Tail pinch induces sexual behavior in olfactory bulbectomized male rats

Adult male Long-Evans rats were subjected to bilateral olfactory bulbectomy, sham surgery or no treatment. Of 34 bulbectomized rats, 24 failed to ejaculate on either of 2 tests with a primed ovariectomized female. All control animals exhibited normal sexual behavior, and 10 bulbectomized animals ejaculated at least once during the 2 tests. Later histological examination revealed a relationship between size of lesion and extent of behavioral deficits. After a third test, 16 nonejaculatory animals were subjected to a tail pinch (TP) procedure, immediately followed by a fourth test. The remaining 8 nonejaculatory animals were tested similarly, but without tail pinch. Ten of the 16 tail pinch animals showed complete sexual behavior on the first test, while 2 additional animals began to copulate after a second TP procedure 4 days later. Only 1 of the 8 animals not receiving TP ejaculated on these tests. Thus, TP applied shortly before sexual behavior tests can induce copulation in some males whose behavior had been disrupted by olfactory bulbectomy.     

Olfactory bulb removal: influences on the aggressive behaviors of male mice

Bilateral removal of the olfactory bulbs of castrated male mice completely prevented the arousal of aggressiveness by exogenous administration of androgen. Unilateralally bulbectomized mice showed fighting comparable to that shown by sham-operated control mice. It was concluded that earlier demonstrations of the abolition of intermale aggressive behavior in mice following olfactory bulb removal could not be attributed to impairment in pituitary-gonadal function. Although in this experiment bulbectomy completely prevented the androgenic arousal of intermale aggression, bulbectomy did not affect the display of aggressive behavior in a competition for food situation.     

Effects of olfactory bulb ablation on estrus-induction and frequency of pregnancy.

Surgical ablation of the olfactory bulbs was used to study the influence of olfaction on estrus induction in M. o. ochrogaster. Of 112 females pretested, 78% were induced to estrus. From a group of 56 operated females, 23 were completely bulbectomized (CB) and 33 were partially bulbectomized (PB) as determined from either microscopic or gross inspection. When housed cage-within-cage with males, CB females failed to become estrus. Similar tests using PB females results in 61% of these animals becoming estrus. When the females were housed in cages with males for one week, the frequency of pregnancy was 17% and 67% for the CB and PB females respectively. Thus, the response following partial bulbectomy was variable. The results show that complete bulbectomy blocked estrus induction and suggest that in this species male induced estrus is mediated via olfaction.     

Effect of bilateral olfactory bulbectomy on discrimination avoidance conditioning in rats

Studies were made with the two-way shuttle box method on the acquisition of discrimination avoidance learning by olfactory bulbectomized rats in relation to changes in emotional behavior. Bulbectomized rats showed a marked increase in locomotor activity, with accompanying augmentation of the reactivity and the appearance of muricidal behavior. Initially, the bulbectomized rats showed elevated conditioned avoidance responses to both the CS+ and the CS-. In later stages, there was a continued slow increase in responses to the CS+ accompanied by a decrease in responses to the CS-, until responses to both stimuli were only slightly elevated above the levels shown by control rats. This result suggests that olfactory bulbectomy does not affect discrimination ability itself, but the impairment of discrimination during the initial stages is resulted from hyperemotionality induced by olfactory bulbectomy.     

Hypoglycemia induced by olfactory denervation in turtle (Chrysemys d'orbigni)

Adult male turtles Chyrsemys d'orbigni with olfactory deficiency caused by olfactory deafferentation or by olfactory bulbectomy were used. Four, six and eight months later the lesioned turtles showed significantly lower blood glucose level than control animals. The hypoglycemia was similar in bulbectomized and deafferented turtles.     

