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PubMed1998

Experience-dependent changes in vibrissae evoked responses in the rodent barrel cortex.

A change in vibrissae complement in rodents leads to long-term changes in vibrissae dominance. These changes involve both potentiation of spared vibrissae responses and suppression of deprived vibrissae responses in adolescent animals. In adult animals only potentiation of spared vibrissae responses was detected. Suppression exhibits hetero- and homosynaptic components and appears to be cortical in origin, as is potentiation. The time course for potentiation and suppression in the barrel cortex of adolescent rats is different, with suppression preceeding potentiation by at least one week. There seems to be no critical period for potentiation in superficial layers of barrel cortex, but there is a critical period for suppression. Suppression cannot be evoked if plasticity is induced later than at 6 months of age nor maintained if experimental manipulations begin later than at three months. The molecular mechanisms that underlie plastic changes in the barrel cortex still remain unclear, although alpha-CamKII and to lesser extend alpha/beta-CREB appear to be involved.

Animals↗
PubMed1992

Trigeminal ganglion cell processes are spatially ordered prior to the differentiation of the vibrissa pad.

The rodent trigeminal system is characterized by the punctate organization of its afferents and neurons that replicate the distribution of mystacial vibrissae and sinus hairs on the snout. We have examined the development of topographic equivalence between the sensory periphery on the snout and the brainstem trigeminal nuclei in rats. Lipophilic tracers Dil (1,1'-dioctodecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate) and DiA [4-(4-dihexadecylaminostyryl)-N-methylpyridinium iodide] were used to label trigeminal ganglion cells and their processes differentially from discrete regions of the presumptive vibrissa field in fixed embryos. Our results show that trigeminal ganglion cell processes are spatially ordered as they reach their peripheral and central targets on embryonic day 12 (E12). Peripheral processes of dorsomedially situated ganglion cells course dorsally toward the presumptive vibrissa field, and those of ventrolaterally situated ganglion cells project ventrally. On E13, the central processes of dorsomedially situated ganglion cells enter the brainstem medially whereas those of ventrolaterally situated ganglion cells enter laterally. This spatial order of trigeminal ganglion cell processes precedes the emergence of vibrissa rows in the periphery and the differentiation of brainstem trigeminal nuclei. Thus, the subsequent transfer of the vibrissa-related pattern to the brainstem trigeminal nuclei occurs along a preexisting, spatially aligned bridge formed by the trigeminal ganglion cells.

Animals↗
PubMedDate not supplied

Effect of vibrissae removal on search accuracy in the water maze.

In two experiments the vibrissae were clipped on either the left, the right or both sides, and the rats were trained to find a submerged platform in the Morris water maze. In both experiments, animals without vibrissae on both sides or on the left consistently spent significantly more time in the 'counter' area twice the platform diameter in size, surrounding the submerged platform, than intact controls. Counter preference was not as consistent across experiments in rats with right vibrissae removed. These results suggest that the vibrissae are required for proprioceptive location of the platform itself, but not for proximal search accuracy. Since ischaemic damage to hippocampal CA1 pyramidal cells has also been reported to prolong counter search during training, the results support the suggestion that impaired hippocampal processing of proprioceptive information from the vibrissae may contribute to the increased latency to find the platform shown by ischaemic rats.

Animals↗
PubMed1993

The influence of vibrissae removal on copulatory behaviour in male rats.

The influence of vibrissae removal on copulatory behaviour was tested in both sexually naive and experienced male rats. The experiment consisted of 3 experimental and 3 control sessions. In some sexually naive rats, the removal of the vibrissae caused absence of copulatory behaviour during the first or all 3 experimental sessions, while in other ones this procedure remained without any apparent influence on copulatory behaviour. Three weeks later, after vibrissae have regrown, all of these rats displayed the copulatory behaviour. However, after the regrowth of the vibrissae, in rats with previously impaired copulatory behaviour a shortening of postejaculatory intervals was observed, while in rats with unaffected copulatory behaviour no such differences were observed. In contrast to observations in the sexually naive rats, in the sexually experienced ones removal of vibrissae led to the activation of copulatory behaviour, manifested by shortening of ejaculation latencies and mean interintromission intervals and an increase in hit rate.

Animals↗
PubMed1978

Response properties of vibrissa units in rat SI somatosensory neocortex.

