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The effect of peripheral olfactory blockade on the social behavior of the male golden hamster
BEHAVIORAL BIOLOGY, 9, 31-42 (1973), Abstract No. 292R
The Effect of Peripheral Olfactory Blockade on the Social Behavior of the Male Golden Hamster 1
MARSHALL DEVOR 2 and MICHAEL R. MURPHY 3
Department of Psychology, Massachusetts Institute o f Technology Cambridge, Massachusetts 02139
Bilateral olfactory bulbectomy eliminates mating and attenuates intermale investigatory and aggressive behavior in male golden hamsters (Mesocricetus auratus). Two reversible methods of peripheral olfactory blockage were found to mimic these effects. They were (1)unilateral olfactory bulbeetomy combined with contralateral nostril occlusion and (2) bilateral reversible destruction of the olfactory epithelium by zinc sulfate infusion. These results indicate that a primary sensory deficit is sufficient to explain the effects of bulbectomy on social behavior and that incidental disruption of central nervous system tissue need not be invoked.
The olfactory sense, while playing a significant role in the regulation of social behavior patterns in many mammalian species appears to be critical to a few species. For example, surgical removal of the olfactory bulbs eliminates mating and drastically reduces some other aspects of social behavior in hamsters, Mesocricetus auratus Waterhouse, and mice, Mus musculus (Murphy and Schneider, 1970; Ropartz, 1968; Rowe and Edwards, 1971, 1972). These effects of olfactory bulbectomy, however suggestive, do not prove conclusively that odor perception is necessary for the organization of social behavior patterns in these species since bulbectomy has some physiological and behavioral effects that are unrelated to the sense o f smell. For example, olfactory bulb removal lowers forebrain norepinephrine level, destroys olfactory bulb osmoreceptor cells, and disrupts some aspects of paleocortical electrical activity (Pohorecky, Zigmond, Heimer, and Wurtman, 1969; Sundsten and Sawyer, 1959; Becker and Freeman, 1968). In addition, bulbectomy 1Supported by N.A.S.A. Grant NGL-22-009-308 and a Grant from the Alfred P. Sloan Foundation both to the M.I.T. Psychology Department. We gratefully acknowledge the advice of Dr. G. E. Schneider and Dr. S. L. Chorover. 2Reprint requests should be sent to: Marshall Devor M.I.T. El0-019 Cambridge, Mass. 02139. 3present address: Research Division, National Zoological Park, Smithsonian Institution, Washington D. C. 20009. 31 Copyright © 1973 by Academic Press, Inc. All rights of reproduction in any form reserved.
32
DEVOR AND MURPHY
invariably damages the vomeronasal system, a chemoreceptive modality that may influence limbic function via its relatively direct access to the amygdala and medial hypothalamus 0Vinans and Scalia, 1970). In order to determine whether such side effects, and not anosmia per se, might be responsible for changes in sexual and social behavior that follow olfactory bulb removal in the golden hamster, the effects of two techniques of reversible peripheral olfactory blockage were studied. Anosmia produced by either method produced behavioral disruption comparable to that of olfactory bulbectomy. These results further emphasize the critical importance of biologically meaningful odors in the sexual and social behavior of the male hamster. METHOD 1 The first technique took advantage of the separation of the two nasal cavities, the ipsilateral projection of the olfactory receptors onto the olfactory bulbs, and the absence of effects of unilateral olfactory bulb removal on mating or social behavior in the hamster (Negus, 1958, Murphy and Schneider, 1970). In 11 unilaterally bulbectomized animals, the sense of smell was impaired by pinching the nostril ipsilateral to the remaining bulb with a 9-mm surgical wound clip (Clay-Adams Inc., N.Y.) dipped in local anaesthetic (Xylocaine, Astra). This experimental treatment left the hamsters with one free nasal passage and one normal olfactory bulb, but precluded any functional connection between them. Control treatments consisted of either occluding the nostril contralateral to the intact bulb or of placing a clip on the snout but not over the nostril on the ipsilateral side. These treatments produced discomfort similar to the experimental treatment without impairing air flow to the side of the intact bulb. In all cases, the hamsters showed little sign of distress after 2 min of habituation to the clip. Subjects
Hamsters were housed individually in plastic cages with Sanicel (Paxton Processing Co., Paxton, I11.) bedding and maintained ad lib. on Purina rat pellets and water. Under sodium pentobarbital anaesthesia (6.5 rag/100 g) one olfactory bulb was removed by suction. Only animals that mated vigorously before and after surgery were used. Following testing, the subjects were perfused transcardially with 10% formol saline. Brains were embedded in albumen gelatin, cut in 30-/am frozen serial sections, and stained with cresylecht violet. Results are based on data from ten adult sexually vigorous male golden hamsters that had undergone complete removal of one olfactory bulb. One animal that showed signs of being able to smell was dropped from the experiment when histology indicated incomplete removal of the olfactory bulb. In the remaining ten subjects one olfactory bulb was completely removed and variable amounts of damage were done to the olfactory peduncle. All damage was unilateral.
PERIPHERALANOSMIAIN HAMSTERS
33
Testing Beginning at least 10 days after surgery, five of the animals were given tests of (1)odor preference, (2)mating and (3)intermale social behavior, under control conditions. At least 1 wk later they were retested under conditions of olfactory blockage. The other five subjects were tested in the reverse order. (1) Odor preference test. Two small narrow necked bottles were placed in opposite corners of the hamster's home cage; one bottle was clean and one contained secretion from the vagina of five females including at least one in an estrus state. The males could not lick the secretion. Time spent sniffing, with the tip of the snout closely applied to any part of the two bottles was measured during a 300-sec period. (2)Mating test. Immediately following the olfactory preference test a sexually receptive female hamster was placed in the cage of each male for 300 sec. The females, which had been spayed, were made receptive by subcutaneous injections of 0.1 mg oestradiol benzoate in oil (Progynon, Schering) 48 hr before testing and 0.2 mg progesterone in propylene glycol 3-6 hr before testing. Before use, the females were proved to be receptive with a stud male. Using a set of hand operated keys to operate pens of a continuous event recorder, the occurrences of eight mutually exclusive behavior categories were registered. These included: (1)investigation or licking of female's head or body, (2) licking the anal-vaginal area, (3) mounting, (4) intromission, (5) lickhag of penis, (6) ejaculation, (7) eating, and (8) attacking the female. Duration and number of particular categories, parameters that were representative of the animals' overall performances, were derived from these records. "Total sexual" (see Table 1) is the sum of the durations (sec) of all but (7) and (8). f3) Intermale social behavior. Several days after the mating test, intermale investigatory and aggressive behavior was observed by introducing a bilaterally bulbectomized male into the home cage of each experimental animal for a 300-see period. Since the stimulus animals ignored the experimental subjects (Murphy, 1972), all social interaction was initiated by the latter. Records of the subjects' behavior registered five relevant behavior categories which have been described in detail elsewhere (Murphy, 1972). These were: (1)investigation of opponent, (2)attacking, (3)fighting, (4)submission, and (5)non-social behavior.