Changes in amygdaloid afterdischarges and kindling effect following olfactory bulbectomy in the rat

Changes in the thresholds for afterdischarges and the formation of kindling effect in the medial amygdala following olfactory bulbectomy were investigated in the rat with chronic electrode implants. The threshold for afterdischarges in the amygdala of the olfactory bulbectomized rat (OB rat) was significantly decreased on day 4 after olfactory bulbectomy, however, no significant difference was found between OB and sham operated rats on days 7, 14 and 21 since the threshold in the sham group was also decreased at these periods after the surgery. The formation of kindling effect was remarkably accelerated in the OB rats. In this case, the number of days required to reach the stage 1 (Racine's classification) was significantly shortened. These results suggest that the activity of the medial amygdaloid nucleus is increased following olfactory bulbectomy.     

Morphofunctional state of neurons in the temporal cortex and hippocampus in relation to the level of spatial memory in rats after ablation of the olfactory bulbs

Ablation of the olfactory bulbs (bulbectomy) in mice and guinea pigs evokes a neurodegenerative process which, in terms of its morphological, biochemical, and behavioral features, is similar to Alzheimer’s disease. We report here studies of the long-term sequelae of bulbectomy in rats. One year after surgery, testing of spatial memory in bulbectomized rats (BER) allowed the animals to be divided into two groups-those with good memory (BER-gm) and those with poor memory (BER-pm). Quantitative analysis of the morphofunctional state of neurons showed that BER-pm, as compared with the BER-gm group, had more marked pathological lesions in neurons of the temporal cortex and hippocampus, with significant increases in the numbers of cells showing pyknosis, karyolysis, cytolysis, and vacuolization. Both groups showed decreases in the distribution density of cells in the cortex. In terms of the level of brain β-amyloid, the study groups fell in the order: BER-pm > BER-gm > control sham-operated rats. These results provide evidence of the long-term nature of changes in the morphofunctional state of neurons in the brains of BER, correlating with their levels of spatial memory. __________ Translated from Morfologiya, Vol. 131, No. 2, pp 32–36, March–April, 2007.     

Effects of bulbectomy on hibernation,food intake and body weight in the european hamster,Cricetus cricetus

Bulbectomy was performed on European male wild hamsters in autumn, habitual phase of weight decline and entrance into hibernation. Total bulbectomy suppresses both nest building behavior and hibernation, and is followed by an immediate increase in food intake and obesity. The body weight curve of totally bulbectomized animals is in opposition of phase with that of the controls. Incomplete bulbectomy suppresses nest building behavior but hibernation is present with a diminution of periodic arousals. Hyperphagia starts in spring after the terminal arousal; it is similar to that of the total bulbectomized animals. Anosmic animals do not differ from the control animals.     

Sexual impairment of inexperienced male rats following pre- and postpuberal olfactory bulbectomy.

Olfactory bulbectomy of sexually inexperienced male rats prevented the occurrence of sexual behavior in most of the operated animals. This effect was observed in rats bulbectomized before puberty as well as after puberty. Bulbectomized rats which had heterosexual experience prior to the operation did not deviate from intact rats. Males living in cohabition with intact males prior to the operation showed only minor deficits in their mating performances. It was concluded that the olfactory lobe while of only minor importance for maintenance of mating once sexual behavior has been initiated, plays an important role in initiation of sexual behavior of the male rat. Furthermore, since treatment with testosterone of prepuberally bulbectomized rats did not stimulate the animals to sexual activity it was concluded that the sexual impairment following bulbectomy of isolated males presumably is not due to an impaired production of gonadal secretions.     

Olfactory bulbectomy: influences on maternal behavior in primiparous and multiparous rats

Bilateral olfactory bulb ablation resulted in deficits in several components of maternal behavior in lactating, primiparous female rats. These females frequently cannibalized pups shortly after parturition. Furthermore, bilaterally bulbectomized, primiparous females spent less time nursing their pups and retrieved fewer pups than unilaterally bulbectomized or sham-operated females. In contrast to the situation in primiparous females, in multiparous females bilateral bulbectomy failed to influence any parameter of maternal behavior.     

