Deep brain stimulation of the inferior colliculus: A possible animal model to study paradoxical kinesia observed in some parkinsonian patients?

Sound elicits stereotyped facial movements that provide a sensitive index of hearing abilities in mice

Sound elicits rapid movements of muscles in the face, ears, and eyes that protect the body from injury and trigger brain-wide internal state changes. Here, we performed quantitative facial videography from mice resting atop a piezoelectric force plate and observed that broadband sounds elicited rapid and stereotyped facial twitches. Facial motion energy (FME) adjacent to the whisker array was 30 dB more sensitive than the acoustic startle reflex and offered greater inter-trial and inter-animal reliability than sound-evoked pupil dilations or movement of other facial and body regions. FME tracked the low-frequency envelope of broadband sounds, providing a means to study behavioral discrimination of complex auditory stimuli, such as speech phonemes in noise. Approximately 25% of layer 5-6 units in the auditory cortex (ACtx) exhibited firing rate changes during facial movements. However, FME facilitation during ACtx photoinhibition indicated that sound-evoked facial movements were mediated by a midbrain pathway and modulated by descending corticofugal input. FME and auditory brainstem response (ABR) thresholds were closely aligned after noise-induced sensorineural hearing loss, yet FME growth slopes were disproportionately steep at spared frequencies, reflecting a central plasticity that matched commensurate changes in ABR wave 4. Sound-evoked facial movements were also hypersensitive in Ptchd1 knockout mice, highlighting the use of FME for identifying sensory hyper-reactivity phenotypes after adult-onset hyperacusis and inherited deficiencies in autism risk genes. These findings present a sensitive and integrative measure of hearing while also highlighting that even low-intensity broadband sounds can elicit a complex mixture of auditory, motor, and reafferent somatosensory neural activity.

Paradoxical kinesia may no longer be a paradox waiting for 100 years to be unraveled

Parkinson's disease (PD) is a progressive neurodegenerative disorder mainly characterized by bradykinesia and akinesia. Interestingly, these motor disabilities can depend on the patient emotional state. Disabled PD patients remain able to produce normal motor responses in the context of urgent or externally driven situations or even when exposed to appetitive cues such as music. To describe this phenomenon Souques coined the term "paradoxical kinesia" a century ago. Since then, the mechanisms underlying paradoxical kinesia are still unknown due to a paucity of valid animal models that replicate this phenomenon. To overcome this limitation, we established two animal models of paradoxical kinesia. Using these models, we investigated the neural mechanisms of paradoxical kinesia, with the results pointing to the inferior colliculus (IC) as a key structure. Intracollicular electrical deep brain stimulation, glutamatergic and GABAergic mechanisms may be involved in the elaboration of paradoxical kinesia. Since paradoxical kinesia might work by activation of some alternative pathway bypassing basal ganglia, we suggest the IC as a candidate to be part of this pathway.

Processing of auditory information in forebrain regions after hearing loss in adulthood: Behavioral and electrophysiological studies in a rat model

Background

Hearing loss was proposed as a factor affecting development of cognitive impairment in elderly. Deficits cannot be explained primarily by dysfunctional neuronal networks within the central auditory system. We here tested the impact of hearing loss in adult rats on motor, social, and cognitive function. Furthermore, potential changes in the neuronal activity in the medial prefrontal cortex (mPFC) and the inferior colliculus (IC) were evaluated.

Materials and methods

In adult male Sprague Dawley rats hearing loss was induced under general anesthesia with intracochlear injection of neomycin. Sham-operated and naive rats served as controls. Postsurgical acoustically evoked auditory brainstem response (ABR)-measurements verified hearing loss after intracochlear neomycin-injection, respectively, intact hearing in sham-operated and naive controls. In intervals of 8 weeks and up to 12 months after surgery rats were tested for locomotor activity (open field) and coordination (Rotarod), for social interaction and preference, and for learning and memory (4-arms baited 8-arms radial maze test). In a final setting, electrophysiological recordings were performed in the mPFC and the IC.

