Behavioral effects of unilateral basal gangliar lesions in neonatal rats

Behavioral Effects of Unilateral Basal Gangliar Lesions in Neonatal Rats

CAROL VAN HARTESVELDT DAVID LINDQUIST

Department of Psychology University of Florida

Gainesville, Florida

Two-day-old rats were given unilateral lesions of the caudate-putamen, globus pallidus, o r hippocampus and their postural orientation was observed for 30 min immediately after surgery. All groups with damage to the caudate-putamen and/or globus pallidus showed a significant postural deviation toward the side ipsilateral to the lesion. At this age, neurogenesis in the basal ganglia is complete but synapses, neurotransmitters, and enzymes for neurotransmitter synthesis are far below adult levels. These results indicate that the basal ganglia have a role in motor function prior to their full maturation as measured by neuroanatomical and biochemical techniques.

The purpose of the present experiment was to determine the maturity of the caudate-putamen in the neonatal rat using postural deviation as a behavioral measure of this maturity. The development of this brain region has been traced using neuroanatomical and biochemical techniques. In the caudate-putamen, neurogenesis only is complete at 2 days after birth (Das & Altman, 1970), and the number of synapses (Hattori & McCeer, 1973), the activities of enzymes involved in synthesis of the catecholamines (Coyle, 1974) and acetylcholine (Hattori & McCeer, 1973), and the presence of the catecholamines (Loizou, 1972; Olson, Seiger, & Fuxe, 1973) are all at small percentages of adult values at this age. However, whether these measures are related to the maturation of behaviors regulated by the caudate-putamen is not known.

In the adult, the caudate-putamen is involved in the regulation of postural orientation and rotational behavior. Unilateral damage results in turning toward the side of the lesion (Anden, Dahlstrom, Fuxe, & Larsson, 1966; Lotti, 1971). We chose to determine whether the caudate-putamen participates in the regulation of these behaviors in the rat at 2 days after birth, a time at which this structure is immature by neuroanatomical and biochemical standards.

Method

Subjects

Fifty-six male and female Long-Evans hooded rats (Rattus nowegicus) 48-72 hr old were used.

Reprint requests should be sent to Dr. Carol Van Hartesveldt, Department of Psychology, University of Florida, Gainesville, Florida 326 11, U.S.A.

Received for publication 25 August 1976 Revised for publication 9 March 1977 Developmental Psychobiology, l l ( 2 ) : 151-160 (1978) 0 1978 by John Wiley & Sons, Inc. 0012-1620/78/0011-015 1$01.00

153, HARTESVELDT AND LINDQUIST

Apparatus

A dental cement mold was made around the bottom of an average size 2-day-old rat’s head, in order to immobilize and orient the infant’s skull for stereotaxic implantation. The mold was mounted on a platform which could be adjusted in 3 dimensions and the platform was mounted in a stereotaxic frame.

For behavioral observation, rats were placed in a circular arena, 17.5 cm in diameter, under a 20-W bulb to maintain body temperature.

Procedure

Each rat was pretested for 10 rnin prior to receiving the lesion using the procedure outlined below. If a turning preference was discerned during the pretest, the lesion was made on the side opposite the preferred side. Thus, if the lesion had an effect, the animal would deviate toward the side opposite that of its preference.

Each animal was anesthetized with ethyl ether and its head was secured in the mold with strips of tape over the snout and around the back of the skull. The platform was adjusted so that lambda and bregma, visible through the skin, were at the same horizontal plane and aligned in the anterior/posterior plane. The bregma was used as a landmark for the medial/lateral and anterior/posterior measurements. The courdi- nates used were, approximately, .O-.5 mm anterior to bregma, 2.0-2.5 rnm lateral, and 3.0-4.0 mm ventral to the skull surface. (Because no atlas is available for the brain of the 2-day-old rat, coordinates were determined empirically in pilot animals.) More posterior coordinates were used to produce a control group with lesions in the hippocampus. The electrode was lowered directly through skin and skull using an electrode carrier. (At this age the skull is thin enough that this can be accomplished with minimal compression of underlying tissue.) Lesions were produced with currents of 1-2 mA for durations of 5-15 sec passed through electrodes made from Size 00 insect pins covered with Insulex and bared .5 mrn at the tip. Saline-soaked sponges wrapped around the animal’s body were used for the indifferent electrode. After withdrawing the electrode the pup was placed in a warming tray until it regained the righting response (approximately 10 min). The animal was then placed in the testing arena and observed during 6 consecutive 5-min intervals: postural deviation was recorded whenever an imaginary line from the tip of the nose and the base of the tail was not straight; duration of ipsilateral and of contralateral postural deviation was recorded during each interval on running time meters accurate to l/l00 min. A difference measure was obtained by subtracting time deviated contralateral from time dt-viated ipsilateral during each interval.

