Turning behaviour in animals

Amphetamine-induced rotation reveals post 6-OHDA lesion neurochemical reorganization

Early postlesion amphetamine-induced contralateral rotation has been linked to intraneuronal dopamine (DA) accumulation and transmitter release associated with axonal degeneration. Animals in the present study sustained severe unilateral depletion of striatal DA with or without a near-complete loss of ipsilateral mesolimbic DA. Contralateral rotation to 1.0 mg/kg (+)-amphetamine was observed on days 1 and 4 postlesion, and was greatly enhanced in mesolimbic-lesioned animals on day 4. On days 7 and 14, very little contralateral turning was observed and there was an emergence of low-rate ipsilateral rotation. These changes in direction and magnitude of rotational response suggest neurochemical adaptations which continue beyond initial periods of intraneuronal accumulation and degeneration-induced release.

Eye movements induced by microinjection of GABA agonist in the rat substantia nigra pars reticulata

Injection of muscimol (GABA agonist) in the substantia nigra pars reticulata (SNr) of the alert rat induced a continual repetition of fast eye movements to the contralateral side, each of which was followed by a slow returning movement. The fast eye movements were similar to spontaneous saccades. Larger saccades were accompanied by contralateral neck muscle activity. We suggest that the SNr plays an important role in control of eye movements in the rat.

Delayed emergence of striatal dopaminergic hyperactivity after anterolateral ischemic cortical lesions in humans; evidence from turning behavior

To test the hypothesis that striatal dopaminergic hyperactivity in humans may be an aftermath of anterior cortical ischemic insults, we utilized earlier observations that in several species, including humans with hemiparkinson's disease, asymmetric striatal dopaminergic activity results in spontaneous asymmetric turning away from the hemisphere with higher dopaminergic activity. In this study, electronic monitoring showed that, compared to normal controls, outpatients with old frontal and inferior-parietal cortical strokes exhibit a marked tendency to turn away from the side of the lesion. This delayed ipsilateral neglect suggests a delayed emergence of lasting ipsilateral striatal dopaminergic hyperactivity after unilateral anterolateral cortical insult in humans. Old ischemic insults to anterolateral cortical areas could be one etiological mechanism in human brain disorders that are associated with cortical dysfunction and delayed subcortical dopamine hyperactivity.

Circling behavior: ethological analysis and functional considerations

Head-turning and circling movements evoked by substantia nigra (pars compacta) (SNpc) stimulation have been ethologically analyzed in order to attribute a functional meaning to these lateralization processes. It has been shown that these motor acts, separated by a constant interval, may be considered a fixed action pattern. The duration of the single acts depends on the SNpc stimulation parameters: the increase in the stimulus strength produces an increase in the number of turns but does not induce the disappearance of the orientation movement. The body movement is always preceded by the head-movement. Haloperidol administration induces a dose-related increase of the orientation component of the motor pattern. These data together with others in the literature suggest the participation of the SNpc in the mechanism of shift in the focus of attention from one point to another in the contralateral surrounding environment.

Bilateral tectal projection of single nigrostriatal dopamine cells in the rat

Employing fluorescent retrograde double/triple labeling techniques, we found that a substantial population of substantia nigra pars reticulata cells send divergent axon collaterals to both the ipsilateral striatum and bilateral superior colliculi in the rat. These multi-collateralized neurons were localized predominantly in the ventrolateral portion of the substantia nigra pars reticulata at its rostral level. Furthermore, tyrosine hydroxylase immunofluorescence histochemistry combined with fluorescent retrograde tracing techniques showed that the vast majority (more than 85%) of such specifically branched cells are dopaminergic. This novel nigral cell population seems to be in a strategic position to evoke dopamine-mediated motor impairments (i.e. abnormal saccadic eye movements in Parkinsonism) and/or behavioral syndromes (i.e. compulsive turning behavior) through the GABA-containing nigrotectal pathway.

