Motor changes in presymptomatic Huntington disease gene carriers.

OBJECTIVE: To determine whether changes in motor function and reaction time are present in presymptomatic individuals carrying the Huntington disease (HD) allele. DESIGN: A case-control, double-blind study comparing asymptomatic at-risk subjects, with or without the HD allele, and subjects clinically determined to have early manifest HD. SETTING: The Department of Medical and Molecular Genetics at Indiana University School of Medicine, Indianapolis. PARTICIPANTS: We studied 383 patients at risk for HD. Each subject was asymptomatic by self-report. MEASURES: Genotype for the HD allele was determined by polymerase chain reaction testing. A battery of 8 physiological tests measuring speed of movement and reaction time was performed with a computer-driven system. RESULTS: Following neurologic examination, 17 of the 120 gene carriers (GCs) had symptoms sufficient for a clinical diagnosis of manifest HD. The remaining 103 GCs were designated presymptomatic GCs. When the non-GCs were compared with the presymptomatic GCs (1-way analysis of covariance and the Fisher protected t test), results on 3 of the 8 physiological tests--movement time, movement time with decision, and auditory reaction time--were different. Additionally, the number of trinucleotide (CAG) repeats significantly correlated with test performance for movement time with decision and visual reaction time with decision when both the entire group of GCs and the presymptomatic GCs alone were considered. CONCLUSION: These results suggest that subtle subclinical changes in motor function are present in presymptomatic individuals who have inherited the HD allele.

Direct evidence for an important species difference in the mechanism of 8-OH-DPAT-induced hypothermia.

1. Parallel series of experiments were carried out in the rat and mouse in order to investigate the mechanism(s) underlying the hypothermia induced in rodents by the selective 5-HT1A receptor agonist, 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT). 2. In the mouse, lesioning of central 5-hydroxytryptaminergic neurones (by use of the neurotoxin, 5,7-dihydroxytryptamine; 5,7-DHT) abolished the hypothermic response to 8-OH-DPAT, and depletion of brain 5-hydroxytryptamine (5-HT) levels (with the 5-HT synthesis inhibitor, p-chlorophenylalanine) markedly attenuated the response in this species. These pretreatments did not significantly attenuate 8-OH-DPAT-induced hypothermia in the rat, except for a significant attenuation of the response in 5,7-DHT-lesioned rats at the top dose of 8-OH-DPAT (1.0 mg kg-1, s.c.). 3. Pharmacological pretreatments which facilitate 5-HT release (selective 5-HT uptake inhibitors, precursor (5-hydroxytryptophan) loading, or fenfluramine), markedly attenuated or abolished 8-OH-DPAT-induced hypothermia in the mouse. These pretreatments generally had no significant effect on 8-OH-DPAT-induced hypothermia in the rat. 4. The selective noradrenaline uptake inhibitor, desipramine, had no effect on the hypothermic response to 8-OH-DPAT in either species. The selective dopamine uptake inhibitor, nomifensin, significantly increased the hypothermic response to 8-OH-DPAT in the mouse, but did not affect the response in the rat except at high, motor stimulant doses, when the response was attenuated. 5. These data are consistent with the hypothesis that 8-OH-DPAT-induced hypothermia is mediated by presynaptic autoreceptors in the mouse and by postsynaptic 5-HT1A receptors in the rat. Preliminary data also indicate an involvement of dopamine release in the mouse but not in the rat.

The effects of acute and chronic desipramine on the thermogenic and hypoactivity responses to alpha 2-agonists in reserpinized and normal mice.

