Turning behaviour in animals

Turning behavior in rats with unilateral lesions of the subthalamic nucleus: synergism between D1 and D2 receptors

Rats with unilateral kainic acid lesion of the subthalamic nucleus showed a dose dependent rotational response to the lesioned side (ipsilateral) after systemic administration of the non-selective dopaminergic agonist apomorphine. Both D2 and D1 selective antagonists ((-)sulpiride and SCH23390) inhibited the response to apomorphine in these rats. Selective D2 and D1 agonists (quinpirole and SKF38393) were unable to induce turning behavior. However, an ipsilateral circling response was obtained after the simultaneous application of both agonists. The interaction mechanism between dopaminergic receptor subtypes seems to be similar to that of other normosensitive models of turning previously studied (Barone et al., 1986; Robertson and Robertson, 1986; Arnt and Perregard, 1987; Asim et al., 1990; Pazo et al., 1993). It is proposed that the ipsilateral turning response to dopaminergic agonists in rats with subthalamic nucleus lesion results from an impaired behavioral expression of the action of dopaminergic agonists on one side, leading the rats to turn away from the intact hemisphere.

Impairments and compensatory adjustments in spontaneous movement after unilateral dopamine depletion in rats

Rats with unilateral dopamine (DA) depletions (hemi-Parkinson rats) display directional biases in their locomotion in spontaneous and drug induced tests. These biases have been explained as being due either to changed responsiveness to sensory stimulation, changes in motor ability, or to central changes, but as yet their basis is not fully understood. The purpose of the present experiment is to examine the posture of immobility and the posture and strategies of locomotion in rats with unilateral DA depletions. The rats are found to display impairments in their bad limbs (contralateral-to-lesion limbs) in adjusting posture and moving. They compensate by supporting themselves mainly on their good hindlimb, using the bad hindlimb and tail for balance and by disproportionately relying upon their good limbs to turn and to walk. Thus, their center of gravity is shifted to the good side and movement is preferentially directed toward the good side, in part to maintain equilibrium and in part to remove weight from the bad limbs so that they can enter the swing phase of the stepping cycle. It is proposed that the bad limbs may be unable to apply force to adjust posture and produce movement. These results provide a basis for predicting the movements that the animals will use in various situations and they expand the test repertoire this hemi-Parkinson model provides for studying recovery processes after loss of dopamine.

Intrastriatal and intrasubthalamic stimulation of metabotropic glutamate receptors: a behavioral and Fos immunohistochemical study

Prior work has shown that intrastriatal injection of the metabotropic glutamate receptor agonist 1S,3R-ACPD results in pronounced contralateral rotation, and the basis for this effect is thought to be increased activity of dopaminergic nigrostriatal neurons. We tested this hypothesis by determining the expression of Fos-like immunoreactivity after intrastriatal injection of 1S,3R-ACPD. Intense Fos-like immunoreactivity was noted in the globus pallidus, entopeduncular nucleus, subthalamic nucleus and substantia nigra pars reticulata. Ablation of the subthalamic nucleus 10 days prior to intrastriatal injection of 1S,3R-ACPD abolished rotational behaviour but not Fos-like immunoreactivity in the globus pallidus, entopeduncular nucleus and substantia nigra. Intrasubthalamic injection of 1S,3R-ACPD produced marked contralateral rotation and a pattern of Fos-like immunoreactivity similar to that seen after intrastriatal 1S,3R-ACPD injection. These results suggest that stimulation of striatal metabotropic glutamate receptors inhibits striatal projection neuron activity, while stimulation of subthalamic metabotropic glutamate receptors increases subthalamic nucleus activity. Increased subthalamic nucleus activity is necessary and sufficient for the expression of rotational behavior. These results also suggest that metabotropic glutamate receptor antagonists may be useful in the treatment of Parkinson's disease.

Circulating adrenal hormones are not necessary for the development of sensitization to the psychomotor activating effects of amphetamine

We reported previously that when amphetamine is given in NOVEL test cages both its acute psychomotor activating effects (rotational behaviour and locomotor activity) and the degree of sensitization are greater than when amphetamine is given in HOME cages that are physically identical to the NOVEL test cages. Since exposure to the NOVEL environment increases plasma corticosterone levels (Experiment 1) it is possible that the enhancement in the effects of amphetamine in the NOVEL condition is mediated by corticosterone. If this hypothesis is correct adrenalectomy (ADX) should abolish the difference between the HOME and NOVEL groups. This was tested in three independent experiments, in which the response (rotational behavior in Experiments 2 and 3; locomotor activity and rearing behavior in Experiment 4) to repeated injections of amphetamine was assessed in rats that underwent adrenalectomy (ADX) or a sham operation (SHAM). ADX animals received either no corticosterone replacement or one of two corticosterone replacement treatments. Adrenalectomy, with or without corticosterone replacement treatment, had no significant effect on the development of amphetamine sensitization, either in the HOME or the NOVEL environment. By contrast, the effects of adrenalectomy on the acute response to amphetamine varied depending on the behavioral measure and possibly on the dose of amphetamine (2.0 mg/kg, 3.0 mg/kg and 1.5 mg/kg IP, in Experiments 2, 3 and 4, respectively). We conclude that: (i) a stress-induced secretion of adrenal hormones is not responsible for the enhancement in sensitization to amphetamine seen in animals tested in a NOVEL environment; (ii) circulating adrenal hormones are not necessary for development of sensitization to the psychomotor activating effects of amphetamine.

Dissimilarities between cholinergic and dopaminergic turning elicited by nucleus accumbens stimulation in freely moving rats

Contralateral turning was produced by unilateral injection of carbachol (0.5, 2.5, 5 micrograms) into the nucleus accumbens, but not into the dorsal or ventral striatum. This behaviour was inhibited by muscarinic M1 acetylcholine receptor blockade in the nucleus accumbens, and less effectively by blockade of muscarinic M2 and nicotinic acetylcholine receptors. Unilateral injection of a mixture of the dopamine D1 receptor agonist 1-phenyl-2,3,4,5-tetrahydro-1H-3-benzazepine-7,8-diol (SKF 38393, 5 micrograms) and the dopamine D2 receptor agonist quinpirole (10 micrograms) also produced contralateral turning. The stepping pattern, however, completely differed from that induced by carbachol. The number of carbachol-induced turnings was reduced by dopamine D1 or D2 receptor blockade (8-chloro-2,3,4,5-tetrahydro-3-methyl-5-phenyl-1H-3-benzazepine-7-ol (SCH 23390) and l-sulpiride, respectively) in the nucleus accumbens. However, the reduction was due to a change in the turning pattern. Blockade of muscarinic acetylcholine receptors in the nucleus accumbens did not change the contralateral turning induced by unilateral injection of dopamine receptor agonists into the nucleus accumbens. The results demonstrate that there is no functional interaction between the cholinergic and dopaminergic substrates involved, although blockade of the dopamine receptors elicited behavioural deficits that competed with the turning elicited by carbachol. The contralateral turning elicited by carbachol injection into the nucleus accumbens requires an intact dopamine activity at the level of dopamine D1 and D2 receptors in the ipsilateral, but not contralateral, ventrolateral striatum.

Modifications of head turning and circling movement following sulpiride microinjections into nucleus accumbens in the rat

The aim of this study was to determine whether a relationship exists between nucleus accumbens D2 receptors, circling behavior, and its first stage, the head turning. Rats were unilaterally lesioned in the substantia nigra with 6-hydroxydopamine and afterward treated with d-amphetamine IP following bilateral intraaccumbens microinjections (1, 5, 10 micrograms/0.5 microliters) of sulpiride, a D2 receptor antagonist. Computer-assisted video analysis allowed the study of some parameters (number of turns, type of turn, head turning duration, degree and speed) characterizing rotatory activity. Sulpiride microinfusion resulted in a dose-dependent decrease of the number of turns and head rotation speed and in a dose-dependent increase of head-turning duration. Two turn types were observed in relation to the animal's position: a large head-to-tail position with a short-diameter turn type following sulpiride microinjection, and a close head-to-tail position in relation to a wide diameter turn type in the control condition (saline). The results show a relationship between head turning parameters, circling behavior, and D2 receptors in nucleus accumbens, which may be also involved in the regulation of some mechanisms related to sensory-motor integration in the rat.