1. Glass microelectrodes were used to record extracellular responses from 308 SI cortical neurons to deflections of the contralateral vibrissae in 21 unanesthetized, paralyzed rats. Controlled deflections of individual hairs were produced by means of an electromechanical stimulator. Fast green dye marks were made to aid histological reconstructions of electrode tracks. 2. TS) were observed throughout layers II--VI; "fast" cortical spikes (FS) were less frequently encountered and largely restricted to layer IV. Although both types of potentials had similar negative-positive waveforms. FSs were distinguished from RSs by their comparatively rapid time course, about half that of RSs. RS units (RSU) discharged spontaneously at rates of less than 1--15/s, whereas FS units (FSU) displayed rates of 15--50/s. The amplitudes of FSs, which were generally smaller than those of RSs, often decreased during high-frequency discharges. 3. With sinusoidal oscillations of a vibrissa FSUs responded more reliably and over a broader range of frequencies (3 to at least 40 Hz) than did RSUs , particularly in layer IV. In addition, FSUs typically responded to whisker deflections over a range of 360 degrees, whereas many RSUs in layer IV displayed sharp spatial-tuning charcteristics, responding over a restricted range of less than 90 degrees. 4. Of all units, 58% responded preferentially to stimulus transients (vibrissal movements), 32% displayed sustained responses to stimulus stead-states (fixed vibrissal displacement). For the remaining 10% of units the appropriate stimulus could not be specified; these units were particularly common in layer V. 5. Computation of quantitative stimulus-response relations showed that many units increased their rate of discharge with increasing stimulus intensities. 6. Most units were directionally selective, responding preferentially to deflections of a whisker in one or more of four quadrants. 7. In radial penetrations through the cortex there was a columnar patern so that units were activated at least by the same (i.e., the "principal") whisker. In a number of cases these could be directly correlated with the barrels. Of all units, 55% responded to deflections of single vibrissa only, the remaining 45% to 2--12 adjacently situated vibrissae. For most multiple-whiser units the responses elicited by deflection of any one hair activating the neuron was qualitatively similar to those elicited by deflection of any other hair activating it. The principal whisker of the penetration was typically associated with the most vigorous responses. 8. In layer IV, 85% of neurons responded to deflections of one hair only, the remaining 15% to two or more hairs. In layers II and III 39% of units were activated by more than one vibrissa; in layers V and VI multiple-whisker units predominated (64%). Whisker configurations in the deep layers were larger than those in other layers. 9...

Animals↗
PubMed1982

[Responses of the primary somatosensory cortex to rhythmic stimulation of the vibrissae in the cat].

Extracellular and intracellular responses of cortical neurons localized in SI cortex to repetitive mechanical stimulation of vibrissae were studied in unanesthetized immobilized cats. Spike responses of neurons to stimulation of vibrissae could reproduce somewhat higher frequencies than those in response to electrical stimulation of the infraorbital nerve. An increase in frequency of vibrissae stimulation led to a limitation of peripheral receptive fields. Cortical neurons being able to reproduce relatively high frequencies of vibrissae stimulation and having a tendency to bursting activity were found; correlation between the pattern of discharges in such neurons and IPSPs in other cortical neurons makes it possible to regard such bursting neurons as inhibitory ones. Interaction between excitatory and inhibitory processes in cortical neurons during repetitive vibrissae stimulation is discussed.

Animals↗
PubMed1982

[Cytoarchitectonic and quantitative characteristics of cell groupings in layer IV of the cerebral cortex in the vibrissa representation area of the rat].

The multicellular neuronal groups named "barrels", which make the posterior-medial subfield of barrels and situate in IV layer of the somatosensory area of the rat cerebral cortex in the zone of the vibrissa representation have been studied. Average volumetric meanings and the number of neurons have been obtained in the barrels of various size and in the parts composing them (walls and cavities). As comparison of the results obtained demonstrated, there is a not proportional increase of the characteristics studied in the large and small barrels. An attempt is made to state the dependence of the quantitative characteristics of the barrels on the length of corresponding vibrissae and on the function they perform. It is possible to suggest that the size of the cortical projections of certain vibrissae depend not on the length of the vibrissae themselves, but rather on the volume of information they obtained. Analysing the peculiar features of morpho-functional organization of the posterio-medial subfield of the barrels, it is possible to suggest that complication of the vibrissa function is morphologically expressed as an increasing number of neurons predominantly in the walls of their corresponding barrels and in increasing volume of the cavities filled with the thalamo-cortical specific afferents.