Results

Locomotor activity did not differ between deaf and control rats, whereas motor coordination on the Rotarod was disturbed in deaf rats (P < 0.05). Learning the concept of the radial maze test was initially disturbed in deaf rats (P < 0.05), whereas retesting every 8 weeks did not show long-term memory deficits. Social interaction and preference was also not affected by hearing loss. Final electrophysiological recordings in anesthetized rats revealed reduced firing rates, enhanced irregular firing, and reduced oscillatory theta band activity (4–8 Hz) in the mPFC of deaf rats as compared to controls (P < 0.05). In the IC, reduced oscillatory theta (4–8 Hz) and gamma (30–100 Hz) band activity was found in deaf rats (P < 0.05).

Conclusion

Minor and transient behavioral deficits do not confirm direct impact of long-term hearing loss on cognitive function in rats. However, the altered neuronal activities in the mPFC and IC after hearing loss indicate effects on neuronal networks in and outside the central auditory system with potential consequences on cognitive function.

The Arousal-motor Hypothesis of Dopamine Function: Evidence that Dopamine Facilitates Reward Seeking in Part by Maintaining Arousal

Dopamine facilitates approach to reward via its actions on dopamine receptors in the nucleus accumbens. For example, blocking either D1 or D2 dopamine receptors in the accumbens reduces the proportion of reward-predictive cues to which rats respond with cued approach. Recent evidence indicates that accumbens dopamine also promotes wakefulness and arousal, but the relationship between dopamine's roles in arousal and reward seeking remains unexplored. Here, we show that the ability of systemic or intra-accumbens injections of the D1 antagonist SCH23390 to reduce cued approach to reward depends on the animal's state of arousal. Handling the animal, a manipulation known to increase arousal, was sufficient to reverse the behavioral effects of the antagonist. In addition, SCH23390 reduced spontaneous locomotion and increased time spent in sleep postures, both consistent with reduced arousal, but also increased time spent immobile in postures inconsistent with sleep. In contrast, the ability of the D2 antagonist haloperidol to reduce cued approach was not reversible by handling. Haloperidol reduced spontaneous locomotion but did not increase sleep postures, instead increasing immobility in non-sleep postures. We place these results in the context of the extensive literature on dopamine's contributions to behavior, and propose the arousal-motor hypothesis. This novel synthesis, which proposes that two main functions of dopamine are to promote arousal and facilitate motor behavior, accounts both for our findings and many previous behavioral observations that have led to disparate and conflicting conclusions.

Lateralization in hemi-parkinsonian rats is affected by deep brain stimulation or glutamatergic neurotransmission in the inferior colliculus

After unilateral lesion of the medial forebrain bundle (MFB) by 6-OHDA rats exhibit lateralized deficits in spontaneous behavior or apomorphine-induced rotations. We investigated whether such lateralization is attenuated by either deep brain stimulation (DBS) or glutamatergic neurotransmission in the inferior colliculus (IC) of Wistar rats. Intracollicular DBS did not affect spontaneous lateralization but attenuated apomorphine-induced rotations. Spontaneous lateralization disappeared after both glutamatergic antagonist MK-801 or the agonist NMDA microinjected in the IC. Apomorphine-induced rotations were potentiated by MK-801 but were not affected by NMDA intracollicular microinjection. After injecting a bidirectional neural tract tracer into the IC, cell bodies and/or axonal fibers were found in the periaqueductal gray, superior colliculus, substantia nigra, cuneiform nucleus and pedunculo-pontine tegmental nucleus, suggesting the involvement of these structures in the motor improvement after IC manipulation. Importantly, the side of the IC microinjection regarding the lesion (ipsi- or contralateral) is particularly important and this effect may not involve the neostriatum directly.Significance StatementThe inferior colliculus, usually viewed as an auditory structure, when properly manipulated may counteract motor deficits in Parkinsonian rats. Indeed, the present study showed that 30 Hz deep brain stimulation or glutamatergic neural network in the inferior colliculus reduced body asymmetry induced by medial forebrain bundle unilateral 6-OHDA lesion in rats, an animal model of Parkinsonism. Understanding how glutamatergic mechanisms in the inferior colliculus influence motor control, classically attributed to the basal nuclei circuitry, could be useful in the development of new therapeutics to treat Parkinson's disease and other motor disorders.

