Cat odor, but not trimethylthiazoline (fox odor), activates accessory olfactory and defense-related brain regions in rats.

Cat odor and trimethylthiazoline (TMT, a component of fox feces) are two stimuli widely used in rodent models of fear and anxiety. Recent studies suggest that these odorants have distinct behavioral effects, raising questions as to whether TMT is a true "predator odor." Here we used c-Fos immunohistochemistry to compare patterns of neural activation produced by cat odor and TMT. Rats were exposed to either (1) three pieces of a collar that had been worn by a domestic cat, (2) three collar pieces impregnated with TMT (30 microl/piece), (3) three collar pieces impregnated with 4% formaldehyde (200 microl/piece, an acrid but non-predatory odor), or (4) three control (no odor) collar pieces. Odors were presented in a small well-ventilated plastic box. All odorants (cat odor, TMT and formaldehyde) produced increased defecation in rats compared with the control group, and formaldehyde exposure also decreased rearing. Cat odor increased contact with the stimulus relative to all other groups, while TMT increased contact compared with the formaldehyde and clean air groups. Only cat odor decreased grooming and elicited escape attempts. In addition, only cat odor caused pronounced activation of Fos in the accessory olfactory bulb and its projection areas, anterior olfactory nucleus, medial prefrontal cortex, striatum, and a medial hypothalamic circuit associated with defensive behavior. In contrast, the only areas activated by TMT were the internal granular layer of the main olfactory bulb and central amygdala, while both cat odor and TMT activated the glomeruli of the main olfactory bulb, piriform cortex, ventral orbital cortex and anterior cortical amygdala. Results indicate that the effects of cat odor and TMT are easily distinguished both behaviorally and at a neural level, and suggest that TMT lacks the "pheromone-like" quality of cat odor that engages key hypothalamic sites involved in defensive behavior.

Instinctive predatory behavior of the ferret (Putorius putorius furo L.) modified by chlordiazepoxide hydrochloride (Librium).

The predatory behavior of ferrets (Putorius putorius furo L.) consists mainly of instinctive behavioral patterns that are elicited by simple external stimuli. For the ferret, the time needed to catch and kill rats depends on the size of the rats in relation to that of the ferret. Killing success decreases with a relative increase in prey size. Chlordiazepoxide hydrochloride injections (1 mg/kg, i.m.) modified this behavior. Drugged ferrets needed less time and less bites to kill relatively large rats; killing success was also increased. Chlordiazepoxide seemed to disinhibit the ferrets when they were presented with large rats, which they normally attack more cautiously.

[Psychopharmacological influence on the prey catching behavior of ferrets (Putorius furo L.) (author's transl)]. / Psychopharmakologische Beeinflussung des Beutefangverhaltens beim Frettchen (Puttorius furo L)

The prey-catching behavior of ferrets (Putorius furo L.) consists mainly of instinctive behavior patterns, which can be elicited only through their releaser. Then they are performed stereotypically. To get information concerning the central background and the hierarchical structure of this behavior the neuroleptics Haloperidol (0.14 mg/kg), Clozapine (10 mg/kg) and Chlorpromazine (4 mg/kg) were injected i.m. under controlled conditions. In a conditioning experiment the reactivity of the animals was examined. This conditioned reaction was strongly decreased by the drugs. The reaction to the natural stimulus the prey was changed, but not suppressed. The modification of the predatory behavior was manifedsted in an "improvement" of orientation reactions when pursuing the prey and in a better placement of bites. This effect, most evident with Haloperidol, is possibly due to the specific neuroleptic component of the substances. A delay in approaching the prey, or even the total suppression of the prey-catching behavior is suggested to be due to a sedative component which was most obvious in some experiments with Clozapine. On the other hand, there are behavioral elements like the use of paws which are not effected by the neuroleptics. From these and other observations, it is concluded, that the predatory behavior of the ferret has a hierarchically organisated structure. Further it is suggested that some functional connected parts of the behavior have distinct central representation, for they are not influenced in the same way by these drugs.

Bioelectronic noses: a status report. Part I.

The present state of the art to record or mimic electronically the human senses of olfaction and taste is characterized. In this part I, an introduction to our present understanding in the development of electronic and bioelectronic noses is given. Finally the natural olfactory system is described in detail.

Changes in granule cells of the ferret olfactory bulb associated with imprinting on prey odours.

The maturation of the granule cells of the ferret olfactory bulb around the time of odour imprinting has been examined. Rapid Golgi impregnation studies revealed a temporal overshoot in the development of the spines on the external and internal dendrites of the granule cells. In contrast, the number of somatic spines decreased continuously. Electron microscopical examinations of the synaptic contacts in the external plexiform layer revealed that the time course of synapse and reciprocal synapse formation was similar to that of the formation of the spines on the external dendrites. The results were taken as evidence that both the Golgi and the electron microscopical investigations described the same developmental process of postnatal synaptic rearrangement.

Olfactory deprivation enhances normal spine loss in the olfactory bulb of developing ferrets.