Animals↗
PubMed1997

Spatial organization of facial vibrissae and cortical barrels in the guinea pig and golden hamster.

The arrangements of vibrissae in guinea pigs and golden hamsters were previously reported to be different from those in mice and rats. Whereas the mystacial pads in mice and rats include four straddlers and five rows of vibrissae, guinea pigs were described to possess six rows of irregularly aligned mystacial vibrissae and no straddlers, and golden hamsters to include seven vibrissal rows and also no straddlers. We found that all of these four species possess similar vibrissal arrangements within the mystacial pad. To demonstrate this similarity, we developed a new method of sinus hair visualization in flattened and cleared preparations of the mystacial pad. Intrinsic muscles of the mystacial pad that were revealed in thick histological preparations showed clearly the structural and functional relationships between straddlers and vibrissal rows. To verify this finding, and to extend the knowledge of vibrissal cortical representations in guinea pigs and golden hamsters, we have investigated the spatial organization and the functional vibrissal representations of barrels in the posteromedial barrel subfield (PMBSF) of these rodents. The barrel morphology was clearly preserved in Nissl-stained sections and sections processed for cytochrome oxidase of flattened cerebral cortices. We demonstrate that the vibrissal arrangement in the mystacial pad is replicated in the PMBSF of guinea pigs and golden hamsters and that this arrangement is similar to that found in mice and rats. To facilitate comparative studies, these findings strongly recommend the use, in guinea pigs and golden hamsters, of the same classifications and nomenclatures that are used in mice and rats to describe mystacial vibrissae and cortical barrels.

Animals↗
PubMed2000

Clorgyline treatment elevates cortical serotonin and temporarily disrupts the vibrissae-related pattern in rat somatosensory cortex.

Manipulation of cortical serotonin (5-HT) levels in perinatal rodents produces significant alterations in the development of the layer IV cortical representation of the mystacial vibrissae. Monoamine oxidase A (MAO(A)) knockout mice have highly elevated cortical 5-HT and completely lack barrels in somatosensory cortex (S-I). The present study was undertaken to determine whether the effects on thalamocortical development seen in MAO(A) knockout mice can be replicated in perinatal rats treated with an MAO(A) inhibitor and, second, to determine whether these effects persist with continued treatment or after discontinuation of the drug. Littermates were injected with either clorgyline (5 mg/kg) or sterile saline five times daily. Clorgyline administration from birth to postnatal day (P) 6, 8, or 10 produced increases of 1,589.4 +/- 53.3%, 1660.2 +/- 43.1% and 1,700.5 +/- 84.5 %, respectively, in cortical 5-HT as compared with controls. Serotonin immunocytochemistry, 1,1;-dioctadecyl-3,3,3", 3;-tetramethylindocarbocyanine perchlorate (DiI) labeling of thalamocortical afferents and Nissl and cytochrome oxidase staining of layer IV cellular aggregates demonstrated that clorgyline treatment from P0 to P6 produced a complete absence of any segmentation of vibrissae-related patches in S-I. However, continued treatment until P8 or P10 did not prevent the appearance of these patches. Animals treated with clorgyline from birth to P6 and killed on P8 or P10 had increases of 546.8 +/- 33.2% and 268.8 +/- 6.3% in cortical 5-HT and they had qualitatively normal vibrissae-related patterns in S-I. These results indicate that clorgyline treatment produces a transient disruption of vibrissae-related patterns, despite the continued presence of elevated cortical 5-HT.

Age Factors↗
PubMed2000

Localisation of members of the notch system and the differentiation of vibrissa hair follicles: receptors, ligands, and fringe modulators.