Effects of Immediate Aversive Stimulation on Haloperidol-Induced Catalepsy in Rats

In animal models, the administration of the dopaminergic D2 antagonist haloperidol affects the nigrostriatal pathway, inducing catalepsy, a state of immobility similar to Parkinson’s disease (PD) bradykinesia and akinesia. In PD, the motor impairments are due to difficulties in selecting and executing motor actions, associated with dopamine loss in basal ganglia and cortical targets. Motor and affective limbic networks seem to be integrated via a striato-nigro-striatal network, therefore, it is not surprising that the motor impairments in PD can be influenced by the patient’s emotional state. Indeed, when exposed to aversive stimuli or life-threatening events, immobile patients are capable of performing sudden movements, a phenomenon known as paradoxical kinesia. Thus, the present study investigated the effects of unconditioned and conditioned aversive stimulation on haloperidol-induced catalepsy in rats. First, male Wistar rats received intraperitoneal administration of saline or haloperidol (1 or 2 mg/kg) and were evaluated in the catalepsy bar test to assess the cataleptic state induced by the different doses of haloperidol over time. Next, we evaluated the effects of two types of unconditioned aversive stimuli–100 lux light (1 and 20 s) or 0.6 mA footshock (1 s)–on the catalepsy. Finally, we evaluated the effects of light conditioned stimuli (Light-CS), previously paired with footshocks, on the cataleptic state. Catalepsy was observed following haloperidol 1 and 2 mg/kg administration. Exposure to footshocks, but not to light, significantly reduced step-down latency during the catalepsy test. Although unconditioned light did not affect catalepsy, paired Light-CS did reduce step-down latency. Here, we have provided evidence of face validity for the study of paradoxical kinesia. In addition to demonstrating that immediate exposure to an aversive stimulus is capable of disrupting the cataleptic state, our findings show that haloperidol-induced catalepsy seems to be differently influenced depending on the modality of aversive stimulation. Our data suggest that the selective recruitment of threat response systems may bypass the dysfunctional motor circuit leading to the activation of alternative routes to drive movement.

Haloperidol-induced catalepsy as an animal model for parkinsonism: A systematic review of experimental studies

Several useful animal models for parkinsonism have been developed so far. Haloperidol-induced catalepsy is often used as a rodent model for the study of motor impairments observed in Parkinson's disease and related disorders and for the screening of potential antiparkinsonian compounds. The objective of this systematic review is to identify publications that used the haloperidol-induced catalepsy model for parkinsonism and to explore the methodological characteristics and the main questions addressed in these studies. A careful systematic search of the literature was carried out by accessing articles in three different databases: Web of Science, PubMed and SCOPUS. The selection and inclusion of studies were performed based on the abstract and, subsequently, on full-text analysis. Data extraction included the objective of the study, study design and outcome of interest. Two hundred and fifty-five articles were included in the review. Publication years ranged from 1981 to 2020. Most studies used the model to explore the effects of potential treatments for parkinsonism. Although the methodological characteristics used are quite varied, most studies used Wistar rats as experimental subjects. The most frequent dose of haloperidol used was 1.0 mg/kg, and the horizontal bar test was the most used to assess catalepsy. The data presented here provide a framework for an evidence-based approach to the design of preclinical research on parkinsonism using the haloperidol-induced catalepsy model. This model has been used routinely and successfully and is likely to continue to play a critical role in the ongoing search for the next generation of therapeutic interventions for parkinsonism.

Low frequency deep brain stimulation in the inferior colliculus ameliorates haloperidol-induced catalepsy and reduces anxiety in rats

Deep brain stimulation (DBS) of the colliculus inferior (IC) improves haloperidol-induced catalepsy and induces paradoxal kinesia in rats. Since the IC is part of the brain aversive system, DBS of this structure has long been related to aversive behavior in rats limiting its clinical use. This study aimed to improve intracollicular DBS parameters in order to avoid anxiogenic side effects while preserving motor improvements in rats. Catalepsy was induced by systemic haloperidol (0.5mg/kg) and after 60 min the bar test was performed during which a given rat received continuous (5 min, with or without pre-stimulation) or intermittent (5 x 1 min) DBS (30Hz, 200–600μA, pulse width 100μs). Only continuous DBS with pre-stimulation reduced catalepsy time. The rats were also submitted to the elevated plus maze (EPM) test and received either continuous stimulation with or without pre-stimulation, or sham treatment. Only rats receiving continuous DBS with pre-stimulation increased the time spent and the number of entries into the open arms of the EPM suggesting an anxiolytic effect. The present intracollicular DBS parameters induced motor improvements without any evidence of aversive behavior, pointing to the IC as an alternative DBS target to induce paradoxical kinesia improving motor deficits in parkinsonian patients.

