODS
Animals Animals were 51 female rats of Holtzman strain purchased commercially. The females were divided into two groups: one group of 21 animals (Group 1) was housed in groups of 4-6 per cage and the remaining 30 females (Group 2) were housed individually from 30 days of age. F o o d and water were always available and animals were maintained on a 14-10 reversed day-night light cycle (lights on at 11 a.m.). The animals were ovariectomized at 60-65 days of age.
Procedure Beginning two weeks after ovariectomy, experimental females were treated daily with 1 mg testosterone propionate (TP) to increase the frequency of mounting. On days 7 and 14 of TP treatment females of Group 1 were placed in a test arena for 40 min, 10 min with each of four incentive females, to achieve mounting experience. The females of Group 2 were allowed no mounting experience, and were therefore considered inexperienced. The behavioral characteristics of the four incentive females were (a) sexually receptive active, (b) non-receptive active, (c) sexually receptive inactive, and (d) non-receptive inactive. The inactive conditions (c and d) were achieved by administration of reserpine (Serpasil Ciba) one hr prior to testing which
XThis investigation was supported by PHS Training Grant: GM 01751-01 from National Institute of General Medical Sciences. 263
264 resulted in sedation and immobility, but did not eliminate lordosis in the receptive female. All incentive females were spayed and sexual receptivity was induced by subcutaneous injections of 3 t~g estradiol benzoate (EB) for two days followed by 0.5 mg progesterone on the morning of behavioral testing. Following the day 14 mounting experience session (day 14 of TP treatment), females whichhad shown mounting behavior were divided into lesion (N = 8) and sham (N = 5) conditions. Non-mounters were discarded from further analysis. On day 14 of TP treatment, subjects of Group 2 were randomly assigned to lesion (N = 14) or sham (N = 16) conditions.
Surgical Procedures While the animals were anesthetized with an intraperitoneal injection of sodium methohexital (Brevital-Lilly) a horizontal aperture was made in the skull approximately 6 mm anterior to bregma, and additional openings were drilled over each olfactory bulb. A small blade was inserted through the horizontal aperture to make an incision anterior to the frontal pole of the neocortex in order to prevent tearing of the neocortex during aspiration. The anterior portion of both olfactory bulbs was then aspirated. Attempts were made to destroy all olfactory filaments at their emergence through the cribiform plate. Sham operated animals were similarly treated except that no brain tissue was cut or removed after trephination of the skull.
Behavioral Testing On Day 28 of TP administration, following a two week recovery period from surgery, all animals were tested for mounting in each of the four incentive female conditions. Testing was conducted in Plexiglas observation arenas which measured 18 x 20 × 23 in. and had wood chip shavings on the floor. Experimental females were placed in the observation arenas for I0 min before testing. F o u r females, each in separate arenas, were tested simultaneously. Each female was presented with one of the four incentive females for 5 min at a time. The incentive females were then rotated to another arena for 5 min until each experimental female had been tested for two 5 min periods with each incentive condition. A counterbalanced order of presentations insured all combinations of presentation. Experimental females were scored on frequency of mounting; that is, mounting the incentive female from the rear with palpation and thrust. Behavioral testing was conducted 3-5 hr after the onset of the dark period in a room which was dimly illuminated by a 60 W bulb of a gooseneck lamp which was directed against the wall. TP treatment was terminated on the day following mounting tests. Experimental females were then food deprived for 24--48 hr and given an odor discrimination test. Two small stainless steel bowls, one containing rat pellets, the other empty, were covered with perforated aluminium foil and arranged at either end of the test arena. The amount of time subject spent directly in front of each container during a five min period was recorded. Positions of the containers were alternated between each subject.
