Temporal effects of discrete lesions in the olfactory and limbic systems on open-field behavior and dyadic encounters in male hooded rats

The spontaneous and dyadic behavior patterns of five matched groups of male hooded rats were compared to SHAMs following selective lesions of the olfactory and limbic system. One group received bilateral lateral olfactory tract lesions (LOT); a second bilateral anterior olfactory nucleus lesions (AON); a third sham operations (SHAM); a fourth bilateral AON and LOT lesions combined (ANLT); and a fifth cortico-medial amygdalar lesions (AMYG). When tested alone in the open field, LOT, ANLT, and, to some extent, AON lesioned animals were hyperactive. Activity scores for the AMYGs were not significantly different from that of the SHAMs. High rearing time scores were seen in the LOT, ANLT, and AMYG groups while high sniffing frequency and rearing frequency scores were associated with LOT and ANLT lesions. AONs had significantly higher and LOTs significantly lower sniffing time scores than any other groups. The AMYGs had the highest and LOTs the lowest sniffing bout lengths. Sniffing time for the ANLTs did not differ significantly from that of the SHAMs. Freezing was reduced in all lesioned groups as compared to SHAMs. These differences did not become clearly apparent until 7 to 10 days following surgery and were evident 40 days postsurgically. All lesioned animals were hyperirritable and difficult to handle following surgery with the LOTs, ANLTs, and AMYGs particularly so. This irritability was evident on the first day following surgery and persisted through postoperative day 40. When tested in pairs in a circular open field, all animals spent a large proportion of their time in direct contact. All lesioned animals, however, spent more time in aggressive interactions than did the SHAMs. The results were discussed against a background of other olfactory and limbic system lesions with particular reference to possible functional and anatomical substrates mediating behavioral changes typically reported following olfactory system lesions.     

Hyperreactivity following temporary chemical lesions in the region ventral to the anterior septum but not in the anterior olfactory nucleus,the lateral olfactory tract,or the olfactory bulb

Bilateral temporary chemical lesions were produced by slow infusion of the general blocking agent lidocaine into several anterior forebrain sites which have been implicated in the increase in reactivity following lesions of the olfactory bulbs. There was an increase in reactivity with infusions of the blocking agent lidocaine into the region ventral to the anterior septum but not with infusions into the region of the anterior olfactory nucleus, or the olfactory bulbs. A control group in which lidocaine was infused into the vicinity of the lateral olfactory tract also showed no increase in reactivity to the experimenter. Infusions of 0.9% NaCl produced no change in reactivity at any of these sites. The results are consistent with previous evidence that lesions of the olfactory bulbs increase reactivity to the experimenter as a result of incidental damage to more caudal tissue. The present findings suggest that the important caudal region lies ventral to the anterior septum between the vertical arm of the diagonal band of Broca and the rostral limb of the anterior commissure.     

The effects of olfactory system lesions and food deprivation on spontaneous behavior patterns of male hooded rats

The behavior of normal male rats was observed in an exploration field in which a number of olfactory cues were present. Locomotor activity, freezing, grooming, sniffing, rearing and boluses dropped were quantified over days and correlations between them were obtained. Following olfactory nerve sections at the bulb surface or total olfactory bulb and peduncle destruction, the measures were made again and lesion induced changes in them and olfactory cue exploration were noted. After a period of food deprivation, the measures were made a third time to assess possible motivational factors on the results. Both lesions and food deprivation altered many variables with the deeply lesioned animals more affected than the shallowly lesioned animals. Possible interactions between partial or complete anosmia and lesion induced changes in reactivity were considered. Some problems associated with the production of and tests for anosmia were also discussed.     

Structures posterior to the olfactory bulb which are responsible for the mouse killing and hyperreactivity following lesions of the olfactory bulb

Male hooded rats with aspiration lesions of the olfactory bulb or electrolytic lesions of the anterior olfactory nucleus or of the region ventral to the anterior septum were tested for reactivity to the experimenter and mouse killing. Increased mouse killing in the home cage occurred at the first test session postoperatively in animals with lesions ventral to the anterior septum but not until 14 days postoperatively in animals with lesions in the anterior olfactory nucleus. Mouse killing in a novel environment occurred only in rats with lesions ventral to the anterior septum. Only rats with lesions ventral to the anterior septum showed a reactivity level greater than that of sham lesioned rats. It is suggested that the increase in reactivity which sometimes occurs following aspiration lesions of the olfactory bulb is the result of incidental damage to the region ventral to the anterior septum while the increase in mouse killing is the result of incidental damage to the anterior olfactory nucleus or the region ventral to the anterior septum or both.     