Results and Discussion (1) Odor preference test. Under the control conditions all subjects showed a strong attraction to the bottle containing the female hamster genital secretion; however, under the experimental olfactory blockade condition, they showed no bottle preference and indeed little interest in either bottle (see Table 1). Although one cannot be certain that the animals were completely
34
DEVOR AND MURPHY TABLE 1
Odor Preferences and Social Behavior of Hamsters with Peripheral Olfactory Impairment Nostril clipping Experimental (anosmic) Secretion investigation scented bottle (see) clean bottle (see)
Nasal cauterization
Control pa
Zinc sulfate
Saline
pa
<.01 39.0 >0.2 37.8
124.0 34.8
<.01 >0.2
>300
54.1
<.01
26.2 17.9
77.2 12.8
-
-
Mating behavior vaginal licking (see) mounts (no.) totalsexual (sec)
1.2 0. 19.7
21.3 27.0 206.3
<.01 4.5 <.01 3.0 <.01 90.5
36.6 17.1 219.8
<.01 <.01 <.01
Intermale social behavior investigation (see) attacking (No./N)
16.0 0/10
193.6 8/10
<.01 46.0 <.01 b 1/6
207.0 5/6
<.01 <.05 b
Food finding (see)
aConfidence levels are based on two-tailed Student's t tests, bConfidence levels based on the Fisher exact probabilities test (Siegel, 1956). anosmic, occlusion of the nasal passage on the side of the intact olfactory bulb effectively abolished the normal investigatory response to a potent olfactory stimulus. In species that have incomplete separation of the nasal cavities it may be necessary to artificially extend the septum in order to obtain a corresponding result. This may or may not be necessary in the rat (Bennett, 1971 ; Teitelbaum, 1971). (2) Sexual behavior. Under control conditions, all hamsters mated vigorously in a normal manner despite any discomfort that may have been caused by the nostril clip. Under the experimental condition o f olfactory impairment, mating behavior was completely eliminated. There were no attempts to mount the female and all other signs of sexual arousal were greatly reduced (e.g., vaginal licking, see Table 1). Instead, the temporarily "anosmic" subjects explored, groomed, and otherwise behaved as if they were alone in their cage. Reversibility of mating behavior. The nostril occlusion technique permits short-term as well as long-term control of olfactory acuity. Taking advantage of this flexibility, after each 300-sec mating test with one nostril blocked, the female was removed, the clip rapidly switched to the other nostril, and after a total delay interval of 60-500 sec, the female was replaced for another 300 sec. In many cases the clip was reversed a second time, and in some, a third and fourth.
PERIPHERAL ANOSMIA IN HAMSTERS
35
In each instance, removal of the occluder from the nostril of the side of the intact bulb led to immediate sexual arousal upon reintroduction of the female and vigorous mating for the duration of the test (Figs. 1 A and B). secretion in mouth
A
l
B
C
r~:l
_,. F I I I I I E
175 ~-sec.~
D
_ . I-Igl
I/II/-IF
m m m m m m m m m m
I
J
g
g
I
I
ipsilateral clip
300 s e c .
......
1 m mm
lift1 , m m m m m m
(anosmic)
contralateral clip (control)
Fig. 1. In unilaterally bulbectomized male hamsters mating was turned off and on by blocking, with the use of a small clip, the nostril ipsilateral to the intact bulb (anosmic condition) or the contralateral nostril (control condition) as in records A, B, D. The blocks indicate that the female was present. Single narrow lines within the blocks represent single mounts and broader black areas represent bouts of several consecutive mounts. Mating often persisted when absence of the female (no block) during clip reversal was less than 123 sec as in record C. Female hamster vaginal secretion placed in the mouth of the animal in record A did not trigger copulation. Records A and B are from the same animal as are records C and D.
After the reverse procedure, blocking the previously open passage on the side of the intact bulb, the elimination or persistence of mating depended on the interval before reintroduction of the female. Mating failed to resume whenever it had been interrupted for more than 123 sec during clip reversal. In about half of the cases where the intertest interval was less than 123 sec, the now anosmic male resumed mating (see Figs. 1C and D and Table 2) and often continued to mate for the full 300 sec of the test period (e.g., Fig. 1C and Table 2 animal #NB3). This observation indicates that olfactory stimulation is necessary to initiate the copulatory sequence but not to maintain it. Thus, the male hamster's sexual interest in the female is highly malleable. By choosing appropriate time parameters it was possible to initiate or terminate mating behavior merely by switching a nostril occluder from one nostril to the other. (3}Intermale social behavior. Under the control condition, all subjects vigorously investigated the intruding male and eight of the ten attacked the intruder. Under the experimental condition, however, these same subjects never attacked the intruder and they spent relatively little time investigating him (see Table 1). Instead, like bilaterally bulbectomized hamsters, they tended to ignore the presence of their partner.
DEVOR AND MURPHY
36
TABLE 2 Persistence of Mating after Olfactory Blockade in Hamsters that had Spent the Previous 300-see Engaged in Sexual Behavior
Animal No. NB 4 NB 16 NB 3 NB 21 NB 17 NB 19 NB 19 NB 21 NB 14 NB 4 NB 3 NB 5 NB 17 NB 2 NB 13 NB 5 NB 2 NB 13 NB 14
Delay interval before reintroduction of female (sec)
Mating foUowing reintroduction of female (sec)
64 70 72 75 80 99 104 115 121 123 128 128 176 224 264 328 328 368 448
0 230 300 0 280 86 0 0 300 96 0 0 0 0 0 0 0 0 0
Peripheral nostril occlusion has disruptive effects on sexual and intermale investigatory and aggressive behavior that closely resemble those of bilateral bulbectomy. It is thus unnecessary to invoke bilateral damage to a lirnbic brain structure, as opposed to blockage o f a sense modality, to account for the deficits in these behaviors that follow bilateral olfactory bulb removal.
METHOD 2 The second technique of peripheral olfactory blockade, one which avoided even unilateral central nervous system damage, was based on the finding of Alberts and Galef (1971) that perfusion of the nasal cavity with a zinc sulfate solution renders rats unable to find buried odorous food pellets. This treatment selectively destroys the olfactory epithelium. Complete histological recovery, which occurs in m a n y species, takes a number o f w e e k s (IVlulvaney and Heist, 1971; Takagi, !971).