Ferrets show a sensitive phase in their postnatal development during which they can become imprinted to food odors. At the same time the number of granule cell spines in the olfactory bulb reaches a maximum, declining significantly thereafter. In ferrets, exposed continuously to saturated levels of geraniol odor in the cage environment, the normal decline in spine number (occurring between day 60 and 90) is significantly enhanced. No such effects were observed during earlier ontogenetic phases. This late postnatal phase is further associated with a marked and significant decrease in total brain weight. The significance of these events to olfactory imprinting and plasticity in the developing brain is discussed.

Selective and reversible reduction of odor sensitivity in the rat by concanavalin A.

Rats were trained using an olfactometer to detect low concentrations of ethyl acetate (EA) or dimethyl disulphide vapor (DMDS). Concanavalin A (ConA) applied to the olfactory mucosa had no effect on ability of rats to detect low concentrations of EA but produced a marked deficit in detection in DMDS. DMDS detection performance returned to control levels 3 days after the ConA treatment. These results provide the first behavioral evidence for odor-specific inhibition by chemical modification of the olfactory epithelium and support the notion that ConA selectively inactivates one or more types (subclasses) of olfactory receptor proteins.

Instinctive predatory behavior of mustelids (Mustela putorius f. furo, Mustela vison f. dom.) modified by benzodiazepine derivatives.

The predatory behavior of the ferret and of the mink consists mainly of instinctive behavioral patterns that are elicited by simple external stimuli. An important stimulus is size of the prey; the time needed to catch and kill defensive prey depends on the size of the prey in relation to that of the predator. Benzodiazepine derivatives like chlordiazepoxide or lorazepam affect the prey catching of both species significantly. Drugged animals (2 mg/kg orally) need less time to overpower their prey. The experiments indicate that low concentrations of benzodiazepine derivatives disinhibit mustelids when hunting relatively large prey.

Occurrence of non-ortho, mono-ortho and di-ortho substituted PCB congeners in polecats, stone martens and badgers from the state of Baden-Württemberg, Germany.

The concentrations of non-ortho, mono-ortho and di-ortho substituted PCB congeners in tissues of three European mustelid species--polecat, stone marten and badger--were determined. Median congener concentrations are comparable in the three species and are lower than in previous studies on polecats. In all samples PCB-126 contributes most to the TCDD-TEQ; it occurs in considerably higher concentrations in polecats. Additionally, amphibs, the main prey of polecats, were analysed. The total PCB intake of polecats feeding solely on amphibs would be below a critical level, considering the NOAEL for the reproduction of mink, a closely related species.

Imprinting on prey odours in ferrets (Mustela Putorius F. Furo L. ) and its neural correlates.

The effect of different feeding conditions during ontogeny was investigated in the carnivorous ferret. Behavioral tests and cardiac responses towards known and unknown odours as well as food choice tests showed that in this species olfaction plays an important role for prey recognition. Yet, the knowledge of the prey odours has to be learned during a sensitive phase which was found to exist between postnatal days 60 and 90. In adult ferrets, searching for prey can be elicited reliably by familiar odours, unknown odours are not reacted to. The maturation of the granule cells of the ferret olfactory bulb around the time of prey odour imprinting has been analysed. Rapid Golgi impregnation studies reveal a temporal overshoot in the development of the spines on the external dendrites of the granule cells. Electron microscopical examinations of the synaptic contacts in the external plexiform layer indicate that the time course of synapse and reciprocal synapse formation is similar to that of the formation of the spines on the external dendrites. The results show that the maturation of the external plexiform layer with respect to the number of dentritic spines and synapses, occurs at a time when the animal is most sensitive to olfactory imprinting stimuli.

The quantitative effect of visual and tactile stimuli on the prey-catching behaviour of ferrets (Putorius furo L.).

The influence of visual and tactile stimuli on the elicitation of prey-catching behaviour of ferrets was to be studied. For this study 16 animals, males and females, some naive and others experienced in catching and killing mice and rats were used. The behaviour of the ferrets toward 16 dummies with different characteristics was analysed under standardized conditions. Prey catching reactions of ferrets can be elicited by moving dummies. Dummies up to a certain size reliably elicit hunting reactions if they are moving at a speed of 25 cm/sec to 45 cm/sec. Moving objects, more than double the size of a ferret, cause avoiding reactions. Objects with a fur-like surface release more biting than objects with a hard surface. When hunting, ferrets-innately-tend to aim at the most anterior part of the "prey" and to bite into it, independent of whether there is a head-like structure with a neck or not.

The use of lectins as a non-invasive approach to the study of odour detection in mammals.