His tology

Immediately after behavioral observations the animals were sacrificed with ether, perfused intracardially with 10% formalin, and their brains removed. The brains were embedded in celloidin, sectioned at 30 ,urn, and stained with thionin. On the basis of histological examination the animals were placed in the following groups (Figs. 1 and 2):

AV: damage to the ventral caudate-putamen, anterior to the globus pallidus ( n = 8). AD: damage to the dorsal caudate-putamen, anterior to the globus pallidus ( n = 9). M/GP: damage to the medial globus pallidus at the interface with the internal

UNILATERAL BASAL GANGLIAR LESIONS 153

Fig. 1. Representation of typical brain damage in rats in Group AD, top row; Group AV, 2nd row; Group M/GP, 3rd row; Group DL/GP, 4th row; Group GP, 5th row; and Group Hpc, bottom row.

capsule (n = 10). (Most of these animals also had damage to the ventral caudate-putamen anterior to the globus pallidus.)

DL/GP: damage to the dorsal and lateral globus pallidus (n = 11). (Most of these animals also had damage to the caudate-putamen anterior to the globus pallidus.)

GP: extensive damage to the globus pallidus (n = 11). (Most of these animals also had damage to the caudate-putamen anterior to the globus pallidus.)

Hpc: damage to the dorsal hippocampus (n = 8). (Some of these animals also had damage in the lateral thalamus and/or internal capsule.)

The extent of the lesions varied among these groups. The lesion size was quantified for each animal by placing a grid over a projection of each of 10 selected brain sections, .8 mm apart, and counting the number of squares falling over the lesion. A lesion score was obtained for total damage, damage only to the caudate- putamen (CPu), and damage only to the globus pallidus (GP) in each animal. Both behavioral and lesion size results are shown in Figure 3 .

154 HARTESVELDT AND LINDQUIST

Fig. 2 . Photomicrographs of brain damage in animals representing each lesion group: (a) G r o u p AD, lesion on right; (b) Group AV, lesion on left; (c) Group M/GP, lesion on left; (d) Group DL/GP, lesion on right; (e) Group GP, lesion on right; (f) Group Hpc, lesion on right.

UNILATERAL BASAL GANGLIAR LESSIONS 155

(4

Fig. 2. (continued from the previous page)


(f)

Fig. 2. (continued from the previous page)


: mean minr deviated i p s -

3 4 z Q CPU lesion s t o r e LD

a total lesion score a

3 ’

u

0 - - n Y -

2 - m D

n

- - 2

0 I - -

D -

HPC A D A V M / G P DL/GP GP

Fig. 3. Mean postural deviation in minutes and extent of damage to the CPu, GP, and total lesion damage for each group. Postural deviation score refers to difference between contralateral and ipsilateral duration of postural deviation averaged over the 6 consecutive 5-min postoperative intervals.

Results

Statistical analyses of the postural deviation scores (obtained by subtracting contralateral from ipsilateral duration of postural deviation for each of the 6 consecutive 5-min postoperative intervals) showed that all groups with basal gangliar damage had significant ipsilateral postural deviation as compared to the control (Hpc) group. A 2-way analysis of variance for repeated measures (unweighted means solution) revealed significant differences between groups (p < .05); no differences were significant over time nor were any interaction effects. Duncan’s Multiple Range Test on the group means for postural deviation scores showed that the Hpc group was significantly different (p < .001) from all other groups; Student’s t-test showed that the postural deviation of the Hpc group was not significantly different from zero.

