Sex differences in fear memory and extinction of mice with forebrain-specific disruption of the mineralocorticoid receptor.

Previous studies showed that the mineralocorticoid receptor (MR) is needed for behavioral flexibility in a fear conditioning paradigm. Female mice with forebrain-specific deletion of the MR gene (MR(CaMKCre) ) were unable to show extinction of contextual fear, and could not discriminate between cue and context fear unlike control mice. In the present study, male and female (MR(CaMKCre) ) mice and control littermates were used to study sex-specific fear conditioning, memory performance and extinction. The fear conditioning paradigm assessed both context- and cue-related fear within one experimental procedure. We observed that at the end of the conditioning all mice acquired the fear-motivated response. During the first minutes of the memory test, both male and female MR(CaMKCre) mice remembered and feared the context more than the control mice. Furthermore, female MR(CaMKCre) mice were not able to extinguish this memory even on the second day of memory testing. The female mutants also could not discriminate between cue (more freezing) and context periods (less freezing). In contrast, male MR(CaMKCre) mice and the controls showed extinction and were capable to discriminate, although the MR(CaMKCre) mice needed more time before they started extinction. These findings further support the relevance of MR for behavioral flexibility and extinction of fear-motivated behavior. In conclusion, the loss of MR in the forebrain results in large differences in emotional and cognitive behaviors between female and male mice, which suggests a role of this receptor in the female prevalence of stress- and anxiety-regulated disorders.

Stress or no stress: mineralocorticoid receptors in the forebrain regulate behavioral adaptation.

Corticosteroid effects on cognitive abilities during behavioral adaptation to stress are mediated by two types of receptors. While the glucocorticoid receptor (GR) is mainly involved in the consolidation of memory, the mineralocorticoid receptor (MR) mediates appraisal and initial responses to novelty. Recent findings in humans and mice suggest that under stress, the MR might be involved in the use of different learning strategies. Here, we used male mice lacking the MR in the forebrain (MR(CaMKCre)), which were subjected to 5-10 min acute restraint stress, followed 30 min later by training trials on the circular hole board. Mice had to locate an exit hole using extra- and intra-maze cues. We assessed performance and the use of spatial and stimulus-response strategies. Non-stressed MR(CaMKCre) mice showed delayed learning as compared to control littermates. Prior stress impaired performance in controls, but did not further deteriorate learning in MR(CaMKCre) mice. When stressed, 20-30% of both MR(CaMKCre) and control mice switched from a spatial to a stimulus-response strategy, which rescued performance in MR(CaMKCre) mice. Furthermore, MR(CaMKCre) mice showed increased GR mRNA expression in all CA areas of the hippocampus and an altered basal and stress-induced corticosterone secretion, which supports their role in the modulation of neuroendocrine activity. In conclusion, our data provide evidence for the critical role of MR in the fast formation of spatial memory. In the absence of forebrain MR spatial learning performance was under basal circumstances impaired, while after stress further deterioration of performance was rescued by switching behavior increasingly to a stimulus-response strategy.

SGLT2 Inhibition and Uric Acid Excretion in Patients with Type 2 Diabetes and Normal Kidney Function.