PERIPHERALANOSMIAIN HAMSTERS
37
Subjects and treatment. After having been deprived of food for 48 hr, six sexually experienced adult male hamsters were perfused intranasally with zinc sulfate and six were perfused with saline solution. At intervals after injection they were tested for responsiveness to odors, sexual vigor, and intermale social behavior. The zinc sulfate perfusion method of Alberts and Galef (1971) was modified in order to reduce the possibility of incomplete perfusion due to mucosal swelling, or mucous secretion following ether anaesthesia. Histological evidence of such incomplete damage has been obtained by H.I. Dinc (personal communication). Hamsters were pretreated with atropine sulfate (0.07 mg per 100 g body weight ip) and 10 min later, under the short-acting barbiturate anaesthetic sodium methohexital (Brevital sodium, Lilly, 4 rag/100 g ip), they were injected intranasally with 2 ml aqueous 5% zinc sulfate solution, or 0.9% saline via the posterior naris as described by Alberts and Galef (1971). Solutions were infused slowly and the nasal passage was subsequently drained by gently shaking the animal. Effluent collected from the anterior nares measured 1.6-1.9ml. In order to preclude the possibility that effects of nasal perfusion were due to systemic absorption of the ZnSO4, a group of five unoperated control animals were given intraperitoneal injections of 0.5 ml 5% zinc sulfate solution. This treatment caused severe lethargy and hunched posture 1-5 hr after injection, an effect not observed in the experimental animals. Twenty-four hours after systemic injection, these control animals appeared healthy and mated normally. The olfactory bulbs of animals that had undergone multiple injections of zinc sulfate showed no sign of cellular damage in cresylecht violet stained sections. Initial testing. During a 3-hr period beginning 24 hr after treatment the animals were tested, using a single blind procedure, for secretion odor preference, mating, and intermale social behavior as described above. An additional test of olfactory acuity, similar to the one used by Alberts and Galef (1971), was also administered. A food pellet was buried under the home cage bedding of the now 72 hr food deprived hamsters. The latency to find the pellet and the time required to begin eating it were measured. If the pellet was not uncovered in 300 sec, the hamster was handed a food pellet and observed until it began to eat. Subsequently the pellet was reburied and the latency to find it measured again. After completion of the four tests the animals were fed ad lib. Recovery testing. Alberts and Galef (1971) reported that zinc sulfatetreated rats recover their ability to find buried food in 2-14 days. In order to determine if the same was true for zinc sulfate-treated hamsters, and whether their social behavior recovers correspondingly, performance of the experimental animals was re-examined periodically. Each subject was retested until it found buried food on at least one of the trials, spent more than twice as long sniffing the secretion scented bottle as the clean bottle, mounted the female at least once, and spent at least 100 sec investigating the intruding male.
38
DEVOR AND MURPHY
Results and Discussion Initial tests (24hr after treatment). ( 1 ) F o o d finding test: All six saline-treated animals found the food within 300 sec on each of the two successive trials, with a mean latency of 54 sec. The mean interval between finding the pellet and beginning to eat was 17 sec. None of the six zinc sulfate treated animals found the food within 300sec on either trial. Despite occasional sneezing, these animals did not appear to be sick; they actively explored their cage and, when offered a food pellet, began to eat it within 10 sec on the average (see Table 1). (2) Secretion preference test: Five of the six saline-treated animals were strongly attracted to the bottle containing vaginal secretion and spent more than twice as long sniffing it than the clean bottle; none of the zinc sulfate treated animals were attracted to the secretion (see Table 1). (3)Mating test: Saline-treated animals spent an average of 220 sec interacting with the female and five of the six mated vigorously. Only one of the six zinc sulfate treated animals mated with the female. The remaining five averaged only 73 sec investigating her. Vaginal licking was also greatly depressed (see Table 1). A similar result has recently been reported by Lisk et al. (1972). (4) Interrnale social behavior: The six saline-treated animals all behaved normally, spending an average of 207 sec investigating the intruder. Five of these animals attacked him. The six zinc sulfate-treated animals were largely indifferent to the male intruder and spect an average of only 46 sec investigating him. Only one brief attack was observed. This disruption of sexual and intermale investigative and aggressive behavior is very similar to the previously reported effects of bilateral bulbectomy (Murphy and Schneider, 1970) and the effects of nostril occlusion described above. Recovery of function. On each of the tests, a hamster either behaved as if he were anosmic or performed at the level of control animals, well above criterion. Intermediate performance was rarely observed and eventual recovery on all four tests was the rule. In several cases, normal mating and intermale social behavior was observed before ability to find food had recovered (see Fig. 2). For example, by 6 days after treatment with zinc sulfate, five of the six animals mated normally (mean of 20 mounts) and all six showed normal social behavior (mean of 213 sec investigating intruder). The animal that failed to mate had not yet recovered a preference for the odor of vaginal secretion, but he and two others were still unable to find buried food on either of the two trials. Thus failure to find buried food dearly does not indicate complete anosmia. An animal that appears anosmic on one test may respond to the more salient odors involved in certain other odor-guided behaviors. The choice of inappropriate behavioral tests for establishing anosmia and the lack of
PERIPHERAL ANOSMIA IN HAMSTERS
o 6 •:® •~ 5 u
t.o.~ ~lk ~ . ~N,N,
39
~ food finding o secretion pref. . mating ~ intermale social
~
-~ 3 '~6 2 < Z
~
8 1
6
14
Days after ZnSO 4
Fig. 2. Recovery of odor preferences and social behaviors of six male hamsters after cauterization of the olfactory epithelium with ZnSO4. (#) represents individual animals. Criteria of recovery are given in the text. histology or other corroborating evidence may thus confound the interpretation of experimental results and may account for some recent claims that "anosmic" rats, mice and hamsters are less impaired in certain forms of social behavior after chemical or surgical destruction of the olfactory mucosa than after bulbectomy (rats: Alberts and Friedman, 1972; Fleming, 1972; Spector and Hull, 1972; mice: Rowe and Smith, 1972; Edwards, Thompson and Burge, 1972; hamsters: Powers and Winans, in press).