1. The effects of acute and chronic (14 day) administration of the noradrenaline uptake inhibitor, desipramine (DMI), on the thermogenic responses to clonidine in reserpine-treated mice, and on the hypothermic and hypoactivity responses to the alpha 2-agonist, UK-14,304, in untreated mice were examined. 2. Taking the capacity of DMI to delay the onset of reserpine-induced hypothermia as an indicator of noradrenaline (NA) uptake inhibition, the lowest dose of DMI to inhibit uptake significantly for 12 h in the mouse was shown to be between 10 and 20 mg kg-1 orally. 3. Chronic (every 12 h for 14 days), but not acute treatment with DMI (15 mg kg-1, orally), attenuated the thermogenic responses to low doses (0.02-0.225 mg kg-1, i.p.) of clonidine (injected 20 h after the last dose of DMI) in reserpinized mice. 4. Acute DMI administration slightly attenuated the hypothermia and hypoactivity induced by UK-14,304 (0.25-1.0 mg kg-1, i.p.) when injected 2h, but not when injected 18-21h before the agonist. In contrast, 18-21h after withdrawal from chronic DMI both of these responses to UK-14, 304 were markedly attenuated. 5. As the thermogenic response to clonidine in reserpinized mice appears to involve central post-synaptic alpha 2-adrenoceptors, these results suggest that prolonged inhibition of NA uptake decreases the sensitivity of postsynaptic alpha 2-adrenoceptors. The results of the studies using UK-14,304 indicate that central alpha 2-adrenoceptors involved in mediating other behavioural and pharmacological responses to alpha 2-agonists are also down-regulated by chronic inhibition of NA uptake.

The thermogenic actions of alpha 2-adrenoceptor agonists in reserpinized mice are mediated via a central postsynaptic alpha 2-adrenoceptor mechanism.

1. The dose-related effects of the selective alpha 2-adrenoceptor agonists clonidine, UK-14,304 and B-HT 933 on the body temperature of untreated and reserpine-treated mice were investigated. 2. In untreated mice all three agonists induced a dose-related hypothermia. The highest doses of UK-14,304 and B-HT 933, 3 and 100 mg kg-1 respectively, elicited a marked (10 degrees C) hypothermia, whereas the maximal hypothermic effect of clonidine (5.5 degrees C) was less pronounced and reached a plateau at a dose of 0.5 mg kg-1 i.p. 3. Reserpine (2.5 mg kg-1, s.c.) induced a marked hypothermia in the mouse; 18 h after injection body temperature had decreased to only slightly (0.5-1.5 degrees C) above ambient (19 degrees C). 4. All three alpha 2-agonists produced a partial dose-related reversal of reserpine-induced hypothermia; maximal thermogenic responses (9-10 degrees C increases in body temperature) were elicited by doses of 0.2, 0.5 and 16 mg kg-1 i.p. of clonidine, UK-14,304 and B-HT 933 respectively, and the log dose-response curves for all 3 agonists were bell-shaped. 5. Following intracerebroventricular administration to reserpine-treated mice, the thermogenic response to clonidine was more rapid in onset, and the agonist was 20 fold more potent than when injected i.p. 6. The selective alpha 2-adrenoceptor antagonists, idazoxan (0.05-0.5 mg kg-1), Wy 26392 (0.3-5.0 mg kg-1) and yohimbine (0.1-1.6 mg kg-1) given orally attenuated the thermogenic responses to all 3 agonists in reserpinized mice in a dose-related manner. Pretreatment with a single dose of idazoxan (0.3 mg kg-1, orally) elicited a 6 fold parallel shift to the right in the dose-response curve to clonidine. 7. The selective alpha 1-adrenoceptor antagonists, prazosin (10 mg kg-1) and indoramin (3-10 mg kg-1), and the beta-adrenoceptor antagonist, propranolol (10 mg kg-1), only partially attenuated the thermogenic responses to the alpha 2-agonists in reserpinized mice. These effects were variable and not clearly dose-related. 8. Pretreatment of reserpinized mice with the catecholamine synthesis inhibitor, alpha-methyl-p-tyrosine, markedly attenuated (60-95%) the thermogenic response to the noradrenaline uptake inhibitor, desipramine (0.13-12.5 mg kg-1, i.p.), but only slightly reduced (10-35%) that to clonidine (0.032-0.5 mg kg-1, i.p.). 9. These results suggest that alpha2-adrenoceptor agonists reverse reserpine-induced hypothermia via a central mechanism involving activation of postsynaptic alpha 2-adrenoceptors.