Playback of 50-kHz ultrasonic vocalizations overcomes psychomotor deficits induced by sub-chronic haloperidol treatment in rats

RATIONALE

In rodents, acute haloperidol treatment induces psychomotor impairments known as catalepsy, which models akinesia in humans and is characterized as an animal model of acute Parkinsonism, whereas sub-chronic haloperidol reduces exploratory behavior, which resembles bradykinesia. Haloperidol-induced catalepsy in rats can be ameliorated by playback of 50-kHz ultrasonic vocalizations (USV), an emotionally and motivationally relevant appetitive auditory stimulus, representing an animal model of paradoxical kinesia. In a condition like PD where patients suffer from chronic motor impairments, it is paramount to assess the long-term symptom relief in an animal model of Parkinsonism.

OBJECTIVES

We investigated whether 50-kHz USV playback ameliorates psychomotor deficits induced by haloperidol in a sub-chronic dosing regimen.

METHODS

In phase 1, distance traveled and number of rearing behavior were assessed in an activity chamber in order to investigate whether sub-chronic haloperidol treatment induced psychomotor impairments. In phase 2, we investigated whether 50-kHz USV playback could overcome these impairments by assessing exploratory behaviors and approach behavior towards the sound source in the 50-kHz USV radial maze playback paradigm.

RESULTS

Sub-chronic haloperidol treatment led to psychomotor deficits since the distance traveled and number of rearing behavior were reduced as compared to saline control group or baseline. These psychomotor impairments were ameliorated during playback of 50-kHz USV, with haloperidol treated rats showing a clear social approach behavior towards the sound source exclusively during playback.

CONCLUSIONS

This study provides evidence that 50-kHz USV playback induces paradoxical kinesia in rats exhibiting motor deficits after sub-chronic haloperidol, as we previously showed after acute haloperidol treatment.

Influence of aversive stimulation on haloperidol-induced catalepsy in rats

Catalepsy - an immobile state in which individuals fail to change imposed postures - can be induced by haloperidol. In rats, the pattern of haloperidol-induced catalepsy is very similar to that observed in Parkinson's disease (PD). As some PD symptoms seem to depend on the patient's emotional state, and as anxiety disorders are common in PD, it is possible that the central mechanisms regulating emotional and cataleptic states interplay. Previously, we showed that haloperidol impaired contextual-induced alarm calls in rats, without affecting footshock-evoked calls. Here, we evaluated the influence of distinct aversive stimulations on the haloperidol-induced catalepsy. First, male Wistar rats were subjected to catalepsy tests to establish a baseline state after haloperidol or saline administration. Next, distinct cohorts were exposed to open-field; elevated plus-maze; open-arm confinement; inescapable footshocks; contextual conditioned fear; or corticosterone administration. Subsequently, catalepsy tests were performed again. Haloperidol-induced catalepsy was verified in all drug-treated animals. Exposure to open-field, elevated plus-maze, open-arm confinement, footshocks, or administration of corticosterone had no significant effect on haloperidol-induced catalepsy. Contextual conditioned fear, which is supposed to promote a more intense fear, increased catalepsy over time. Our findings suggest that only specific defensive circuitries modulate the nigrostriatal system mediating the haloperidol-induced cataleptic state.