Rotational swimming tendencies in the dolphin (Tursiops truncatus)

Anecdotal evidence suggests that dolphins placed in a pool exhibit stereotypic swimming in circles. The present study confirmed these observations in a sample of thirteen dolphins. The majority of dolphins (84.6%) showed highly consistent directional swimming in counterclockwise circles. The latter directionality held throughout the circadian cycle and resisted environmental manipulations. Only social interaction was capable of altering the directionality of circumnavigation. The consistency of unidirectional swimming is considered paradoxical in view of the existing evidence regarding the alternating of hemispheric activity in sleeping dolphins.

Motor fluctuations in levodopa treated parkinsonian rats: relation to lesion extent and treatment duration

The pathogenesis of the motor fluctuations that complicate levodopa treatment of most parkinsonian patients remains uncertain. To evaluate the contribution of the degree of dopamine neuron loss and the duration of levodopa exposure, rats whose nigrostriatal system had been previously lesioned unilaterally by 6-hydroxydopamine received twice daily levodopa (25 mg/kg) injections for three weeks. The magnitude of the rotational response to levodopa more than doubled during the first week of treatment (P < 0.01), but remained essentially constant thereafter. Rats with over 95 percent loss of dopaminergic neurons evidenced a progressive shortening in the duration of levodopa's motor effects (P < 0.01) as well as a failure of nearly 8 percent of levodopa injections to elicit any response after the first week of treatment. In contrast, response changes resembling those associated with end of dose deterioration and on-off fluctuations in parkinsonian patients did not occur in the less severely lesioned rats. These results suggest that the extent of a dopamine neuron loss must exceed a relatively high threshold before intermittent levodopa treatment produces changes favoring the rapid appearance of motor fluctuations of the wearing-off and on-off types.

Intranigral but not intrastriatal microinjection of the NMDA antagonist MK-801 induces contralateral circling in the 6-OHDA rat model

When systemically administered to unilaterally 6-OHDA lesioned rats, the non-competitive antagonist of N-methyl-D-aspartate (NMDA) receptors MK-801 ((+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine) produces a marked rotation response toward the lesioned side. In addition, the same type of injection in non-denervated rats increases locomotor activity without direction predominance. These findings suggest that MK-801 interacts with the dopaminergic pathway to induce motor activity. However, intracerebral injection of MK-801 (5 micrograms/0.5 microliter) in the substantia nigra pars reticulata (SNr), either on the lesioned side or the intact side, induces a significant circling response, contraversive to the injection side. A similar injection of MK-801 (5 micrograms/1.0 microliter) in the striatum causes no rotation response. These results show that the non-competitive NMDA antagonist can induce motor activity in the presence or in the absence of the dopaminergic pathway and that in the latter case its action is exerted predominantly at the level of the substantia nigra, perhaps through suppression of the excitatory subthalamic drive.

Accumbens microinjection of LY 171555 and sulpiride: effects on circling behaviour, in the rat

In rats with unilateral 6-hydroxydopamine lesions of the substantia nigra (pars compacta) and amphetamine i.p. some parameters of the rotational activity, following intra-accumbens microinjection of D2 agonist (LY 171555) and antagonist (sulpiride), have been analyzed. An increase in the number of turns was observed with LY 171555, whereas sulpiride determined a decrease. The type of circling was also analyzed: D2 agonist induced a very close turn around the central axis of the animal and D2 antagonist a close turn in the centre of the cage. Data were compared with control condition, which exhibited a large turn around the walls of the cage. The results show that pharmacological manipulation of nucleus accumbens influences rotational behaviour with a specific role for D2 receptors.

Comparison of delta opiate receptor agonist induced reward and motor effects between the ventral pallidum and dorsal striatum

The role of the ventral pallidum and the dorsal striatum in mediating the rewarding effects of the delta receptor specific agonist [2-D-penicillamine, 5-D-penicillamine]enkephalin (DPDPE) were evaluated in the rat using the intracranial self-stimulation paradigm. Reward shifts were indicated by the change in frequency required to maintain half-maximal responding while motor/performance changes were identified by increases or decreases in the maximum responding. Each hour-long test session consisted of three identical, consecutive 20 min rate-frequency curves. In an effort to ascertain possible heterogeneity of function along the rostrocaudal axis, DPDPE (0.0 nmol = saline dose, 0.3 nmol = low dose, 1.0 nmol = medium dose, 3.0 nmol = high dose) was microinjected into either the rostral or caudal region of the two structures. Microinjections into the caudate were positioned directly above the ventral pallidum placements resulting in centromedial or caudomedial caudate placements. DPDPE microinjections into the rostral ventral pallidum resulted in a significant reward increase (28% increase or -0.14 log Hg shift) only at the high dose. In contrast, caudal ventral pallidal DPDPE microinjections showed a dose-response effect with reward increases of 19, 22 and 31% (-0.09, -0.11 and -0.16 log Hz) for the low, medium and high dose, respectively. DPDPE microinjections into the centromedial caudate resulted in a large reward increase (29% or -0.15 log Hz) at the high dose, while caudomedial caudate DPDPE microinjections had no effect on reward. Motor/performance effects tended to follow the pattern of reward effects, with most regions showing motor increases ranging from 25 to 75% over baseline activity. The only exception was found in the caudomedial caudate, where microinjections of the high dose of DPDPE resulted in an approximate 20% suppression of motor/performance activity. These results demonstrate that the ventral pallidum and the mediocentral caudate play a role in modulating opiate rewards, and adds to the growing body of literature regarding the regional heterogeneity within the caudate and ventral pallidum.

Role of the nucleus accumbens and the striatum in the production of turning behaviour in intact rats

Recent knowledge of the mechanisms underlying turning or circling behaviour in intact rats is reviewed. Most interest has been directed towards the striatum because of the classical hypothesis that turning behaviour results from lateral differences in the activity of the bilateral nigrostriatal pathway. However, the assumption that asymmetrical activation of the striatum is a necessary condition for dopamine-dependent turning behaviour has been questioned by several studies showing that unilateral injection of amphetamine or dopamine receptor agonists into the nucleus accumbens, a target of the mesolimbic dopaminergic system, also produces reliable circling away from the side of injection. Apart from discussing differences in stepping patterns of turning and discussing the role of the dopamine D1/D2 receptor interaction, the present survey focuses attention upon the two-component hypothesis, especially in relation to our recent studies in which activities of dopamine D1 and D2 receptors in the striatum and the nucleus accumbens have been manipulated separately in intact rats. It is hypothesized that turning behaviour is produced by asymmetry within nucleus accumbens circuits which involve neuronal connections from the nucleus accumbens to the A9 cell area, which in turn projects to the ventrolateral striatum that determines the direction of turning.