BACKGROUND AND OBJECTIVES: Sodium-glucose transporter 2 (SGLT2) inhibitor-induced uric acid lowering may contribute to kidney-protective effects of the drug class in people with type 2 diabetes. This study investigates mechanisms of plasma uric acid lowering by SGLT2 inhibitors in people with type 2 diabetes with a focus on urate transporter 1. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: We conducted an analysis of two randomized clinical trials. First, in the Renoprotective Effects of Dapagliflozin in Type 2 Diabetes study, 44 people with type 2 diabetes were randomized to dapagliflozin or gliclazide for 12 weeks. Plasma uric acid, fractional uric acid excretion, and hemodynamic kidney function were measured in the fasted state and during clamped euglycemia or hyperglycemia. Second, in the Uric Acid Excretion study, ten people with type 2 diabetes received 1 week of empagliflozin, urate transporter 1 blocker benzbromarone, or their combination in a crossover design, and effects on plasma uric acid, fractional uric acid excretion, and 24-hour uric acid excretion were measured. RESULTS: In the Renoprotective Effects of Dapagliflozin in Type 2 Diabetes study, compared with the fasted state (5.3±1.1 mg/dl), acute hyperinsulinemia and hyperglycemia significantly reduced plasma uric acid by 0.2±0.3 and 0.4±0.3 mg/dl (both P<0.001) while increasing fractional uric acid excretion (by 3.2%±3.1% and 8.9%±4.5%, respectively; both P<0.001). Dapagliflozin reduced plasma uric acid by 0.8±0.8 during fasting, 1.0±1.0 in hyperinsulinemic-euglycemic state, and 0.8±0.7 mg/dl during hyperglycemic conditions (P<0.001), respectively, whereas fractional uric acid excretion in 24-hour urine increased by 3.0%±2.1% (P<0.001) and 2.6%±4.5% during hyperinsulinemic-euglycemic conditions (P=0.003). Fractional uric acid excretion strongly correlated to fractional glucose excretion (r=0.35; P=0.02). In the Uric Acid Excretion study, empagliflozin and benzbromarone both significantly reduced plasma uric acid and increased fractional uric acid excretion. Effects of combination therapy did not differ from benzbromarone monotherapy. CONCLUSIONS: In conclusion, SGLT2 inhibitors induce uric acid excretion, which is strongly linked to urinary glucose excretion and is attenuated during concomitant pharmacologic blockade of urate transporter 1. CLINICAL TRIAL REGISTRY NAME AND REGISTRATION NUMBER: Renoprotective Effects of Dapagliflozin in Type 2 Diabetes (RED), NCT02682563; SGLT2 Inhibition: Uric Acid Excretion Study (UREX), NCT05210517.

Basic mechanisms of motor fluctuations.

Patients with Parkinson's disease generally have a smooth clinical response from levodopa therapy for the first 3 to 5 years. Motor fluctuations later become noticeable and may ultimately give way to unpredictable responses to treatment. Mechanisms responsible for motor fluctuations are not fully understood, but can be separated into three groups: (1) central pharmacokinetics, or delivery of dopamine from the presynaptic to the postsynaptic receptor; (2) peripheral pharmacokinetics, or delivery of levodopa from an exogenous source to the brain; and (3) pharmacodynamics, or alterations in the interactions between dopamine and the striatal receptor. Changes in central pharmacokinetics caused by diminished presynaptic dopamine storage capacity probably account for early end-of-dose "wearing-off." As patients lose further storage capacity, peripheral levodopa pharmacokinetics may play an important role in the fluctuation response from erratic gastric emptying or variables that change gut-to-blood and blood-brain barrier transport. Finally, erratic motor responses (eg, the "on-off" phenomenon) in advanced Parkinson's disease may be caused in part by alterations at the striatal dopamine receptor.

The rationale for continuous dopaminergic stimulation in patients with Parkinson's disease.

Continuous dopaminergic stimulation has been shown to stabilize motor fluctuations in patients with advanced Parkinson's disease (PD) who do not respond to more conventional forms of therapy. Levodopa infusions confer immediate benefit as a direct result of maintaining steady plasma levodopa concentrations. Fluctuations of synaptic dopamine inherent in the usual oral treatment of PD might result in deleterious postsynaptic changes. Some of these presumed receptor alterations might revert as a consequence of continuous levodopa infusion.

Levodopa-nonresponsive Lewy body parkinsonism: clinicopathologic study of two cases.