GENERAL DISCUSSION Central vs peripheral anosmia. Reversible peripheral olfactory blockage by either nostril occlusion or zinc sulfate infusion eliminated mating and drastically reduced intermale investigatory and aggressive behavior in adult male golden hamsters. Equivalent effects were previously produced by bilateral olfactory bulb removal (Murphy and Schneider, 1970). It thus appears that odor perception is essential to these behaviors and that bilateral central nervous system tissue damage is not necessary to disrupt them. Olfactory bulb removal, which produces anosmia, disrupts many different behavior patterns to a greater or lesser degree in a large variety of mammalian species (for a recent review see Cheal and Sprott, 1972). In many of these instances, however, one or more of the side effects of bulbectomy, and not anosmia per se may be the direct cause of the resulting behavioral changes. Failure to replicate the effects of bulbectomy after damage to the olfactory receptor sheet has been presented in support of this possibility for certain behaviors in certain species. (Alberts and Friedman, 1972; Fleming, 1972; Spector and Hull, 1972; Rowe and Smith, 1972; Edwards, Thompson,
40
DEVOR AND MURPHY
and Burge, 1972; Powers and Winans, in press). It has yet to be demonstrated, though, that these peripherally treated animals were indeed unable to detect odors relevant to the specific behavior under investigation, and at concentrations appropriate to the behavioral situation. Trigerninal, vomeronasal, or olfactory? Trigeminal, vomeronasal and olfactory receptors can respond to airborn odors (Tucker, 1971). Thus in principle, any or all of these modalities may be critical for social behavior in male hamsters. The available evidence, though not conclusive, suggests that olfactory function is the sensory modality necessary for the normal expression of these behaviors. Bilateral olfactory bulb removal, which leaves the trigeminal system intact, produces the full symptoms described here (Murphy and Schneider, 1970). Gross dissections have suggested that in the hamster, as in the rat (Kratzing, 1972) the vomeronasal organ opens into the nasal cavity close to the opening of the spheno-palatine duct. Odors admitted through the duct during precopulatory vaginal licking, though, are not sufficient to trigger mating as: (I)prevention of licking by suturing the mouth shut did not drastically alter mating and (2)sexual interest was not aroused by placing vaginal secretion on the roof of the mouth in nostril clipped or zinc sulfate-treated animals (see Fig. 1A). In addition, severance of the vomeronasal nerve along its caudad traverse between the olfactory bulbs had no effect on mating behavior (Devor and Murphy, unpublished observations). Initiation of behavior vs its organization. The anosmic hamster does not initiate normal social interactions with female or male conspecifics. He is capable, however, of engaging in these highly organized behavior patterns. An anosmic male; for instance, will often continue mating in the normal manner with a female if she is returned to him within 2 rain of peripheral olfactory occlusion (Fig. 1C). Similarly, if attacked by an intruder male, a bilaterally bulbectomized male will fight back and sometimes win the fight (Murphy, 1972). Behaviorally meaningful odors associated with conspecifics are necessary for the initiation of such species typical behavior patterns. The postural adjustments characteristic to these organized behavior patterns, though, are not directed by olfactory cues alone (Herrick, 1933). Furthermore, while necessary for the initiation of social interactions, behaviorally meaningful odors in the hamster are not sufficient to elicit these behaviors. Vaginal secretion, for instance, does not elicit sexual responses in vacuo; adequate non-olfactory stimuli must also be present (Devor and Murphy, 1972). The fact that these nonolfactory cues appear to lose their social importance when olfactory perception is impaired has led to the hypothesis that anosmia produces "social agnosia" in the male golden hamster (Murphy, 1972; Devor and Murphy, 1972). The results we have presented underline the importance of behaviorally meaningful odors in the facilitation of central mechanisms subserving several aspects of mammalian social behavior. The demonstration that odors are
PERIPHERAL ANOSMIA IN HAMSTERS
41
critical for mating and intermale social behavior in hamsters makes this species exceptionally useful for studies of the modes of analysis of olfactory information within the forebrain. The combination of unilateral brain lesions with occlusion of the contralateral nostril could prove useful in such research. REFERENCES Alberts, J. R., and Galef, B. G., Jr. (1971). Acute anosmia in the rat: a behavioral test of a peripherally induced olfactory deficit. Physiol. Behav. 6, 619-621. Alberts, J. R., and Friedman, M. I., (1972). Olfactory bulb removal but not anosmia increases emotionality and mouse killing. Nature 238, 454-455. Becker, C. J., and Freeman, W. J. (1968). Prepyriform electrical activity after loss of peripheral or central input, or both. Physiol. Behav. 3,597-599. Bennett, M. H. (1971). A reversible nasal block for the rat. Physiol. Behav. 7, 269-270. Cheal, M. L., and Sprott, R. L. (1971). Social olfaction: a review of the role of olfaction in a variety of animal behaviors. Psychol. Rev. 29, 195-243. Devor, M., and Murphy, M. R. (1972). Social agnosia produced by peripheral olfactory blockage in hamsters. Amer. Zool. 12, 653. Edwards, D. A., Thompson, M. L., and Burge, K. G. (1972). Olfactory bulb removal vs peripherally induced anosmia: differential effects on the aggressive behavior of male mice. Behav. Biol. 7, 823-828. Fleming, A. S. (1972). Olfactory and experimental factors underlying maternal behavior in the lactating and cycling female rat. Doctoral dissertation, Rutgers University, Newark. Herrick, C. J. (1933). The functions of the olfactory parts of the cerebral cOrtex. Proc. Nat. Acad. ScL 19, 7-14. Kratzing, J. E. (1971). The fine structure of the sensory epithelium of the vomeronasal organ in suckling rats. Aust. J. BioL Sci. 24,787-796. Lisk, R. D., Zeiss, J , and Ciaccio, L. A. (1972). The influence of olfaction on sexual behavior in the male golden hamster (Mesocricetus auratus). J. Exp. Zool. 181, 69-78. Mulvaney, B. D., and Heist, H. E. (1971). Regeneration of rabbit olfactory epithelium. Amer. J. Anat. 131, 241-252. Murphy, M. R., and Schneider, G. E. (1970). Olfactory bulb removal eliminates mating behavior in male hamsters. Science 167, 302-303. Murphy, M. R., (1972). Different effects of olfactory bulb removal on different kinds of aggression in male Syrian golden hamsters. Doctoral dissertation, Department of Psychology, M.I.T. Cambridge. Negus, V. (1958). "The Comparative Anatomy and Physiology of the Nose and Paranasal Sinuses," London, Livingston. Pohorecky, L. A., Zigmund, M. J., Heimer, L., and Wurtman, R. J. (1969). Olfactory bulb removal: effects on brain norepinephrine. Proc. Nat. Acad. ScL 62, 1052-1055. Powers, J. B., and Winans, S. S. (in press). Sexual behavior in peripherally anosmic male hamsters. Physiol. Behav. Ropartz, P. (1968). The relation between olfactory stimulation and aggressive behavior in mice. Animo Behav. 16, 97-100. Rowe, F. A., and Edwards, D. A. (1971). Olfactory bulb removal: influences on the aggressive behaviors of male mice. Physiol. Behav, 7, 889-892.
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Rowe, F. A., and Edwards, D. A. (1972). Olfactory bulb removal: influences on the mating behavior of male mice. Physiol. Behav. 8, 37-41. Rowe, F. A., and Smith, W. E. (1972). Effects of peripherally induced anosmia on mating behavior of male mice. Psychon. Sci. 27, 33-34. Siegel, S. (1956). "Non-parametric Statistics," New York: McGraw-Hill. Spector, S. A., and Hull, E. M. (1972). Anosmia and mouse killing by rats: a nonolfactory role for the olfactory bulbs. J. Comp. Physiol. Psychol. 80, 354-356. Sundsten, J. W., and Sawyer, C. W. (1959). Electroencephalographic evidence of osmosensitive elements in olfactory bulb of dog brain. Soc. Exp. Biol. Med. 101, 524-527. Takagi, S. F. (1971). Degeneration and regeneration of the olfactory epithelium. In L. M. Beidler (Ed.), "Handbook of Sensory Physiology," New York: Springer-Vedag. Teitelbaum, H. (1971). Lateralization of olfactory memory in the split-brain rat. J. Comp. Physiol. Psychol. 76, 51-66. Tucker, D. (1971). Nonolfactory responses from the nasal cavity: Jaeobson's organ and the trigeminal system. In L. M. Beidler (Ed.), "Handbook of Sensory Physiology," New York: Springer-Verlag. Winans, S. S., and Scalia, F. (1970). Amygdaloid nucleus: new afferent input from the vomeronasal organ. Science 197,330-332.
