Removal Of Vibrissae Research Articles

Involvement of various senses in responses to individual housing in laboratory albino mice: 2.The tactile sense

Abstract ‘Isolation’ of male mice to induce aggressiveness as practised in most laboratories does not preclude communication between neighbouring conspecifics. Indeed, a companion paper (Brain el al., 1982) has already shown the importance of olfactory cues in this connexion. The experiments here examine the possible role of the mystacial vibrissae in the control of ‘isolation-induced’ social conflict in male mice. Young and mature, naive and experienced male fighters were subjected to removal of vibrissae. In subsequent tests with ‘standard opponents’, removal of the vibrissae appeared to have only minor effects on subsequent social investigation and fighting. Consequently, in this species tactile influences seem less important than olfactory in modulating isolation-induced aggression.

Histochemical changes in cytochrome oxidase of cortical barrels after vibrissal removal in neonatal and adult mice.

The posteromedial barrel subfield of the somatosensory cortex of mice was examined histochemically for cytochrome oxidase activity (cytochrome c oxidase; ferrocytochrome c:oxygen oxidoreductase, EC 1.9.3.1). In normal mice a high enzymatic activity was found within the barrel hollows, rather than in the sides and septa. Electron microscopic examination indicated that within the hollows reactive mitochondria reside in many dendrites, in some axonal terminals, and in a few neuronal perikarya. After neonatal cauterization of selected row(s) of vibrissae, the corresponding row(s) of barrels appeared as narrowed fused band(s) and their cytochrome oxidase activity was much reduced. Removal of vibrissae in the adult, by either cauterization or repeated plucking, did not cause size changes of cortical barrels. However, there was a significant decrease in the oxidative enzymatic activity within these barrels. Thus, the deprivation of sensory input through damage to, or removal of, the peripheral sensory organ induces an enzymatic response in neurons that are at least two to three synapses away from the periphery.

The development of vibrissae representation in subcortical trigeminal centers of the neonatal rat.

In every station of the trigeminal system of the young rat, the segmented activity of the mitochondrial enzyme succinic dehydrogenase (SDH) clearly delineates the representation of the mystacial vibrissae. In the trigeminal complex of the medulla, three parallel representation can be seen, two in the spinal trigeminal nucleus and one in the principal trigeminal nucleus. In the next station, the ventrobasal complex of the thalamus, a single representation occurs. Likewise, layer IV of somatosensory cortex contains one representation of the vibrissae. Further, neonatal damage to the mystacial vibrissae results in anomalies within each representation. The present study delineates both the normal development of subcortical trigeminal stations and the aberrant organization seen after vibrisse removal. The results of a similar study on somatosensory cortex (Killackey and Belford, '79) and the present data allow the comparison of the development of each of the five vibrissae representations in the trigeminal system. In the brainstem, each of the three trigeminal complex representations are present at birth, although the pattern becomes more distinct over the first several days of life. Interestingly, vibrissae removal at birth induces an aberrant pattern that is distinct by postnatal Day 3. Although details are not equally discernible in each representation, the abnormalities appear to be similar. The SDH segmentation in the ventrobasal complex develops during postnatal Days 1 through 4. At Day 1, portions of the matrix of high density SDH activity break up into bands. Clusters can be discerned within these bands on Day 2. By Day 4 the pattern is sharply delineated. Vibrissae removal at birth results in anomalies that are a part of the initial development of segmentation, not a later reorganization. Comparison of the present data with that of our previous studies indicates that there is a sequential development of the central somatosensory structures related to the vibrissae, beginning with the most peripheral station. Further, there are many similarities in the development of each station. There are also differences which are particularly important in comparing the trigeminal nuclei with the later stations. The unique features in the abnormal development of the trigeminal nuclei are likely due to their direct connections with the periphery.

The formation of afferent patterns in the somatosensory cortex of the neonatal rat.

In the rat, the clustered pattern of thalamocortical afferent terminals to the "barrel field" portion of primary somatosensory cortex replicates the arrangement of vibrissae on the face, and the pattern of the terminals can be altered by the removal of vibrissae on the face, and the pattern of the terminals can be altered by the removal of vibrissae at birth (Killackey et al., '76). These patterns of terminals were studied using enzyme succinic dehydrogenase (SDH) because in somatosensory cortex the activity levels of SDH closely correspond to the patterns of thalamocortical afferent terminals. The present experiments show that the pattern of high SDH segmentation in the portion of layer IV of somatosensory cortex that is related to the vibrissae develops during postnatal Day 3 through 6. Activity related to the centers of individual clusters is first visible, with indistinct boundaries. At later times the edges of individual clusters become apparent. Further, in animals with Row C of vibrissae removed at birth, the abnormal SDH segmentation in somatosensory cortex develops with a time course similar to that of normal animals. At ages when edge boundaries are first distinct, a fused band corresponding to the removed row of vibrissae is present. Thus the aberrant organization seen in the adult cortex is the result of an abnormal initial development, not a later reorganization from a normal pattern. And indeed, vibrissae removal at Day 5 or 6 does not result in an aberrant cortical SDH pattern. Finally, after removal of all five rows of mystacial vibrissae at birth, the cortical SDH pattern seen at postnatal Days 6 and 7 consists of five bands in place of the normally present five rows of clusters. This may indicate that closer relationships exist between vibrissae within one row than vibrissae in adjacent rows.

Vibrissae removal and the phenomenon of unexplained sudden death.

Two earlier theories on the effect of vibrissae removal in rats were tested. One theory stating that vibrissae removal produces impairment of spatial orientation capacity was confirmed. The other stating that it causes a depressive state of hopelessness and sudden death could not be confirmed. It is concluded that the extrapolation from the particular animal experiment to human psychological processes is not justified.