Hair vibrissa follicle morphogenesis involves several cell segregation phases, in the dermis as well as in the epidermis. The expression of Notch-related genes, which are well established mediators of multiple cell segregation events in Drosophila development, was studied by in situ hybridisation during embryonic mouse vibrissa follicle morphogenesis and the first adult hair cycle. The results show that two receptors, Notch1 and -2, three ligands, Delta1, Serrate1, and -2, and the three Fringe regulators, Lunatic, Manic, and Radical, are expressed in different locations and morphogenetic stages. First, the appearance of hair vibrissa primordia involves the expression of complementary patterns of Notch2, Delta1, and Lunatic Fringe in the dermis and of Notch1, Serrate2, and Lunatic Fringe in the epidermis. Second, this expression pattern is no longer found after stage 3 in the dermis. Meanwhile, in the epidermis, the expression of Notch1, Serrate2, and Lunatic Fringe before the formation of the placode may be involved in determining two populations of epidermal cells in the developing follicle. Third, complementary expression patterns for Notch1, Manic, and Lunatic Fringe, as well as Serrate1 and -2 as previously shown (Powell et al., 1998), are progressively established from stage 4 of embryonic development both in the outer root sheath and in the hair matrix. These patterns are consistent with the one found in the adult anagen phase. During the hair vibrissa cycle, Notch1 and Manic Fringe display temporal and spatial changes of expression, suggesting that they may intervene as modulators of trichocyte activities.

Animals↗
PubMed1988

Anatomical consequences of neonatal infraorbital nerve transection upon the trigeminal ganglion and vibrissa follicle nerves in the adult rat.

A large body of experimental literature has demonstrated that neonatal infraorbital nerve damage in rodents produces anatomical and/or functional alterations of the normal whisker representation in central trigeminal structures. Less is known about the organization of primary afferent components of the trigeminal system following this manipulation. Such information provides an important basis for interpreting the central changes observed following damage of infraorbital nerve fibers at birth. We have therefore examined the composition and order of peripheral innervation in the pathway from the trigeminal ganglion to the vibrissa follicles in adult rats subjected to unilateral neonatal infraorbital nerve transection. Electron microscopy was used to determine the number and diameter of myelinated and unmyelinated fibers in vibrissa follicle nerves of these animals. Wheat germ agglutinin-horseradish peroxidase and fluorescent retrograde tracers were employed to examine the number and diameter, as well as the topographic organization and branching, of ganglion cells innervating the vibrissae in these rats. The data presented below indicate that neonatal infraorbital nerve transection has the following consequences within the adult trigeminal nerve and ganglion: 1) an alteration of the gross morphology of vibrissal nerves, 2) a significant reduction in the average number (85.4%) and diameter (32.6%) of myelinated, but not unmyelinated, follicle nerve axons, 3) a significant decrease in the average number (36.8%) of trigeminal ganglion cells innervating vibrissa follicles, 4) no significant change in the distribution of ganglion cell diameters, 5) an increase in peripheral branching (1.8-fold) of these ganglion cell axons, and 6) an alteration of somatotopic order within the trigeminal ganglion. Taken together, these data indicate that neonatal infraorbital nerve transection produces a profound reorganization of the primary afferent component of the trigeminal neuraxis.

Animals↗
PubMed1992

Dual innervation of the rat vibrissa: responses of trigeminal ganglion cells projecting through deep or superficial nerves.

The rat vibrissal follicle-sinus complex is innervated by a deep vibrissal nerve (DVN) and several smaller fascicles traveling in the dermis [conus or superficial vibrissal nerves, (SVNs)]. The function of the SVNs is unknown, although it has been suggested in a comparative study that they form part of a diffuse, multivibrissal system. Anatomical and electrophysiological methods were used to test this hypothesis and to determine if DVN and SVN fibers have differing response profiles. No ganglion cells were double-labeled after retrograde tracer injections in the DVN and SVNs of single follicles. Electron microscopy showed that selective transection of the DVN caused no SVN degeneration or vice versa. Thus, the dual innervation of the vibrissa arises from separate ganglion cells that project through separate nerves. Ganglion cells with A-row vibrissa receptive fields were studied before and after cutting the DVN and/or SVNs to the responsive vibrissa in order to identify their peripheral trajectories. In this sample, 83% projected through a DVN and 17% via a SVN. SVN or DVN cells were not spontaneously active. All cells responded to single vibrissae only; none were responsive to intervibrissal hairs or skin. Latencies to electrical stimulation were similar for DVN and SVN cells. Adaptation rates and threshold measurements were also similar in the two groups: 60% of the DVN cells and 80% of the SVN cells gave slowly adapting responses to sustained vibrissal displacement; threshold displacements ranged from less than 1 degrees to greater than 15 degrees for both SVN and DVN cells. Direction sensitivity was found in all DVN and SVN slowly adapting cells, with most cells responding to movements in one or two quadrants. For SVN cells, sequential circumferential nerve sections indicated that the fiber's directional sensitivity matched the direction of the fiber's entry into the follicle. The two groups differed in their responses to pushing in or pulling on the hair shaft. All the DVN cells were responsive to both of these stimuli, while for SVN cells pushing activated only 40% and none were responsive to pulling the hair. Another difference in the two groups was that no injury discharges occurred after cutting SVNs, but were present in 44% of DVN cells. These data suggest that DVN and SVNs are similar in the majority of response properties. There is also no evidence to support the hypothesis that SVNs provide diffuse, multivibrissal inputs.