Picolinic acid blocks the neurotoxic but not the neuroexcitant properties of quinolinic acid in the rat brain: evidence from turning behaviour and tyrosine hydroxylase immunohistochemistry

Previous results suggest that the tryptophan metabolite, picolinic acid may have the unusual properties of antagonizing the neurotoxic but not the neuroexcitant effects of another tryptophan metabolite, quinolinic acid in the central nervous system. The present experiments tested this possibility utilizing behavioural and tyrosine hydroxylase immunohistochemical techniques. In the first series of experiments, rats received injections of relatively high concentrations of 6-hydroxydopamine (12 micrograms in 1 or 2 microliters), quinolinic acid (120 nmol in 0.5 microliters), picolinic acid (480 nmol in 0.5 microliters) or co-treatments (0.5 microliters) with quinolinic (120 nmol) plus picolinic acid (480 nmol) into the region of the substantia nigra. Results revealed that 6-hydroxydopamine and quinolinic acid alone produced a large loss of tyrosine hydroxylase-positive cells in the pars compacta of the substantia nigra. Behavioural results for all 6-hydroxydopamine (n = 10) and for some quinolinate-treated rats (n = 5) revealed ipsi- and contraversive circling following amphetamine (1 mg/kg, i.p.) and apomorphine (0.5 mg/kg, s.c.), respectively, consistent with unilateral loss of dopamine cells in the substantia nigra. The remaining quinolinate-treated rats (n = 9) circled ipsiversively following either stimulant suggesting damage to the pars reticulata. Groups treated with picolinic acid alone (n = 6) or co-injected (n = 6) showed no loss of tyrosine hydroxylase-positive cells in the substantia nigra and no circling response to the stimulants. In the second series of experiments, low concentrations of quinolinic acid (2.5, 5.0, 7.5 nmol), picolinic acid (10, 20, 30 nmol), or the two together (7.5 plus 30 nmol, respectively) were microinjected (0.5 microliter) into the dorsal striatum and circling behaviour evaluated. These results revealed dose-dependent contralateral circling with either quinolinate or picolinate; co-injection of the two tryptophan metabolites also produced contralateral circling. It was concluded that picolinic acid blocks the neurotoxic but not the neuroexcitant effects of quinolinic acid.

Defensive reactions evoked by activation of NMDA receptors in distinct sites of the inferior colliculus

The inferior colliculus (IC) is primarily involved in conveying auditory information to higher cortical structures. Recently we have shown that this structure may also be part of a brain system commanding defensive behaviour. There is evidence that the neural substrates responsible for defensive behaviour in the inferior colliculus are regulated by GABAergic, serotonergic and opioid mechanisms and that these substrates may also be depressed by benzodiazepines as part of their anxiolytic action. Here we present evidence for the involvement of excitatory amino acids in the IC in the expression of defensive reactions. Microinjections of NMDA (5-40 nmol)--an excitatory amino acid--into the ventrolateral division of the central nucleus of the IC of rats placed inside a circular arena induced aversive reactions, characterized by running, rearing, and jumping. This hyperactivity was interspersed by immobility states which often progressed to convulsive seizures. These reactions were inhibited by the NMDA specific antagonist AP7 previously microinjected into the IC. It is suggested that NMDA receptor mediated mechanisms are called into play during the display of the defensive behaviour.

Neuropeptide Y: intrastriatal injections produce contralateral circling that is blocked by a dopamine antagonist in rats

The brain is rich in neuropeptide Y (NPY) but its function is poorly understood. Previous studies have shown that intrastriatal injections of NPY stimulate dopamine (DA) release. In the present paper, behavioral studies evaluated the possibility that unilateral intrastriatal injections of NPY would produce contralateral circling that could be blocked by coinjection with a DA antagonist. Four experiments examined circling behavior in rats after unilateral intrastriatal microinjections (0.5 microliter) of: 1) amphetamine alone; 2) amphetamine with the DA antagonist cis-flupenthixol; 3) NPY alone; and 4) NPY with cis-flupenthixol. Each experiment consisted of seven test sessions; the first and seventh were preceded by no injection, the second and sixth by a control injection (saline or cis-flupenthixol with saline) and the third, fourth, and fifth by drug injections. Animals were scored during two 5-min intervals of a 20-min test session that began with the central injection and placement in a circular arena (30 cm diam.). Results indicated that the 25.0- but not the 6.0- or 12.0-micrograms doses of amphetamine and the 0.10- but not the 0.01- or 1.0-microgram doses of NPY produced contralateral circling. This directional bias was antagonized by cis-flupenthixol (20 micrograms in 0.5 microliter) in the case of amphetamine and fully blocked in the case of NPY. Results raise the intriguing possibility that contralateral circling induced by unilateral intrastriatal NPY may be mediated by DA.

Bilateral imbalance in striatal DA-uptake controls rotation behavior

We tested the relation between bilateral imbalance in striatal DA uptake and asymmetric rotation behavior. Rats were screened for either spontaneous or amphetamine-induced preferred direction of rotation and the presynaptic DA transporter in the ipsi- and contralateral striatum was characterized in vitro by measuring [3H]DA uptake or [3H]GBR-12935 binding. DA uptake was lower in the striatum contralateral to either the spontaneous or amphetamine-induced preferred direction of rotation. Similar imbalance in the density of the transporter was confirmed by the binding experiments. These results support the hypothesis that striatal imbalance in DA uptake produces asymmetric behavior during spontaneous rotation. Further studies are required to assess the involvement of DA transporter imbalance in amphetamine-induced behavioral asymmetry.

Modulation of striatal adenosine A1 and A2 receptors induces rotational behaviour in response to dopaminergic stimulation in intact rats

The intraperitoneal injection of d-amphetamine (5 mg/kg i.p.), preceded (10 min before) by intrastriatal injection of an adenosine A2 receptor agonist (CGS 21680, 5-10 micrograms) or followed (5 min later) by an intrastriatal adenosine A1 receptor agonist (N6-cyclopentyladenosine, CPA, 30 micrograms), induced ipsilateral rotations in rats. The opposite effect (contralateral rotations) was observed with adenosine receptor antagonists (A2 antagonist, 3,7-dimethyl-1-propargylxanthine, DMPX, 10 micrograms; A1 antagonist, 8-cyclopentyl-1,3-dimethylxanthine, CPT, 2.5 micrograms). These results confirm that both adenosine A2 and A1 receptors modulate striatal dopaminergic neurotransmission.

Stereotypy, schizophrenia and dopamine D2 receptor binding in the basal ganglia

Animal models suggest a relationship between disturbed striatal dopaminergic function and stereotyped behaviour. Several studies show increased stereotypy in schizophrenic patients compared to normal controls. We investigated the performance of 12 antipsychotic-drug-free schizophrenic patients, and 15 healthy control subjects on a neuropsychological measure of stereotypy--the two-choice guessing task--and correlated this with in vivo striatal dopamine D2 receptor binding, as measured by 123I-iodobenzamide single photon emission tomography. Patients and controls did not differ with respect to the measures of stereotypy derived from the task. However, there was a significant correlation between one of these measures (RR Information) and the degree of striatal D2 receptor binding asymmetry in the patient group only. In view of research connecting striatal and frontal lesions with stereotypy in animals and cognitive inflexibility in humans, these data could suggest a similar disturbance underlying the phenomenon in schizophrenia.

Influence of Body Morphology on Turning Behavior in Carnivores

The present work illustrates how three carnivore species with different body morphologies differ in the performance of a basic motor component-turning. Marbled polecats, which have an elongated and slender trunk, turn while sharply bending the trunk laterally. Grey wolves possess elongated legs and turn by maneuvering with their legs while slightly bending the trunk laterally and lowering the head to contact the ground. Honey badgers feature a wide and massive bear-like shape and rarely bend the trunk, but rather turn either by maneuvering with their legs or while elevating parts of the trunk in the vertical domain. It is suggested that these strategies shorten the radius of turning and thus reduce the moment of inertia. A lower moment of inertia may optimize turning behavior in terms of speed, energy cost, and the smoothness of transition between turning and bouts of forward progression or arrest.