Histology At the completion of testing, animals were anesthetized and perfused with saline followed by I0 % formalin solution. The skull, cleaned of surrounding tissue, was then placed in formalin for at least 24 hr. The skull of several animals in each group were decalcified in 6 % nitric acid in 80 % alcohol for two weeks. Brain and surrounding skull were embedded in either collodion or paraffin and sectioned at 30 ~. Cresyl
CONIGLIO AND CLEMENS violet and Luxol Fast Blue were used to stain the paraffin embedded tissues. Weil and Heidenhain stains were used with the collodion sections. Sections were then observed to analyze the extent of the lesion. In the remainder gross examination of the lesion site was made but the brain was not sectioned. RESULTS
Figure 1 shows the p r e - a n d post-operative mean mount frequency and odor discrimination data for experienced females. Pre- and post-operative scores did not differ significantly for the lesioned or sham females in any incentive female condition (p>0.05 Wilcoxin). Mount frequencies of lesioned females were not significantly different from sham females in the post-operative test (p >0.05 Mann-Whitney U). A statistically significant variation in mounting frequency was observed pre- and post-operatively for the experienced females across the four incentive female conditions in both lesion and sham operated animals (p <0.025 Freidman). In comparing mounting frequencies in each of the four incentive female conditions, active incentive females were mounted more often than inactive females (p<0.01 Wilcoxin). In addition, sexually receptive active females elicited, or at least permitted a higher frequency of mounting than did the non-receptive females (p <0.01 Wilcoxin). In the odor discrimination test (Fig. 1) sham operated animals spent significantly more time at the food container than did the lesioned animals (p <0.01 Mann-Whitney U). With the inexperienced females, 7 of the 16 sham operated animals and 12 of the 14 lesioned animals showed mounting behavior in the post operative test. This difference was found to be significantly different (p <0.05 X2). Figure 2 shows the mean mount frequency and odor discrimination data for all animals (Fig. 2A) and for mount-positive inexperienced animals (Fig. 2B). Mount positive females of both lesion and sham groups showed a significant variation in mounting frequency across the four incentive female conditions (p <0.01 Freidman), and both groups mounted active females more than inactive females (p <0.01 Wilcoxin). Odor discrimination data (Fig. 2) showed that sham operated animals spent significantly more time at the food container than did lesioned animals (p<0.02 Mann-Whitney U). In comparing mount frequency between experienced and inexperienced females, a significant difference occurred only in the active receptive condition (p <0.05 Mann-Whitney U). Histological analysis of the brains indicated total removal of 6 0 - 7 0 ~ of the rostral portion of the olfactory bulbs. However, portions of the olfactory bulbs ventral to the frontal poles were left intact. Damage to the frontal poles was minimal and could not be correlated with behavioral results. DISCUSSION
Results of the present study indicate that testosterone treated female rats with olfactory impairment mount receptive females as frequently as do females without olfactory impairment, and that mounting frequency is dependent upon the condition of the stimulus female. The finding that both lesioned and sham operated mounted active incentive females to a greater extent than they mounted inactive incentive females confirms the suggestion of Stone [15] that in the receptive female movement, and particularly the solicitation movements of hopping, darting, and crouching, may be of
MOUNTING BEHAVIOR IN FEMALE RATS
265
A. PRE-OPERATIVE
B. POST-OPERATIVE
o o
o
o
u.. |
z
I ACTIVE • tCEPTIVE
INACTIVE NON
R~CtPt*vt
~tcePtlvt
~OM ~ECFpVcV!
FIG. 1. Mean mounting frequency under four incentive female conditions and odor discrimination data for experienced female rats; (A) pre-operative, (B) post-operative.
primary importance in eliciting mounting behavior. Confirmation of Stone's suggestion with the present tests on female mounting support the idea that mounting behavior in both males and females is regulated by similar systems [ 12, 14]. The higher mount frequencies achieved by the experienced females (Group 1) in the active receptive condition is in agreement with Beach and Rasquin [4] who found that mounting proficiency of female rats increased as testing progressed. The effect of social isolation has also been shown to reduce mounting behavior in female guinea pigs [10] and in male rats [9]. However, the present study does not allow separation of mounting experience and living
condition and the extent to which each contribute to this difference. Comparison of the effects of olfactory lesions in female rats with the effect of similar lesions in males is difficult since, for the male, much of the effect relates to ejaculation latencies and frequencies [11, 5] for which comparable measures are not available in the female. However, Bermant and Taylor [5] report that bilateral olfactory bulb lesions in sexually inexperienced, individually housed males did not reduce the probability that they would achieve intromission and, in that sense, these findings parallel the effects of bulbectomy on mounting in similarly treated females (Group 2).