Inhibition and excitation of neck and shoulder muscles during unilateral electrical stimulation of the rat neostriatum

Electrical stimulation of the caudate-putamen (Cd-Pt) in anesthetized adult male rats was used to determine the nature and extent of the control exerted by the Cd-Pt over the following neck and shoulder muscles: the trapezius, biventer cervicis, rectus capitis and scalenus dorsalis. Unilateral Cd-Pt stimulation resulted in a pattern of muscle responses marked by immediate inhibition of ipsilateral spontaneous activity and subsequent excitation of contralateral activity. Lesions of the substantia nigra pars reticulata blocked the excitation in 3 of the 4 muscles, while globus pallidus lesions had equivocal results. However, control ablations of the frontoparietal motor cortex, which blocked excitation in all muscles, and kainic acid lesions of the Cd-Pt, which had no effect on excitation, suggested that the excitation of muscle activity can only be attributed to the stimulation of corticofugal fibers passing through this region (i.e. the Cd-Pt). The inhibition of spontaneous activity does appear to be attributable to stimulation of the Cd-Pt.

The iminodipropionitrile (IDPN) model of persistent spasmodic dyskinesias: regional serotonin metabolism in rat brain

Chronic administration of iminodipropionitrile (IDPN) in rats causes a persistent behavioral syndrome which consists of lateral and vertical twitches, random circling, and hyperactivity. These abnormalities are very similar to those induced by the acute injection of serotonin (5-HT) agonists. The present study reveals significant increases in the levels of 5-HT and 5-hydroxyindoleacetic acid (5-HIAA) in the caudate-putamen and in the nucleus accumbens during treatment with IDPN. In the striatum, these changes lasted up to one month after the last injection of the drug. There were less prominent increases in 5-HT and decreases in 5-HIAA in the brainstem of these animals. These data are consistent with our previous study in which we found significant decreases in the number of 5-HT2 receptors in both the striatum and the accumbens of rats which were suffering from the IDPN-induced syndrome for a period of one month. These results are discussed in terms of their support for a possible role of the serotonin system in both the appearance and the persistence of this dyskinetic syndrome.

Two kinds of nigrostriatal asymmetry: relationship to dopaminergic drug sensitivity and 6-hydroxydopamine lesion effects in Long-Evans rats

Recent work in this laboratory has provided evidence for a two-population model of normal rotational behavior: some rats circle predominantly away from the side containing the striatum with the greater dopamine levels and some rats circle predominantly towards the side containing the striatum with the greater dopamine levels. The two populations also respond differently to 6-hydroxydopamine lesions of the substantia nigra ipsilateral to the preferred direction of circling. The present study replicated these findings in another strain of rats and showed further that the two populations could be distinguished behaviorally by their relative responses to indirectly acting (D-amphetamine, cocaine) and directly acting (apomorphine, pergolide) dopamine agonists. The results suggest that the two populations differ with respect to the balance between pre- and postsynaptic elements within the striatum.

Normalization of extracellular dopamine in striatum following recovery from a partial unilateral 6-OHDA lesion of the substantia nigra: a microdialysis study in freely moving rats

It has been hypothesized that striatal dopamine (DA) terminals undergo compensatory changes in response to partial damage of the mesostriatal DA system, which results in higher concentrations of DA in the extracellular space than would be predicted by DA concentrations in post-mortem tissue. But, this hypothesis has never been tested directly in vivo, and therefore, the present study was designed signed to do so. Microdialysis was used in freely moving rats to estimate the concentration of DA, dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA) and 5-hydroxyindoleacetic acid (5-HIAA) in striatal extracellular fluid; simultaneously from the hemisphere with unilateral 6-hydroxydopamine (6-OHDA) lesion of the substantia nigra and from the intact hemisphere. It was found that following recovery from a 6-OHDA lesion, and during the resting state, the extracellular concentrations of DA were normal on the lesion side, even after that side was depleted of up to 99.0% of the DA measured in post-mortem tissue. Furthermore, the extracellular concentrations of DA were elevated in the intact hemisphere of animals with a greater than 95% DA depletion. In rats with a less than 95% DA depletion amphetamine (1.5 mg/kg) caused a large increase in the extracellular concentration of DA in both the lesion and intact hemispheres (intact greater than lesion), but in rats with a greater than 95% tissue DA depletion amphetamine only enhanced extracellular DA on the intact side; on the lesion side amphetamine produced a progressive decrease in extracellular DA to nondetectable levels. Animals rotated towards the lesion side. Unlike DA, the extracellular concentrations of DOPAC and HVA were greatly reduced on the lesion side, and the extent of the depletion was highly correlated with lesion size. It is concluded that following partial unilateral damage to mesostriatal DA projections there are massive changes in the remaining DA terminals that are sufficient to normalize the extracellular (and presumably synaptic) concentrations of DA. The normalization of extracellular DA concentrations seen after extensive (but incomplete) damage to the mesostriatal system must play a major role in the sparing and recovery of behavioral function that is so characteristics of this system. After extensive damage the capacity of the remaining DA neurons to respond to increased demand is limited, however, and this may explain why behavioral deficits can be reinstated by stimuli that challenge the system.