Dynorphin-immunoreactive terminals in the rat nucleus accumbens: cellular sites for modulation of target neurons and interactions with catecholamine afferents

Dynorphin facilitates conditioned place aversion and reduces locomotor activity through mechanisms potentially involving direct activation of target neurons or release of catecholamines from afferents in the nucleus accumbens. We examined the ultrastructural substrates underlying these actions by combining immunoperoxidase labeling for dynorphin 1-8 and immunogold silver labeling for the catecholamine synthesizing enzyme, tyrosine hydroxylase (TH). The two markers were simultaneously visualized in single coronal sections through the rat nucleus accumbens. By light microscopy, dynorphin immunoreactivity was seen as patches of immunoreactive varicosities throughout all rostrocaudal levels of the nucleus accumbens. The dynorphin-immunoreactive terminals identified by electron microscopy ranged from 0.2 to 1.5 microns in cross-sectional diameter, contained numerous small (30-40 nm) clear vesicles, as well as one or more large (80-100 nm) dense core vesicles. From the dynorphin-immunoreactive terminals quantitatively examined in single sections, 74% (173/370) showed symmetric synaptic junctions mainly with large unlabeled dendrites. Of the dynorphin-immunoreactive terminals forming identifiable synapses, approximately 30% contacted more than one dendritic target. In addition, single dendrites frequently received convergent input from more than one dynorphin-labeled terminal. Irrespective of their dendritic associations, dynorphin-immunoreactive terminals also frequently showed close appositions with other axons and terminals; these included unlabeled (41%), TH-labeled (10%) or dynorphin-labeled axons (14%). In contrast to dynorphin-immunoreactive terminals, TH-labeled terminals formed primarily symmetric synapses with small dendrites and spines or lacked recognizable specializations in the plane of section analyzed. In some cases, single dendrites were postsynaptic to both dynorphin and TH-immunoreactive terminals. We conclude that dynorphin-immunoreactive terminals potently modulate, and most likely inhibit, target neurons in both subregions of the rat nucleus accumbens. This modulatory action could attenuate or potentiate incoming catecholamine signals on more distal dendrites of the accumbens neurons. The findings also suggest potential sites for presynaptic modulatory interactions involving dynorphin and catecholamine or other transmitters in apposed terminals.

Subdivisional ischemic injury of the unilateral striatum causes apomorphine-induced rotational behavior in rats

Behavioral and histological studies were performed on a reversible ischemia model in rats. At 60 days after unilateral transient middle cerebral artery occlusion for 30 min, the operated rats exhibited the ipsiversive rotational behavior elicited by systemic administration of dopamine receptor agonist apomorphine in a dose-dependent manner. Histologically, the ipsilateral striatum of the rats showed a subdivisional ischemic injury, while the nigral dopaminergic neurons appeared intact. The striatal lesions having a cell type-specific injury were located in the dorsolateral portion of the rostral striatum and in the lateral portion of the caudal part of the nucleus. Thus, the transient cerebral ischemia could successfully produce selective damage of a striatal subdivision, which causes an abnormality in motor controls in response to dopamine receptor stimulation. The present data may provide a part of functional and anatomical basis for understanding the movement disorders associated with basal ganglia dysfunction (e.g., parkinsonism), which may occur in patients with cerebrovascular disorders.

Effects of intranigral injections of colchicine on the expression of some neuropeptides in the rat forebrain: an immunohistochemical and in situ hybridization study

In the present study, we describe the neurochemical effects of intranigral injections of colchicine in the rat forebrain using immunohistochemistry and in situ hybridization. The observations on the injected side are compared to the contralateral one and to the sham-operated rats. We demonstrate that such injections are able to strongly enhance the immunoreactivity for Met-enkephalin (ME), substance P (SP) and neuropeptide Y (NPY) in numerous nerve cell bodies of the limbic system (injected side), whereas the levels of the corresponding mRNAs are differently modified according to the region examined. A clear correlation between the enhancement of the immunostaining for ME and SP and that of the preproenkephalin (PPA) and preprotachychinin gene transcripts was observed in neuronal perikarya of the medial amygdaloid nucleus (SP), of the dorsolateral hypothalamus (ME) and of the ventromedial hypothalamic nucleus (SP). These observations are interpreted as an induction--or increased expression--of neuropeptide genes in neuronal perikarya postsynaptic to nerve fibers originating in the midbrain and brain stem. In this case, colchicine is thought to block the electrophysiological activity of ascending nerve fibers (anterograde and postsynaptic effect). In the case where the enhancement of the immunoreactivity for the studied neuropeptides was associated with no change or a decreased expression of the corresponding genes in the same brain areas, colchicine may have blocked the axoplasmic transport of peptides in nerve fibers projecting to the midbrain and/or brain stem (6). This may result in a retrograde accumulation of peptides in the nerve cell bodies of origin and, eventually, in a negative feedback regulation of the corresponding encoding genes in these perikarya (retrograde and presynaptic effect of colchicine). The drastic behavioral effects of bilateral intranigral injections of colchicine, on ingestive behavior in particular, have been studied in a following paper.

1,2,3,4-Tetrahydro-2-methyl-4,6,7-isoquinolinetriol depletes catecholamines in rat brain

1,2,3,4-Tetrahydro-2-methyl-4,6,7-isoquinolinetriol (TMIQ) was synthesised and tested for activity as a dopamine-depleting agent in rat brain. After intracerebroventricular infusion, TMIQ caused reductions in dopamine concentrations in substantia nigra, striatum, hypothalamus, and dorsal raphe, and reduction in noradrenaline concentrations in locus coeruleus. TMIQ also reduced 5-hydroxytryptamine concentrations in dorsal raphe and substantia nigra, although with a lower potency. Comparisons between TMIQ and MPTP showed that they were approximately equipotent in depleting dopamine in the substantia nigra, hypothalamus, and dorsal raphe. Pretreatment of animals with a combination of monoamine oxidase A and B inhibitors completely prevented the TMIQ-induced reductions in dopamine concentrations in substantia nigra and hypothalamus. Direct unilateral intrastriatal injections of TMIQ produced marked ipsilateral reductions in striatal dopamine, correlating with a behavioural response consisting of turning towards the side of injection. The results suggest that TMIQ should be evaluated further as a possible MPTP-like compound, which may derive from endogenous beta-hydroxylated catecholamines.

In vivo electrochemical studies of gradient effects of (SC) cocaine on dopamine and serotonin release in dorsal striatum of conscious rats

Cocaine (20 mg/kg) was administered subcutaneously (SC) to conscious male Sprague-Dawley rats after exploration in a novel chamber. (SC) cocaine was studied for its influence on in vivo dopamine (DA) and serotonin (5-HT) release in dorsal striatum (STr), with a further study of an anterior-posterior dorsal subdivision in a range of +/- 400 microns. Semiderivative voltammetry, a circuit for in vivo electrochemical biotechnologies, was used in combination with a stearate microelectrode to concurrently detect in separate electrochemical signals the electroactive species for DA and 5-HT in dorsal STr. The temporal resolution for detection was in the order of seconds. Concomitantly, cocaine-induced psychostimulant behaviors were studied with infrared photo beam detection. Psychostimulant behaviors classically thought to depend on DA--that is, hyperactivity (increased locomotor activity or ambulations), rearing, and finally stereotypy (fine movements of grooming and head bob)--and a 5-HT-ergic behavior, central ambulations, were monitored. The results showed that (SC) cocaine significantly (p < 0.0001) increased DA release in dorsal STr, whereas the overall effect of (SC) cocaine on 5-HT release was a significant increase (p < 0.0001) followed by an overall small (13%) but statistically significant decrease (p < 0.05). A dramatic cocaine-induced gradient effect on 5-HT release was seen in anterior-posterior dorsal STr, where 5-HT release was significantly (p < 0.0001) increased throughout the entire time period of study. Classically DA-dependent behaviors were significantly and positively correlated with increased DA release in dorsal STr and anterior-posterior dorsal STr (p < 0.001) in the 4-h period of study. However, 5-HT release after cocaine in the anterior-posterior dorsal STr was significantly and positively correlated with the classically DA-dependent behaviors as well (p < 0.001), implicating a role for 5-HT in the effectuation of cocaine-induced psychostimulant behavior. Generally, the 5-HT-ergic response to cocaine was enhanced before the DA-ergic response. Therefore, the data show that 5-HT as well as DA plays a role in the underlying mechanism of action of cocaine in dorsal STr. The data suggest that 5-HT may play a compensatory or adaptive role in the modulation of cocaine-induced nigrostriatal DA-ergic regulation.