Animals↗
PubMed2002

Effects of vibrissae removal on methamphetamine-induced damage to rat somatosensory cortical neurons.

Repeated methamphetamine (mAMPH) damages forebrain monoamine terminals and causes degeneration of nonmonoaminergic cell bodies in rat primary somatosensory cortex (S1). These degenerating cortical neurons can be labeled with the fluorochrome dye Fluoro-Jade (FJ) and are found almost exclusively in layers II/III and IV of the vibrissae representation in S1. Within S1, layer IV is organized into discrete, anatomically identifiable units termed barrels, each of which receives information from a single whisker. We previously reported that mAMPH-damaged neurons in S1 were located within the whisker barrels, suggesting that the prolonged mAMPH-induced whisking contributes to S1 neuronal injury. Here, we investigate effects of vibrissae removal on mAMPH-induced damage to S1 neurons. Rats were anesthetized and vibrissae were trimmed from either the left, right, or neither side of the snout. The next day they were given four injections of either saline (1 ml/kg, s.c.) or mAMPH (4 mg/kg, s.c.) at 2-h intervals. Three days later, cortical sections were processed for FJ histochemistry. The hemivibrissotomy produces a hemispheric asymmetry in FJ-positive neurons in barrel cortex, with fewer damaged neurons contralateral than ipsilateral to whisker removal. Taken together with the demonstration that acute injection of this dose of mAMPH induces the immediate early gene zif/268 and Fos protein in barrel cortex, these data suggest that the prolonged behavioral activity involving the vibrissae contributes to the mAMPH-induced damage to S1 neurons. Thus, some of the injurious effects of drugs may depend on afferent activity occurring as a result of the abnormal behaviors evoked by their administration.

Afferent Pathways↗
PubMed1994

Tactile size discrimination by a California sea lion (Zalophus californianus) using its mystacial vibrissae.

The capability of a blindfolded California sea lion (Zalophus californianus) to discriminate diameter differences of circular discs by means of active touch with its mystacial vibrissae was studied. Using a forced choice paradigm the sea lion was required to choose the larger of two simultaneously presented perspex discs. Absolute difference thresholds (delta D) were determined for 3 standard discs (1.12 cm phi, 2.52 cm phi, 8.74 cm phi) by the psychophysical method of constants. Increasing disc size resulted in an increase in the absolute difference threshold from 0.33 cm for the smallest disc size to 1.55 cm for the largest disc size. The relative difference threshold (Weber fraction) remained approximately constant at a mean value of 0.26. According to a video analysis the sea lion did not move its vibrissae when touching the discs. Instead, it performed precisely controlled lateral head movements, with the touched disc located centrally between the vibrissae of both sides of the muzzle. Since the extent of these head movements was identical at discs to be compared, discs of different size must have led to different degrees of deflection of vibrissae involved in the tactile process, resulting in quantitatively different mechanical stimulations of mechanoreceptors in the follicles. This suggests that the accuracy of the sea lion's size discrimination was determined by the efficiency of two sensory systems: the mechanosensitivity of follicle receptors as well as kinaesthesis.

Animals↗
PubMed1993

Galanin immunoreactivity reveals a vibrissae-related primary afferent pattern in perinatal rats after neonatal infraorbital nerve transection.

Immunocytochemistry was used to demonstrate the distribution of galanin immunoreactivity in the trigeminal (V) brainstem complex of normal rats and rats that sustained neonatal transection of the infraorbital nerve (ION, the V branch that supplies the mystacial vibrissae). In normal adult and perinatal (postnatal day [P-] 7) rats, there is very little galanin immunoreactivity in the rostral part of the V brainstem complex. However, there is dense immunoreactivity for this peptide in layers I and II of V subnucleus caudalis (SpC). There was a marked upregulation of galanin immunoreactivity at all levels of the V brainstem complex of P-7 rats that sustained ION transection on P-0. In V subnucleus interpolaris and the magnocellular part of SpC, this immunoreactivity occurred in clusters which had a pattern resembling that of the mystacial vibrissae. In animals examined at 30 days or more after ION transection, there were a few more galanin-immunoreactive fibers on the deafferented side of the brainstem than on the intact side, but there was no evidence of a vibrissae-related pattern. Our interpretation of these results is that galanin immunocytochemistry reveals a vibrissae-related pattern in the central arbors of axotomized primary afferents for at least 1 week after they have been disconnected from the periphery.