Excitability properties of medial forebrain bundle axons of A9 and A10 dopamine cells

A9 and A10 units identified as dopaminergic were recorded with extracellular micropipettes. The units were antidromically activated by electrical stimulation at the level of the preoptic area. The absolute refractory periods ranged from 1.2 to 2.5 ms. During the 2-8 ms of the relative refractory period, conduction was slower than normal by up to 1.5 ms. The time constant, C, of the strength-duration curve ranged from 0.4 to 0.6 ms. The current (I)-distance (D) relationship, tested by moving the stimulating electrode past the axon, was approximately parabolic (I = K D exp 2), with the constant of the equation, K, ranging from 900 to 2000 microA/mm exp 2, for 0.5 ms pulses. This relationship allows calculation of the radius of the field of dopamine axon excitation at any current. These high K values show that axons of dopamine cells cannot be activated unless high current densities are delivered, even when electrodes are placed near the axons. These data allow determination of the extent to which dopamine axons can be the directly activated substrates for behaviors, such as self-stimulation and circling, which are evoked by electrical stimulation of the medial forebrain bundle or internal capsule.

Alterations in local cerebral glucose utilization during electrical stimulation of the striatum and globus pallidus in rats

Alterations in local cerebral glucose utilization (LCGU) in conscious rats during electrical stimulation of the striatum and the globus pallidus were investigated using the [14C]deoxyglucose method. Stimulation of the globus pallidus produced a marked contraversive circling behavior, while stimulation of the striatum led only to contraversive head turning. Unilateral stimulation of the striatum increased LCGU bilaterally in the globus pallidus and substantia nigra pars compacta, but only ipsilaterally in the entopeduncular nucleus, substantia nigra pars reticulata and subthalamic nucleus. Similar stimulation of the globus pallidus increased LGCU in the globus pallidus, substantia nigra pars reticulata and compacta, entopeduncular nucleus, subthalamic nucleus, lateral habenular nucleus, parafascicular nucleus of the thalamus, deep layers of the superior colliculus and pedunculopontine nucleus, exclusively on the ipsilateral side. These results indicate that the electrical stimulation induces LCGU changes in the respective structures having both monosynaptic and transsynaptic neuronal inputs. Some changes may also be mediated by antidromic activation. They also suggest that activation of a synaptic process whether excitatory or inhibitory results in increases in LCGU. The bilateral modulatory effects of striatal stimulation may cancel out the circling behavior seen during pallidal stimulation, and cause only head turning.

Contraversive circling elicited from the internal capsule and substantia nigra: evidence for a continuous axon bundle mediating circling

Electrical stimulation of many brain sites (e.g., anteromedial cortex, internal capsule, substantia nigra, superior colliculus, rostro-medial tegmentum, and medial pons) evokes circling. The collision method of Shizgal et al. (J. Comp. Physiol. Psychol., 94 (1980) 227-237) was used to determine whether these sites are functionally connected for the production of circling in rats. If connectivity was evidenced, then refractory period and conduction velocity distributions were determined for axons passing through the connected stimulation sites. Collision of up to 90% was found between electrodes placed in internal capsule and substantia nigra, suggesting that these sites are connected by continuous axons that mediate circling. The refractory periods of these axons ranged from 0.5 to 4.5 ms, and the conduction velocities of these axons ranged from 0.9 to 4.4 ms. These velocities are similar to those of striatonigral axons. No collision was found between anteromedial cortex and any other sites tested, nor between pontine sites and internal capsule or substantia nigra.