Neuropeptide Y: intraaccumbens injections produce a place preference that is blocked by cis-flupenthixol

Neuropeptide Y (NPY) has been localized in the nucleus accumbens (NAcc), where it may influence dopamine (DA) neurotransmission. Extensive data implicate NAcc DA in reward-related learning, raising the possibility that NPY microinjected into the NAcc may induce rewarding effects mediated by DA. This hypothesis was tested using the conditioned place preference (CPP) paradigm. Each experiment consisted of three distinct phase: preconditioning (three 15-min exposures to an apparatus with two compartments connected by a tunnel); conditioning (four 30-min pairing of one compartment with drug and four similar pairings of the other compartment with vehicle); and test (three 15-min exposures to the apparatus). A significant increase in the time spent in the drug-paired compartment from preconditioning to test was taken as evidence of a CPP. Two experiments showed that systemic (2.0 mg/kg, IP) or intraaccumbens amphetamine (10.0 micrograms in 0.5 microliters on each side) produced a CPP. The third experiment showed that intraaccumbens NPY (0.1 micrograms in 0.5 microliter on each side) produced a CPP. This CPP was blocked by pretreatment with a dose of the DA receptor blocker cis-flupenthixol (20.0 micrograms in 0.5 microliter on each side in the NAcc) that, alone, produced no CPP effect. These results strongly suggest that NPY applied to the NAcc is rewarding. In addition, these rewarding properties of NPY may be mediated by DA neurotransmission.

Neurological and behavioral effects of a unilateral frontal cortical lesions in fetal kittens. I. Brain morphology, movement, posture, and sensorimotor tests

Nine fetal kittens sustained removal of the left frontal cortex during the last third of gestation (E 43-55) and were compared to animals sustaining a similar lesion postnatally (P 8-14) as well as to littermate controls. Starting after 6 months of age the animals received a comprehensive battery of movement, posture and sensorimotor tests. The prenatal-lesioned cats performed worse in practically all 15 tests applied (significantly in 13 of them) compared to the neonatal-lesioned cats. Impairments included contralateral paresis of the limbs and face, defective limb placing reactions (with almost absence of the contact components) and a slight extensor hypertonus; tactile hypoesthesia in the contralateral face and hind paw; a bias not to use the contralateral forepaw in a food retrieval task, and an ipsilateral body turning bias. The neonatal-lesioned animals only showed minor defects in the contact components of the limb placing reactions and a tendency to a body turning bias. Morphologically, the brains of the prenatal-lesioned cats, but not of neonatal-lesioned or intact control cats, showed bilateral disruption of the cortical sulcal and gyral patterns, shrinkage of the ipsilateral hemisphere, and reduction in volume of the ipsilateral thalamus and cortex. We concluded, contrary to expectations, that the consequences of a prenatal brain lesion in the cat are worse than when a similar lesion is sustained neonatally.

Behavioral responses induced by electrical stimulation of the caudate nucleus in freely moving cats

The caudate nucleus and adjacent structures of 26 freely moving cats were stimulated through multiwire electrodes chronically implanted. Two main effects here observed with trains of pulses of high frequency (100 Hz) and short duration (1 s): (1) contralateral head turning and (2) arrest reaction, which was associated with crouching and escape behavior. The responses follow a certain topographic distribution. Head turning was elicited with the lowest mean threshold in sites located in the internal two-thirds and caudal region of the caudate nucleus, while the arrest reaction was elicited from the ventromedial region of the caudate and adjacent nucleus accumbens. Stimulation of the corpus callosum and internal capsule produces postural instability, ventral flexion of the head and flexion of the contralateral limb. The extra-caudate responses were accompanied by contralateral head turning when the stimulated points were near of the caudate border. Experimental evidence suggested that striatal responses were not due to current spread to adjacent structures or to activation of corticofugal fibers. The head rotation was suppressed following interruption of the ipsilateral striatal outflow by electrolytic lesion of the globus pallidus and adjacent internal capsule. The chemical lesion of the substantia nigra and the ventral pallidum produced a significant increase in the stimulation threshold for head turning and arrest reaction, respectively. These results suggest a topographic arrangement of the responses evoked by electrical stimulation of the caudate nucleus in the cat, which are mediated by the substantia nigra pars reticulata and the ventral pallidum.

Receptor-receptor interactions as an integrative mechanism in nerve cells

Several lines of evidence indicate that interactions among transmission lines can take place at the level of the cell membrane via interactions among macromolecules, integral or associated to the cell membrane, involved in signal recognition and transduction. The present view will focus on this last subject, i.e., on the interactions between receptors for chemical signals at the level of the neuronal membrane (receptor-receptor interaction). By receptor-receptor interaction we mean that a neurotransmitter or modulator, by binding to its receptor, modifies the characteristics of the receptor for another transmitter or modulator. Four types of interactions among transmission lines may be considered, but mainly intramembrane receptor-receptor interactions have been dealt with in this article, exemplified by the heteroregulation of D2 receptors via neuropeptide receptors and A2 receptors. The role of receptor-receptor interactions in the integration of signals is discussed, especially in terms of filtration of incoming signals, of integration of coincident signals, and of neuronal plasticity.

A video image analyzing system for open-field behavior in the rat focusing on behavioral asymmetries

A video image analyzing system is presented which measures turning behavior, thigmotactic scanning and locomotion in rats. The system works by analyzing digitized video images obtained by a black/white video camera. Turning behavior is expressed in different diameter classes and as partial or full turns. Thigmotactic scanning is expressed as distance or time locomoted with the left or right side of the body along one of the walls of the testing environment. Locomotion is measured as distance travelled and is expressed in meters. Examples for the application of these behavioral measures are given which include: the measurement of spontaneous or drug-dependent behavioral asymmetries after brain lesion (the unilateral 6-hydroxydopamine model), a unilateral peripheral manipulation (hemivibrissotomy), and the measurement of open-field behavior (spontaneous or drug-induced) in intact animals. Among others, these examples show that the analysis of thigmotactic scanning may provide an alternative behavioral measure, which may be especially useful in the study of functional asymmetries.

Apomorphine sensitization effects: evidence for environmentally contingent behavioral reorganization processes

Apomorphine-induced behavioral sensitization was investigated with a Pavlovian conditioning paradigm. Rats were administered apomorphine (2.0 mg/kg SC) daily for 7 days either paired or unpaired with a 10-min test environment placement. Initially, apomorphine induced hypolocomotion, but by treatment day 5, hyperlocomotion developed. Utilizing a videoimage analysis program which quantitated angular movement, it was determined that the increase in locomotion induced by repeated apomorphine treatment was due to an increase in rotational locomotion. Critically, rotation per se did not increase, but rather wide angle rotation toward the periphery of the test environment increased. Furthermore, a directional bias of rotation developed and stabilized which was unrelated to the animal's initial asymmetry bias. This emergence of a new locomotion pattern in conjunction with hyperlocomotion pointed to the need to reconceptualize behavioral sensitization phenomena into a new framework consistent with a progressive change in behavioral structure. Behavioral reorganization is presented as an alternative formulation to that of behavioral sensitization, as a drug-environment interactive process which is more compatible with the behavioral dynamics that emerge with repeated intermittent dopaminergic psychostimulant drug treatment.

