| 1. |
- Guillaumin, Adriane, et al.
(författare)
-
Anatomical-functional analysis of the spatially restricted Transient receptor vanilloid-1 (Trpv1)-positive domain within the medial hypothalamic-mesencephalic area
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The distribution pattern and functional role of brain neurons expressing the Transient receptor vanilloid-1 (Trpv1) gene, which in the sensory nervous system regulates body temperature, heat and pain, have remained obscure. Two studies using both in situ hybridization to detect endogenous Trpv1 mRNA and a floxed reporter allel in Trpv1-Cre mice, have detected sparse expression in the caudal aspect of the hypothalamus and the ventral tegmental area of the midbrain. This area has during recent years been associated with aversion processing via glutamatergic neurons expressing the Vesicular glutamate transporter 2 (Vglut2) gene. Glutamatergic neurons of this area thus seem to be selectively correlated with aversion, while dopaminergic neurons in the ventral midbrain have long been associated with reward processing. A previous study from our laboratory found that the Trpv1-positive neuronal population consisted of both glutamatergic and dopaminergic neurons. It was therefore of particular interest to study this population further. Would this small but distinct hypothalamic-mesencephalic neuronal group of neurons regulate any specific type of behaviour if selectively activated? The results presented show that Trpv1 mRNA is primarily detected at the perinatal stage forming a band of neurons stretching from the posterior hypothalamus through to, and including, the ventral tegmental area. In the mature mouse, application of optogenetic constructs to the Trpv1-Cre-positive population enabled the analysis of both projection pattern and behavioural role of the Trpv1 neurons. These rare neurons, forming a hypothalamic-mesenecphalic continuum, project to several areas of the limbic system including the hippocampus, septum, nucleus accumbens and the preoptic area. When optogenetically activated, Trpv1-Cre mice show normal movements in the open field test, but display progressive avoidance behaviour in an optogenetic real-time place preference test. The results identify a new neuronal population tentatively involved in the complex network of aversive behaviour.
|
|
| 2. |
- Guillaumin, Adriane, et al.
(författare)
-
Experimental investigation into the role of the subthalamic nucleus (STN) in motor control using optogenetics in mice
- 2021
-
Ingår i: Brain Research. - : Elsevier. - 0006-8993 .- 1872-6240. ; 1755
-
Tidskriftsartikel (refereegranskat)abstract
- The subthalamic nucleus (STN) is critical for the execution of intended movements. Loss of its normal function is strongly associated with several movement disorders, including Parkinson's disease for which the STN is an important target area in deep brain stimulation (DBS) therapy. Classical basal ganglia models postulate that two parallel pathways, the direct and indirect pathways, exert opposing control over movement, with the STN acting within the indirect pathway. The STN is regulated by both inhibitory and excitatory input, and is itself excitatory. While most functional knowledge of this clinically relevant brain structure has been gained from pathological conditions and models, primarily parkinsonian, experimental evidence for its role in normal motor control has remained more sparse. The objective here was to tease out the selective impact of the STN on several motor parameters required to achieve intended movement, including locomotion, balance and motor coordination. Optogenetic excitation and inhibition using both bilateral and unilateral stimulations of the STN were implemented in freely-moving mice. The results demonstrate that selective optogenetic inhibition of the STN enhances locomotion while its excitation reduces locomotion. These findings lend experimental support to basal ganglia models of the STN in terms of locomotion. In addition, optogenetic excitation in freely-exploring mice induced self-grooming, disturbed gait and a jumping/escaping behavior, while causing reduced motor coordination in advanced motor tasks, independent of grooming and jumping. This study contributes experimentally validated evidence for a regulatory role of the STN in several aspects of motor control.
|
|
| 3. |
- Guillaumin, Adriane, et al.