Electron microscopic study of synaptogenesis and myelination of the olfactory centers in developing rats

Development of the central olfactory system was studied in the rat with an electron microscope at three main structures: the olfactory bulb, the lateral olfactory tract, and the primary olfactory cortex (the piriform cortex). As a parameter of development, the synaptic density was examined quantitatively in the bulbar glomerulus and layer Ia (termination of bulbofugal fibers) of the piriform cortex, which are the key stations of the olfactory pathway. The synaptic densities in the glomerulus and those in layer Ia were 5.7% and 4.6% on embryonic day 19, 15.8% and 12.5% on postnatal day (P) 0, and 57.3% and 37.2% on P10, as compared with the adult (100%). As another parameter of development, the density of myelinated axons in the lateral olfactory tract was examined quantitatively. The densities of myelinated axons in the tract were 0% on P5, 15.1% on P10, and 73.5% on P21 of the adult density. Maturation in the tract was still progressing, even at P21, in terms of bundle formation and the thickness of myelin sheaths. The results show that synaptogenesis in the bulbar glomerulus is followed by synaptogenesis in layer Ia of the piriform cortex, and that myelination in the lateral olfactory tract occurs over a prolonged period, even in the stages after P21.     

Tyrosine hydroxylase immunoreactive structures in the aged human olfactory bulb and olfactory peduncle

We studied the anatomical distribution of dopaminergic structures in the normal, aged, human olfactory bulb and olfactory peduncle with a monoclonal antibody against tyrosine hydroxylase. Three different tyrosine hydroxylase containing cell groups are present in the olfactory bulbs: (1) a group of round, medium-sized cells within and around the glomeruli; (2) cells in the external plexiform layer; and (3) cells that are scattered in the stratum album. Occasionally, a few labeled neurons can be observed in the granule cell layer. In the olfactory peduncle a few labeled cells are present in the superficial layers just underneath the pia. Tyrosine hydroxylase containing terminal-like structures are present in the glomerular layer and the external plexiform layer. In a few cases dense terminal labeling is also observed in the cell groups that constitute the anterior olfactory nucleus. In the olfactory peduncle scattered labeled fibers are present. In addition, the present study makes clear that quantitative differences exist between the individual cases for which no explanation could be found.     

Somatostatin-14-like immunoreactive neurons and fibres in the human olfactory bulb

Summary This study describes the morphological features and the distribution pattern of neurons in the human olfactory bulb which are immunoreactive for an antiserum against the neuropeptide somatostatin-14.Immunoreactive nerve cell bodies were mainly found in the white matter surrounding the cell clusters of the anterior olfactory nucleus. Some immunoreactive neurons were also found scattered throughout the anterior olfactory nucleus and the deeper parts of the inner granule cell layer. Only a few immunoreactive neurons were localized in the glomerular layer and the outer granule cell layer.Immunoreactive fibres were found in all layers of the olfactory bulb. In addition, an impressive number of coiled and kinked immunoreactive fibres were localized within the anterior olfactory nucleus forming a dense plexus. Accumulations of twisted and coiled branches of immunoreactive fibres were rarely found either surrounding or within the olfactory glomerula.The characteristics of somatostatin-14 immunoreactive neurons as seen in the combined pigment-Nissl preparation were studied after decolourizing the chromogen and restaining the preparations with aldehydefuchsin in order to demonstrate the lipofuscin pigment and gallocyanin chrome alum for Nissl material. About 90% of the immunoreactive neurons studied in this manner turned out to be devoid of lipofuscin granules. The remaining 10% displayed different patterns of pigmentation.These findings suggest the presence of different types of somatostatin-14-like immunoreactive neurons in the olfactory bulb of the human adult.     

Responses of olfactory bulb neurons to repeated odor stimulations in awake freely-breathing rabbits

Thirty-one olfactory bulb neurons were recorded in the olfactory bulbs of unanaesthetized rabbits during repeated stimulations. Their single-unit activity associated with the inspiratory phases of the respiratory cycles and that associated with the expiratory phases were processed separately. When responses were classified into 3 types, i.e., excitation, inhibition and null, it was found that a large number of neurons presented variable responses to repeated stimulations with the same stimulus. However, the passage from one type to another was found to be limited: responses by excitation or inhibition to the first stimulation turned into null responses only; null responses turned into either excitation or inhibition. Inspiration- and expiration-related responses were also subjected to a principal component analysis in order to determine whether changes in responses were compatible with a reliable coding of the qualitative properties of a stimulus. The results indicated that the repeated presentations of an odorant induced fairly similar profiles of activity across the set of neurons while different odorants induced clearly discriminable profiles. It is concluded that repeated stimulations do not blur the characteristic features of the across-neuron profile of response of an odorant in the olfactory bulb despite the variability of the responses of the neurons which compose the profile.     