The mean duration of postural deviation differed among groups with basal gangliar damage (Fig. 3). Duncan’s Multiple Range Test showed that the AD and AV groups had a shorter duration of ipsilateral postural deviation than all other groups (p < .001); the M/GP group had a greater duration of ipsilateral postural deviation than the AD or AV groups (p < .001); and the DL/GP and GP groups had a greater duration of ipsilateral postural deviation than all other groups (p < .OOl).

Significant differences (p < .05) in amount of total lesion damage among groups were found using a 1-way analysis of variance. Duncan’s Multiple Range Test revealed that the GP and DL/GP groups had significantly greater damage (p < .O l ) than all other groups. The other groups were not significantly different from each other (Table

Significant differences (p < .05) in amount of damage to the CPu among the groups were found using a 1-way analysis of variance. Duncan’s Multiple Range Test showed that the DL/GP group had significantly greater damage (’p < .05) than all but the GP group (Table 2).

1).


TABLE 1. Total Lesion Damage Dijfererzces in the Ex- perimental Groups (Duncan ’s Multiple Range Test).

AV M/GP DL/GP GP

AD - - p < . o 1 p < . o 1 AV - p < . O l p < . o 1 M/GP p <.01 p< .o1 DL/GP -

TABLE 2. mental Groups (Duncan ’s Multiple Range Test).

Differences in CPu Damage in the Experi-

AV M/GP DL/GP GP

AD AV M/GP DL/GP

- p < . o 1 p < . o s - p < .05 -

p < .05 -

Significant differences (p < .05) in amount of damage to the GP were found using a 1-way analysis of variance. Duncan’s Multiple Range Test showed that the GP group had significantly greater damage (p < .01) than both the M/GP and DL/GP groups (Table 3).

The correlation between total lesion size and behavior when all groups with basal gangliar lesions were combined was significant (Pearson’s product moment test, p < .05, I I = 49). In order to determine the contribution of CPu or GP damage to the overall correlation, we computed separate correlation tests on the groups with CPu damage only (AD and AV) and on the groups with both CPu and GP damage. We found no correlation between lesion size and behavior in the combined AD and AV groups; we did find a significant correlation (JJ < .02) between total lesion size and behavior in the combined MGP, DL/GP, and GP groups and a significant correlation 0, < .02) between CP damage and behavior, but not GP damage and behavior in these 3 groups.

TABLE 3. Differences in GP Damage in the Groups with GP Lesions (Duncan’s Multiple Range Test).

DL/GP GP

M/GP - p < .O1 DL/GP p < .O1


Discussion

The basal ganglia of the 2-day-old rat have a role in modulating postural orientation in that unilateral lesions at this age produced significant postural asym- metry. Therefore, the axons of cells located in the basal ganglia must be capable of transmitting signals to functional motor systems at this time. Because lesions of the Cpu inevitably involve fibers passing to and from the neocortex, damage to them may have contributed to postural deviation. However, to test this possibility by making cortical lesions would be difficult because (a) all regions of the neocortex project to the Cpu (Carpenter, 1976) and (b) neocortical lesions themselves produce transient postural deviation (Click & Greenstein, 1973). The fact that lesions of sirmlar extent in the hippocampus did not produce significant postural deviation shows that the results were a specific effect of interference with a particular structure rather than a nonspecific effect of unilateral brain damage.

Damage to dorsal and to ventral caudate nucleus had virtually equivalent effects, showing that as tested in the present experiment the head of the caudate nucleus is homogeneous with respect to postural orientation. The combined effect of CPu and GP damage was greater than that of CPu damage alone, even in the group (M/GP) in which total lesion size remained the same. Postural deviation was even greater in the groups with larger lesions including both CPu and GP damage; in these groups, amount of CPU damage rather than amount of GP damage was correlated with duration of postural deviation. These results suggest an important role for the GP in relaying signals from the CPu to other motor systems. If CPu signals are “funneled” through the GP, then large lesions of the CPu are required to produce effects equivalent to those of small lesions of the GP.