We report two patients with a primarily akinetic form of parkinsonism who were nonresponsive to treatment with levodopa. At autopsy, both patients had many Lewy bodies in brainstem and diencephalic nuclei, with sparse Lewy bodies in association cortices and more numerous Lewy bodies in the limbic cortices, consistent with the transitional form of Lewy body disease. These cases emphasize that (1) Lewy body Parkinson's disease cannot be excluded on the basis of atypical presentation or levodopa nonresponsiveness, and (2) the clinicopathologic spectrum of Lewy body disease is varied.

Autosomal dominant parkinsonism with benign course and typical Lewy-body pathology.

The few previously reported patients with familial parkinsonism and Lewy-body pathology in the substantia nigra displayed a variety of clinical and pathologic syndromes. We now describe a family with very slowly progressive Parkinson's disease (PD) that has, in most cases, responded poorly to levodopa and includes subjective visual difficult. Four personally confirmed cases--with onset at ages 35, 25, 16, and 16-have occurred in three generations, and four suspicious cases have occurred in three other generations. There has been a trend toward progressively younger age of onset. One autopsied case showed a distribution of cell loss and Lewy bodies typical of PD. The hereditary pattern is most compatible with autosomal dominance. This kindred's illness shows that a presumably single Mendelian dominant gene can cause the clinical and pathologic features of PD, and further extends the clinical spectrum of pathologically typical Lewy-body PD.

Hippocampal degeneration differentiates diffuse Lewy body disease (DLBD) from Alzheimer's disease: light and electron microscopic immunocytochemistry of CA2-3 neurites specific to DLBD.

Immunocytochemistry with antibodies to ubiquitin is currently the most sensitive method for detecting cortical Lewy bodies, which are a sine qua non for the diagnosis of diffuse Lewy body disease (DLBD), an increasingly recognized form of primary degenerative dementia. In the systematic application of ubiquitin immunocytochemistry to sections of hippocampus from control subjects and patients with a wide spectrum of neurodegenerative diseases, we noted the frequent occurrence of ubiquitin-immunoreactive neurites in the CA2-3 region in DLBD. The nature of these neurites was investigated with immunocytochemistry in DLBD, Alzheimer's disease (AD), normal elderly subjects, and Parkinson's disease (PD). Although the number of neurites varied from case to case, they were virtually always detected in DLBD but not in normal, AD, or PD brains. Double immunolabeling studies with anti-ubiquitin demonstrated a small fraction of double-stained neurites with antibodies to neurofilament or Alz-50, but no double staining with an antibody to Alzheimer neurofibrillary tangles. These results are different from those for neurites in AD, which are rarely seen in CA2-3 and which are immunoreactive with all these antibodies. Neuritic degeneration in the CA2-3 region of the hippocampus appears to be a specific histopathologic feature of DLBD.

A clinical genetic study of Parkinson's disease: evidence for dominant transmission.

We used a family history questionnaire, semi-structured interview, and personal examination of secondary cases to collect data on the prevalence of Parkinson's disease (PD) in relatives of patients seen consecutively for 1 year and assessed the proportion of secondary cases of PD as a function of pedigree completeness. Survival analysis methods were applied to estimate the lifetime risk and age-at-onset distribution of PD among first-degree relatives of probands. When we considered siblings of probands with affected parents, the cumulative risk increased significantly over siblings of probands without affected parents, suggesting significant familial aggregation in a subset of randomly ascertained families. We further analyzed 80 multicase families with two or more affected individuals. Age-adjusted segregation ratios approaching 0.5 and similar proportions of affected parents and siblings, as well as the distribution of ancestral secondary cases, were compatible with an autosomal dominant mode of inheritance with reduced penetrance in a subset of PD.

Meige syndrome in the spectrum of Lewy body disease.

We report a patient with Meige syndrome (segmental cranial dystonia) who had neuropathologic changes of Parkinson's disease on postmortem examination. Neuropathologic examination showed typical and atypical Lewy bodies in the pigmented nuclei of the brainstem (substantia nigra, locus ceruleus), the nucleus basalis of Meynert, and the nucleus ambiguus. Neurochemical analysis of postmortem brain tissue showed evidence for decreased dopamine turnover in the substantia nigra, striatum, and nucleus accumbens. We propose that some cases of Meige syndrome may be included in the spectrum of Lewy body disease.