Paradoxical kinesia induced by appetitive 50-kHz ultrasonic vocalizations in rats depends on glutamatergic mechanisms in the inferior colliculus

Paradoxical kinesia is a sudden transient ability of akinetic patients to perform motor tasks they are otherwise unable to perform. This phenomenon is known to depend on the patient's emotional state and external stimuli. Paradoxical kinesia can be induced by appetitive 50-kHz ultrasonic vocalizations (USV) in rats displaying catalepsy following systemic haloperidol. We investigated the role of the inferior colliculus (IC) in paradoxical kinesia induced by 50-kHz USV, since the IC modulates haloperidol-induced catalepsy. We focused on glutamatergic and GABAergic neurotransmission, with male rats receiving intracollicular NMDA or the GABA receptor agonist diazepam 10 min before systemic haloperidol. Catalepsy time was assessed by means of the bar test, during which rats were exposed to playback of 50-kHz USV, white noise, and background noise. Our results show that playback of 50-kHz USV induced paradoxical kinesia by reducing haloperidol-induced catalepsy in rats which had received saline intracollicular microinjection. This paradoxical kinesia effect of 50-kHz USV playback on haloperidol-induced catalepsy was prevented by intracollicular NMDA administration. Although intracollicular diazepam microinjection potentiated haloperidol-induced catalepsy, it did not affect the response to 50-kHz USV playback. Together, NMDA receptor agonist suppressed the effectiveness of 50-kHz USV playback, whereas diazepam did not. These findings suggest that the IC is a key structure involved in paradoxical kinesia, with relevant processes being glutamatergic rather than GABAergic. Our approach thus appears useful for uncovering neural mechanisms of paradoxical kinesia and it might help identifying novel therapeutic targets for Parkinson's disease.

Haloperidol-induced catalepsy is ameliorated by deep brain stimulation of the inferior colliculus

Deep brain stimulation (DBS) has evolved as a promising alternative treatment for Parkinson’s disease (PD), but the underlying mechanisms remain poorly understood. Moreover, conventional DBS protocols targeted at basal ganglia sites can turn out completely ineffective for some PD patients, warranting the search for alternative targets. The inferior colliculus (IC) is a midbrain auditory relay station involved in sensorimotor processes. High-frequency 2500 Hz electrical stimulation of the IC elicits escape behaviour and interferes with haloperidol-induced catalepsy in rats, a state reminiscent of Parkinsonian akinesia, but clinical implication is limited since the protocol is aversive. However, typical DBS stimulation frequencies range between 20–180 Hz. We therefore tested the effects of a low-frequency 30 Hz-DBS protocol on haloperidol-induced catalepsy and aversive behaviour in rats. We show that low-frequency 30 Hz-DBS targeted at the IC strongly ameliorates haloperidol-induced catalepsy without any evidence of stimulation-induced escape behaviour. Furthermore, 30 Hz-DBS of the IC produced no place avoidance in a place conditioning paradigm and induced no anxiety-related behaviour on the elevated plus maze, indicating that the protocol has no aversive or anxiogenic side effects. Our findings provide first evidence that the IC can serve as an alternative, non-conventional DBS target.

Electrical stimulation or MK-801 in the inferior colliculus improve motor deficits in MPTP-treated mice

The inferior colliculus (IC) is an important midbrain relay station for the integration of descending and ascending auditory information. Additionally, the IC has been implicated in processing sensorimotor responses. Glutamatergic and GABAergic manipulations in the IC can improve motor deficits as demonstrated by the animal model of haloperidol-induced catalepsy. However, how the IC influences motor function remains unclear. We investigated the effects of either intracollicular deep brain stimulation (DBS) or microinjection of the glutamatergic antagonist MK-801 or the agonist NMDA in C57BL/6J mice chronically treated with saline or 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). After DBS or microinjections, the mice were submitted to rotarod and open field tests, respectively. DBS in the IC was effective to increase the time spent on the rotarod in MPTP-treated mice. After unilateral microinjection of MK-801, but not NMDA, MPTP-treated mice increased the distance travelled in the open field (p < 0.05). In conclusion, intracollicular DBS or MK-801 microinjection can improve motor performance in parkinsonian mice suggesting the IC as a new and non-conventional therapeutic target in motor impairment.