The Effect of Peripheral Olfactory Blockade on the Social Behavior of the Male Golden Hamster 1
MARSHALL DEVOR 2 and MICHAEL R. MURPHY 3
Department of Psychology, Massachusetts Institute o f Technology Cambridge, Massachusetts 02139
Bilateral olfactory bulbectomy eliminates mating and attenuates intermale investigatory and aggressive behavior in male golden hamsters (Mesocricetus auratus). Two reversible methods of peripheral olfactory blockage were found to mimic these effects. They were (1)unilateral olfactory bulbeetomy combined with contralateral nostril occlusion and (2) bilateral reversible destruction of the olfactory epithelium by zinc sulfate infusion. These results indicate that a primary sensory deficit is sufficient to explain the effects of bulbectomy on social behavior and that incidental disruption of central nervous system tissue need not be invoked.
The olfactory sense, while playing a significant role in the regulation of social behavior patterns in many mammalian species appears to be critical to a few species. For example, surgical removal of the olfactory bulbs eliminates mating and drastically reduces some other aspects of social behavior in hamsters, Mesocricetus auratus Waterhouse, and mice, Mus musculus (Murphy and Schneider, 1970; Ropartz, 1968; Rowe and Edwards, 1971, 1972). These effects of olfactory bulbectomy, however suggestive, do not prove conclusively that odor perception is necessary for the organization of social behavior patterns in these species since bulbectomy has some physiological and behavioral effects that are unrelated to the sense o f smell. For example, olfactory bulb removal lowers forebrain norepinephrine level, destroys olfactory bulb osmoreceptor cells, and disrupts some aspects of paleocortical electrical activity (Pohorecky, Zigmond, Heimer, and Wurtman, 1969; Sundsten and Sawyer, 1959; Becker and Freeman, 1968). In addition, bulbectomy 1Supported by N.A.S.A. Grant NGL-22-009-308 and a Grant from the Alfred P. Sloan Foundation both to the M.I.T. Psychology Department. We gratefully acknowledge the advice of Dr. G. E. Schneider and Dr. S. L. Chorover. 2Reprint requests should be sent to: Marshall Devor M.I.T. El0-019 Cambridge, Mass. 02139. 3present address: Research Division, National Zoological Park, Smithsonian Institution, Washington D. C. 20009. 31 Copyright © 1973 by Academic Press, Inc. All rights of reproduction in any form reserved.
32
DEVOR AND MURPHY
invariably damages the vomeronasal system, a chemoreceptive modality that may influence limbic function via its relatively direct access to the amygdala and medial hypothalamus 0Vinans and Scalia, 1970). In order to determine whether such side effects, and not anosmia per se, might be responsible for changes in sexual and social behavior that follow olfactory bulb removal in the golden hamster, the effects of two techniques of reversible peripheral olfactory blockage were studied. Anosmia produced by either method produced behavioral disruption comparable to that of olfactory bulbectomy. These results further emphasize the critical importance of biologically meaningful odors in the sexual and social behavior of the male hamster. METHOD 1 The first technique took advantage of the separation of the two nasal cavities, the ipsilateral projection of the olfactory receptors onto the olfactory bulbs, and the absence of effects of unilateral olfactory bulb removal on mating or social behavior in the hamster (Negus, 1958, Murphy and Schneider, 1970). In 11 unilaterally bulbectomized animals, the sense of smell was impaired by pinching the nostril ipsilateral to the remaining bulb with a 9-mm surgical wound clip (Clay-Adams Inc., N.Y.) dipped in local anaesthetic (Xylocaine, Astra). This experimental treatment left the hamsters with one free nasal passage and one normal olfactory bulb, but precluded any functional connection between them. Control treatments consisted of either occluding the nostril contralateral to the intact bulb or of placing a clip on the snout but not over the nostril on the ipsilateral side. These treatments produced discomfort similar to the experimental treatment without impairing air flow to the side of the intact bulb. In all cases, the hamsters showed little sign of distress after 2 min of habituation to the clip. Subjects
Hamsters were housed individually in plastic cages with Sanicel (Paxton Processing Co., Paxton, I11.) bedding and maintained ad lib. on Purina rat pellets and water. Under sodium pentobarbital anaesthesia (6.5 rag/100 g) one olfactory bulb was removed by suction. Only animals that mated vigorously before and after surgery were used. Following testing, the subjects were perfused transcardially with 10% formol saline. Brains were embedded in albumen gelatin, cut in 30-/am frozen serial sections, and stained with cresylecht violet. Results are based on data from ten adult sexually vigorous male golden hamsters that had undergone complete removal of one olfactory bulb. One animal that showed signs of being able to smell was dropped from the experiment when histology indicated incomplete removal of the olfactory bulb. In the remaining ten subjects one olfactory bulb was completely removed and variable amounts of damage were done to the olfactory peduncle. All damage was unilateral.
PERIPHERALANOSMIAIN HAMSTERS
33
Testing Beginning at least 10 days after surgery, five of the animals were given tests of (1)odor preference, (2)mating and (3)intermale social behavior, under control conditions. At least 1 wk later they were retested under conditions of olfactory blockage. The other five subjects were tested in the reverse order. (1) Odor preference test. Two small narrow necked bottles were placed in opposite corners of the hamster's home cage; one bottle was clean and one contained secretion from the vagina of five females including at least one in an estrus state. The males could not lick the secretion. Time spent sniffing, with the tip of the snout closely applied to any part of the two bottles was measured during a 300-sec period. (2)Mating test. Immediately following the olfactory preference test a sexually receptive female hamster was placed in the cage of each male for 300 sec. The females, which had been spayed, were made receptive by subcutaneous injections of 0.1 mg oestradiol benzoate in oil (Progynon, Schering) 48 hr before testing and 0.2 mg progesterone in propylene glycol 3-6 hr before testing. Before use, the females were proved to be receptive with a stud male. Using a set of hand operated keys to operate pens of a continuous event recorder, the occurrences of eight mutually exclusive behavior categories were registered. These included: (1)investigation or licking of female's head or body, (2) licking the anal-vaginal area, (3) mounting, (4) intromission, (5) lickhag of penis, (6) ejaculation, (7) eating, and (8) attacking the female. Duration and number of particular categories, parameters that were representative of the animals' overall performances, were derived from these records. "Total sexual" (see Table 1) is the sum of the durations (sec) of all but (7) and (8). f3) Intermale social behavior. Several days after the mating test, intermale investigatory and aggressive behavior was observed by introducing a bilaterally bulbectomized male into the home cage of each experimental animal for a 300-see period. Since the stimulus animals ignored the experimental subjects (Murphy, 1972), all social interaction was initiated by the latter. Records of the subjects' behavior registered five relevant behavior categories which have been described in detail elsewhere (Murphy, 1972). These were: (1)investigation of opponent, (2)attacking, (3)fighting, (4)submission, and (5)non-social behavior.