Amphetamine-induced increase in motor activity is correlated with higher firing rates of non-dopamine neurons in substantia nigra and ventral tegmental area

The responses of non-dopamine neurons in substantia nigra and ventral tegmental area to systemic amphetamine were investigated in the behaving rat chronically implanted with multiple fine-wire electrodes. The neurons were identified with electrophysiological criteria requiring that the signals be of biphasic shape, short duration (less than 2.0 ms), and show high and regular rates of discharge (greater than 20 spikes/s). In recording sessions lasting 240 min, single and multiple unit activity was recorded from seven electrodes, and motor activity was measured automatically with the open-ended wire technique. The movement counts provided an index of gross motor activity, not of the specific movements occurring during DA behaviors. D-Amphetamine, 5.0 mg/kg, given by the intraperitoneal route at 90 min into the session, induced an increase in motor activity and in the firing rate of some non-dopamine neurons. The behavioral and neural responses were correlated for magnitude, latencies and duration. But not all non-dopamine neurons in ventral tegmental area, and substantia nigra showed responses to amphetamine. When unit responses were obtained, they were obtained in subjects which showed large motor responses. In substantia nigra, responsive and non-responsive units were interdigitated and found mainly in the pars reticulata subdivision. In the ventral tegmental area, responsive and non-responsive neurons were interdigitated throughout this structure. The effects of amphetamine were dose-responsive, doses of 1.0, 2.0 and 3.0 mg/kg inducing smaller behavioral and unit responses than 5.0 mg/kg. D-Amphetamine, 5.0 mg/kg, was more effective than L-amphetamine, given at the same dose, in inducing these changes. In rats pretreated with systemic haloperidol, 1.5 mg/kg, the behavioral and neural responses to D-amphetamine, 5.0 mg/kg, were greatly attenuated. In rats pretreated with a subanesthetic dose of urethan, 600 mg/kg, to prevent changes in gross motor activity, the response to D-amphetamine in ventral tegmental area was attenuated, but it was of normal magnitude in substantia nigra. In rats with bilateral electrolytic lesions of nucleus accumbens, D-amphetamine induced a smaller motor response than in controls, but the neural responses in ventral tegmental area and substantia nigra were the same as in controls. These findings support the notion that non-dopamine neurons in ventral tegmental area and substantia nigra, pars reticulata, play a role in the motor function of the A9 and A10 dopamine neurons, and in the behavioral effects of amphetamine.(ABSTRACT TRUNCATED AT 400 WORDS)

Heterogeneous rotational responsiveness in 6-hydroxydopamine-denervated rats: pharmacological and neurochemical characterization

Qualitative differences in pharmacological responsiveness to various types of dopamine agonists have been reported in rats that have undergone unilateral 6-hydroxydopamine (6-OHDA)-induced denervation of the nigro-striatal pathway. The present experiments further characterize these differences, pharmacologically and neurochemically. Rats were classified as having high rotational sensitivity (0.03 mg/kg SC apomorphine sufficient to induce more than 100 rotations/20 min) or low sensitivity (0.3 mg/kg SC apomorphine required to meet this criterion). High sensitivity rats showed marked contralateral rotational behavior (approximately 150 rotations/20 min) in response to apomorphine (ED50 = 0.08 mg/kg IP), CGS 15855A (ED50 = 0.07 mg/kg), CGS 15873A (ED50 = 0.43 mg/kg), (+)-3-PPP (ED50 = 2.3 mg/kg), (-)-3-PPP (ED50 = 0.87 mg/kg) and quinpirole (peak effective dose, 0.03 mg/kg). In low sensitivity rats, 3- to 10-fold higher doses of apomorphine induced a maximal rate of rotational behavior, but only partial effects were produced by quinpirole, CGS 15855A, CGS 15873A, (+)-3-PPP, and (-)-3-PPP (40-80 rotations/20 min). Because apomorphine is a nonselective D1 and D2 agonist, it is proposed that activation of either D1 or D2 receptors suffices to induce high rates of rotation in high sensitivity rats, whereas in low sensitivity rats, D1 or D2 agonism alone induces submaximal rotation rates. The ipsilateral rotational behavior induced by d-amphetamine was more pronounced and occurred at lower doses in the high-sensitivity rats. Striatal dopamine depletion on the lesioned side did not differ between the groups, but low sensitivity rats showed two-fold higher DOPAC/DA ratios on the lesioned side than did high-sensitivity rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Application of the unilateral 6-hydroxydopamine rat model of rotational behavior to the study of conditioned drug effects

In rats with unilateral 6-hydroxydopamine lesions of the substantia nigra apomorphine reliably induces a response of contralateral rotation. The present study shows that this response can readily be conditioned to a test environment which the rats are briefly exposed to during the onset of the apomorphine-induced rotation. This conditioned response can be repeatedly conditioned, extinguished, and differentially conditioned, thereby providing a useful behavioral model for the study of the conditioning of drug-induced movements.