Olfactory control of the sexual behavior of male and female mice

Bilateral removal of the olfactory bulbs virtually eliminates sexual behavior in male and female mice. In the studies reported here, mice were rendered anosmic by intranasal application of a zinc sulfate solution. Peripherally induced anosmia did not affect the sexual behavior of male mice. Peripherally induced anosmia attenuated the hormone induced display of sexual receptivity in female mice, but peripherally anosmic females were significantly more receptive than bulbectomized females. This finding suggests that (1) pheromonal factors may be involved in the full arousal of sexual receptiveness in female mice, but (2) that the effect of bulbectomy upon sexual receptivity in female mice cannot be attributed solely to the surgical production of anosmia. The general failure of peripherally induced anosmia to mimic the effects of olfactory bulb removal upon the display of sexual behavior in male and female mice suggests that the olfactory bulbs are importantly involved in the control of sexual behavior in some manner not related to sense of smell.     

Simultaneous and successive olfactory bulb removal: influences on the mating behavior of male mice

Simultaneous olfactory bulb removal abolished mating behavior in sexually experienced male mice. In contrast to simultaneous bulbectomy, removal of both olfactory bulbs in two operations separated by an interval of 30 days had no effect on the mating behavior of male mice. In successively bulbectomized males, the occurrence or nonocurrence of the opportunity for mating behavior in the interval between the removal of each bulb had no influence on the degree to which mating behavior was spared. It was concluded that the abolition of mating behavior produced by simultaneously removing both olfactory bulbs in male mice is not a consequence of a sensory deficit, but is due to the destruction of tissues directly involved in the mediation of sexual behavior.     

Olfactory bulbectomy depresses ultrasound production and scent marking by female hamsters

Female hamsters were observed for rates of ultrasound production, vaginal marking and flank marking before and after bilateral olfactory bulbectomy, unilateral bulbectomy or sham operations. Unilaterally bulbectomized and sham-operated subjects maintained preoperative levels of each behavior. In contrast, females with bilateral olfactory bulbectomies showed consistent decreases in rates of vocalization and scent marking. These results emphasize the dependence on an intact olfactory system of several courtship or agonistic behaviors that affect hamster reproduction by functioning as noncontact communications. Together with the results of previous studies suggesting that lordosis by female hamsters is unaffected by olfactory bulbectomy, these data also suggest differences in the brain and sensory mechanisms that control distinct types of reproductive behavior.     

Aggression-promoting and aggression-eliciting properties of estrogen in male mice

Two experiments assessed the aggression-promoting and aggression-eliciting properties of estradiol benzoate (EB). When given daily to gonadectomized adult male mice, EB induced attack behavior toward stimulus males at a level similar to that observed in intact males or castrate males treated with testosterone propionate (TP). A second experiment showed that significantly fewer gonadectomized/olfactory bulbectomized males given EB were attacked by adult males in comparison to similarly prepared TP-treated or intact/olfactory bulbectomized males. Thus, EB is as effective as TP in promoting aggression but is less effective in eliciting fighting.     

Unilateral but not bilateral olfactory bulbectomy inhibits body weight gain in hamsters.

The relation of the olfactory bulbs and photoperiod to the regulation of body weight was studied in male golden hamsters. Animals underwent sham operation, bilateral olfactory bulbectomy, or unilateral bulbectomy. They were left on long photoperiod for 5 weeks and then were transferred to short photoperiod for 11 weeks. The unilaterally olfactory bulbectomized hamsters gained less weight on long or short photoperiod than the sham operated group, while the bilaterally bulbectomized hamsters gained at least as much weight as the sham group. Thus, we report the novel finding that unilateral but not bilateral olfactory bulbectomy reduces body weight gain in male golden hamsters.     