Wood-gnawing in rats following cortical, olfactory bulb or limbic lesions

Wood-gnawing was examined in rats following neocortical, olfactory bulb or limbic lesions. Anterior neocortical lesions produced a persistent (50 day) reduction of wood-gnawing which was not due to inability to gnaw or reduced body weight. All other lesions produced a transient (8–12 day) depression of gnawing.     

Delayed deficits in behavior after transection of the olfactory tracts in hamsters

This study compared the effects of transection of the lateral olfactory tracts (LOT) and the accessory olfactory tracts (AOT) in male hamsters on nest building, food piling, and sexual behavior. Autoradiographic tracing of amino acids injected into the olfactory bulbs allowed accurate determination of the location and extent of the transections. Animals with complete bilateral transections of the projections to the amygdaloid targets of the accessory olfactory bulbs and to the main olfactory targets posterior to the olfactory tubercle showed no sexual behavior postoperatively; they did not exhibit extensive genital investigation and did not mount females. In contrast, most of the animals with partial sparing of accessory olfactory bulb efferents to the amygdala did exhibit investigatory and copulatory behaviors postoperatively, although half of the animals with this partial sparing developed delayed deficits in these sexual behaviors. Almost all animals without detectable main olfactory bulb efferents to posterior targets showed delayed deficits in nest building and food piling. This was true whether or not there was partial sparing of accessory olfactory bulb efferents to the amygdala. The animals with LOT transections typically built nests and piled food during the first postoperative week, but stopped building nests and piling food by the fourth postoperative week. Cold stress enhanced these two behaviors in control animals but did not obviate the deficits in experimental animals. Caudally placed transections, which spared a larger portion of the main olfactory projections than rostally placed transections, did not spare more behavior. In fact, the caudally placed transections produced shorter delays in the appearance of deficits in nest building and food piling. These results indicate that the accessory olfactory bulb efferents to the amygdala are more important for sexual behavior than for nest building and food piling in male hamsters. Nest building and food piling are not directly dependent on normal ongoing or sensory evoked activity in the main or accessory olfactory bulb efferents which project through the LOT and AOT. The deficits in nest building and food piling may represent a deterioration in the ability of the animals to organize their living space. The observed delays in the appearance of deficits in behavior may also reflect slow degenerative processes or humoral changes associated with loss of input from the main olfactory bulbs to posterior olfactory target areas, and possibly with interruptions of projections to targets of the accessory olfactory system.     

Effects of olfactory tract lesions on sexual and feeding behavior in the goldfish

The paired olfactory tracts (OTs) of goldfish each have a lateral (LOT) and medial (MOT) olfactory tract, the latter with medial (mMOT) and lateral (lMOT) subdivisions. Bilateral OT section (OTX) reduced, while unilateral OT section (UNI) did not impair, male sexual behavior and feeding responses to a complex food odor; in contrast, female sexual behavior, induced in both sexes by prostaglandin treatment, was little affected by OTX. Experiments in which control fish were given UNI and treatment groups received UNI plus selective section of the remaining OT assessed the role of the OT subdivisions in the two olfactory-influenced behaviors (male sexual behavior and feeding). LOT section did not affect courtship, while MOT section reduced courtship to the low levels seen in OTX males; within the MOT, the mMOT may be more important than the lMOT for courtship expression. In contrast to male sexual behavior, feeding responses were less affected by MOT than LOT section. With respect to male sexual behavior, these findings demonstrate differential functions for the anatomically distinct subdivisions of the goldfish olfactory tracts, possibly related to their distinct fields within the telencephalon.     

Influence of synchronized sleep upon spontaneous and induced discharges of single units in visual system

Summary Changes in the discharge rate of single units in the optic tract (OT), lateral geniculate nucleus (LGN) and thalamic reticular nucleus (TRN) during the sleep wakefulness cycle were studied in cats. The OT and LGN neurons were subdivided into 2 groups, type I (transient) and II (sustained) neurons. During periods of cortical EEG-synchronization the tonic response of type I LGN neurons was strongly depressed, while the response of type II LGN neurons showed little change. The maintained, spontaneous discharge rate was depressed in some LGN neurons during synchronization. No effect was seen in OT neurons, and no consistent effect in TRN neurons. These results are discussed in terms of a modulation of (recurrent) inhibition in LGN.     

