Olfactory Bulb Ablation Research Articles

Effects of olfactory bulb ablation upon emotionality and muricidal behavior in four rat strains.

Effects of olfactory bulb ablation upon emotionality and muricidal behavior in four rat strains.

The olfactory control of meal pattern in rats

The role of the olfactory input in the control system regulating the free food intake of rats has been investigated. In a first experiment it was shown that the mean daily intake of 20 adult male and female rats, made anosmic by the bilateral ablation of olfactory bulbs, did not change significantly after surgery. But, as a result of the bulbar removal, the day to day fluctuation of this daily intake was significantly increased. In a second experiment the pre and postoperative recording of the daily feeding pattern (meal size and intervals) revealed that the olfactory bulbs ablation induced a more or less persistant and typical nibbling pattern. The stereotaxic electrolytic lesion of the cortico-medial amygdaloid olfactory projection, interrupting one of the olfacto-hypothalamic pathways, induced the same disrupted feeding pattern. The results are discussed in relation to control systems regulating meal sizes and meal to meal intervals in normal rats. It is suggested that the orosensory and particularly the olfactory control is responsible for determining the normal feeding pattern made of large and consistant meals followed by long intervals of nonfeeding.

Characteristics in emotional behavior of the rat with bilateral olfactory bulb ablations.

SummaryThe general activity and emotional responses to various stimuli of the rats with olfactory bulb ablations (O.B. rat) were investigated in comparison with those of the rats with either septal or amygdaloid lesions. The results are summarized as follows:1. The rat gradually became to exert hyperemotional responses to various stimuli, following bilateral removal of the olfactory bulb. This hyperemotionality remained unchanged for a long period of time. The rat with septal lesions, on the contrary, exhibited hyperemotionality immediately after lesioning, but the hyperemotionality disappeared within 2 weeks. Amygdaloid lesions caused no change in the emotional responses to stimuli of intact rats but abolished the hyperemotionality of the O.B. rats.2. In the O.B. rats, muricidal behavior and attack response to a rod were more prominent tiian the other responses, whereas in the septal rat, the hyperemotional responses such as startle, flight, jump and squeak were more marked, and muricidal behavior was scarcely observed.Hyperemotionality of the O.B. rat is regarded as active aggressiveness in nature and that of the septal rat would be better expressed as hyperreactivity or hyperirrit‐ability.3. Exploratory behavior such as ambulation and rearing of the O.B. rat in an open‐field situation markedly increased, while that of the septal rat decreased instead even after the hyperemotionality disappeared. Amygdaloid lesions increased exploratory behavior in intact as well as in the O.B. rats, despite of reducing hyperemotionality of the latter.(This study was supported in part by the grant for the research of science from the Department of Education of the Government of Japan.)

Effects of psychotropic drugs on emotional behavior in rats with limbic lesions, with special reference to olfactory bulb ablations.

SummaryThe effects of various psychotropic drugs on emotional behavior of the rats with bilateral ablations of the olfactory bulb (O.B. rat) were compared with those in the intact as well as in the rats with septal or amygdaloid lesions.1. Chlorpromazine markedly reduced both ambulation and rearing in intact as well as limbic lesioned rats. The hyper‐motional responses to all kinds of stimuli were suppressed by this drug in the O.B. and septal rats.2. Diazepam also suppressed the hyper‐emotional responses of the O.B. and septal rats, but on the contrary to chlorpromazine, it increased ambulation whereas it decreased rearing in the intact and amygdaloid rats. Diazepam, however, greatly decreased both ambulation and rearing of the O.B. and septal rats.3. Pentobarbital had no significant effect on the hyperemotionality of the O.B. and septal rats in subhypnotic doses. Pentobarbital, like diazepam, increased ambulation but decreased rearing of the intact rats, although it markedly reduced both ambulation and rearing of the septal rat, and showed less significant effects on ambulation of the O.B. and amygdaloid rats.4. Imipramine, similarly to chlorpromazine, decreased both ambulation and rearing in each group of the rats. Imipramine selectively blocked mouse‐killing behavior without affecting the other hyperemotional responses to stimuli of the O.B. rats. These properties were shared with amitriptyline and nialamide.5. It is suggested that the analyses of drug effects on emotional behaviors of the rats with various limbic lesions are helpful to distinguish the mode of action of various psychotropic agents. (This study was supported in part by the grant for the research of science from the Department of Education of the Government of Japan.)

Olfactory bulb ablation and hormonally induced mating in spayed female mice

Bilateral removal of the olfactory bulbs severely attenuated the estrogen-progesterone induced display of sexual receptivity in spayed female mice of the Swiss-Webster and C57B1/6 strains. This attenuation was observed in both preoperatively sexually inexperienced females and in preoperatively sexually experienced females. Apparently, the olfactory system is importantly involved in the mediation of the hormonally induced display of feminine sexual behavior in mice.

Effects of olfactory bulb removal on aggression: A reevaluation

The effects of olfactory bulb removal on natural frog-killing, mouse-killing, intermale aggression and irritability were examined. Bilateral olfactory bulb lesions suppressed natural frog-killing in nonmouse-killing rats despite the fact that these lesions induced mouse-killing in many of the same rats. The effects of bulbectomy on natural mouse-killing were quite different: the lesions suppressed the natural mouse-killing. Thus the removal of the olfactory bulbs was found to suppress natural killing behavior but also to induce killing in some rats that did not naturally kill mice. Olfactory bulb ablations also affected intermale aggression in several rats and the effects were associated with the extent of the lesions. Those rats in which intermale aggression was facilitated had only partial olfactory bulb lesions, while those rats in which there was a suppression of intermale aggression had complete olfactory bulb ablations and frequently some damage to the olfactory peduncles.