Results and Discussion (1) Odor preference test. Under the control conditions all subjects showed a strong attraction to the bottle containing the female hamster genital secretion; however, under the experimental olfactory blockade condition, they showed no bottle preference and indeed little interest in either bottle (see Table 1). Although one cannot be certain that the animals were completely
34
DEVOR AND MURPHY TABLE 1
Odor Preferences and Social Behavior of Hamsters with Peripheral Olfactory Impairment Nostril clipping Experimental (anosmic) Secretion investigation scented bottle (see) clean bottle (see)
Nasal cauterization
Control pa
Zinc sulfate
Saline
pa
<.01 39.0 >0.2 37.8
124.0 34.8
<.01 >0.2
>300
54.1
<.01
26.2 17.9
77.2 12.8
-
-
Mating behavior vaginal licking (see) mounts (no.) totalsexual (sec)
1.2 0. 19.7
21.3 27.0 206.3
<.01 4.5 <.01 3.0 <.01 90.5
36.6 17.1 219.8
<.01 <.01 <.01
Intermale social behavior investigation (see) attacking (No./N)
16.0 0/10
193.6 8/10
<.01 46.0 <.01 b 1/6
207.0 5/6
<.01 <.05 b
Food finding (see)
aConfidence levels are based on two-tailed Student's t tests, bConfidence levels based on the Fisher exact probabilities test (Siegel, 1956). anosmic, occlusion of the nasal passage on the side of the intact olfactory bulb effectively abolished the normal investigatory response to a potent olfactory stimulus. In species that have incomplete separation of the nasal cavities it may be necessary to artificially extend the septum in order to obtain a corresponding result. This may or may not be necessary in the rat (Bennett, 1971 ; Teitelbaum, 1971). (2) Sexual behavior. Under control conditions, all hamsters mated vigorously in a normal manner despite any discomfort that may have been caused by the nostril clip. Under the experimental condition o f olfactory impairment, mating behavior was completely eliminated. There were no attempts to mount the female and all other signs of sexual arousal were greatly reduced (e.g., vaginal licking, see Table 1). Instead, the temporarily "anosmic" subjects explored, groomed, and otherwise behaved as if they were alone in their cage. Reversibility of mating behavior. The nostril occlusion technique permits short-term as well as long-term control of olfactory acuity. Taking advantage of this flexibility, after each 300-sec mating test with one nostril blocked, the female was removed, the clip rapidly switched to the other nostril, and after a total delay interval of 60-500 sec, the female was replaced for another 300 sec. In many cases the clip was reversed a second time, and in some, a third and fourth.
PERIPHERAL ANOSMIA IN HAMSTERS
35
In each instance, removal of the occluder from the nostril of the side of the intact bulb led to immediate sexual arousal upon reintroduction of the female and vigorous mating for the duration of the test (Figs. 1 A and B). secretion in mouth
A
l
B
C
r~:l
_,. F I I I I I E
175 ~-sec.~
D
_ . I-Igl
I/II/-IF
m m m m m m m m m m
I
J
g
g
I
I
ipsilateral clip
300 s e c .
......
1 m mm
lift1 , m m m m m m
(anosmic)
contralateral clip (control)
Fig. 1. In unilaterally bulbectomized male hamsters mating was turned off and on by blocking, with the use of a small clip, the nostril ipsilateral to the intact bulb (anosmic condition) or the contralateral nostril (control condition) as in records A, B, D. The blocks indicate that the female was present. Single narrow lines within the blocks represent single mounts and broader black areas represent bouts of several consecutive mounts. Mating often persisted when absence of the female (no block) during clip reversal was less than 123 sec as in record C. Female hamster vaginal secretion placed in the mouth of the animal in record A did not trigger copulation. Records A and B are from the same animal as are records C and D.
After the reverse procedure, blocking the previously open passage on the side of the intact bulb, the elimination or persistence of mating depended on the interval before reintroduction of the female. Mating failed to resume whenever it had been interrupted for more than 123 sec during clip reversal. In about half of the cases where the intertest interval was less than 123 sec, the now anosmic male resumed mating (see Figs. 1C and D and Table 2) and often continued to mate for the full 300 sec of the test period (e.g., Fig. 1C and Table 2 animal #NB3). This observation indicates that olfactory stimulation is necessary to initiate the copulatory sequence but not to maintain it. Thus, the male hamster's sexual interest in the female is highly malleable. By choosing appropriate time parameters it was possible to initiate or terminate mating behavior merely by switching a nostril occluder from one nostril to the other. (3}Intermale social behavior. Under the control condition, all subjects vigorously investigated the intruding male and eight of the ten attacked the intruder. Under the experimental condition, however, these same subjects never attacked the intruder and they spent relatively little time investigating him (see Table 1). Instead, like bilaterally bulbectomized hamsters, they tended to ignore the presence of their partner.
DEVOR AND MURPHY
36
TABLE 2 Persistence of Mating after Olfactory Blockade in Hamsters that had Spent the Previous 300-see Engaged in Sexual Behavior
Animal No. NB 4 NB 16 NB 3 NB 21 NB 17 NB 19 NB 19 NB 21 NB 14 NB 4 NB 3 NB 5 NB 17 NB 2 NB 13 NB 5 NB 2 NB 13 NB 14
Delay interval before reintroduction of female (sec)
Mating foUowing reintroduction of female (sec)
64 70 72 75 80 99 104 115 121 123 128 128 176 224 264 328 328 368 448
0 230 300 0 280 86 0 0 300 96 0 0 0 0 0 0 0 0 0
Peripheral nostril occlusion has disruptive effects on sexual and intermale investigatory and aggressive behavior that closely resemble those of bilateral bulbectomy. It is thus unnecessary to invoke bilateral damage to a lirnbic brain structure, as opposed to blockage o f a sense modality, to account for the deficits in these behaviors that follow bilateral olfactory bulb removal.
METHOD 2 The second technique of peripheral olfactory blockade, one which avoided even unilateral central nervous system damage, was based on the finding of Alberts and Galef (1971) that perfusion of the nasal cavity with a zinc sulfate solution renders rats unable to find buried odorous food pellets. This treatment selectively destroys the olfactory epithelium. Complete histological recovery, which occurs in m a n y species, takes a number o f w e e k s (IVlulvaney and Heist, 1971; Takagi, !971).