(författare)
-
Improving well-being and survival in the 6-OHDA lesion model of Parkinson´s disease in mice : Literature review and step-by-step protocol
- 2022
-
Ingår i: Scandinavian Journal of Laboratory Animal Science. - : Scandinavian Society for Laboratory Animal Science. - 0901-3393. ; 48:1, s. 1-21
-
Forskningsöversikt (refereegranskat)abstract
- Parkinson's disease (PD) is the most common neurodegenerative motor disorder and primarily affects movement control but also a range of non-motor functions. With unknown etiology and lack of cure, much research is dedicated to unravel pathological mechanisms and improve clinical prospects for symptom alleviation, prevention and treatment. To achieve these goals, animal models intended to represent symptoms similar to those observed in the complex clinical display of PD play a key role. It is important to bear in mind that, in any studies with laboratory animals, it is crucial to take the 3Rs principle (Refine, Reduce, Replace) into account. The main pathology of PD includes degeneration of dopamine neurons in the substantia nigra pars compacta (SNc). The 6-hydroxydopamine (6-OHDA) lesion model, in which dopaminergic neurons are chemically destroyed, is often favored as a laboratory model of PD in both rodents and primates. However, while reproducing several features of clinical PD, mice exposed to 6-OHDA frequently experience systemic dysfunction causing premature death. To avoid suffering and unnecessary deaths of laboratory mice, there is a need for improved experimental protocols in accordance with the 3Rs principle. Based on current literature and our own previous experiments, we decided to test the effect of three parameters: 1) reduced dose of the 6-OHDA toxin; 2) daily post-operative care to avoid hypothermia and energy loss; 3) shortened interval from surgical injection of toxin to time of sacrifice. By implementing a 6-OHDA lesion protocol using a lower dose of toxin than commonly seen in the literature alongside careful post-operative care and decreased time post-injection, a fully recovered weight post-surgery and high survival rate was obtained. This was achieved despite full expression of the 6-OHDA-induced locomotor phenotype. A step-by-step protocol was formulated. Validation using histological analysis confirmed toxin-induced degeneration of midbrain dopamine neurons with concomitant loss of dopaminergic projections in the lesioned hemisphere. Notably, while SNc dopamine neurons were drastically reduced, those located in the ventral tegmental area (VTA) were less affected in a medialhigh survival to laterallow survival manner. The Refine and Reduce parameters of the 3Rs principle in experimental animal welfare were specifically addressed which allowed us to improve well-being and survival of mice while maintaining characteristic parkinsonian features in the 6-OHDA lesion model. A table summarizing current literature on the 6-OHDA model in rodents and our validated step-by-step experimental protocol are provided.
|
|
| 4. |
- Guillaumin, Adriane, et al.
(författare)
-
Optimization protocol for the 6-OHDA model of Parkinson´s disease in wildtype mice
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Parkinson’s disease is a severe progressive neurodegenerative disease which usually appears in patients above 60 years old. The main motor symptoms are bradykinesia, akinesia, rigidity and tremor. The cause of the disease is still unknown but the consequence is a degeneration of the dopaminergic neurons of the substantia nigra pars compacta (SNc). Current treatments for PD focus on replacing the loss of dopamine or to stimulate at high frequency the subthalamic nucleus. In order to improve treatments for PD, researchers use parkinsonian animal models. Among those, the neurotoxin-based models are commonly used, in particular the 6-hydroxydopamine (6-OHDA) model. The 6-OHDA is a neurotoxin which, when injected intracerebrally, selectively destroys catecholaminergic neurons. The 6-OHDA model reproduces several features of PD including motor impairments and loss of tyrosine hydroxylase (TH) in dopaminergic neurons of the SNc and partially in dopaminergic neurons of the ventral tegmental area (VTA). In this study we optimized the 6-OHDA model in mice to increase the survival rate and well-being of the mice while inducing parkinsonian symptoms.
|
|
| 5. |
- Guillaumin, Adriane, 1991-, et al.