Effects of Psychotropic Drugs on Discrimination Avoidance Conditioning in Rats With Olfactory Bulb Ablations

Effects of Psychotropic Drugs on Discrimination Avoidance Conditioning in Rats With Olfactory Bulb Ablations

Changes in Sensitivity to Convulsion in Mice With Olfactory Bulb Ablation

Since bilateral ablations of the olfactory bulb were found to induce characteristic hyperemotionality in the rat (1–5), this behavior, particularly aggressiveness, has come to be used for evaluating the taming effect of tranquilizing agents, though the neural mechanisms underlying this abnormal behavior have remained unknown (6).

An electron microscopic study of the normal synaptic relationships and early degenerative changes in the rat olfactory tubercle.

The olfactory tubercle of the rat was studied by electron microscopy both in the normal and after ipsilateral olfactory bulb ablation at survival times of from 14 hours to seven days. Particular emphasis was placed on synaptic structures and their changes following the lesion. Normal synapses are similar to those described in previous studies and presynaptic profiles are of at least three types. Types-A and -B contain round vesicles and form asymmetrical contacts and type-C profiles contain flattened vesicles and form symmetrical contacts.

CHANGES IN SENSITIVITY TO CONVULSION IN MICE WITH OLFACTORY BULB ABLATION

Since bilateral ablations of the olfactory bulb were found to induce characteristic hyperemotionality in the rat (1-5), this behavior, particularly aggressiveness, has come to be used for evaluating the taming effect of tranquilizing agents, though the neural mechanisms underlying this abnormal behavior have remained unknown (6). It would be worthwhile to know the changes in drug sensitivity of such abnormal animals, even from the ceinical point of view, and the effects of psychotropic drugs are known to be different qualitatively, as well as quantitatively, depending on the disease. Studies concerning the changes in drug sensitivity in abnormal animals with such brain lesions have so far been few (7-11). Recently, Malick et al. (12) compared the efffects of psychoactive agents on three models of aggression induced by lesioning of the septum, the ventromedial hypothalamus and the olfactory bulb in rats, and found significant differences in potencies of these drugs among these models with lesions in different brain areas. Questions may arise as to whether or not these potency differences are also relevant to effects other than anti-aggressive action, and as to whether the drug sensitivities of these models are different from that of intact animals, as aggressiveness is rarely observed in normal laboratory rats. This investigation was therefore undertaken to determine changes, if any, in sentisivity to electroshock- and drug-induced convulsions in mice with bilateral olfactory bulb ablations, since convulsions could be measured quantitatively and compared between the intact and abnormal animals with brain lesions.

No change in emotionality of rats following bulbectomy

An attempt to replicate the hyperemotionality syndrome seen in rats following olfactory bulb ablation was unsuccessful, despite the use of a single-blind testing procedure and seven response measures. No difference in postoperative emotionality was found when males and females were compared. Procedural differences were discussed which might account for the failure of the present study to replicate previous results.

Effects of olfactory bulb ablation on visual discrimination

The purpose of this study was to assess the possible role of olfactory cues in a situation designed to test visual discrimination. Three groups of rats were tested on visual discrimination problems where the relevance of olfactory cues was varied. Animals tested under conditions where both visual and olfactory cues led to the same response displayed learning set formation similar to that reported by other investigators. Normal animals tested under conditions where visual and olfactory cues led to conflicting responses also gave evidence of learning set formation; however, their performance was consistently poorer than that of the group where both cues led to the same response. Animals who had had their olfactory bulbs ablated show no evidence of learning set formation.

Interactive effects of experience and olfactory bulb lesions in male rat copulation

Abstract Experiment 1 measured the effects of unilateral and bilateral olfactory bulb ablations in male rats with limited prior copulatory experience. Bilateral lesions produced gross prolongations of first and second series ejaculation latencies. When a second female was introduced to the males, however, bilaterally lesioned animals were not at a copulatory disadvantage. In Experiment 2 virgin males were tested for copulatory behavior following olfactory bulb lesions. The probability of ejaculation, but not of intromission, was significantly reduced for bilaterally lesioned males.

Olfactory bulb ablation or nerve section and behavior of pigeons in nonolfactory learning

The possible significance of the primary olfactory system for behavior that does not involve olfaction was examined in a visual learning experiment with pigeons. Four groups were trained, one with bilateral section of the olfactory nerve, one with bilateral destruction of the olfactory bulb, one with an equivalent amount of damage on the hyperstriatal surface bilaterally, and one with anesthesia only. The final task required pecking the left of two keys when both keys were lighted with color 1 and pecking the right when both were lighted with color 2. Training was done in several stages which involved learning to eat from the food hopper in the training box, learning to peck one key while it was lighted with the first color, transferring pecking to the other key, and finally learning the complete task. The two groups with damage in the olfactory pathway were significantly slower in learning to eat from the hopper, in learning to peck the first key, and in transferring pecking to the second key. It is suggested that the olfactory system participates in some way in general limbic system functions.

Water drinking and air drinking: Some physiological determinants

Hypertonic saline injections induced more water and air drinking in 10 nondeprived rats than did isotonic saline. In a second experiment, scopolamine hydrochloride suppressed both water and air drinking in nine thirsty rats, in contrast with isotonic saline. In a third experiment, olfactory bulb ablation had no measurable effect upon air drinking in rats.