Parkinson's disease in twins studied with 18F-dopa and positron emission tomography.

We used 18F-dopa PET to examine concordance for dysfunction of the nigrostriatal dopaminergic system in 18 co-twins of patients with Parkinson's disease (PD) and scanned one clinically concordant monozygotic (MZ) twin pair, 17 asymptomatic co-twins (10 MZ, 7 dizygotic [DZ]), and 13 twins with PD (8 MZ, 5 DZ). Mean 18F-dopa uptake of the twins with PD was significantly reduced in putamen to 38% and in caudate to 66% of normal. Mean putamen 18F-dopa uptake for the 17 asymptomatic co-twins was also significantly reduced (86% of normal), as was putamen tracer uptake for the 10 MZ (87% of normal) and seven DZ (83% of normal) asymptomatic co-twin subgroups. Four of 10 MZ and two of seven DZ asymptomatic co-twins had putamen 18F-dopa uptake reduced more than 2 SDs below the normal mean. Three of these four asymptomatic MZ co-twins had tremor on examination at the time of PET and one has now developed PD 2 years later. Our PET findings give concordances for nigral dysfunction of 45% in the MZ pairs and 29% in the DZ pairs at a 2-SD threshold, and 18% in MZ and 0% in DZ pairs at a 3-SD threshold of significance. These data suggest that the concordance for nigral pathology in PD twins may be higher than previously realized and that the presence of an isolated postural or rest tremor may be a phenotypic expression of PD.

Follow-up study of risk factors in progressive supranuclear palsy.

The cause of progressive supranuclear palsy (PSP) is not known and has been little studied. The one previous controlled epidemiologic survey, performed at our center in 1986, found small-town experience and greater educational attainment as PSP risks, but, in retrospect, these results may have been produced by ascertainment bias. Since that time, several anecdotal reports have implicated heredity and various environmental exposures in the cause of some cases of PSP. To clarify the results of the previous study and to evaluate the more recently implicated candidate factors in a controlled fashion, we mailed a validated 69-item questionnaire to 91 personally examined patients with PSP and 104 unmatched controls with other neurologic conditions for which they had been referred to our tertiary neurologic center. We were able to match 75 subjects from each group by year of birth, sex, and race and subjected them to a separate matched-pair analysis. We allowed surrogates to supply any or all of the responses. Questions concerned hydrocarbon, pesticide, and herbicide exposure; urban/rural living; auto repair and other occupations; head trauma; educational attainment; maternal age; and family history of PSP, parkinsonism, dementia, and other neurologic conditions. A statistically significant finding was that patients with PSP were less likely to have completed at least 12 years of school (matched odds ratio = 0.35, 95% CI = 0.12-0.95, p = 0.022; unmatched odds ratio = 0.44, 95% CI = 0.21-0.89, p = 0.020). We hypothesize that this result may be a proxy for poor early-life nutrition or for occupational or residential exposure to an as-yet unsuspected toxin. Future studies should examine these potential risk factors in PSP.

Genome-wide scan for Parkinson's disease: the GenePD Study.

A genome-wide scan for idiopathic PD in a sample of 113 PD-affected sibling pairs is reported. Suggestive evidence for linkage was found for chromosomes 1 (214 cM, lod = 1.20), 9 (136 cM, lod = 1.30), 10 (88 cM, lod = 1.07), and 16 (114 cM, lod = 0.93). The chromosome 9 region overlaps the genes for dopamine beta-hydroxylase and torsion dystonia. Although no strong evidence for linkage was found for any locus, these results may be of value in comparison with similar studies by others.

Epidemiologic study of 203 sibling pairs with Parkinson's disease: the GenePD study.