266
CONIGLIO AND CLEMENS
,N,,,LS.NC,OSIVE z o
i •
F1 S.,, N.,O m ,
U
LESION
2S z < lz
N,t4
(J Z uJ
Q 0
0 uJ u.
,o ~ 0 (--
z <( uJ =E
Z <
m
B. MOUNT
POSITIVE
ANIMALS
I
~
..2 z
~o z O u
4O a 0 0
U.
so
~
2o
~
+-
,0 z II
ACTIVE RECEPTIVE
INACTIVE NON
~ECEPT~VE
RECEPTIVE
NON RECEPTIVE
FIG. 2. Mean mounting frequency under four incentive female conditions and odor discrimination data for inexperienced female rats; (A) all animals inclusive, (B) mount positive females.
Female rats, like male rats, are not dependent upon olfactory bulbs for the initiation of mounting. Several studies have shown that there are species differences in the relative importance of olfactory stimuli to mounting behavior. Brooks [6] demonstrated that male rabbits continue to copulate after olfactory bulb removal. Murphy and Schneider [13] reported that olfactory bulb removal eliminates mounting and subsequent mating behaviors in sexually naive as well as sexually experienced male hamsters. These findings
were confirmed and extended to include neonatally androgenized female hamsters [8] which are similarly affected by olfactory bulb lesions. In the rat, however, mounting depends not upon any single category of stimuli, such as odor or vision, but rather upon a multisensory pattern in which several modalities are involved with no one modality appearing both necessary and sufficient [2]. Hormones were generously supplied by Preston L. Perlman of Schering Corporation, Serpasil was supplied by R. Gaunt of Ciba Corporation, U.S.A.
REFERENCES 1. Beach, F. A. Analysis of the stimuli adequate to elicit mating behavior in the sexually inexperienced male rat. J. comp. physiol. Psyehol. 33: 163-207, 1942a. 2. Beach, F. A. Analysis of factors involved in the arousal, maintenance, and manifestations of sexual excitement in male animals. Psychosomat. Med. 4: 173-198, 1942b.
3. Beach, F. A. Factors involved in the control of mounting behavior by female mammals. In: Perspectives in Reproduction and Sexual Behavior, edited by M. Diamond, Indiana Univ. Press, 1968, pp. 83-131. 4. Beach, F. A.. and P. Rasquin. Masculine copulatory behavior in intact and castrated female rats. Endocrinology, 31: 393409, 1942.
MOUNTING BEHAVIOR IN FEMALE RATS 5. Bermant, G. and L. Taylor. Interactive effects of experience and olfactory bulb lesions in male rat copulation. Physiol. Behav., 4: 13-18, 1969. 6. Brooks, C. Mc. The role of the cerebral cortex and various sense organs in the excitation of mating activity in the rabbit. Am. J. Physiol., 120: 544-553, 1937. 7. Coniglio, L. and L. G. Clemens. Mounting behavior in the female rat. Amer. Zool. (abst) 10: No. 3, August, 1970. 8. Doty, R. L., C. S. Carter and L. G. Clemens. Olfactory control of sexual behavior in the male and early-androgenized female hamster. Horm. and Behav., 2: 325-335, 1971. 9. Gerall, H., I. L. Ward and A. Gerall. Disruption of the male rat's sexual behavior induced by social isolation, dnim. Behav., 15: 54-58, 1967. 10. Goy, R. W. and W. C. Young. Somatic basis of sexual behavior patterns in guinea pigs. Psychosorn. Med., 19: 144-151, 1957.