The enantiomers of zacopride: an intra-species comparison of their potencies in functional and anxiolytic models.

1. The 5-HT3 receptor antagonist, zacopride, and its enantiomers, R(+)-zacopride and S(-)-zacopride, were examined in three pharmacological models: (i) 5-HT-induced depolarization of the mouse isolated vagus nerve preparation, (ii) the 5-HT-evoked von Bezold-Jarisch reflex in the mouse, and (iii) the mouse light:dark box model of anxiety. Other standard 5-HT3 receptor antagonists were also included for comparison in these studies. 2. Racemic zacopride, and both of the enantiomers, displayed potent 5-HT3 receptor antagonist activity in the isolated vagus nerve and in the von Bezold-Jarisch model. No 5-HT3 receptor agonist or partial agonist effects of these compounds were detected. 3. In the isolated vagus nerve, R(+)-zacopride and ondansetron were surmountable 5-HT3 receptor antagonists (pA2 values of 9.3 and 8.3, respectively), whereas racemic zacopride, S(-)-zacopride and tropisetron were insurmountable antagonists, markedly suppressing the maximum response to 5-HT. 4. In vivo, racemic zacopride, R(+)-zacopride, S(-)-zacopride and WAY100289 were potent antagonists of the 5-HT-evoked von Bezold-Jarisch reflex, with minimum effective doses (lowest dose required to reduce the reflex by > or = 85%; MED85) of 1.0, 3.0, 0.3 and 3.0 micrograms kg-1, s.c., respectively. 5. Racemic zacopride, R(+)-zacopride and S(-)-zacopride were active in the mouse light:dark box model of anxiety, with similar potencies (minimum effective dose 1 microgram kg-1, s.c.) and similar active dose-ranges (1-1000 micrograms kg-1, s.c.). 6. The doses of racemic zacopride, R( + )-zacopride and S(-)-zacopride required to block 5-HT3receptors in vivo correlated reasonably well with their potencies in an anxiety model within the same species. In these studies, there was no evidence of a marked difference between the anxiolytic potencies ofR( + )-zacopride and S(-)-zacopride.

The antinociceptive activity of meptazinol depends on both opiate and cholinergic mechanisms.

1 Antinociceptive responses to meptazinol, morphine and oxotremorine and the effects of pretreatment with naloxone or scopolamine on these responses in mice and rats, were examined. 2 Meptazinol evoked larger increases in nociceptive thresholds in the mouse than in the rat, whereas morphine induced large increases in both species. Oxotremorine was both a more potent and a more effective antinociceptive agent in the mouse than in the rat. 3 Antinociceptive responses to meptazinol were consistently inhibited in animals pretreated with naloxone, whereas scopolamine attenuated the effects of meptazinol in some, particularly the mouse tail immersion test, but not in all of the procedures used. 4 Naloxone inhibited all antinociceptive responses to morphine, and scopolamine inhibited all responses to oxotremorine. However, there was no significant interaction between naloxone and oxotremorine or between scopolamine and various opioid analgesic agents. 5 These results indicate that meptazinol, unlike established opioid drugs, may induce antinociception by a dual action on opiate and cholinergic mechanisms.

Effects of the selective angiotensin II receptor antagonists losartan and PD123177 in animal models of anxiety and memory.

There is increasing interest in the potential functional role of the octapeptide angiotensin II (AII) in psychiatric and cognitive disorders. The novel angiotensin II (AII) receptor antagonists, losartan and PD123177, selective for the AT1 and AT2 receptor subtypes respectively, constitute important pharmacological tools for the assessment of the behavioural consequences of modulation of AII function. The present series of studies investigated the effects of each compound in two animal models of anxiety, the rat elevated zero-maze and mouse light/dark box, and two models of working memory in the rat, the operant delayed matching to position (DMTP) task and the spatial reinforced alternation test in the T-maze. Our data indicate that both compounds (0.01-10 mg/kg s.c.) were without significant effect in any of the behavioural assays. Using the present methods and strains of laboratory rodents, these findings provide no support for the involvement of AII receptor function in the mediation of anxiety of working memory.