OBJECTIVE: To examine patterns of familial aggregation and factors influencing onset age in a sample of siblings with PD. METHODS: Sibling pairs (n = 203) with PD were collected as part of the GenePD study. Standardized family history, medical history, and risk factor data were collected and analyzed. RESULTS: The mean age at onset was 61.4 years and did not differ according to sex, exposure to coffee, alcohol, or pesticides. Head trauma was associated with younger onset (p = 0.03) and multivitamin use with later onset (p = 0.007). Age at onset correlation between sibling pairs was significant (r = 0.56, p = 0.001) and was larger than the correlation in year of onset (r = 0.29). The mean difference in onset age between siblings was 8.7 years (range, 0 to 30 years). Female sex was associated with increased frequency of relatives with PD. The frequency of affected parents (7.0%) and siblings (5.1%) was increased when compared with frequency in spouses (2.0%). CONCLUSIONS: The greater similarity for age at onset than for year of onset in sibling pairs with PD, together with increased risk for biological relatives over spouses of cases, supports a genetic component for PD. Risk to siblings in this series is increased over that seen in random series of PD cases; however, patients in this sample have similar ages at onset and sex distribution as seen for PD generally. These analyses suggest that factors influencing penetrance are critical to the understanding of this disease.

Pharmacokinetics of continuous-release carbidopa/levodopa.

This article reviews the pharmacokinetics of Sinemet CR, a controlled-release (CR) levodopa preparation. The main influences on the kinetic profile are as follows: absorption, which depends on the dissolution characteristics of the tablet, the pattern of gastric emptying, and the rate of uptake in the small intestine; distribution, which is determined by rates of levodopa transport from gut to blood and from blood to brain; and biotransformation, which is affected peripherally by L-aromatic amino acid decarboxylase (LAAAD) and catechol-O-methyl transferase (COMT), and centrally by LAAAD, COMT, and monoamine oxidase. The kinetics of Sinemet CR are limited by rates of absorption (which depend on the dose administered), the conformation of the tablet, and daily variations in the patterns of gastric emptying (influenced by the presence or absence of food). Levodopa must also compete with food-derived amino acids for transport across the gut-blood and blood-brain barriers; this competition effectively limits the drug's rate of distribution. Finally, biotransformation is limited by the activity of LAAAD and COMT in the periphery. Plasma profiles of levodopa after administration of Sinemet CR can vary, depending on the age of the patient and the time of day when the drug is administered. Nevertheless, the pharmacokinetic profile of the preparation has a number of advantages over that of Sinemet, in that it offers a steadier climb to peak plasma concentrations that are less extreme and of greater duration.

Lumping and splitting the Parkinson Plus syndromes: dementia with Lewy bodies, multiple system atrophy, progressive supranuclear palsy, and cortical-basal ganglionic degeneration.

The atypical parkinsonian or Parkinson Plus syndromes are often difficult to differentiate from Parkinson's disease and each other. In this article, the clinicopathological characteristics of dementia with Lewy bodies, multiple system atrophy, progressive supranuclear palsy, and cortical-basal ganglionic degeneration are discussed. These disorders, although clinically distinct, may have more similarities than previously thought, based on modern immunocytochemical techniques and new genetic findings. These intriguing interconnections at a basic molecular level have provided the scientific rationale for lumping these diseases into two groups, the synucleinopathies and the tauopathies.

An analysis of treatment options and outcome in patients with Parkinson's disease and severe dyskinesias.