267 11. Heimer, L. and K. Larsson. Mating behavior of male rats after olfactory bulb lesions. Physiol Behav., 2: 207-209, 1967b. 12. Hitt, J. C., S. E. Hendricks, I. Stevens and J. H. Lewis. Disruption of male, but not female, sexual behavior in rats by medial forebrain bundle lesions. J. comp. physiol. Psychol. 73: 377-384, 1970. 13. Murphy, M. R. and G. E. Schneider. Olfactory bulb removal elimates mating behavior in the male Golden Hamster. Science 167: 302-304, 1970. 14. Singer, J. Hypothalamic control of male and female sexual behavior in female rats. J. comp. physiol. Psychol. 66" 738742, 1968. 15. Stone, C. Congenital sexual behavior of young male albino rats. J. comp. Psychol. 2: 95-153, 1922. 16. Whalen, R. E. and D. A. Edwards. Hormonal determinants of the development of masculine and feminine behavior in male and female rats. Anat. Rec., 157: 173-180, 1967.
BRIEF COMMUNICATION Stimulus and Experiential Factors Controlling Mounting Behavior in the Female Rat' L. C O N I G L I O A N D L. G. C L E M E N S
Department of Zoology, Michigan State University, East Lansing, Michigan 48823, U.S.A. (Received 30 A u g u s t 1971) L. ANDL. G. CLEMENS. Stimulusandexperientialfactors controllingmountingbehaviorin thefemale rat. PHYSIOL. BEHAV. 9 (2) 263-267, 1972.--Spayed adult female rats treated with testosterone propionate were tested for mounting behavior under four incentive female conditions; (a) sexually receptive active, (b) non-receptive active, (c) sexually receptive inactive, (d) non-receptive inactive. Experimental females were given mounting experience subsequent to which they were divided into two groups. One group received olfactory bulb lesions and the other was sham operated. Females with olfactory impairment mounted sexually receptive active incentive females as frequently as did females without impairment. Active incentive females were mounted more often than inactive incentive females. However, the sexually receptive active females elicited a higher frequency of mounting than did the non-receptive active females. When experimental females were given no pre-operative mounting experience, similar results were obtained indicating that movement, particularly the movement of the sexually receptive female, is of primary importance in elieiting mounting behavior in female rats. CON|GLIO,
Female rat
Mounting behavior
Olfactory bulb lesion
FOLLOWINGexogenous treatment with testosterone propionate female rats show high frequencies of mounting behavior when placed with a sexually receptive female [7, 16]. While mounting is typically referred to as a masculine behavior pattern, studies of its frequency of occurrence, hormonal regulation, or neural control often do not support the frequent assumption of mounting being a sexually dimorphic character in the rat. In fact, as pointed out in a recent review, it might be suggested that the factors regulating mounting in the male are not different from those regulating mounting in the female [3]. However, in order to adequately assess the validity of this hypothesis, further investigation of the role of sensory and environmental stimuli is required. Using sexually experienced male rats, Beach [1] and Heimer and Larsson [11] found that ejaculation frequency decreased following olfactory bulb lesions. Olfactory bulb lesions in inexperienced males appear to have even greater effects on the level of sexual behavior [1, 5]. In addition to the olfactory and experiential factors influencing mounting behavior in male rats, Stone [15] proposed that movements of the sexually receptive female supply stimuli which initiate mounting in the male. In order to determine whether the factors which influence mounting in the female are similar to those reported to influence mounting in the male, experiments are reported here in which mounting experience and the condition of the incentive female were varied.
Heterotypical behavior
I~THODS
Animals Animals were 51 female rats of Holtzman strain purchased commercially. The females were divided into two groups: one group of 21 animals (Group 1) was housed in groups of 4-6 per cage and the remaining 30 females (Group 2) were housed individually from 30 days of age. F o o d and water were always available and animals were maintained on a 14-10 reversed day-night light cycle (lights on at 11 a.m.). The animals were ovariectomized at 60-65 days of age.