Anomalous organization of SMI somatotopic map consequent to vibrissae removal in the newborn rat

Anomalous organization of SMI somatotopic map consequent to vibrissae removal in the newborn rat

Acute whisker removal reduces neuronal activity in barrels of mouse SmL cortex.

The autoradiographic 2-deoxy-D glucose (2-DG) method has been used to map relative changes in metabolic activity in the CNS during various functional states (Plum et al., '76). Here we describe the application of the 2-DG method to assay regional activity in the posteromedial barrel subfield (PMBSF) region of the mouse SmI cortex after acute removal of mystacial vibrissae. One day prior to isotope injection, various combinations of vibrissae (e.g., all vibrissae, row-C only, rows-B and -D only) were plucked from adult male Swiss Webster mice under anesthetic. The next day, 5 muCi of 14C-2-DG were injected into a tail vein, and the mice were allowed to actively explore an empty cage for 45 minutes. The animals were then sacrificed, the brains quickly removed, frozen, and sectioned either parallel or perpendicular to the pia at 80 mum in a cryostat. The sections were mounted, dried on coverslips, and were used to expose X-ray film, after which the sections were stained with thionin and the X-ray film developed. The tissue sections and matching autoradiograms were compared directly from photomicrographs of each. The autoradiograms showed areas of higher activity in barrels for which corresponding vibrissae were present and lower activity in barrels for which appropriate vibrissae were missing. In tangential sections from animals with all vibrissae intact, the PMBSF was uniformly and consistently higher in activity than in cases with all vibrissae missing. The removal of row-C or rows-B and -D resulted in strips of decreased activity in the corresponding PMBSF rows. The same patterns of increased or decreased activity were also seen in sections normal to the pia, but the changes in activity, while greatest in layer IV, extended through all layers of the cortex. Finally, in a number of the autoradiograms, density patterns could be recognized which later were shown to relate directly to sides of individual barrels. The results indicate: (1) Acute removal of the peripheral vibrissal hairs is sufficient to deprive the related contralateral cortical barrel neurons of normal activity. Thus in the mouse somatosensory system it may be possible to determine the relative importance of sensory deprivation and neonatal peripheral lesions in normal cortical development. (2) The barrels are part of a functional cortical columnar organization similar to that in other sensory systems. And, (3) the 14C-2-DG-X-ray technique is sufficiently sensitive to reveal parts of individual barrels in autoradiograms and thus, with some modification, may be suitable for the study of small populations of neurons.

Functions of the vibrissae in the defensive and aggressive behavior of the rat

Removal of mystacial vibrissae for strange rats placed in an established rat colony produced reliable decrements in defensive boxing for these animals, and corresponding increases in freezing. In a subsequent experiment, removal of the vibrissae of the attacking colony males did not change the attack behavior of the vibrissectomized animals. These results indicate that the vibrissae are involved in defensive boxing behavior, but play no essential role in the elicitation or maintenance of conspecific attack in the rat.

Role of the mystacial vibrissae in the control of isolation induced aggresion in the mouse

Adult male Swiss Albino mice were isolated from conspecific contact for 10 days. Removal of the mystacial vibrissae and subsequent anesthesia of the vibrissal pad reduced the number of aggressive social encounters that normally ensue upon the reintroduction of a conspecific. This reduction occurred under conditions in which latencies for initial social contact were essentially unchanged. These results are consistent with previous reports upon the importance of vibrissal integrity in the control of attack behaviors in a variety of other aggressive paradigms, and extend previous observations to a novel species and attack paradigm. Recent developments in the study of agonistic behavior have pointed to the importance of highly specific sensory input for the elaboration of a variety of aggressive responses. In particular, trigeminal mechanisms including the sensory organs located at the facial lipline and the mystacial vibrissae have been shown to influence the occurrence of terminal attack components such as facial orientation and biting in many models of aggression. For example, Flynn and his colleagues (Flynn, 1967, 1972; Flynn et al. 1971; MacDonnell and Flynn, 1966a, b) have pointed to the importance of sensory factors in the control of centrally elicited attack in the cat, both through the direct alteration of sensory fields subsequent to central stimulation of aggression producing sites, and additionally through the disruption of terminal attack patterns subsequent to the interruption '~f afferent trigeminal input. In addition, afferent factors have been implicated in the control of shock elicited, biochemicaUy induced, and predatory aggression in the rat via a variety of peripheral manipulations including facial anesthesia and vibrissal removal (Thor and Ghiselli, 1973, 1974a, b, 1975). It would appear from

Anomalous organization of thalamocortical projections consequent to vibrissae removal in the newborn rat and mouse

Anomalous organization of thalamocortical projections consequent to vibrissae removal in the newborn rat and mouse

Changes in pyramidal cell density consequent to vibrissae removal in the newborn rat

Changes in pyramidal cell density consequent to vibrissae removal in the newborn rat

Vibrissae amputation in mice and completion of a learned food-acquisition task

The effect of vibrissae amputation on completion of a learned food-acquisition excursion was tested. The mice were trained to pass from a startbox through a tunnel to a food box. The vibrissae of one group were amputated, and the running time of that group was compared to the times of three control groups. The difference in running times between groups was not significant, indicating that vibrissae removal in mice does not significantly inhibit performance of a function vital to survival.

The Effects of Visual Impairment on Aggressive Behavior

Aggressive behavior in response to electric shock was measured under conditions of ( 1) normal vision ( 2 ) temporary visual impairment (3) permanent visual impairment and (4) combined permanent vision and vibrissa impairment. Paired rats with visual impairment demonstrated less aggression to foot shock than did unimpaired Ss. Combined visual impairment and vibrissae removal produced a greater drop in aggressive responses than did visual impairment alone.