A two-population model of rat rotational behavior: effects of unilateral nigrostriatal 6-hydroxydopamine on striatal neurochemistry and amphetamine-induced rotation

Rats received intrastriatal or intranigral injections of 6-hydroxydopamine (6-OHDA) on the same side towards which they made most of their turns during a previous test of amphetamine-induced rotational behavior. One week later they were retested for amphetamine-induced rotational behavior and it was found that only approximately half of them increased their rotational behavior towards the lesioned side more than non-lesioned controls. In fact, compared to their pre-operative behavior numerous rats decreased or actually reversed their net turning towards the lesioned side. While the post-lesion rotational behavior of the two groups of rats was clearly different, pre-operative turning was not. Furthermore, the neurochemical effects of the intracerebral 6-OHDA injections were not different in the two groups of rats, either with respect to the magnitude of the resulting dopamine (DA) depletion, or with respect to the compensatory increase in the turnover of DA by surviving DA neurons on the lesioned side. The data are discussed in terms of their lack of support for current notions about the role of nigrostriatal DA in turning, and in terms of their support for a two-population model we have previously proposed. An additional, unrelated, finding from the present work was that bilateral striatal serotonin (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) levels decreased bilaterally one week following unilateral intrastriatal administration of 6-OHDA.

Synergistic interaction between dopamine D-1 and D-2 receptor agonists: circling behaviour of rats with hemitransection

Circling behaviour induced by dopamine (DA) agonists with different D-1/D-2 receptor selectivity was studied in rats with hemitransection at a level caudal to the striatum. The mixed D-1/D-2 agonist apomorphine induced ipsilateral circling behaviour after administration of doses similar to those that induced stereotyped behaviour in unlesioned rats. The effect of apomorphine was not influenced by co-treatment with SK & F 38393 or quinpirole, indicating that apomorphine induces a comparable D-1 and D-2 receptor stimulation in vivo also. Three selective D-1 agonists, SK & F 38393, SK & F 75670 and Lu 24-040 had no effects alone, while the preferential D-2 agonists quinpirole, pergolide and (-)-N-propylnorapomorphine induced ipsilateral circling of weaker intensity than did apomorphine. After co-treatment with SK & F 38393 the effects of these compounds were markedly increased. Combination of SK & F 38393, SK & F 75670 or Lu 24-040 with quinpirole induced circling with intensities similar to those seen after apomorphine. Pretreatment with the D-1 antagonist SCH 23390 or the D-2 antagonist YM 09151-2 completely antagonized the ipsilateral circling induced by either apomorphine or quinpirole + SK & F 38393. A range of partial (autoreceptor) D-2 agonists, i.e. (-)-3-PPP, (+)-3-phenethyl-PP, terguride, EMD 23448 and B-HT 920 were all ineffective as was the alpha 2-adrenoceptor agonist clonidine. However, B-HT 920 induced strong ipsilateral circling after combination with SK & F 38393, whereas (-)-3-PPP was ineffective.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of unilateral intracerebroventricular microinjections of cholecystokinin (CCK) on circling behavior of rats

Unilateral intracerebroventricular (ICV) injections of a high dose of CCK7 have been reported to elicit barrel rotations accompanied by contralateral postural asymmetry; there was no spontaneous locomotor activity other than barrel rolling. The aim of the present study was to investigate the effects of lower doses of CCK-peptides on circling behavior; it was reasoned that if ambulation was present following unilateral ICV administrations of lower doses of CCK, then the contralateral postural asymmetry previously reported might be expressed as contraversive circling. In the present study, spontaneous locomotor activity was observed following ICV injections of lower doses of CCK sulfated octapeptide (CCK8), desulfated CCK octapeptide (dCCK8) and CCK tetrapeptide (CCK4). As postulated, contraversive circling was induced by CCK8 (0.5-5000 ng, ICV); the two other CCK fragments, dCCK8 and CCK4, were inactive in this respect. In addition, the contraversive circling bias induced by CCK8 (5.0 ng, ICV) was attenuated by co-injections of the CCK antagonist proglumide (10 and 100 ng) and by intraperitoneal injections of the dopamine (DA) antagonist haloperidol (0.05 and 0.1 mg/kg, 45 min prior to ICV CCK8). These data suggest that the effect is medited by CCK receptors and through a facilitatory influence on central DA function.