Dopamine receptors in the basal ganglia: relevance to Parkinson's disease

At least five receptors for dopamine (D1-D5) have been recognised from molecular biological studies, and their pharmacological properties and brain localisations have been determined. The D1 and D2 subtypes are the principal subtypes in brain, and their cellular localisations in the caudate nucleus and putamen have been determined. With recent advances in the understanding of basal ganglia neuronal function, these localisation data enable insights into the mode of action of drugs used at present and in the future to treat Parkinson's disease.

Amphetamine-induced rotational behavior in rats: relationship to hypothalamic and striatal degeneration

When lesions are placed unilaterally in the nigrostriatal system of experimental animals, rotational behavior occurs in response to peripheral administration of dopamine (DA) agonists. In spite of considerable evidence to the contrary, it is assumed that in order for this rotation to occur, an almost complete depletion of striatal DA must be achieved. To test this hypothesis further, 20 male Sprague-Dawley rats were injected unilaterally with 2 microL of 8 micrograms/microL of 6-hydroxydopamine (6-OHDA) via acute injection needles or chronically indwelling cannulae. Acute injection of 6-OHDA resulted in a rotation rate of 7.2 to 18.9 revolutions per minute in response to peripheral amphetamine injection (5 mg/Kg) while injection of 6-OHDA through chronically indwelling cannulae produced rotation ranging from 1.4 to 9.9 rotations per minute. Under the conditions of either method of injection, the animals displaying the most severe rotation still showed partial denervation of striatal DA as revealed by catecholamine fluorescence histochemistry. Conversely, numerous animals demonstrating very low rates of amphetamine-induced rotation often displayed a complete loss of striatal, accumbens, and olfactory tubercle catecholamine fluorescence. Moreover, large quantities of lateral hypothalamic amine accumulation were observed in rotating rats indicating that this neurochemical change may be of functional significance for rotational responses. The present results, when taken into consideration with previous work, indicate that the routine selection of rotating animals for pharmacological testing for potential antiParkinsonian medication or intracerebral grafting purely on the basis of their rotational behavior does not necessarily imply that complete striatal denervation has occurred. Moreover, these findings demonstrate that amine accumulation in the lateral hypothalamus of rotating animals with DA depleting lesions is an important phenomenon implicated in the expression of rotational behavior in animals and possibly in the pathophysiology of Parkinson's disease.

Motoric sensitization and levodopa accumulation after chronic levodopa treatment in an animal model of Parkinson's disease

One month after rats were subjected to unilateral injections of either 6-hydroxydopamine (6-OHDA) or vehicle into the midbrain tegmentum, they were given daily injections of either saline or levodopa (10 mg/kg and 1 mg/kg carbidopa) for 30 days. On the first and last day of treatment the spontaneous behavior of the rats was evaluated with a video image analysis system that detected directional movement asymmetries. Although vehicle-injected rats exhibited very little movement asymmetry, the 6-OHDA rats were strongly asymmetric. On day 1, both saline and levodopa-treated 6-OHDA rats exhibited rotational movement directed toward the dopamine-deficient hemisphere. On day 30 of treatment, however, the chronic levodopa group displayed a complete reversal and exaggeration of the rotational bias, and all asymmetric movement was directed toward the dopamine-intact hemisphere. Thus chronic levodopa treatment shifted behavioral dominance from the intact to the dopamine-denervated hemisphere. Subsequent biochemical measurement of dopamine and levodopa in striatal and limbic tissue samples indicated that chronic levodopa treatment did not alter dopamine tissue concentrations but did substantially increase levodopa concentrations, both in the dopamine-denervated striatum and in limbic tissue. This increased levodopa loading in brain with chronic levodopa treatment occurring in 6-OHDA rats but not in vehicle-injected rats that were given the same levodopa regimen. This selectivity in the effect of chronic levodopa treatment to the 6-OHDA rats appeared to rule out the possibility of peripheral metabolic factors for the levodopa accumulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Reevaluation of the two-component hypothesis for turning behaviour by manipulating activities in the striatum and the nucleus accumbens of intact rats

The role of dopamine D1 and D2 receptor stimulation in the production of turning behaviour in rats was studied. In rats pretreated with unilateral injections of the non-selective dopamine D1/D2 receptor antagonist, cis(Z)-flupentixol (10 micrograms/0.5 microliter), into the ventral striatum, quinpirole (1, 3, 5, 10 mg/kg i.p.), a selective dopamine D2 receptor agonist, induced dose-dependent turning behaviour, while SKF 38393 (1, 3, 5, 10 mg/kg i.p.), a selective dopamine D1 receptor agonist, did not. The effect of the two drugs together was much greater than the effect of quinpirole alone and was reduced by additional blockade of dopamine D1/D2 receptors in either the ipsilateral or contralateral nucleus accumbens. The role of the nucleus accumbens in turning behaviour was determined from the effects of unilateral injections of SKF 38393 and quinpirole into the nucleus accumbens. The results show that unilateral injections of a mixture of the two drugs (SKF 38393 5 micrograms + quinpirole 10 micrograms/0.5 microliter) into the nucleus accumbens produced turning while injections of single drugs did not. Turning was abolished by the blockade of dopamine D1/D2 receptors in the ipsilateral but not contralateral ventral striatum. Turning was also reduced by the blockade of the contralateral nucleus accumbens. Moreover, turning was not produced by injections of the drug mixture into the dorsal or ventral striatum.

Opposite effects of intranigral ibotenic acid and 6-hydroxydopamine on motor behavior and on striatal neuropeptide Y neurons

Unilateral lesions of the basal ganglia circuit induce a disequilibrium of motor processing, most obviously expressed by the resulting circling behavior. Compensatory events, which reduce the motor asymmetry, could be accompanied by changes in neurotransmitter/modulator parameters in the involved brain regions. In the present investigation, the effects of an interruption of the striato-nigro-thalamic loop by ibotenic acid (IBO)-induced lesions of total substantia nigra (SN) on circling behavior and on striatal neuropeptide Y (NPY) neurons were compared with those after the selective destruction of the dopaminergic nigrostriatal projection with 6-hydroxydopamine (6-OHDA). Directly after the operation, IBO-lesioned rats showed a high circling rate to the side contralateral to the lesion, whereas 6-OHDA-lesioned rats showed ipsiversive circling. With the lesion-induced development of dopamine receptor supersensitivity, 6-OHDA-treated rats, when stimulated with the dopaminergic agonist apomorphine, change their circling direction to the contralateral side. Complete IBO lesions of the SN abolished this effect: rats continued to circle to the contralateral side. These observations suggest that not only the dopaminergic denervation of the striatum but also the imbalance in the activity of the thalamo-cortical projection (reduced after 6-OHDA, augmented after IBO) are instrumental in determining the degree and direction of circling. Quantification of NPY-immunoreactive neurons in striatum revealed a decrease in 6-OHDA lesioned rats after 3 days on the side contralateral to the lesion, an effect even more pronounced after 4 month's survival time. IBO-induced lesions of the SN had an opposite effect on NPY-immunoreactivity in the striatum: neuron counts were lower on the ipsi- than on the contralateral side. In addition, a time-dependent variation in total number of NPY-neurons was noted: during the early postoperative periods an increase, followed by a prolonged decrease to values below 50% of the controls after 4 months. Taken together, these results provide evidence that a dopaminergic deafferentation and its consequences on the nigro-thalamo-cortical loop will determine NPY expression in the striatal interneurons. In particular, it is suggested that the number of striatal NPY-neurons and the imbalance in cortical activity are tightly coupled in terms of a negative correlation.