Mouse and weanling rat killing by spontaneous mouse killing rats,and by rats with lesions of the lateral septum or the region ventral to the anterior septum: Similarities in killing latency and prey eating

Mouse and rat pup killing by male rats with lesions of the lateral septum or of the region ventral to the anterior septum were compared with that of spontaneous mouse killing rats. Latency to kill, latency to eat, and the amount of the prey eaten were similar for all groups. The killing and eating of weanling rats and mice were also similar across groups and occurred in a novel environment as well as in the home cage. However, the tendency to kill weanling rats is significantly higher in lesioned animals that kill mice than in natural killers which kill mice. In addition, some lesioned rats but no unlesioned rats also killed and ate young (150 to 200 g) male rats. It is argued that the killing behavior of rats with lesions of the lateral septum or of the region ventral to the anterior septum represents an enhanced predatory behavior.     

Selective olfactory system lesions in rats and changes in appetitive and aversive behavior

Male rats with bilateral lesions in different parts of the olfactory system differed on a variety of behavioral measures. All lesioned animals were hyperreactive when handled and learned shuttle box avoidance faster than sham operates. However, activity in an open field, Y-maze, and startle chamber separated the groups. Animals with lesions confined to the olfactory bulb tip (LB) were least active whereas those sustaining peduncle destruction (DB) were most active. Bar pressing for continuous reinforcement also differentiated the groups. The LBs became inactive initially while DBs learned fastest but were more resistant to extinction. Only DBs failed to learn a passive avoidance task whereas, in one replication, only SHAMs failed to extinguish this task once learned. Differential lesions thus produced an activity or reactivity gradient that was low in LBs, moderate in MBs (bulb removed), and highest in DBs. The arousing properties of the measures used also interacted with lesions to produce a family of responses. The results are discussed in terms of possible olfactory-limbic interactions and evidence for a role of the olfactory system in modulations of arousal or affect is considered.     

Modulation of agonistic behavior by the dual olfactory system in male mice

This study analyzed the effects of deafferentation of the main, vomeronasal or both olfactory systems on the agonistic behavior of male mice in response to unfamiliar male intruder mice. In every animal, regardless of the technique used, disruption of the vomeronasal system led to consistent reductions in agonistic behavior. All animals receiving bulbectomies, vomeronasal tract transections or a combined treatment of vomeronasal cuts and ZnSO₄ nasal flush reliably suppressed agonistic responding toward the intruder. Animals treated with intranasal ZnSO₄ alone or those receiving control procedures continued to respond to the intruders at rates similar to pretreatment. These results indicate that the vomeronasal system is directly involved in the perception of the male chemosignals modulating agonistic behavior and, therefore, is capable of modulating the male's response to these signals.     

Olfactory cues and accessory olfactory bulb lesion: effects on sexual behavior in the cyclic female rat

The influence of olfactory cues and accessory olfactory bulb (AOB) lesion on female sexual behavior was studied in virgin female Wistar rats. In Experiment 1, it appeared that distance or contact exposure to male urine soiled bedding for 8 hours before testing increased sexual receptivity, i.e., the number of receptive females at 18:00-19:00 on proestrus. In Experiment 2, we observed that sexual receptivity at 18:00-19:00 on proestrus was not affected by AOB lesion as compared to sham-operated females. In Experiment 3 the effects of both AOB lesion and olfactory cues were analyzed. Sexual receptivity at 18:00-19:00 on proestrus did not significantly differ in sham-operated and accessory olfactory bulbectomized females both exposed to the odor of male urine. Regarding lordosis quotient in the three experiments, no significant difference was observed. Mechanisms whereby olfactory cues and/or AOB lesion modified female sexual behavior on proestrus in virgin female rats were discussed in the light of previous and present observations.     

Immunohistochemical demonstration of salmon olfactory glutathione S-transferase class pi (N24) in the olfactory system of lacustrine sockeye salmon during ontogenesis and cell proliferation