Behavioural and pharmacological characterisation of the elevated "zero-maze" as an animal model of anxiety.

The elevated "zero-maze" is a modification of the elevated plus-maze model of anxiety in rats which incorporates both traditional and novel ethological measures in the analysis of drug effects. The novel design comprises an elevated annular platform with two opposite enclosed quadrants and two open, removing any ambiguity in interpretation of time spent on the central square of the traditional design and allowing uninterrupted exploration. Using this model, the reference benzodiazepine anxiolytics, diazepam (0.125-0.5 mg/kg) and chlordiazepoxide (0.5-2.0 mg/kg) significantly increased the percentage of time spent in the open quadrants (% TO) and the frequency of head dips over the edge of the platform (HDIPS), and reduced the frequency of stretched attend postures (SAP) from the closed to open quadrants. In contrast, the anxiogenic drug m-chlorophenyl-piperazine (mCPP; 0.25-1.0 mg/kg) induced the opposite effects, decreasing %TO and HDIPS, and increasing SAP. The 5-HT1A receptor agonist 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT; 0.001-0.1 mg/kg) had no effects on either %TO or HDIPS, but did decrease SAP at 0.01 mg/kg although not at higher or lower doses. Similarly, the 5-HT3 receptor antagonist, ondansetron (0.0001-1.0 mg/kg) decreased SAP and increased %TO at 0.01 mg/kg, but not at other doses. The present data suggest that a combination of the novel "zero-maze" design and a detailed ethological analysis provides a sensitive model for the detection of anxiolytic/anxiogenic drug action.

Behavioural and pharmacological characterisation of the canopy stretched attend posture test as a model of anxiety in mice and rats.

The behavioural element, stretched attend posture (SAP), is an important component of the "risk-assessment" repertoire of defensive behaviour in rodents. The present experimental paradigm was devised as a novel and simple method of eliciting high levels of SAP in mice and rats. The SAP test apparatus comprised an elevated black Perspex circular platform. A smaller clear red Perspex circular "Canopy" was supported directly above the platform by a central pillar, thus dividing the platform into an inner, dimly lit covered zone and an outer, brightly lit exposed zone. In both the rat and mouse version of this model, vehicle-treated animals exhibited a marked preference for exploring the covered zone and also exhibited high baseline levels of SAP, particularly at the covered zone boundary whilst they investigated the exposed zone. In the mouse SAP test, the benzodiazepine receptor agonists, diazepam (0.5 mg/kg s.c.) and chlordiazepoxide (2 mg/kg s.c.), and the 5-HT1A receptor agonists, buspirone (1 and 3 mg/kg s.c.), ipsapirone (3 mg/kg s.c.) and 8-OH-DPAT (0.2 mg/kg s.c.), all significantly decreased the frequency of SAP without impairing motor activity. In the rat SAP test, diazepam (0.5 mg/kg s.c.) significantly decreased, whilst the anxiogenic 5-HT2C/1B receptor agonist, mCPP (0.25 and 0.5 mg/kg s.c.), significantly increased, the frequency of SAP. Ipsapirone (3 mg/kg s.c.) induced a non-specific behavioural inhibition. These data suggest that the "Canopy" SAP test is a useful paradigm to investigate risk assessment behaviour in both rats and mice, and may provide a sensitive novel rodent model of anxiety.

Electrophysiological, biochemical, neurohormonal and behavioural studies with WAY-100635, a potent, selective and silent 5-HT1A receptor antagonist.