Several pathways might be involved in the change of postural orientation following lesions, electrical stimulation, or chemical stimulation of the basal ganglia. In the rat, cells of the caudate nucleus project to the globus pallidus and to the substantia nigra (Hattori, Fibinger, & McGeer, 1975; Hadju, Hassler, & Bale, 1973). Cells in the globus pallidus also project to the substantia nigra (Hattori et al., 1975 and to the thalamus (Severin, Young, & Massopust, 1976). In other species, cells of the globus pallidus also project to ventral anterior, ventral lateral, and centromedian thalamic nuclei and to the pedunculopontine and the subthalamic nuclei (Carpenter & Strominger, 1967). Any or all of these pathways might be involved in the effect of the lesions found in the present study. Because lesions or electrical stimulation of the substantia nigra also cause changes in postural orientation (Arbuthnott & Crow, 1971; Schwartz, Gunn, Sharp, & Evarts, 1976), we are tempted to speculate that the projections from the CPu and GP to the substantia nigra are important for the results of the present study.

References

Anden, N.-E., Dahlstrom, A., Fuxe, K., and Larsson, K. (1966). Functional role of the

Arbuthnott, G. N., and Crow, R. J. (1971). Relation of contraversive turning to unilateral release

Carpenter, M. B. (1976). Anatomy of the basal ganglia and related nuclei: A review. A h . Neurol.,

nigm-neostriatal dopamine neurons. Acta Pharrnatol. Toxicol., 24: 263-274.

of dopamine from the nigrostriatal pathway in rats. Exp. NeuroC, 30: 484-491.

14: 748.


Carpenter, M. B., and Strominger, N. L. (1967). Efferent fibers of the subthalamic nucleus in the monkey. Am. J. Anat., 121: 41-72.

Coyle, J. T. Jr. (1974). Development of the central catecholaminergic neurons. In F. 0. Schmitt and F. G. Worden (Eds.), The Neurosciences Third Study Program. Cambridge, Mass.: MIT

Das, G. D. , and Altman, J. (1970). Postnatal neurogenesis in the caudate nucleus and nucleus accumbens septi i n the r a t Brain Res., 21: 122-127.

Glick, S. D., and Greenstein, S. (1973). Possible modulating influences of frontal cortex on nigro-striatal function. Brit. J. Pharmucol., 49: 3 16-321.

Hadju, F., Hassler, R., and Bak, 1. S. (1973). Electron microscopic study of the substantia nigra and the strionigral projection in the rat. Z . Zellforsch., 146: 207-221.

Hattori, T., Fibiger, H. C., and McGeer, P. L. (1975). Demonstration of a pallido-nigr;il projection innervating dopaminergic neurons. J. Cornp. Neurol., 162: 487-504.

Hattori, T., and McGeer, P. L. (1973). Synaptogenesis in the corpus striatum of infant rat. Exp. Neurol., 38: 70-79.

Loizou, L. A. (1972). The postnatal ontogeny of monoaminccontaining neurons in the central nervous system of the albino rat. Bruin Rex, 40: 395-418.

Lotti, J. (1971). Action of various centrally acting agents in mice with unilateral caudate brain lesions. Life Sci., 10: 781-789.

Olson, L., Seiger, A., and Fuxe, K. (1972). Hcterogeneity of striatal and limbic dopamine innervation: Highly fluorescent islands in developing and adult rats. Bruin Rex, 419: 283-288.

Schwartz, W. J., Gunn, R. H., Sharp, F. R., and Evarts, E. V. (1976). Unilateral electrolytic lesions of the substantia nigra cause contralateral circling in rats. Bruin Res., 105: 358-361,

Severin, C. M., Young, P. A., and Massopust, L. C. (1976). Pallidothalamic projections in the rat. J. Cornp. Neurof., 166: 491-501.

PICSS. Pp. 877-884.

Documents

Behavioral effects of unilateral basal gangliar lesions in neonatal rats