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Although Parkinson's disease (PD) is characterized primarily by loss of nigrostriatal dopaminergic neurons, there is a concomitant loss of norepinephrine (NE) neurons in the locus coeruleus. Dopaminergic lesions induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) are commonly used to model PD, and although MPTP effectively mimics the dopaminergic neuropathology of PD in mice, it fails to produce PD-like motor deficits. We hypothesized that MPTP is unable to recapitulate the motor abnormalities of PD either because the behavioral paradigms used to measure coordinated behavior in mice are not sensitive enough or because MPTP in the absence of NE loss is insufficient to impair motor control. We tested both possibilities by developing a battery of coordinated movement tests and examining motor deficits in dopamine ␤-hydroxylase knockout (Dbh؊/؊) mice that lack NE altogether. We detected no motor abnormalities in MPTP-treated control mice, despite an 80% loss of striatal dopamine (DA) terminals. Dbh؊/؊ mice, on the other hand, were impaired in most tests and also displayed spontaneous dyskinesias, despite their normal striatal DA content. A subset of these impairments was recapitulated in control mice with 80% NE lesions and reversed in Dbh؊/؊ mice, either by restoration of NE or treatment with a DA agonist. MPTP did not exacerbate baseline motor deficits in Dbh؊/؊ mice. Finally, striatal levels of phospho-ERK-1/2 and ⌬FosB/FosB, proteins which are associated with PD and dyskinesias, were elevated in Dbh؊/؊ mice. These results suggest that loss of locus coeruleus neurons contributes to motor dysfunction in PD.dopamine ͉ Parkinson's disease ͉ dyskinesias ͉ dopamine ␤-hydroxylase P arkinson's disease (PD) affects Ϸ1% of the world's aging population (1). Despite this high prevalence and intensive research into its origins, the etiology of PD remains largely unknown. The disease is characterized by degeneration of dopamine (DA) neurons in the substantia nigra pars compacta (SN), and symptoms, which tend to manifest when Ϸ80% of striatal DA is lost, include bradykinesia, postural instability, rigidity, and resting tremor. 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), a neurotoxin, is known to produce parkinsonism in humans and causes severe DA loss in animals (2). Because of its ability to recapitulate the neuropathology of PD, MPTP is used widely in PD research. However, MPTP has been unable to reliably reproduce the motor symptoms of PD in mice, which limits the utility of MPTP-treated mice as an animal model of the disease (3). Differences in mouse strain and experimental paradigms may at least partially account for these inconsistencies.Despite the focus on DA, PD is more accurately described as a multisystem disorder that features a profound albeit underappreciated loss of locus coeruleus (LC) neurons, as well as variable damage to other brain regions (4-6). Postmortem studies indicate that neuronal degeneration in the LC is comparable to that in the substantia nigra pars compacta, and that it may a...

The basal ganglia are comprised of the striatum, the external and internal segment of the globus pallidus (GPe and GPi, respectively), the subthalamic nucleus (STN), and the substantia nigra pars compacta and reticulata (SNc and SNr, respectively). Dopamine has long been identified as an important modulator of basal ganglia function in the striatum, and disturbances of striatal dopaminergic transmission have been implicated in diseases such as Parkinson's disease (PD), addiction and attention deficit hyperactivity disorder. However, recent evidence suggests that dopamine may also modulate basal ganglia function at sites outside of the striatum, and that changes in dopaminergic transmission at these sites may contribute to the symptoms of PD and other neuropsychiatric disorders. This review summarizes the current knowledge of the anatomy, functional effects and behavioral consequences of the dopaminergic innervation to the GPe, GPi, STN, and SNr. Further insights into the dopaminergic modulation of basal ganglia function at extrastriatal sites may provide us with opportunities to develop new and more specific strategies for treating disorders of basal ganglia dysfunction.

Background Degeneration of the locus ceruleus (LC), the major noradrenergic nucleus in the brain, occurs early and is ubiquitous in Alzheimer’s disease. Experimental lesions to the LC exacerbate AD-like neuropathology and cognitive deficits in several transgenic mouse models of AD. Because the LC contains multiple neuromodulators known to affect Aβ toxicity and cognitive function, the specific role of noradrenaline (NA) in AD is not well understood. Methods To determine the consequences of selective NA deficiency in an AD mouse model, we crossed dopamine β-hydroxylase (DBH) knock-out mice with APP/PS1 mice, overexpressing mutant amyloid precursor protein and presenilin-1. DBH (−/−) mice are unable to synthesize NA but otherwise have normal LC neurons and co-transmitters. Spatial memory, hippocampal long-term potentiation (LTP), and synaptic protein levels were assessed. Results The modest impairments in spatial memory and hippocampal LTP displayed by young APP/PS1 or DBH(−/−) single mutant mice were augmented in DBH(−/−)/APP/PS1 double mutant mice. Deficits were associated with reduced levels of total Ca2+/calmodulin-dependent protein kinases II (CaMKII) and N-Methyl-D-aspartate receptor 2A (NR2A), increased N-Methyl-D-aspartate receptor 2B (NR2B) levels and were independent of Aβ accumulation. Spatial memory performance was partly improved by treatment with the NA precursor drug L-threo-DOPS. Conclusions These results indicate that early LC degeneration and subsequent NA deficiency in AD may contribute to cognitive deficits via altered levels of CaMKII and N-Methyl-D-aspartate receptors, and suggest that NA supplementation could be beneficial in early AD.