Although considerable progress has been made in characterising the 5-HT1A receptor using agonists, partial agonists or non-selective antagonists, further studies of 5-HT1A receptor function have been hindered by the lack of highly selective antagonists. The term 'silent' antagonist has been used for such compounds in order to distinguish them unequivocally from several 5-HT1A receptor partial agonists which were initially designated 'antagonists'. In this report we provide a comprehensive review of the biochemical, pharmacological and behavioural properties of the first potent, selective and silent 5-HT1A receptor antagonist, WAY-100635 (N-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl)-N-(2- pyridinyl)cyclohexanecarboxamide trihydrochloride). WAY-100635 had an IC50 (displacement of specific [3H]8-OH-DPAT binding to 5-HT1A receptors in the rat hippocampus) of 1.35 nM and was > 100-fold selective for the 5-HT1A site relative to a range of other CNS receptors. [3H]WAY-100635 was also characterised as the first 5-HT1A antagonist radioligand, displaying the same regional distribution of binding sites as [3H]8-OH-DPAT in rat brain. As would be expected for the binding of an antagonist to a G-protein-coupled receptor, the Bmax of [3H]WAY-100635 specific binding was consistently 50-60% greater than that of the agonist radioligand, [3H]8-OH-DPAT. Mn2+, but not guanine nucleotides, inhibited [3H]WAY-100635-specific binding. [3H]WAY-100635 was also shown to bind selectively to brain 5-HT1A receptors in vivo, following intravenous administration to mice. In vitro electrophysiological studies demonstrated that WAY-100635 had no 5-HT1A receptor agonist actions, but dose-dependently blocked the effects of agonists at both the postsynaptic 5-HT1A receptor in the CA1 region of the hippocampus, and the somatodendritic 5-HT1A receptor located on dorsal raphe 5-HT neurones. In vivo, WAY-100635 also dose-dependently blocked the ability of 8-OH-DPAT to inhibit the firing of dorsal raphe 5-HT neurones, and to induce the '5-HT syndrome', hypothermia, hyperphagia and to elevate plasma ACTH levels. In the mouse light/dark box anxiety model, WAY-100635 induced anxiolytic-like effects. WAY-100635 had no intrinsic effect on cognition in the delayed-matching-to-position model of short-term memory in the rat, but reversed the disruptive effects of 8-OH-DPAT on motor motivational performance. These data clearly demonstrate that WAY-100635 is the first potent, selective and silent 5-HT1A receptor antagonist. Furthermore, [3H]WAY-100635 is the first antagonist radioligand to become available for 5-HT1A receptor binding studies both in vitro and in vivo. The positive effects of WAY-100635 in an anxiety model also indicate that a postsynaptic 5-HT1A receptor antagonist action may contribute to the anxiolytic properties of 5-HT1A receptor partial agonists.

Behavioural studies on WAY100289, a novel 5-HT3 receptor antagonist, in two animal models of anxiety.

The novel 5-HT3 receptor antagonist, WAY100289, was examined in two animal models of anxiety: the mouse two-compartment light: dark box, and the rat potentiated acoustic startle paradigm. The activity of WAY100289 in the light: dark box model was also compared with that of the selective 5-HT3 receptor antagonists ondansetron, zacopride, ICS-205,930 and quaternary ICS-205,930 (QICS). WAY100289 mimicked the activity profile of benzodiazepine positive controls in the mouse light: dark box, i.e. WAY100289 markedly and significantly increased the exploratory activity of mice in the more aversive light compartment, at doses of 0.01-1.0 mg/kg s.c. and 0.1-10.0 mg/kg p.o. Zacopride and ondansetron induced comparable effects at doses of 0.001-1.0 mg/kg s.c. ICS-205,930 displayed a markedly biphasic dose-response relationship; being active at 0.01 mg/kg s.c., but not at higher or lower doses. QICS was not active in the light: dark box up to a dose of 10 mg/kg s.c., suggesting that the compound does not enter the brain readily. WAY100289 was also active in the rat potentiated acoustic startle model, significantly attenuating the potentiated startle response at doses of 0.03 and 0.3 mg/kg s.c. The activity profile of WAY100289 in this model resembled that of ondansetron. These data strongly suggest that WAY100289 may possess anxiolytic properties in the clinic.