Circling behavior in honey bees

Unilateral microinjections of gamma-aminobutyric acid (GABA), acetylcholine (ACh) and related substances into central parts of the brain of the honey bee elicit a quantifiable circling behavior. GABA (40 nl, 10(-2) M, muscimol (40 nl, 10(-4) M) and flaxedil (10(-3) M, 40 nl) induce contralateral circling whilst ACh (40 nl, 10(-2) M), nicotine (40 nl, 10(-4) M) and picrotoxin (40 nl, 10(-3) M) induce ipsilateral circling if injected in the proximity of the alpha-lobe (50-100 microns) of the of the mushroom body. Mechanical lesions of the pedunculus induce ipsilateral circling. This can be reversed by ipsilateral injections of GABA and flaxedil. Intracellular recordings demonstrate a hyperpolarizing effect of GABA and a depolarising effect of ACh on individual neurons in this region. These results suggest that circling behavior in the bee is controlled by the balance of GABA in the alpha-lobes and mediated by acetylcholinergic neurons.

Hypothalamic substrates for brain stimulation-induced grooming, digging and circling in the rat

Despite a great number of studies concerned with the induction of specific behavioural responses from the rat hypothalamus by electrical brain stimulation, hypothalamic response areas and underlying neural substrates have never been determined accurately. In this study the boundaries of the hypothalamic response areas for grooming, digging and circling were delimited using moveable electrodes, an enriched environment containing a variety of goal objects, and an appropriate statistical technique. A total of 641 hypothalamic sites in 71 male CPB/WU Wistar rats were electrically stimulated. Results are plotted on a detailed stereotaxic brain atlas of the rat hypothalamus. Positive sites for any behavioural response cluster into restricted hypothalamic areas. Discriminant analysis of both positive and negative electrode localizations yields areas with high, intermediate or low probabilities of inducing the behavioural response concerned. Each response has its own response area where probabilities are high, although there may be overlap. Even within response areas a distinction can be made between areas in which the response can be induced at relatively high or low threshold current intensities. Lowest threshold sites within electrode tracks are often clustered. In search of neuroanatomical correlates, grooming is related to the distribution of ACTH-immunoreactive neural elements, digging is related to the distribution of efferent fibres from the bed nucleus of the stria terminalis, and circling is related to the distribution of dopaminergic fibres of the nigrostriatal pathway. The results clearly point to the stimulation site being the most important determinant of the evoked behavioural response. Evidently behavioural specificity does exist within the hypothalamus.

Regional differences in the cat caudate nucleus as to the effectiveness in inducing contraversive head-turning by electrical stimulation

An attempt was made to re-examine regional differences in the cat caudate nucleus as to the effectiveness in inducing contraversive head-turning by electrical stimulation and to analyze the time course of head-turning quantitatively. In 5 of the total 9 cats, the right sensorimotor cortex and its surrounding areas had been ablated chronically. While the awake, unrestrained cat maintained a stable standing posture facing forward, stimulation was applied systematically to various points in and around the caudate nucleus with a movable stimulating electrode. Trains of stimulating current pulses of less than 300 microA were given, mostly at a rate of 100 Hz for 5 s. In most experiments in which stimulation was given to the side of the intact cerebral cortex, stimulation of caudal portions of the head of the caudate nucleus was effective in inducing contraversive head-turning, but that of its rostral portions was ineffective. In experiments on the side of chronic cortical ablation, similar results were obtained. These results suggested that head-turning induced by stimulation of the caudate nucleus was brought about not by the activation of the corticofugal fibers from these cortical areas by a current spreading to the internal capsule, but by the activation of caudate neurons. Hence, it was demonstrated that there were regional differences in the cat caudate nucleus as to the effectiveness in inducing head-turning. The mean of the shortest latencies of the onset of head-turning for individual stimulation points was 396 ms (S.D., 210 ms) for the side of the intact cerebral cortex, and 454 ms (S.D., 289 ms) for the side of the cortical ablation. Statistically, there was no significant difference between them. Therefore, it was further revealed that the elimination of the sensorimotor cortex did not affect the caudate-induced head-turning in terms of the latency of its onset.