Transplantation of embryonic mesencephalic and medullary raphe neurons to the neostriatum of rats with unilateral 6-hydroxydopamine lesions

The implantation of dopamine-rich mesencephalic grafts into the 6-hydroxydopamine (6-OHDA)-lesioned neostriatum of rats was accompanied by marked hyperinnervation by serotonin (5-HT) fibers. The purpose of this study was to examine the possibility that the graft-derived 5-HT hyperinnervation is governed by target-related effects present in the host neostriatum and the question of whether grafts rich in 5-HT cells can ameliorate the drug-induced motor asymmetry resulting from unilateral 6-OHDA lesions. Rats were allocated to one of two groups: lesion plus mesencephalic raphe grafts (group R5-HT/L); and lesion plus medullary raphe grafts (group C5-HT/L). A third group, sham-lesion plus mesencephalic raphe grafts (group R5-HT/S) was included. Complete recovery of (+)-amphetamine-induced rotation was observed only in rats which received 5-HT grafts derived from medullary raphe neurons. There was no marked recovery of apomorphine-induced rotation in either of the R5-HT/L and C5-HT/L groups. Immunohistochemistry showed that the R5-HT/L and C5-HT/L groups had 5-HT hyperinnervation in the neostriatum of the lesioned side. There was no target-related effect of the 6-OHDA-lesioned neostriatum specific for the different types of 5-HT tissue. It seems likely that the 5-HT tissue derived from the medullary raphe may contain additional neurotransmitters which contribute to the behavioral recovery.

N-methyl-D-aspartate unilaterally injected into the dorsal striatum of rats produces contralateral circling: antagonism by 2-amino-7-phosphonoheptanoic acid and cis-flupenthixol

To evaluate the possible contribution of dorsal striatal glutamate receptors to motor behavior, circling responses were observed in rats following unilateral intrastriatal microinjections of the agonist, N-methyl-D-aspartate (NMDA) or the antagonist, 2-amino-7-phosphonoheptanoic acid (APH). The role of dopamine (DA) in NMDA-produced circling also was evaluated. In experiment 1, an NMDA dose of 5.0 micrograms (in 0.5 microliter), but not 0.5 or 0.05 microgram produced significant contraversive circling. In experiment 2, an APH dose of 10.0 micrograms but not 1.0 or 0.1 microgram produced significant ipsiversive circling. In experiment 3, microinjection of the ineffective 0.1 microgram dose of APH or a dose (20 micrograms) of the DA antagonist, cis-flupenthixol, that did not produce circling when administered alone, significantly reduced the circling response produced by the 5.0 micrograms dose of NMDA. As NMDA produced circling in the same direction as that seen following similar unilateral injections of locomotion-stimulating DA agonists, the present results suggest that glutamate, acting via NMDA receptors in the dorsal striatum, may exert an excitatory influence on motor systems. The observation that a DA receptor blocker antagonized the NMDA response further suggests that the observed motor excitatory effect of glutamate at NMDA receptors requires concurrent stimulation of DA receptors in the same region of the striatum.

Sensitivity of dopamine receptors in the lateral hypothalamus is altered in 6-hydroxydopamine treated rats

Amine accumulation is observed in the lateral hypothalamus (LH) after nigrostriatal neurons degenerate. It has been proposed that this accumulation is a source of amines which are released into the hypothalamus thereby affecting the function of adjacent aminergic receptors. To approximate this condition of continuous exposure of LH receptors to endogenous amines, dopamine (DA) was injected into the LH of rats once daily for 5 consecutive days. A control group received 4 daily injections of tartaric acid vehicle and then DA on day 5. Rats pretreated with DA showed severe impairment of open field performance and motor reflex control on day 5 when they were compared to control animals which received vehicle pretreatment. In a second study, the DA receptor antagonist haloperidol was injected into the area of amine accumulation in the LH to determine whether this might block amine release from areas of accumulation thereby to attenuate lesion-induced rotation. Haloperidol administered once daily for 4 out of 7 days, once daily for 7 days or via a continuous infusion for 7 days, all reduced d,l-amphetamine-induced turning to control levels. These results suggest that prolonged exposure of hypothalamic DA receptors alters their sensitivity to subsequent doses of DA and that amine released from areas of accumulation may be blocked by haloperidol to enhance behavioral recovery from DA depleting lesions. Moreover, these findings indicate that the hypothalamus participates in the behavioral effects induced by DA depleting lesions and highlight the importance of hypothalamic pathology in Parkinson's disease.

Preoperative operant circling training facilitates recovery following unilateral substantia nigra lesion in rats

This study was undertaken to examine (1) whether pre- and/or postoperative training, using water reinforcement, to turn in circles (rotation) affects the behavioral symptoms induced by unilateral 6-hydroxydopamine (6-OHDA)-induced DA denervation of the rat substantia nigra (SN); (2) whether there was any influence of this training on the temporal pattern of recovery; and (3) whether the rotational training influences turning induced by systemic injection of dopaminergic drugs. In the first experiment, rats were trained either ipsi- or contraversive (TI or TO) to the side to be damaged 11 days before and 23 days after lesion, and tested in an open field for rotational behavior following systemic administration of apomorphine and amphetamine. In the second experiment rats were trained only before the lesion was made and tested in the open field for spontaneous circling and thigmotactic behavior. The results of the first experiment indicated maintenance of the training performance after the lesion. At the 14th day after the lesion, the ipsiversive trained group showed a higher contraversive circling frequency after apomorphine injection in relation to the contralateral trained group. In the second experiment, rats trained only before the surgery, showed asymmetrical spontaneous circling in the trained direction before and 14 days after surgery, indicating, in a drug free condition, that training direction can be restored after unilateral SN lesions, even to the contralateral body side. Moreover, thigmotactic behavior indicated a lack of habituation in an open field in unilateral lesion rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Amelioration of experimental parkinsonism by intrahypothalamic administration of haloperidol

Accumulation of amines in the degenerating axons of ascending catecholamine-containing neurons in the hypothalamus has been proposed as a site of function neurotransmitter release and may thereby participate in the development of motor impairment seen after central dopamine-depleting lesions. To test this hypothesis further the dopamine receptor antagonist haloperidol (1 microL of a 14 nmol solution) was injected directly into the lateral hypothalamus (LH) in 6 different injection regimes to determine whether amphetamine-induced turning could be attenuated with this treatment. The injection of haloperidol at 1 and 24 h (group 1), 24 h (group 2) or 6+ 7 d (group 3) after 6-hydroxydopamine (6-OHDA) did not modify amphetamine-induced turning. However, the injection of haloperidol at 1 h, 24 h, 7 d, and 8 d (group 4), days 1-7 (group 5), or gradual infusion (14 nmol/microliters/h) for 7 days (group 6) all reduced the 6-OHDA-induced turning to a level similar to that of controls. These results add further support to the contention that amines are released from the axons of degenerating neurones in the hypothalamus and that this phenomenon participates in the elicitation of behavioral impairment attributed solely to the loss of functional neurotransmitters from terminal fields. Furthermore, the data emphasize the importance of hypothalamic pathology in the development of Parkinsonism and suggest that intrahypothalamic administration of dopamine blocking agents might be useful in the treatment of Parkinsonism.

Non-cholinergic action of exogenous acetylcholinesterase in the rat substantia nigra. II. Long-term interactions with dopamine metabolism

Within the substantia nigra acetylcholinesterase (AChE) has a novel non-cholinergic action that is functionally manifest as chronic circling behaviour in rats. The aim of this study was to explore the possible biochemical mechanisms that could underlie the long-term behavioural effects of this protein, infused unilaterally into one substantia nigra. A single treatment of acetylcholinesterase induced modest but consistent circling behaviour in the presence of a systemic amphetamine challenge for the maximum time tested, up to 50 days: comparable infusions of saline were without effect. When animals received a challenge of the direct dopamine agonist apomorphine, no AChE-induced circling was observed: this result suggested that the phenomenon did not entail a down-regulation of striatal dopamine receptors. On the other hand, a challenge of the dopamine uptake inhibitor nomifensine resulted in AChE-induced circling that was indistinguishable from that seen in the presence of amphetamine: hence the circling behaviour seen could be attributable to an AChE-induced increase in availability of extracellular dopamine. In animals where AChE caused contraversive rotation, indicative of an enhanced activity in the nigrostriatal pathway, there was a significant elevation in the dopamine content of the striatum on the treated side. It is concluded that AChE can chronically enhance the release of dopamine from the nigrostriatal pathway such that motor behaviour is correspondingly modified, but to an extent sufficiently modest to avoid compensatory synaptic reversal mechanisms.