Awakenings in rats by ultrasounds: A new animal model for paradoxical kinesia

Paradoxical kinesia refers to a sudden transient ability of akinetic patients to perform motor tasks they are otherwise unable to perform. The mechanisms underlying this phenomenon are unknown due a paucity of valid animal models that faithfully reproduce paradoxical kinesia. Here, in a first experiment, we present a new method to study paradoxical kinesia by "awakening" cataleptic rats through presenting appetitive 50-kHz ultrasonic vocalizations (USV), which are typical for social situations with positive valence, like juvenile play or sexual encounters ("rat laughter"). Rats received systemic haloperidol to induce catalepsy, which was assessed by means of the bar test. During that test, 50-kHz USV, time- and amplitude-matched white noise (NOISE), or background noise (BACKGROUND) were played back and compared to SILENCE. Every animal was exposed to all four acoustic stimuli in random order, with four independent groups of rats being tested. Only when exposed to playback of appetitive 50-kHz USV, the otherwise akinetic rats rapidly started to move efficiently. The acoustic control stimuli, in contrast, did not release rats from catalepsy, despite eliciting the auditory pinna reflex and head movements towards the sound source. Moreover, in a second experiment, playback of aversive 22-kHz USV and relevant acoustic control stimuli did also not significantly affect catalepsy time. Together, our animal model provides a completely new approach to study mechanisms of paradoxical kinesia, which might help to improve behavioral therapies for Parkinson's disease and other disorders, where akinetic or cataleptic states occur.

CB1 cannabinoid receptor-mediated anandamide signaling mechanisms of the inferior colliculus modulate the haloperidol-induced catalepsy

The inferior colliculus (IC), a midbrain structure that processes acoustic information of aversive nature, is distinguished from other auditory nuclei in the brainstem by its connections with structures of the motor system. Previous evidence relating the IC to motor behavior shows that glutamatergic and GABAergic mechanisms in the IC exert influence on systemic haloperidol-induced catalepsy. There is substantial evidence supporting a role played by the endocannabinoid system as a modulator of the glutamatergic neurotransmission, as well as the dopaminergic activity in the basal nuclei and therefore it may be considered as a potential pharmacological target for the treatment of movement disorders. The present study evaluated if the endocannabinoid system in the IC plays a role in the elaboration of systemic haloperidol-induced catalepsy. Male Wistar rats received intracollicular microinjection of either the endogenous cannabinoid anandamide (AEA) at different concentrations (5, 50 or 100pmol/0.2μl), the CB₁ cannabinoid receptor antagonist AM251 at 50, 100 or 200pmol/0.2μl or vehicle, followed by intraperitoneal (IP) administration of either haloperidol at 0.5 or 1mg/kg or physiological saline. Systemic injection of haloperidol at both doses (0.5 or 1mg/kg, IP) produced a cataleptic state, compared to vehicle/physiological saline-treated group, lasting 30 and 50min after systemic administration of the dopaminergic receptors non-selective antagonist. The midbrain microinjection of AEA at 50pmol/0.2μl increased the latency for stepping down from the horizontal bar after systemic administration of haloperidol. Moreover, the intracollicular administration of AEA at 50pmol/0.2μl was able to increase the duration of catalepsy as compared to AEA at 100pmol/0.2-μl-treated group. Intracollicular pretreatment with AM251 at the intermediate concentration (100pmol/0.2μl) was able to decrease the duration of catalepsy after systemic administration of haloperidol. However, neither the intracollicular microinjection of AM251 at the lowest (50pmol/0.2μl) nor at the highest (200pmol/0.2μl) concentration was able to block the systemic haloperidol-induced catalepsy. Furthermore, the intracollicular administration of AM251 at 100pmol/0.2μl was able to decrease the duration of catalepsy as compared to AM251 at 50pmol/0.2μl- and AM251 at 200pmol/0.2-μl-treated group. The latency for stepping down from the horizontal bar - induced by haloperidol administration - was decreased when microinjection of AEA at 50pmol/0.2μl was preceded with blockade of CB1 receptor with AM251 (100pmol/0.2μl). Our results strengthen the involvement of CB1-signaled endocannabinoid mechanisms of the IC in the neuromodulation of catalepsy induced by systemic administration of the dopaminergic receptors non-selective antagonist haloperidol.

[Paradoxical kinesia in Parkinson's disease: theories and practical application]

This literature review addresses the phenomenon of paradoxical kinesia (PK) in patients with Parkinson's disease (PD). PK is the sudden ability of the patient wit hPD to perform movements that were previously disturbed. This ability can be caused by different internal or environmental stressors. Different theories explaining the mechanism of paradoxical kinesia were proposed. In recent years, in the context of a search for new effective methods of treatment of akinesia I PD, methods of correction of motor impairment based on the phenomenon of PK are being developed.