PERIPHERALANOSMIAIN HAMSTERS
37
Subjects and treatment. After having been deprived of food for 48 hr, six sexually experienced adult male hamsters were perfused intranasally with zinc sulfate and six were perfused with saline solution. At intervals after injection they were tested for responsiveness to odors, sexual vigor, and intermale social behavior. The zinc sulfate perfusion method of Alberts and Galef (1971) was modified in order to reduce the possibility of incomplete perfusion due to mucosal swelling, or mucous secretion following ether anaesthesia. Histological evidence of such incomplete damage has been obtained by H.I. Dinc (personal communication). Hamsters were pretreated with atropine sulfate (0.07 mg per 100 g body weight ip) and 10 min later, under the short-acting barbiturate anaesthetic sodium methohexital (Brevital sodium, Lilly, 4 rag/100 g ip), they were injected intranasally with 2 ml aqueous 5% zinc sulfate solution, or 0.9% saline via the posterior naris as described by Alberts and Galef (1971). Solutions were infused slowly and the nasal passage was subsequently drained by gently shaking the animal. Effluent collected from the anterior nares measured 1.6-1.9ml. In order to preclude the possibility that effects of nasal perfusion were due to systemic absorption of the ZnSO4, a group of five unoperated control animals were given intraperitoneal injections of 0.5 ml 5% zinc sulfate solution. This treatment caused severe lethargy and hunched posture 1-5 hr after injection, an effect not observed in the experimental animals. Twenty-four hours after systemic injection, these control animals appeared healthy and mated normally. The olfactory bulbs of animals that had undergone multiple injections of zinc sulfate showed no sign of cellular damage in cresylecht violet stained sections. Initial testing. During a 3-hr period beginning 24 hr after treatment the animals were tested, using a single blind procedure, for secretion odor preference, mating, and intermale social behavior as described above. An additional test of olfactory acuity, similar to the one used by Alberts and Galef (1971), was also administered. A food pellet was buried under the home cage bedding of the now 72 hr food deprived hamsters. The latency to find the pellet and the time required to begin eating it were measured. If the pellet was not uncovered in 300 sec, the hamster was handed a food pellet and observed until it began to eat. Subsequently the pellet was reburied and the latency to find it measured again. After completion of the four tests the animals were fed ad lib. Recovery testing. Alberts and Galef (1971) reported that zinc sulfatetreated rats recover their ability to find buried food in 2-14 days. In order to determine if the same was true for zinc sulfate-treated hamsters, and whether their social behavior recovers correspondingly, performance of the experimental animals was re-examined periodically. Each subject was retested until it found buried food on at least one of the trials, spent more than twice as long sniffing the secretion scented bottle as the clean bottle, mounted the female at least once, and spent at least 100 sec investigating the intruding male.
38
DEVOR AND MURPHY
Results and Discussion Initial tests (24hr after treatment). ( 1 ) F o o d finding test: All six saline-treated animals found the food within 300 sec on each of the two successive trials, with a mean latency of 54 sec. The mean interval between finding the pellet and beginning to eat was 17 sec. None of the six zinc sulfate treated animals found the food within 300sec on either trial. Despite occasional sneezing, these animals did not appear to be sick; they actively explored their cage and, when offered a food pellet, began to eat it within 10 sec on the average (see Table 1). (2) Secretion preference test: Five of the six saline-treated animals were strongly attracted to the bottle containing vaginal secretion and spent more than twice as long sniffing it than the clean bottle; none of the zinc sulfate treated animals were attracted to the secretion (see Table 1). (3)Mating test: Saline-treated animals spent an average of 220 sec interacting with the female and five of the six mated vigorously. Only one of the six zinc sulfate treated animals mated with the female. The remaining five averaged only 73 sec investigating her. Vaginal licking was also greatly depressed (see Table 1). A similar result has recently been reported by Lisk et al. (1972). (4) Interrnale social behavior: The six saline-treated animals all behaved normally, spending an average of 207 sec investigating the intruder. Five of these animals attacked him. The six zinc sulfate-treated animals were largely indifferent to the male intruder and spect an average of only 46 sec investigating him. Only one brief attack was observed. This disruption of sexual and intermale investigative and aggressive behavior is very similar to the previously reported effects of bilateral bulbectomy (Murphy and Schneider, 1970) and the effects of nostril occlusion described above. Recovery of function. On each of the tests, a hamster either behaved as if he were anosmic or performed at the level of control animals, well above criterion. Intermediate performance was rarely observed and eventual recovery on all four tests was the rule. In several cases, normal mating and intermale social behavior was observed before ability to find food had recovered (see Fig. 2). For example, by 6 days after treatment with zinc sulfate, five of the six animals mated normally (mean of 20 mounts) and all six showed normal social behavior (mean of 213 sec investigating intruder). The animal that failed to mate had not yet recovered a preference for the odor of vaginal secretion, but he and two others were still unable to find buried food on either of the two trials. Thus failure to find buried food dearly does not indicate complete anosmia. An animal that appears anosmic on one test may respond to the more salient odors involved in certain other odor-guided behaviors. The choice of inappropriate behavioral tests for establishing anosmia and the lack of
PERIPHERAL ANOSMIA IN HAMSTERS
o 6 •:® •~ 5 u
t.o.~ ~lk ~ . ~N,N,
39
~ food finding o secretion pref. . mating ~ intermale social
~
-~ 3 '~6 2 < Z
~
8 1
6
14
Days after ZnSO 4
Fig. 2. Recovery of odor preferences and social behaviors of six male hamsters after cauterization of the olfactory epithelium with ZnSO4. (#) represents individual animals. Criteria of recovery are given in the text. histology or other corroborating evidence may thus confound the interpretation of experimental results and may account for some recent claims that "anosmic" rats, mice and hamsters are less impaired in certain forms of social behavior after chemical or surgical destruction of the olfactory mucosa than after bulbectomy (rats: Alberts and Friedman, 1972; Fleming, 1972; Spector and Hull, 1972; mice: Rowe and Smith, 1972; Edwards, Thompson and Burge, 1972; hamsters: Powers and Winans, in press).