Procedure Beginning two weeks after ovariectomy, experimental females were treated daily with 1 mg testosterone propionate (TP) to increase the frequency of mounting. On days 7 and 14 of TP treatment females of Group 1 were placed in a test arena for 40 min, 10 min with each of four incentive females, to achieve mounting experience. The females of Group 2 were allowed no mounting experience, and were therefore considered inexperienced. The behavioral characteristics of the four incentive females were (a) sexually receptive active, (b) non-receptive active, (c) sexually receptive inactive, and (d) non-receptive inactive. The inactive conditions (c and d) were achieved by administration of reserpine (Serpasil Ciba) one hr prior to testing which
XThis investigation was supported by PHS Training Grant: GM 01751-01 from National Institute of General Medical Sciences. 263
264 resulted in sedation and immobility, but did not eliminate lordosis in the receptive female. All incentive females were spayed and sexual receptivity was induced by subcutaneous injections of 3 t~g estradiol benzoate (EB) for two days followed by 0.5 mg progesterone on the morning of behavioral testing. Following the day 14 mounting experience session (day 14 of TP treatment), females whichhad shown mounting behavior were divided into lesion (N = 8) and sham (N = 5) conditions. Non-mounters were discarded from further analysis. On day 14 of TP treatment, subjects of Group 2 were randomly assigned to lesion (N = 14) or sham (N = 16) conditions.
Surgical Procedures While the animals were anesthetized with an intraperitoneal injection of sodium methohexital (Brevital-Lilly) a horizontal aperture was made in the skull approximately 6 mm anterior to bregma, and additional openings were drilled over each olfactory bulb. A small blade was inserted through the horizontal aperture to make an incision anterior to the frontal pole of the neocortex in order to prevent tearing of the neocortex during aspiration. The anterior portion of both olfactory bulbs was then aspirated. Attempts were made to destroy all olfactory filaments at their emergence through the cribiform plate. Sham operated animals were similarly treated except that no brain tissue was cut or removed after trephination of the skull.
Behavioral Testing On Day 28 of TP administration, following a two week recovery period from surgery, all animals were tested for mounting in each of the four incentive female conditions. Testing was conducted in Plexiglas observation arenas which measured 18 x 20 × 23 in. and had wood chip shavings on the floor. Experimental females were placed in the observation arenas for I0 min before testing. F o u r females, each in separate arenas, were tested simultaneously. Each female was presented with one of the four incentive females for 5 min at a time. The incentive females were then rotated to another arena for 5 min until each experimental female had been tested for two 5 min periods with each incentive condition. A counterbalanced order of presentations insured all combinations of presentation. Experimental females were scored on frequency of mounting; that is, mounting the incentive female from the rear with palpation and thrust. Behavioral testing was conducted 3-5 hr after the onset of the dark period in a room which was dimly illuminated by a 60 W bulb of a gooseneck lamp which was directed against the wall. TP treatment was terminated on the day following mounting tests. Experimental females were then food deprived for 24--48 hr and given an odor discrimination test. Two small stainless steel bowls, one containing rat pellets, the other empty, were covered with perforated aluminium foil and arranged at either end of the test arena. The amount of time subject spent directly in front of each container during a five min period was recorded. Positions of the containers were alternated between each subject.