Asymmetric rotational (circling) behavior, a dopamine-related asymmetry: preliminary findings in unmedicated and never-medicated schizophrenic patients

Circling behavior is one of the best understood behaviors in animals. It is, for the most part, dopaminergically mediated and related to asymmetry in dopaminergic activity between the left and right basal ganglia or left and right frontal cortex. As a rule, animals rotate toward the hemisphere with lower striatal dopaminergic activity. A direct technique to find human analogs of circling behavior was not available. We have developed an automated rotometer with which we can apply the circling rodent model to humans. Left-prone circling behavior (neglect of right-sided turning) was found in 10 unmedicated schizophrenic patients, whereas 85 normal controls demonstrated almost equal right and left turning. These preliminary results may suggest the presence of a dopaminergic asymmetry in some unmedicated schizophrenic patients; that is, right anterior subcortical or cortical structures of the brain may manifest a relative dopaminergic overactivity compared to left anterior structures in at least some unmedicated patients with schizophrenia.

Behavioural evidence for a selective GABA-A antagonistic activity of SR 95103 and SR 42641 after intrastriatal injection in mice

Two pyridazinyl GABA derivatives, SR 95103 and SR 42641 have recently been described as selective GABAA receptor antagonists. We have now investigated the behavioural effects of SR 95103 and SR 42641 after intrastriatal injection in mice. When injected into the right striatum, SR 95103 (0.01-0.5 microgram), SR 42641 (0.0001-0.01 microgram) and bicuculline methiodide (0.005-0.05 microgram) induced contralateral rotations which were antagonized by intraperitoneal injection of muscimol. In contrast, the intrastriatal injection of the GABAA receptor agonist muscimol induced ipsilateral rotations. Muscimol-induced turning was antagonized by SR 95103 (10-30 mg/kg), SR 42641 (1-10 mg/kg) and (+)-bicuculline (0.125-0.5 mg/kg) injected intraperitoneally, but not by strychnine. Intrastriatal glycine also induced ipsilateral rotations which were antagonized by strychnine (0.01-0.3 mg/kg i.p.) but not by (+)-bicuculline, SR 95103 or SR 42641. These results suggest that SR 95103 and SR 42641 induce turning through a selective blockade of GABAA receptors within the striatum.

Rotational movement (circling) in normal humans: sex difference and relationship to hand, foot and eye preference

An endogenous asymmetry in striatal dopaminergic function has been identified in rats, and related to spontaneous and drug-induced circling (rotation, turning). We have developed an electronic device for measuring in humans the same kinds of rotational movements observed in rats. Our data indicate that, without being aware of the type of information being obtained, normal men and women rotate preferentially to the left or to the right during a routine day. Women had higher average rates of rotation than men. Males that were consistently right-sided (left-hemisphere dominant) for hand, foot and eye dominance rotated more to the right than to the left, whereas left-hemisphere dominant females rotated more to the left than to the right. Subjects tested on two occasions, 6 weeks apart, exhibited consistent (significantly correlated) rotational preferences--this was much more evident in left-hemisphere dominant than in mixed dominance individuals. In view of similar animal data, the device used in this study may become a useful and objective means for obtaining quantitative information regarding the status of basal ganglia function in humans.

Dopamine and serotonin metabolism in brain sites ipsi- and contralateral to direction of conditioned turning in rats

Concentrations of dopamine, serotonin, and some of their metabolites were analyzed by means of HPLC in brain samples obtained from rats operantly conditioned to turn in circles to obtain water reinforcement. In experiment 1 using Wistar rats, no differences in the levels of transmitters or metabolites were detected between brain samples (frontal cortex, ventral striatum, dorsal striatum, septum, amygdala, substantia nigra) from the hemispheres located ipsi- and contralateral to the direction of turning. A higher dopamine metabolism (indicated by higher metabolite/transmitter ratios) in ventral striatum, dorsal striatum, and amygdala was found after 15 min than after 5 min of turning in both hemispheres. A higher dopamine metabolism was found in water-deprived rats compared to nondeprived rats independently of whether or not deprived rats were trained to turn for water reinforcement. In two additional experiments, no differences in dopamine metabolism were found between the ipsi- and contralateral striatum of Wistar rats after 25 min and Sprague-Dawley rats after 10 min of operantly conditioned turning. The present results confirm that dopamine metabolism can change with different behavioral or physiological states; they do not support the hypothesis that conditioned turning is correlated with asymmetrical changes in the metabolism of dopamine or serotonin in the brain.