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Slow-onset adaptive changes that arise from sustained antidepressant treatment, such as enhanced adult hippocampal neurogenesis and increased trophic factor expression, play a key role in the behavioral effects of antidepressants. ␣ 2 -Adrenoceptors contribute to the modulation of mood and are potential targets for the development of faster acting antidepressants. We investigated the influence of ␣ 2 -adrenoceptors on adult hippocampal neurogenesis. Our results indicate that ␣ 2 -adrenoceptor agonists, clonidine and guanabenz, decrease adult hippocampal neurogenesis through a selective effect on the proliferation, but not the survival or differentiation, of progenitors. These effects persist in dopamine ␤-hydroxylase knock-out (Dbh Ϫ/Ϫ ) mice lacking norepinephrine, supporting a role for ␣ 2 -heteroceptors on progenitor cells, rather than ␣ 2 -autoreceptors on noradrenergic neurons that inhibit norepinephrine release. Adult hippocampal progenitors in vitro express all the ␣ 2 -adrenoceptor subtypes, and decreased neurosphere frequency and BrdU incorporation indicate direct effects of ␣ 2 -adrenoceptor stimulation on progenitors. Furthermore, coadministration of the ␣ 2 -adrenoceptor antagonist yohimbine with the antidepressant imipramine significantly accelerates effects on hippocampal progenitor proliferation, the morphological maturation of newborn neurons, and the increase in expression of brain derived neurotrophic factor and vascular endothelial growth factor implicated in the neurogenic and behavioral effects of antidepressants. Finally, short-duration (7 d) yohimbine and imipramine treatment results in robust behavioral responses in the novelty suppressed feeding test, which normally requires 3 weeks of treatment with classical antidepressants. Our results demonstrate that ␣ 2 -adrenoceptors, expressed by progenitor cells, decrease adult hippocampal neurogenesis, while their blockade speeds up antidepressant action, highlighting their importance as targets for faster acting antidepressants.

ObjectivesWe aimed to identify existing outcome measures for functional neurological disorder (FND), to inform the development of recommendations and to guide future research on FND outcomes.MethodsA systematic review was conducted to identify existing FND-specific outcome measures and the most common measurement domains and measures in previous treatment studies. Searches of Embase, MEDLINE and PsycINFO were conducted between January 1965 and June 2019. The findings were discussed during two international meetings of the FND-Core Outcome Measures group.ResultsFive FND-specific measures were identified—three clinician-rated and two patient-rated—but their measurement properties have not been rigorously evaluated. No single measure was identified for use across the range of FND symptoms in adults. Across randomised controlled trials (k=40) and observational treatment studies (k=40), outcome measures most often assessed core FND symptom change. Other domains measured commonly were additional physical and psychological symptoms, life impact (ie, quality of life, disability and general functioning) and health economics/cost–utility (eg, healthcare resource use and quality-adjusted life years).ConclusionsThere are few well-validated FND-specific outcome measures. Thus, at present, we recommend that existing outcome measures, known to be reliable, valid and responsive in FND or closely related populations, are used to capture key outcome domains. Increased consistency in outcome measurement will facilitate comparison of treatment effects across FND symptom types and treatment modalities. Future work needs to more rigorously validate outcome measures used in this population.

The noradrenergic neurons of the locus coeruleus (LC) are damaged in Parkinson's disease (PD). Neurotoxin ablation of the LC noradrenergic neurons has been shown to exacerbate the dopaminergic toxicity of MPTP, suggesting that the noradrenergic system protects dopamine neurons. We utilized mice that exhibit elevated synaptic noradrenaline (NA) by genetically deleting the noradrenaline transporter (NET), a key regulator of the noradrenergic system (NET KO mice). NET KO and wild-type littermates were administered MPTP and striatal dopamine terminal integrity was assessed by HPLC of monoamines, immmunoblotting for dopaminergic markers and tyrosine hydroxylase (TH) immunohistochemistry. MPTP significantly reduced striatal dopamine in wild-type mice, but not in the NET KO mice. To confirm that the protection observed in the NET KO mice was due to the lack of NET, we treated wild-type mice with the specific NET inhibitor, nisoxetine, and then challenged them with MPTP. Nisoxetine conferred protection to the dopaminergic system. These data indicate that NA can modulate MPTP toxicity and suggest that manipulation of the noradrenergic system may have therapeutic value in PD.