(författare)
-
Optogenetic investigation into the role of the subthalamic nucleus in motor control
- 2024
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The subthalamic nucleus is important achieve intended movements. Loss of its normal function is strongly associated with several movement disorders. Classical basal ganglia models postulate that two parallel pathways, the direct and indirect pathways, exert opposing control over movement, with the subthalamic nucleus part of the indirect pathway through which competing motor programs are prevented. The subthalamic nucleus is regulated by both inhibitory and excitatory projections but experimental evidence for its role in motor control has remained sparse. The objective here was to tease out the selective impact of the subthalamic nucleus on several motor parameters required to achieve intended movement, including locomotion, balance and motor coordination. Optogenetic excitation and inhibition using both bilateral and unilateral stimulations of the subthalamic nucleus were implemented in freely-moving mice. The results demonstrate that selective optogenetic inhibition of the subthalamic nucleus enhances locomotion while its excitation reduces locomotion. These findings lend experimental support to basal ganglia models in terms of locomotion. However, further analysis of subthalamic nucleus excitation revealed grooming and disturbed gait. Selective excitation also caused reduced motor coordination, independent of grooming, in advanced motor tasks. This study contributes experimental evidence for a regulatory role of the subthalamic nucleus in motor control.
|
|
| 6. |
- Guillaumin, Adriane
(författare)
-
The subthalamic nucleus in motor and affective functions : An optogenetic in vivo-investigation
- 2020
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The basal ganglia form a group of subcortical interconnected nuclei involved in motor, limbic and cognitive functions. According to the classical model of the basal ganglia, two main pathways exert opposing control over movement, one facilitating movement and the other suppressing movement. The subthalamic nucleus (STN) plays a critical role in this function, and has also been implicated in reward processing. Despite ample knowledge of the role of the STN in motor dysfunctions in relation to Parkinson’s disease, less is known about STN’s natural role in healthy subjects.The studies described in this thesis aimed to address the functional role of the STN in its natural neurocircuitry by using a transgenic mouse line which expresses Cre recombinase under the Pitx2 promoter. The Pitx2 gene is restricted to the STN and the use of Pitx2-Cre mice thereby allows selective manipulation of STN neurons by using optogenetics. By expressing Channelrhodopsin (ChR2) or Archaerhodopsin (Arch) in Pitx2-Cre neurons, we could optogenetically excite or inhibit STN Pitx2-Cre neurons and investigate the role of the STN in motor and affective functions. We showed that optogenetic inhibition and excitation of the STN induce opposite effects on motor activity. STN excitation reduced locomotion while STN inhibition enhanced locomotion, thereby providing experimental evidence to classical motor models postulating this role. We also showed that optogenetic excitation of the STN induces potent place avoidance, a behaviour relevant to aversion. Projections from the STN to the ventral pallidum (VP) exist that when excited induced the same behaviour. The VP projects to the lateral habenula (LHb), a structure known for its role in aversion. A glutamatergic multi-synaptic connection between the STN and the LHb was confirmed.Aversive behaviour is also mediated by the hypothalamic-mesencephalic area. The Trpv1 gene is expressed within the posterior hypothalamus. By applying optogenetics in a Trpv1-Cre mouse line, projection patterns to limbic brain areas were identified, and optogenetic excitation of Trpv1-Cre neurons was found to induce place avoidance.The STN and posterior hypothalamus are thereby demonstrated as new players in the aversion neurocircuitry, while the long-assumed role of the STN in motor behaviour is confirmed. To enable future analyses of how STN manipulation might rescue motor and affective deficiency relevant to human disorders, a neuronal degeneration mouse model was generated.To conclude, the results presented in this thesis contribute to enhanced neurobiological understanding of the role played by the STN in motor and affective functions.
|
|
| 7. |
- Serra, Gian Pietro, et al.
(författare)
-
A role for the subthalamic nucleus in aversive learning
- 2023
-
Ingår i: Cell Reports. - : Elsevier. - 2211-1247. ; 42:11
-
Tidskriftsartikel (refereegranskat)abstract
- The subthalamic nucleus (STN) is critical for behavioral control; its dysregulation consequently correlated with neurological and neuropsychiatric disorders, including Parkinson's disease. Deep brain stimulation (DBS) targeting the STN successfully alleviates parkinsonian motor symptoms. However, low mood and depression are affective side effects. STN is adjoined with para-STN, associated with appetitive and aversive behavior. DBS aimed at STN might unintentionally modulate para-STN, causing aversion. Alternatively, the STN mediates aversion. To investigate causality between STN and aversion, affective behavior is addressed using optogenetics in mice. Selective promoters allow dissociation of STN (e.g., Pitx2) vs. para-STN (Tac1). Acute photostimulation results in aversion via both STN and para-STN. However, only STN stimulation-paired cues cause conditioned avoidance and only STN stimulation interrupts on-going sugar self-administration. Electrophysiological recordings identify post-synaptic responses in pallidal neurons, and selective photostimulation of STN terminals in the ventral pallidum replicates STN-induced aversion. Identifying STN as a source of aversive learning contributes neurobiological underpinnings to emotional affect.