Facilitation of amphetamine-induced rotation by muscarinic antagonists is correlated with M2 receptor affinity

This study examined the relationship between the affinity of cholinergic drugs for muscarinic receptor subtypes and their potency in potentiating or inhibiting amphetamine-induced rotation. The ascending nigrostriatal dopaminergic pathway was unilaterally lesioned in male Wistar rats using 6-hydroxydopamine. In these rats, ipsiversive rotation induced by amphetamine sulphate (1 mg/kg, s.c.) was dose-dependently inhibited by the cholinergic agonists oxotremorine, RS86 and pilocarpine and by the acetylcholinesterase inhibitor physostigmine. In contrast the cholinergic antagonists scopolamine, secoverine and dicyclomine facilitated amphetamine-induced rotation. Agonist and antagonist potencies were then compared with M1 and M2 binding site affinities estimated by displacing [3H]pirenzepine from forebrain and [3H]QNB from brainstem homogenates. The data suggest a relationship between antagonist potency and M2 binding site affinity.

Spontaneous asymmetric circling behavior in hemi-parkinsonism; a human equivalent of the lesioned-circling rodent behavior

When induced experimentally in rodents, hemispheric asymmetry in basal ganglia dopamine results in spontaneous asymmetric circling toward the hemisphere with the lower level of dopamine. A similar asymmetry has long been thought to exist in the brains of hemi-Parkinsonian patients. Using an electronic turn counter, we demonstrated that, like unilaterally lesioned rats, and without being aware of it, five ambulating outpatients with hemi-Parkinson's disease exhibit spontaneous rotation toward the hemisphere containing less striatal dopaminergic activity.

Topography of dopamine behaviours mediated by D1 and D2 receptors revealed by intrastriatal injection of SKF 38393, lisuride and apomorphine in rats with a unilateral 6-hydroxydopamine-induced lesion

Stereotaxic injections of a dopamine D1 receptor agonist (SKF 38393) into different regions of the supersensitive striatum of rats with a unilateral 6-hydroxydopamine-induced lesion duplicated the systemic effects of the drug in a topographical manner. Although there was considerable overlap, it was possible to recognize discrete active zones or "hot-spots" giving rise to prominent sniffing, head movements and contralaterally directed circling, posture and grooming, both in the coronal plane and along the rostro-caudal axis. Two behaviours peculiar to D1 stimulation included contralateral forepaw myoclonus and forepaw nibbling, which paradoxically was directed mainly ipsilaterally. Each of the behavioural elements occurred independently of the others and after an inexplicably long latency. They were inhibited by the D1 antagonist SCH 23390, but not by the D2 blocking drug metoclopramide. Comparable circling responses were evoked by a D2 agonist (lisuride) injected into the neostriatum after a short delay, and instantaneously by apomorphine (D1/D2 agonist). Both drug behaviours originated diffusely from all parts of the denervated striatum with no obvious "hot-spots", except for circling which exhibited a bimodal distribution rostro-caudally. The actions of lisuride were blocked by systemic metoclopramide, but not by SCH 23390, while the actions of apomorphine were inhibited by both antagonists. Topographies of D2 receptor-mediated events were quite different from those encountered for D1 receptor stimulation by SKF 38393, though neither corresponded to the autoradiographic distribution of D1 and D2 binding sites in the intact striatum. These results reiterate the importance of D1 receptors in motor control and provide a basis for future investigations of the output pathways subserving D1-mediated behaviours.

Induction of turning by direct intrastriatal injection of dopaminomimetic drugs in mice: pharmacological analysis of a simple screening model

A new simple model designed for the screening of dopaminomimetic drugs in mice is presented. When injected directly into the right striatum of conscious mice, the dopamine (DA) receptor agonists apomorphine, SKF 38393 and bromocryptine, the indirect DAmimetic drugs (+)-amphetamine and nomifensine, the atypical DAergic antidepressant drug minaprine, induced contralateral rotations. Rotations induced by DA mimetics were antagonized by i.p. injected haloperidol. A pretreatment with the D1 antagonist SCH 23390 (s.c.) antagonized the turning induced by apomorphine or by the D1 agonist SKF 38393, and, to a lesser extent, that induced by the D2 agonist bromocryptine. In contrast, the D2 antagonist (-)-sulpiride (i.p.) blocked the effects of the 3 agonists to the same extent. A pretreatment with alpha-methylparatyrosine (i.p.) antagonized rotations induced by bromocryptine, (+)-amphetamine and minaprine, but not those induced by nomifensine or apomorphine. The results suggest that this model could represent a useful screening tool for the search of new DAmimetic drugs, and for the assessment of DA receptor blockade.