Forty-one patients with Parkinson's disease and severe dyskinesias were analyzed retrospectively to determine if some general principles would emerge to aid physicians handling this complication of treatment. Dyskinesia type (high dopa chorea [HDC], low dopa chorea [LDC], high dopa dystonia [HDD], and low dopa dystonia [LDD]) predicted response to treatment and whether or not levodopa dose reduction would benefit dyskinesias without producing unacceptable "offs." High dopa chorea improved best but at the expense of increased "off" time, followed by LDD, HDD, and LDC. Levodopa reduction was an acceptable strategy in ameliorating HDC and LDD only. Adjunctive therapy benefited all dyskinesia types, although the majority of patients (12/17) helped by selegiline had LDD or LDC. Generally, low doses of dopamine agonists were helpful (bromocriptine < 20 mg/day; pergolide < 2 mg/day). When adding adjunctive therapy (except for selegiline or controlled-release carbidopa/levodopa), concomitant reduction in daily dose of levodopa was not an effective strategy to decrease dyskinesias. Serial trials of multiple drug regimens are useful in these patients.

Controlled-release carbidopa-levodopa (Sinemet) in combination with standard Sinemet in advanced Parkinson's disease.

Twelve of 23 patients with Parkinson's disease and motor fluctuations who entered a double-blind study comparing controlled-release carbidopa/levodopa (Sinemet CR-4) with standard Sinemet (SS) continued into open label follow-up on a combination of CR-4 and SS (C/S); the rest continued on CR-4 alone. Significant improvement on C/S compared with CR-4 was noted for shorter duration and reduced disability of dyskinesias, and more hours "on" without dyskinesias (all p less than 0.05). Total number of hours "off" was improved on C/S over SS (p less than 0.01). Sinemet CR-4 proved to be better than C/S for sleep disturbance (p less than 0.05). Although the total number of tablets and doses per day of CR-4 was reduced during the C/S period, total levodopa dosage per day was not significantly changed from either of the previous periods. The C/S therapy for advanced parkinsonism can be more efficacious for fluctuators than either CR-4 or SS alone.

Long-term efficacy of controlled-release carbidopa/levodopa in patients with advanced Parkinson's disease.

Twenty-one patients with Parkinson's disease and motor fluctuations who completed a double-blind study comparing controlled-release carbidopa/levodopa (Sinemet CR4) with standard Sinemet (SS) were evaluated one year following completion of the study. Five patients remained on CR4 alone; 16 continued on CR4 plus SS, and one also required addition of bromocriptine. Patients were significantly worse (p less than 0.05) at one year compared with double-blind CR4 phase (DBCR) for nine parameters of the motor exam, six activities of daily living (ADL), Hoehn & Yahr staging, and physician's global assessment. Compared with baseline SS, patients were worse at one year for four points of the motor exam, two of mentation, behavior, and mood, and 11 parameters of ADL. Improvement at one year was noted for less action and postural tremor and decreased duration of dyskinesias for both comparison periods. There was elimination of early morning dystonia at one year over the DBCR period and more hours "on" without dyskinesias and fewer hours "on" with dyskinesias compared with baseline SS. Total levodopa dosage was not significantly changed over the year. These data suggest that, in long-term use, CR4 remains more efficacious than SS alone for Parkinson's patients experiencing motor fluctuations, although disease progression continues despite optimal medication.

The human subfornical organ: an anatomic and ultrastructural study.

The subfornical organ (SFO), one of the circumventricular organs (CVO) and a thirst-regulating structure, was examined in humans. In 21 autopsy specimens, the SFO was identified as one mm grey nodule on the ventral surface of the fornix at the foramina of Monro. The SFO is a neuronal-vascular organ on a loose glial background, lined by ependyma. Ultrastructural examination reveals deep, narrow invaginations in most neuronal nuclei, characteristically seen in the SFO of other species, but unlike neuronal nuclei in the rest of the human brain. Ovoid, clear vesicles in synaptic complexes and dense-core granules in non-synaptic neuronal process are seen. Ependymal channels are observed. Capillaries have luminal tongue-like projections and pinocytotic vesicles in the endothelial wall, as well as both tight and non-tight junctions between endothelial cells; endothelial fenestrations are not found. These specializations may permit access of macromolecules to receptor sites in the SFO, facilitating its functions as a chemoreceptor organ in drinking behavior. The anatomy of the human SFO is consistent with that of other CVO's and with that of the SFO in other species.