Olfaction is one of the most important sensory systems for many mammalian species. Yet, the extent to which olfactory stimuli control the behaviour of a specific species is difficult to establish. Traditionally, massive invasive techniques like destruction of the olfactory sensory epithelium or bulbectomy are applied to estimate the effect of olfactory stimuli. However, for behavioural research less invasive methods are required. Application of lectins to the olfactory epithelium seems to be a promising new approach to study the releasing effect of odours on behaviour. This new approach is demonstrated in 30 adult male Wistar rats for the lectins Concanavalin A, lotus tetragonolobus and wheat germ agglutinin. Rats were trained to detect low concentrations of ethyl acetate, 1-methyl naphthalene or methacrylic acid. The lectins applied to the olfactory mucosa had selective inhibitory effects on odour detection; in each case detection inhibition was reversible within 4-48 h after lectin application. These results provide behavioural evidence for odour-specific inhibition without destruction to the animal. This new approach is discussed with the traditional invasive techniques use to inhibit odour detection.

Effects of cyproterone acetate on mating behavior, testicular morphology, testosterone level, and body temperature in male ferrets in comparison with normal and castrated males.

Effects of surgical castration of 60-day-old male ferrets are compared with the effects of a chemical castration with cyproterone acetate from postnatal day 60 until 360. Investigations were made on mating behavior, intermale aggression, testicular morphology, plasma testosterone level and body temperature. While controls show seasonal variations in all parameters, according to the annual cycle of sexual activity and inactivity, both, surgically and chemically castrated ferrets show throughout the year constant parameters similar to that of controls during the sexual inactive period. All investigated effects of a long-term treatment with cyproterone acetate are fully reversible within 2 years after termination of drug administration.

Developmental patterns of thyroid hormones and testosterone in ferrets.

Plasma levels of thyroxine (T4) and triiodothyronine (T3) were measured in male and female ferrets at regular intervals between postnatal day 20 and 150 as well as in adult animals. In addition, testosterone level in male ferrets was measured. All hormones showed characteristic developmental patterns. There is a T4 maximum prior to a T3 maximum in subadult animals which in both cases surpasses adult levels. Testosterone level shows a different developmental pattern. There is an outstanding peak in subadult males around day 60-80, which, however, is surpassed by adult levels during the mating season.

The olfactory system as a portal of entry for airborne polychlorinated biphenyls (PCBs) to the brain?

Ferrets, mammalian carnivores, kept in an indoor enclosure were continuously exposed to low concentrations of polychlorinated biphenyls (PCBs) in the ambient air for 5 years. After that time PCB concentrations were quantified in the olfactory bulbs and in the remaining brain, adipose tissue and liver. The results revealed unexpectedly high PCB concentrations in the olfactory bulbs, surpassing those in the remaining brain and the peripheral tissues. The PCB congener pattern in the olfactory bulbs resembled that found in the ambient air and the less chlorinated volatile PCBs were found in higher concentrations. We, therefore, assume that airborne PCBs enter directly via the olfactory system and are transported through the axons to the olfactory bulbs where they accumulate.

The vomeronasal organ of the male ferret.

The vomeronasal organ (VNO) is known to play a major role in sexual behavior in many mammals. This study is the first report that the adult male ferret has a VNO, which is considerably smaller and morphologically different from the usually crescent-shaped epithelium in several mammalian species, particularly rodents. There were no differences in the size or structure of the ferret VNO between the mating season in spring and the sexually quiescent season in autumn, although plasma testosterone, testis size and brain size are dramatically increased in spring and behavior changes significantly. The histological data suggest that the VNO might be not as important a structure in male ferret sexual behavior as in rodents.

PCBs and their putative effects on polecat (Mustela putorius) populations in Central Europe.

In Europe polecat populations are declining for unknown reasons during the last decades. Data on the river otter, another mustelid predator, indicate that PCB levels are high enough in some populations to interfere with the reproduction of this aquatic species. Since the diet of the polecats consists to a large amount of aquatic prey (amphibians) it appears reasonable to assume that PCBs ingested with the prey are a factor in the decline of polecats. To test this assumption PCB residues in amphibians and in adipose tissue and liver of polecats from Southwest Germany were quantified and the results were compared with literature data on the reproductive toxicity of PCBs in feral mink. According to the current data total PCB levels in polecats (adipose tissue, mean 1244 ng/g lipids; liver, mean 1677 ng/g lipids) and their prey (frogs, mean 9279 ng/kg fresh weight; toads, 4948 ng/kg fresh weight) are comparatively low. Using the toxic equivalent approach, it was calculated that polecats could feed exclusively on amphibians without consuming a harmful amount of PCBs. Therefore, PCBs cannot be an agent currently affecting polecat populations in Central Europe. Other environmental factors like habitat destruction or road accidents are more likely to have a negative impact on polecat populations.

Predator odour and its impact on male fertility and reproduction in Phodopus campbelli hamsters.

This study investigated the influence of cat urine odour in suppressing development and fertility in Campbell's hamster males. Exposure to this odour from postnatal day 11 until day 45 (sexual maturation) resulted in reduced sex organ weights, reduced testosterone levels and in an increase in abnormalities of the synaptonemal complex in both sex chromosomes and autosomes. Subsequent breeding experiments revealed a significant decrease in litter size. All these data indicate a severe effect of predator odour on the breeding success of potential prey species. It is assumed that these effects are caused by the sulphurous compounds in the urine; however, the underlying mechanisms are not yet known.