Animals↗
PubMed1994

Effects of postnatal blockage of cortical activity with tetrodotoxin upon lesion-induced reorganization of vibrissae-related patterns in the somatosensory cortex of rat.

Previous studies have shown that postnatal blockade of thalamocortical activity with either tetrodotoxin (TTX) or the NMDA receptor antagonist DL-2-amino-5-phosphonovalerate (APV) does not prevent the formation of vibrissae-related patterns. In the present study, blockade of cortical activity with TTX was combined with ablation of a row of vibrissae follicles or transection of the infraorbital nerve (ION, the trigeminal nerve branch that supplies the vibrissae follicles) to determine whether the cortical reorganization that follows these lesions in otherwise untreated animals was dependent upon neuronal activity that could be blocked with TTX. The results demonstrated that cortical TTX implants had no quantitative or qualitative effects upon the cortical reorganization that followed either vibrissae follicle cauterization or ION transection.

2-Amino-5-phosphonovalerate↗
PubMed1995

Abnormal ipsilateral functional vibrissae projection onto Purkinje cells multiply innervated by climbing fibers in the rat.

We have previously shown that synapse elimination occurring in the climbing fiber (CF)-Purkinje cell (PC) relationships during normal postnatal development is likely involved in the refinement of vibrissae projections onto the cerebellar cortex. In normal adult rats, CF-mediated vibrissae projections onto cerebellar Purkinje cells of the vermis of lobule VII are strictly contralateral and located in a narrow microzone whereas they are widely distributed in rats whose PCs remained multiply innervated by CFs due to postnatal irradiation. Given the proximity of this microzone to the midline, the question arose as to whether this synapse elimination process could participate in the segregation of ipsilateral and contralateral projections. In the present study, we compared the topographical map of the ipsilateral and contralateral CF-mediated projections of the third row of vibrissae onto the vermal PCs of lobule VII in adult normal rats and in polyinnervated rats. Using intracellular electrophysiological recordings, we examined the responsiveness of PCs to mechanical stimulation of vibrissae, and positioned responsive cells on an averaged planar map of lobule VII. In normal rats no ipsilateral responses were found, while in irradiated rats ipsilateral responses were distributed evenly from the midline to 700 microns apart. These results suggest that synapse elimination participates in the segregation of ipsi and contralateral mystacial inputs to the vermis.

Animals↗
PubMed1986

Apomorphine reverses direction of asymmetry in facial scanning after 10 days of unilateral vibrissae removal in rat: vibrissotomy-induced denervation supersensitivity?

Sensorimotor asymmetries of hemivibrissotomized rats were investigated in an open field. To examine possible behavioral plasticity after unilateral removal of the vibrissae, we compared two groups of rats which had experienced the sensory imbalance for different durations. One group was shaved on one side of the face daily for 10 days before behavioral testing (group 10-Days). The other group was first shaved 4 h prior to the behavioral testing and was sham-shaved for the preceding 10 days (group 4-H). On day 11, the undrugged behavior was examined, and then, one hour later, the behavior induced by apomorphine (0.75 mg/kg, s.c.) was analyzed. In the undrugged state both groups tended to scan the walls of the enclosure with the vibrissae side of the face. After injection of apomorphine, the 4-H group also scanned the walls preferentially with the vibrissae side. In contrast, the 10-Days group reversed the scanning asymmetry under the influence of this drug. That is, animals in this latter group now preferred to scan the walls with the shaved side of the face. These findings are suggestive of a plasticity in dopamine transmission subsequent to unilateral removal of vibrissae. The reversal in direction of asymmetry under apomorphine of the 10-Days group is reminiscent of the apomorphine-induced reversal in sensorimotor asymmetries found after unilateral 6-hydroxydopamine lesion of the substantia nigra, which has been attributed to dopamine receptor supersensitivity.

Animals↗