Histology At the completion of testing, animals were anesthetized and perfused with saline followed by I0 % formalin solution. The skull, cleaned of surrounding tissue, was then placed in formalin for at least 24 hr. The skull of several animals in each group were decalcified in 6 % nitric acid in 80 % alcohol for two weeks. Brain and surrounding skull were embedded in either collodion or paraffin and sectioned at 30 ~. Cresyl
CONIGLIO AND CLEMENS violet and Luxol Fast Blue were used to stain the paraffin embedded tissues. Weil and Heidenhain stains were used with the collodion sections. Sections were then observed to analyze the extent of the lesion. In the remainder gross examination of the lesion site was made but the brain was not sectioned. RESULTS
Figure 1 shows the p r e - a n d post-operative mean mount frequency and odor discrimination data for experienced females. Pre- and post-operative scores did not differ significantly for the lesioned or sham females in any incentive female condition (p>0.05 Wilcoxin). Mount frequencies of lesioned females were not significantly different from sham females in the post-operative test (p >0.05 Mann-Whitney U). A statistically significant variation in mounting frequency was observed pre- and post-operatively for the experienced females across the four incentive female conditions in both lesion and sham operated animals (p <0.025 Freidman). In comparing mounting frequencies in each of the four incentive female conditions, active incentive females were mounted more often than inactive females (p<0.01 Wilcoxin). In addition, sexually receptive active females elicited, or at least permitted a higher frequency of mounting than did the non-receptive females (p <0.01 Wilcoxin). In the odor discrimination test (Fig. 1) sham operated animals spent significantly more time at the food container than did the lesioned animals (p <0.01 Mann-Whitney U). With the inexperienced females, 7 of the 16 sham operated animals and 12 of the 14 lesioned animals showed mounting behavior in the post operative test. This difference was found to be significantly different (p <0.05 X2). Figure 2 shows the mean mount frequency and odor discrimination data for all animals (Fig. 2A) and for mount-positive inexperienced animals (Fig. 2B). Mount positive females of both lesion and sham groups showed a significant variation in mounting frequency across the four incentive female conditions (p <0.01 Freidman), and both groups mounted active females more than inactive females (p <0.01 Wilcoxin). Odor discrimination data (Fig. 2) showed that sham operated animals spent significantly more time at the food container than did lesioned animals (p<0.02 Mann-Whitney U). In comparing mount frequency between experienced and inexperienced females, a significant difference occurred only in the active receptive condition (p <0.05 Mann-Whitney U). Histological analysis of the brains indicated total removal of 6 0 - 7 0 ~ of the rostral portion of the olfactory bulbs. However, portions of the olfactory bulbs ventral to the frontal poles were left intact. Damage to the frontal poles was minimal and could not be correlated with behavioral results. DISCUSSION
Results of the present study indicate that testosterone treated female rats with olfactory impairment mount receptive females as frequently as do females without olfactory impairment, and that mounting frequency is dependent upon the condition of the stimulus female. The finding that both lesioned and sham operated mounted active incentive females to a greater extent than they mounted inactive incentive females confirms the suggestion of Stone [15] that in the receptive female movement, and particularly the solicitation movements of hopping, darting, and crouching, may be of
MOUNTING BEHAVIOR IN FEMALE RATS
265
A. PRE-OPERATIVE
B. POST-OPERATIVE
o o
o
o
u.. |
z
I ACTIVE • tCEPTIVE
INACTIVE NON
R~CtPt*vt
~tcePtlvt
~OM ~ECFpVcV!
FIG. 1. Mean mounting frequency under four incentive female conditions and odor discrimination data for experienced female rats; (A) pre-operative, (B) post-operative.
primary importance in eliciting mounting behavior. Confirmation of Stone's suggestion with the present tests on female mounting support the idea that mounting behavior in both males and females is regulated by similar systems [ 12, 14]. The higher mount frequencies achieved by the experienced females (Group 1) in the active receptive condition is in agreement with Beach and Rasquin [4] who found that mounting proficiency of female rats increased as testing progressed. The effect of social isolation has also been shown to reduce mounting behavior in female guinea pigs [10] and in male rats [9]. However, the present study does not allow separation of mounting experience and living
condition and the extent to which each contribute to this difference. Comparison of the effects of olfactory lesions in female rats with the effect of similar lesions in males is difficult since, for the male, much of the effect relates to ejaculation latencies and frequencies [11, 5] for which comparable measures are not available in the female. However, Bermant and Taylor [5] report that bilateral olfactory bulb lesions in sexually inexperienced, individually housed males did not reduce the probability that they would achieve intromission and, in that sense, these findings parallel the effects of bulbectomy on mounting in similarly treated females (Group 2).
266
CONIGLIO AND CLEMENS
,N,,,LS.NC,OSIVE z o
i •
F1 S.,, N.,O m ,
U
LESION
2S z < lz
N,t4
(J Z uJ
Q 0
0 uJ u.