GENERAL DISCUSSION Central vs peripheral anosmia. Reversible peripheral olfactory blockage by either nostril occlusion or zinc sulfate infusion eliminated mating and drastically reduced intermale investigatory and aggressive behavior in adult male golden hamsters. Equivalent effects were previously produced by bilateral olfactory bulb removal (Murphy and Schneider, 1970). It thus appears that odor perception is essential to these behaviors and that bilateral central nervous system tissue damage is not necessary to disrupt them. Olfactory bulb removal, which produces anosmia, disrupts many different behavior patterns to a greater or lesser degree in a large variety of mammalian species (for a recent review see Cheal and Sprott, 1972). In many of these instances, however, one or more of the side effects of bulbectomy, and not anosmia per se may be the direct cause of the resulting behavioral changes. Failure to replicate the effects of bulbectomy after damage to the olfactory receptor sheet has been presented in support of this possibility for certain behaviors in certain species. (Alberts and Friedman, 1972; Fleming, 1972; Spector and Hull, 1972; Rowe and Smith, 1972; Edwards, Thompson,
40
DEVOR AND MURPHY
and Burge, 1972; Powers and Winans, in press). It has yet to be demonstrated, though, that these peripherally treated animals were indeed unable to detect odors relevant to the specific behavior under investigation, and at concentrations appropriate to the behavioral situation. Trigerninal, vomeronasal, or olfactory? Trigeminal, vomeronasal and olfactory receptors can respond to airborn odors (Tucker, 1971). Thus in principle, any or all of these modalities may be critical for social behavior in male hamsters. The available evidence, though not conclusive, suggests that olfactory function is the sensory modality necessary for the normal expression of these behaviors. Bilateral olfactory bulb removal, which leaves the trigeminal system intact, produces the full symptoms described here (Murphy and Schneider, 1970). Gross dissections have suggested that in the hamster, as in the rat (Kratzing, 1972) the vomeronasal organ opens into the nasal cavity close to the opening of the spheno-palatine duct. Odors admitted through the duct during precopulatory vaginal licking, though, are not sufficient to trigger mating as: (I)prevention of licking by suturing the mouth shut did not drastically alter mating and (2)sexual interest was not aroused by placing vaginal secretion on the roof of the mouth in nostril clipped or zinc sulfate-treated animals (see Fig. 1A). In addition, severance of the vomeronasal nerve along its caudad traverse between the olfactory bulbs had no effect on mating behavior (Devor and Murphy, unpublished observations). Initiation of behavior vs its organization. The anosmic hamster does not initiate normal social interactions with female or male conspecifics. He is capable, however, of engaging in these highly organized behavior patterns. An anosmic male; for instance, will often continue mating in the normal manner with a female if she is returned to him within 2 rain of peripheral olfactory occlusion (Fig. 1C). Similarly, if attacked by an intruder male, a bilaterally bulbectomized male will fight back and sometimes win the fight (Murphy, 1972). Behaviorally meaningful odors associated with conspecifics are necessary for the initiation of such species typical behavior patterns. The postural adjustments characteristic to these organized behavior patterns, though, are not directed by olfactory cues alone (Herrick, 1933). Furthermore, while necessary for the initiation of social interactions, behaviorally meaningful odors in the hamster are not sufficient to elicit these behaviors. Vaginal secretion, for instance, does not elicit sexual responses in vacuo; adequate non-olfactory stimuli must also be present (Devor and Murphy, 1972). The fact that these nonolfactory cues appear to lose their social importance when olfactory perception is impaired has led to the hypothesis that anosmia produces "social agnosia" in the male golden hamster (Murphy, 1972; Devor and Murphy, 1972). The results we have presented underline the importance of behaviorally meaningful odors in the facilitation of central mechanisms subserving several aspects of mammalian social behavior. The demonstration that odors are
PERIPHERAL ANOSMIA IN HAMSTERS
41
critical for mating and intermale social behavior in hamsters makes this species exceptionally useful for studies of the modes of analysis of olfactory information within the forebrain. The combination of unilateral brain lesions with occlusion of the contralateral nostril could prove useful in such research. REFERENCES Alberts, J. R., and Galef, B. G., Jr. (1971). Acute anosmia in the rat: a behavioral test of a peripherally induced olfactory deficit. Physiol. Behav. 6, 619-621. Alberts, J. R., and Friedman, M. I., (1972). Olfactory bulb removal but not anosmia increases emotionality and mouse killing. Nature 238, 454-455. Becker, C. J., and Freeman, W. J. (1968). Prepyriform electrical activity after loss of peripheral or central input, or both. Physiol. Behav. 3,597-599. Bennett, M. H. (1971). A reversible nasal block for the rat. Physiol. Behav. 7, 269-270. Cheal, M. L., and Sprott, R. L. (1971). Social olfaction: a review of the role of olfaction in a variety of animal behaviors. Psychol. Rev. 29, 195-243. Devor, M., and Murphy, M. R. (1972). Social agnosia produced by peripheral olfactory blockage in hamsters. Amer. Zool. 12, 653. Edwards, D. A., Thompson, M. L., and Burge, K. G. (1972). Olfactory bulb removal vs peripherally induced anosmia: differential effects on the aggressive behavior of male mice. Behav. Biol. 7, 823-828. Fleming, A. S. (1972). Olfactory and experimental factors underlying maternal behavior in the lactating and cycling female rat. Doctoral dissertation, Rutgers University, Newark. Herrick, C. J. (1933). The functions of the olfactory parts of the cerebral cOrtex. Proc. Nat. Acad. ScL 19, 7-14. Kratzing, J. E. (1971). The fine structure of the sensory epithelium of the vomeronasal organ in suckling rats. Aust. J. BioL Sci. 24,787-796. Lisk, R. D., Zeiss, J , and Ciaccio, L. A. (1972). The influence of olfaction on sexual behavior in the male golden hamster (Mesocricetus auratus). J. Exp. Zool. 181, 69-78. Mulvaney, B. D., and Heist, H. E. (1971). Regeneration of rabbit olfactory epithelium. Amer. J. Anat. 131, 241-252. Murphy, M. R., and Schneider, G. E. (1970). Olfactory bulb removal eliminates mating behavior in male hamsters. Science 167, 302-303. Murphy, M. R., (1972). Different effects of olfactory bulb removal on different kinds of aggression in male Syrian golden hamsters. Doctoral dissertation, Department of Psychology, M.I.T. Cambridge. Negus, V. (1958). "The Comparative Anatomy and Physiology of the Nose and Paranasal Sinuses," London, Livingston. Pohorecky, L. A., Zigmund, M. J., Heimer, L., and Wurtman, R. J. (1969). Olfactory bulb removal: effects on brain norepinephrine. Proc. Nat. Acad. ScL 62, 1052-1055. Powers, J. B., and Winans, S. S. (in press). Sexual behavior in peripherally anosmic male hamsters. Physiol. Behav. Ropartz, P. (1968). The relation between olfactory stimulation and aggressive behavior in mice. Animo Behav. 16, 97-100. Rowe, F. A., and Edwards, D. A. (1971). Olfactory bulb removal: influences on the aggressive behaviors of male mice. Physiol. Behav, 7, 889-892.
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Rowe, F. A., and Edwards, D. A. (1972). Olfactory bulb removal: influences on the mating behavior of male mice. Physiol. Behav. 8, 37-41. Rowe, F. A., and Smith, W. E. (1972). Effects of peripherally induced anosmia on mating behavior of male mice. Psychon. Sci. 27, 33-34. Siegel, S. (1956). "Non-parametric Statistics," New York: McGraw-Hill. Spector, S. A., and Hull, E. M. (1972). Anosmia and mouse killing by rats: a nonolfactory role for the olfactory bulbs. J. Comp. Physiol. Psychol. 80, 354-356. Sundsten, J. W., and Sawyer, C. W. (1959). Electroencephalographic evidence of osmosensitive elements in olfactory bulb of dog brain. Soc. Exp. Biol. Med. 101, 524-527. Takagi, S. F. (1971). Degeneration and regeneration of the olfactory epithelium. In L. M. Beidler (Ed.), "Handbook of Sensory Physiology," New York: Springer-Vedag. Teitelbaum, H. (1971). Lateralization of olfactory memory in the split-brain rat. J. Comp. Physiol. Psychol. 76, 51-66. Tucker, D. (1971). Nonolfactory responses from the nasal cavity: Jaeobson's organ and the trigeminal system. In L. M. Beidler (Ed.), "Handbook of Sensory Physiology," New York: Springer-Verlag. Winans, S. S., and Scalia, F. (1970). Amygdaloid nucleus: new afferent input from the vomeronasal organ. Science 197,330-332.