Recovery from lateralized neocortical damage: dissociation between amphetamine-induced asymmetry in behavior and striatal dopamine neurotransmission in vivo

It has been hypothesized that neocortical damage is accompanied by secondary changes in other brain areas (the shock or diaschisis of von Monakow), which contributes to initial non-specific behavioral depression. The relation between behavioral changes and dopamine (DA), serotonin (5-HT), and their metabolites, measured with intracerebral microdialysis in freely moving rats and by tissue assay postmortem, was examined during postsurgical recovery from unilateral hemidecortications. Rats were tested for rotational asymmetry and extracellular concentration of DA was measured both during rest and after amphetamine (1.5 mg/kg). It was found that: (1) during the first few postsurgical days the hemidecorticate rats rotated ipsilateral to their lesions after amphetamine but thereafter on tests given up to 121 days postsurgery concentration of DA or its metabolites at any time after surgery; (3) the 5-HT metabolite 5-hydroxyindoleacetic acid (5-HIAA) was elevated acutely for a few days following surgery; (4) during the first 3 postoperative days, both baseline extracellular 3,4-dihydroxyphenylacetic acid (DOPAC) and amphetamine-induced DA release were significantly elevated bilaterally. These findings demonstrate that the acute behavioral asymmetry in rotation produced by hemidecortication is not related to unilateral changes in striatal DA activity and its metabolites. Thus, the behavioral asymmetries might be related to other striatal changes (i.e. 5-HIAA) or other damage, such as to the corticospinal projections of the lesioned hemisphere. Nevertheless, unilateral lesions did produce acute bilateral increases in DA levels, which may be a correlate of generalized neural shock produced by the lesion.

Brain dopamine D-2 receptor mechanisms in spontaneously hypertensive rats

Brain dopaminergic function was studied in spontaneously hypertensive rats (SHR) with the selective dopamine D-2 antagonist sulpiride. Sulpiride dose-dependently inhibited locomotor activity of normotensive Wistar-Kyoto rats (WKY). SHR showed an increase in locomotor activity in response to low doses of sulpiride, whereas no effect was observed of higher doses. In a two-bottle salt-preference test, WKY showed increased preference for an 0.9% saline solution after treatment with sulpiride, whereas total fluid intake remained the same. In SHR, sulpiride influenced neither salt-preference nor total fluid intake. SHR and WKY with a unilateral lesion of the median forebrain bundle showed similar turning behaviour in response to treatment with amphetamine. Pretreatment with 100 mg/kg sulpiride virtually abolished amphetamine-induced turning in WKY, but had little effect in SHR. Sulpiride dose-dependently increased serum prolactin concentrations in WKY and SHR. However, the increase was significantly greater in SHR. Dopamine D-2 receptor binding was measured with in vitro autoradiography, using [125I]-sulpiride as the ligand. Binding density was similar in the caudate nucleus and substantia nigra of SHR and WKY brain. Concentrations of the dopamine metabolites DOPAC and HVA, but not of dopamine itself, were significantly increased in frontal cortex, striatum and hypothalamus after treatment with 100 mg/kg sulpiride. There were no significant differences between SHR and WKY in the increase in the DOPAC/DA and HVA/DA ratio. These data show that SHR show differential changes in their response to central dopamine D-2 blockade when compared to WKY. Thus, in some tests (locomotor activity after high doses, salt preference, turning behaviour), SHR respond less to sulpiride.(ABSTRACT TRUNCATED AT 250 WORDS)

Factors in amphetamine-induced contralateral rotation in the unilateral 6-OHDA lesion rat model during the first-week postoperative: implications for neuropathology and neural grafting

Amphetamine induced ipsilateral rotation in rats with chronic unilateral 6-hydroxydopamine (6-OHDA) lesions is a widely accepted line of evidence supportive of dopaminergic mediation of amphetamine effects on motoric behavior. However, there is literature indicating that amphetamine induces contralateral rotation, in the early postoperative phase of a unilateral 6-OHDA lesion. In an attempt to reconcile these opposite amphetamine effects on rotation in terms of dopaminergic mechanisms, a series of 4 experiments were conducted. These studies showed that amphetamine reliably elicits contralateral rotation for up to 7 days postoperative but only ipsilateral rotation thereafter. The amphetamine induced contralateral rotation differed behaviorally in several respects from subsequent ipsilateral rotation induced by amphetamine. It was comparatively more intense; and, while onset of peak rotation was dose dependent, rate of rotation was independent of dose level (0.5, 1.0 and 2.5 mg/kg). Dopamine and dopamine metabolite analyses by HPLC-EC after 3 postoperative intervals (days 3, 6, and 9) indicated a progressive and severe depletion of striatal dopamine in conjunction with elevated dopamine turnover. Importantly, after 6 days postoperative, dopamine was reduced to less than 0.06% after intact hemisphere but yet, amphetamine (1.0 mg/kg) elicited contralateral rotation. It was proposed that amphetamine could release a small amount of dopamine present in a sparse number of residual degenerating terminals and this dopamine, unrestricted by reuptake, could widely access supersensitive dopamine receptors to elicit contralateral rotation. This possibility calls into question amphetamine tests for neural graft efficacy in animal models which use amphetamine induced contralateral rotation as the criterion response.

Control of turning behavior under apomorphine by sensory input from the face

It has been shown that peripheral manipulation of sensory input by removal of vibrissae on one side of the rat's face induces turning behavior which is directed towards the contralateral vibrissae-intact side, under the influence of the dopamine receptor agonist apomorphine. In the present experiment, we examined whether rats under apomorphine turn towards the side with more sensory input, or simply away from the manipulated side. Thus, an experimental manipulation was designed to increase sensory input. Sensory stimulation was applied by attaching a clip into the fur on one side of the face. Rats injected with apomorphine in doses of 0.5-5.0 mg/kg (but not with 0.05 mg/kg or vehicle) exhibited turning behavior towards the side of the clip. This sensory stimulation was also found to influence spontaneous behavioral asymmetries. These results show that an imbalance in sensory input is sufficient to produce turning under apomorphine.

Pavlovian conditioning of L-dopa induced movement

Using the unilateral 6-hydroxydopamine (6-OHDA) substantia nigra pars compacta (SNC) lesion rat model and a Pavlovian conditioning protocol, the present investigation determined that the contralateral rotation response induced by the antiparkinsonian dopaminergic drug L-dopa can become conditioned to exteroceptive test environment stimuli. Two non-drug conditioning tests indicated that contralateral rotation was elicited by the test environment without the presence of L-dopa. This conditioned response had a rotation diameter profile that was qualitatively the same as the L-dopa induced contralateral rotation response. Additionally, drug tests with the combined dopaminergic receptor antagonists, SCH 23390 (0.1 mg/kg) and haloperidol (0.5 mg/kg), at doses sufficient to block spontaneous behavior and L-dopa (20 mg/kg)-induced rotation, revealed that the conditioned contralateral rotation response, unlike L-dopa-induced contralateral rotation, is not affected by D1/D2 receptor blockade. Thus, the conditioned stimuli of the test environment can elicit the contralateral rotation response even in animals rendered akinetic by D1/D2 antagonists. This activation of a conditioned dopaminergic drug response by the situational stimuli, independent of dopaminergic mechanisms, may, therefore, contribute to the untoward overstimulation clinical effects of L-dopa through summation of conditioned and drug-induced effects. Furthermore, the use of conditioning procedures to elicit movement in akinetic animals may provide a new research methodology to investigate the phenomenon of paradoxical kinesia.