In mammals, glutathione S-transferase (GST) in the olfactory epithelium is involved in assistance of the olfactory reception by the xenobiotic metabolism. We previously reported the protein and gene expressions of salmon olfactory GST class pi (soGST) in the olfactory receptor cells (ORCs) of the salmonid fish. However, the chronological appearances of soGST in ORCs during ontogeny and cell proliferation are still unknown in this species. In this study, we performed immunohistochemistry of soGST using an antibody specific to soGST in the olfactory system (olfactory placode, olfactory pit, olfactory epithelium, olfactory nerve and olfactory bulb) of lacustrine sockeye salmon (Oncorhynchus nerka) embryos and 5-bromo-2-deoxyuridine (BrdU) experimental fish. The projection of olfactory nerve bundles from the olfactory pit to the presumptive olfactory bulb was identified at embryonic day 28 after fertilization. The olfactory cilia were first detected on the apical surface of ORCs at day 43. soGST-immunoreactivity was first detected within the olfactory pit cells at day 55. At 58 day, the number of soGST-immunoreactive cells increased markedly in the olfactory epithelia, and soGST-immunoreactive fibers were observed in the olfactory nerves and olfactory bulbs. By in vivo uptake of BrdU in 1-year-old fish, we observed for the first time at day 7 after labeling that the olfactory epithelia showed ORCs in which both soGST-immunoreactivity and BrdU coexisted. These results indicate that soGST is synthesized in the mature ORCs of lacustrine sockeye salmon after cell formation and differentiation.     

Effect of bilateral accessory olfactory bulb lesions on volatile urinary odor discrimination and investigation as well as mating behavior in male mice

Previous research raises the possibility that urinary volatiles from estrous female mice activate mitral cells in the accessory olfactory bulb (AOB) of male mice following detection via the main olfactory epithelium as opposed to the vomeronasal organ. We asked whether bilateral lesions of the AOB would disrupt the ability of male mice to discriminate between urinary volatiles from mice of different sexes or endocrine states, or affect their interest in investigating these odors when they were presented sequentially in home-cage habituation/dishabituation tests. Males with either partial or complete bilateral lesions of the AOB resembled sham-operated control males in their ability to discriminate between ovariectomized and estrous female urinary volatiles as well as between male and estrous female urinary volatiles. However, males with either complete or partial AOB lesions spent significantly less time than sham-operated control males investigating urinary volatiles from estrous females, especially during tests when the alternative stimulus presented was male urine. Placement of AOB lesions failed to disrupt males' mating performance. Our results suggest that the incentive value of opposite-sex (female) volatile urinary odors which are initially detected by the main olfactory system is enhanced when they are further processed by the male's AOB.     

Alterations in axons and synapses of olfactory cortex following olfactory bulb lesions in newborn rats

Summary The olfactory cortex of rats is being studied at various survival times following deafferentating olfactory bulb ablation on the day of birth. The neonatal axons and synaptic terminals undergo rapid, flocculent degeneration and fragmentation. Most are not electron-dense and therefore probably not argyrophilic at this particular age of the lesion. The degeneration and removal of debris is far more rapid than in adults, yielding a markedly enlarged extracellular space with a relative absence of glia at the vacated postsynaptic thickenings. Denervated postsynaptic thickenings become occupied by neuronal and nonneuronal profiles and profiles of uncertain origin, singly or in various combinations, or the sites may remain partially vacant. One or more axons with synaptic vesicles often aggregated at the site are commonly involved. Certain terminals form contacts on progressively greater lengths of the thickening until typical synaptic contacts predominate by 14 days survival. The results suggest a competitive reinnervation process and provide a fine structural explanation for the events leading to alterations in this pathway following neonatal deafferentation.This project was supported in part by NIH Research Grants DE 04942, awarded by the National Institute of Dental Research, and Grants NS 09678 and NS 04053 from the National Institute of Neurological and Communicative Disorders and Stroke, PHS/DHEWDr. Westrum is also an affiliate of the Child Development and Mental Retardation Center, University of Washington     

二乙基二硫化氨基甲酸盐对大鼠外侧嗅束髓鞘碱性蛋白表达的影响

目的:检测二乙基二硫化氨基甲酸盐(DDTC)干预后大鼠外侧嗅束髓鞘碱性蛋白(MBP)表达的变化.方法:成年SD大鼠分为DDTC干预组、溶媒对照组和空白对照组,实验动物分别存活3、7、14和28 d,免疫组织化学和免疫印迹检测大鼠外侧嗅束MBP的表达变化.结果:正常大鼠和溶媒对照组大鼠外侧嗅束MBP免疫组织化学显色均匀,呈点状分布特征,免疫印迹主要显示相对分子质量为21 500、18 000、17 000和14 000等阳性条带.模型组大鼠外侧嗅束MBP的免疫组织化学显色和免疫印迹条带分布末见明显变化,但其表达在3 d和7 d时逐渐下调,14 d和28 d表达逐渐上调.结论:DDTC处理后早期大鼠外侧嗅束町能出现脱髓鞘化,晚期可能出现再髓鞘化.