|
|
| 8. |
- Serra, Gian Pietro, et al.
(författare)
-
Aversion encoded in the subthalamic nucleus
- 2024
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Activation of the subthalamic nucleus (STN) is associated with the stopping of ongoing behavior via the basal ganglia. However, we recently observed that optogenetic STN excitation induced a strong jumping/escaping behavior. We hypothesized that STN activation is aversive. To test this, place preference was assessed. Optogenetic excitation of the STN caused potent place aversion. Causality between STN activation and aversion has not been demonstrated previously. The lateral habenula (LHb) is a critical hub for aversion. Optogenetic stimulation of the STN indeed caused firing of LHb neurons, but with delay, suggesting the involvement of a polysynaptic circuit. To unravel a putative pathway, the ventral pallidum (VP) was investigated. VP receives projections from the STN and in turn projects to the LHb. Optogenetic excitation of STN-VP terminals caused firing of VP neurons and induced aversive behavior. This study identifies the STN as critical hub for aversion, potentially mediated via an STN-VP-LHb pathway.
|
|
| 9. |
- Serra, Gian Pietro, et al.
(författare)
-
Midbrain Dopamine Neurons Defined by TrpV1 Modulate Psychomotor Behavior
- 2021
-
Ingår i: Frontiers in Neural Circuits. - : Frontiers Media S.A.. - 1662-5110. ; 15
-
Tidskriftsartikel (refereegranskat)abstract
- Dopamine (DA) neurons of the ventral tegmental area (VTA) continue to gain attention as far more heterogeneous than previously realized. Within the medial aspect of the VTA, the unexpected presence of TrpV1 mRNA has been identified. TrpV1 encodes the Transient Receptor Potential cation channel subfamily V member 1, TRPV1, also known as the capsaicin receptor, well recognized for its role in heat and pain processing by peripheral neurons. In contrast, the brain distribution of TrpV1 has been debated. Here, we hypothesized that the TrpV1+ identity defines a distinct subpopulation of VTA DA neurons. To explore these brain TrpV1+ neurons, histological analyses and Cre-driven mouse genetics were employed. TrpV1 mRNA was most strongly detected at the perinatal stage forming a band of scattered neurons throughout the medial VTA, reaching into the posterior hypothalamus. Within the VTA, the majority of TrpV1 co-localized with both Tyrosine hydroxylase (Th) and Vesicular monoamine transporter 2 (Vmat2), confirming a DA phenotype. However, TrpV1 also co-localized substantially with Vesicular glutamate transporter 2 (Vglut2), representing the capacity for glutamate (GLU) release. These TrpV1+/Th+/Vglut2+/Vmat2+ neurons thus constitute a molecularly and anatomically distinct subpopulation of DA-GLU co-releasing neurons. To assess behavioral impact, a TrpV1Cre-driven strategy targeting the Vmat2 gene in mice was implemented. This manipulation was sufficient to alter psychomotor behavior induced by amphetamine. The acute effect of the drug was accentuated above control levels, suggesting super-sensitivity in the drug-na ve state resembling a “pre-sensitized” phenotype. However, no progressive increase with repeated injections was observed. This study identifies a distinct TrpV1+ VTA subpopulation as a critical modulatory component in responsiveness to amphetamine. Moreover, expression of the gene encoding TRPV1 in selected VTA neurons opens up for new possibilities in pharmacological intervention of this heterogeneous, but clinically important, brain area.
|
|