Changes in blood pressure and heart rate following bilateral olfactory bulbectomy in rats

Changes in blood pressure and heart rate following bilateral olfactory bulb ablation were investigated in unanesthetized and unrestrained rats with chronic arterial cannula implants. After bilateral olfactory bulbectomy, the rat exhibited a marked increase of emotional responses to given stimuli and a high incidence of muricide. Blood pressure and heart rate at 5 and 10 days after olfactory bulbectomy were significantly lower than in intact rats (rats before bulbectomy) and/or sham operated rats. Marked decreases in blood pressure and heart rate were seen especially in the period when the animals showed exploratory behavior after being transferred to the experimental cage from the home cage. These results suggest that olfactory bulbectomy has a great influence not only on emotionality but also on the central regulatory system of blood pressure in the rat.     

A comparison between house mouse lines selected for attack latency or nest-building: Evidence for a genetic basis of alternative behavioral strategies

House mouse lines bidirectionally selected for either nest-building behavior or attack latency were tested for both attack latency and nest-building behavior under identical conditions. Male mice selected for high nest-building behavior had shorter attack latencies, i.e., were more aggressive, than those selected for low nest-building behavior and their randomly bred control lines. Conversely, male wild house mice selected for short attack latency showed more nest-building behavior than those selected for long attack latency when tested at 110 days of age. These findings imply a common genetic basis for control of aggression and nesting and support earlier proposals as to how animals may exhibit fundamentally different responses to environmental challenges, either reacting actively to aversive situations (aggressive and high-nesting animals: active copers) or adopting a passive strategy (nonaggressive and low-nesting animals: passive copers).     

Brain transplants enhance rather than reduce the impairment of spatial memory and olfaction in bulbectomized rats

The possibility to compensate the loss of olfactory and non-olfactory functions due to removal of the olfactory bulb by embryonal brain grafts was investigated in adult rats. Spatial working memory was examined in an 8-arm radial water maze task 6 weeks after bulbectomy. During 15 daily trials, performance gradually improved in bulbectomized controls (n = 10) and in rats with olfactory bulb transplants (n = 9), but did not attain that of intact controls (n = 10). No improvement was observed in the rats with substantia nigra grafts (n = 8). Eleven weeks after bulbectomy, the same rats were tested in the water tank navigation task. The performance improved during ten 12-trial sessions in bulbectomized rats less than in intact controls, but more than in the transplanted rats. The olfactory food retrieval test performed 14 weeks after bulbectomy revealed almost full recovery of smell in bulbectomized rats, but not in the transplanted animals. It is concluded that the spatial memory deficit is probably due to bulbectomy-induced interference with septohippocampal function which is not alleviated, but rather enhanced by transplantation. The results suggest that the effect of brain grafting is not always beneficial.     

Male copulatory behavior and female maternal behavior in neonatally bulbectomized rats

Olfactory bulbs were destroyed in six-day-old male and female rats, and anosmia was confirmed in adulthood. Bulbectomized males initiated apparently normal sexual activity at the same age as did control animals. As virgins, bulbectomized females did not injure foster young; when allowed to mate and deliver young, they displayed apparently normal maternal behavior. It was concluded that neonatal olfactory bulbectomy does not preclude the development of essentially normal copulatory behavior in the male rat and maternal behavior in the female rat.     

The effect of olfactory bulb lesions on agonistic, locomotory and social behavior in mice housed in aggregate

Eleven Dublin ICR mice sustaining nearly complete bilateral aspiration lesions of the olfactory bulbs were compared to 16 sham-operated mice on the frequency of agonistic, locomotory, social, and maintenance behaviors. The animals were housed in aggregate with two cages of bulbectomized mice and two cages of shams. A time sampling technique was used to quantify the frequency of the various behaviors three times per week during one preoperative and four postoperative weeks. During the first two postoperative weeks the bulbectomized mice were observed to make frequent single bites of the head incision and tail of mice passing directly in front of them, with the bites resulting in mild to severe lesions. Following surgery, the bulbectomized mice also showed a temporary increase in locomotory responses and permanent suppression of social responses.