,o ~ 0 (--
z <( uJ =E
Z <
m
B. MOUNT
POSITIVE
ANIMALS
I
~
..2 z
~o z O u
4O a 0 0
U.
so
~
2o
~
+-
,0 z II
ACTIVE RECEPTIVE
INACTIVE NON
~ECEPT~VE
RECEPTIVE
NON RECEPTIVE
FIG. 2. Mean mounting frequency under four incentive female conditions and odor discrimination data for inexperienced female rats; (A) all animals inclusive, (B) mount positive females.
Female rats, like male rats, are not dependent upon olfactory bulbs for the initiation of mounting. Several studies have shown that there are species differences in the relative importance of olfactory stimuli to mounting behavior. Brooks [6] demonstrated that male rabbits continue to copulate after olfactory bulb removal. Murphy and Schneider [13] reported that olfactory bulb removal eliminates mounting and subsequent mating behaviors in sexually naive as well as sexually experienced male hamsters. These findings
were confirmed and extended to include neonatally androgenized female hamsters [8] which are similarly affected by olfactory bulb lesions. In the rat, however, mounting depends not upon any single category of stimuli, such as odor or vision, but rather upon a multisensory pattern in which several modalities are involved with no one modality appearing both necessary and sufficient [2]. Hormones were generously supplied by Preston L. Perlman of Schering Corporation, Serpasil was supplied by R. Gaunt of Ciba Corporation, U.S.A.
REFERENCES 1. Beach, F. A. Analysis of the stimuli adequate to elicit mating behavior in the sexually inexperienced male rat. J. comp. physiol. Psyehol. 33: 163-207, 1942a. 2. Beach, F. A. Analysis of factors involved in the arousal, maintenance, and manifestations of sexual excitement in male animals. Psychosomat. Med. 4: 173-198, 1942b.
3. Beach, F. A. Factors involved in the control of mounting behavior by female mammals. In: Perspectives in Reproduction and Sexual Behavior, edited by M. Diamond, Indiana Univ. Press, 1968, pp. 83-131. 4. Beach, F. A.. and P. Rasquin. Masculine copulatory behavior in intact and castrated female rats. Endocrinology, 31: 393409, 1942.
MOUNTING BEHAVIOR IN FEMALE RATS 5. Bermant, G. and L. Taylor. Interactive effects of experience and olfactory bulb lesions in male rat copulation. Physiol. Behav., 4: 13-18, 1969. 6. Brooks, C. Mc. The role of the cerebral cortex and various sense organs in the excitation of mating activity in the rabbit. Am. J. Physiol., 120: 544-553, 1937. 7. Coniglio, L. and L. G. Clemens. Mounting behavior in the female rat. Amer. Zool. (abst) 10: No. 3, August, 1970. 8. Doty, R. L., C. S. Carter and L. G. Clemens. Olfactory control of sexual behavior in the male and early-androgenized female hamster. Horm. and Behav., 2: 325-335, 1971. 9. Gerall, H., I. L. Ward and A. Gerall. Disruption of the male rat's sexual behavior induced by social isolation, dnim. Behav., 15: 54-58, 1967. 10. Goy, R. W. and W. C. Young. Somatic basis of sexual behavior patterns in guinea pigs. Psychosorn. Med., 19: 144-151, 1957.
267 11. Heimer, L. and K. Larsson. Mating behavior of male rats after olfactory bulb lesions. Physiol Behav., 2: 207-209, 1967b. 12. Hitt, J. C., S. E. Hendricks, I. Stevens and J. H. Lewis. Disruption of male, but not female, sexual behavior in rats by medial forebrain bundle lesions. J. comp. physiol. Psychol. 73: 377-384, 1970. 13. Murphy, M. R. and G. E. Schneider. Olfactory bulb removal elimates mating behavior in the male Golden Hamster. Science 167: 302-304, 1970. 14. Singer, J. Hypothalamic control of male and female sexual behavior in female rats. J. comp. physiol. Psychol. 66" 738742, 1968. 15. Stone, C. Congenital sexual behavior of young male albino rats. J. comp. Psychol. 2: 95-153, 1922. 16. Whalen, R. E. and D. A. Edwards. Hormonal determinants of the development of masculine and feminine behavior in male and female rats. Anat. Rec., 157: 173-180, 1967.