A pharmacological profile of the selective silent 5-HT1A receptor antagonist, WAY-100635.

WAY-100635 (N-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-N-(2- pyridinyl)cyclohexanecarboxamide trihydrochloride) is an achiral phenylpiperazine derivative that binds with high affinity and selectivity to the 5-HT1A receptor. WAY-100635 displaced specific binding of the 5-HT1A radioligand, [3H]8-OH-DPAT (8-hydroxy-2-(di-n-propylamino)tetralin), to rat hippocampal membranes with a pIC50 of 8.87. This represented a greater than 100-fold selectivity relative to binding at other 5-HT receptor subtypes and major neurotransmitter receptor, reuptake and ion channel sites. In functional assays, WAY-100635 was a potent 5-HT1A receptor antagonist, with no evidence of any 5-HT1A receptor agonist or partial agonist activity. In the isolated guinea-pig ileum WAY-100635 was a potent and, at high concentrations, an insurmountable antagonist of the 5-HT1A receptor agonist action of 5-carboxamidotryptamine, with an apparent pA2 value (at 0.3 nM) of 9.71. WAY-100635 blocked the inhibitory action of 8-OH-DPAT on dorsal raphe neuronal firing in the anaesthetised rat at doses which had no inhibitory action per se. In behavioural models, WAY-100635 itself induced no overt behavioural changes but potently antagonised the behavioural syndrome induced by 8-OH-DPAT in the rat and guinea-pig (minimum effective dose = 0.003 mg/kg s.c. and ID50 = 0.01 mg/kg s.c., respectively). WAY-100635 also blocked the hypothermia induced by 8-OH-DPAT in the mouse and rat with ID50 values of 0.01 mg/kg s.c. These data indicate that WAY-100635 will be used as a standard antagonist in further studies of 5-HT1A receptor function.

WAY100135: a novel, selective antagonist at presynaptic and postsynaptic 5-HT1A receptors.

The novel phenylpiperazine derivative, (+/-)-WAY100135 (N-tert-butyl-3-(4-(2-methoxyphenyl)piperazin-1-yl)-2-phenylpro pionamide dihydrochloride), is a selective antagonist at both somatodendritic and postsynaptic 5-HT1A receptors. The IC50 of (+/-)-WAY100135 at the rat hippocampal 5-HT1A receptor was 34 nM, whereas its IC50 at a range of other receptor sites was > 2 microM. Up to a dose of 2.5 mg/kg i.v. (+/-)-WAY100135 induced a maximum 30% inhibition of raphe neuronal firing and (at 0.5 mg/kg i.v.) antagonised the inhibition of firing induced by 8-OH-DPAT (8-hydroxy-2-(di-n-propylamino)tetralin) in anaesthetised rats. (+/-)-WAY100135 antagonised the action of 5-carboxamidoiodotryptamine in the guinea-pig ileum, with a pA2 of 7.2. (+/-)-WAY100135 had no agonist-like behavioural effects but antagonised the behavioural syndrome and hypothermia induced by 8-OH-DPAT in the rat and mouse, respectively. The interaction of (+/-)-WAY100135 with the 5-HT1A receptor was stereoselective; the (+)-enantiomer being markedly more active in binding, functional and behavioural studies. These data indicate that (+/-)-WAY100135 is the first highly selective antagonist at both somatodendritic and postsynaptic 5-HT1A receptors.

Dental office access for patients with disabling conditions.

Today's professional health care centers are becoming more accessible to patients with handicapping conditions each year. The increase in numbers of these persons in society, along with their desire to be treated locally, will result in a much higher influx of persons with disabling conditions seeking professional services. Dental professionals should be aware and make appropriate responses to the needs of these special patients. State codes for facilities access vary widely, but are clearly becoming more defined as federal legislation and federal regulations continue to support the rights of persons with disabling conditions to access work, study, leisure, and services. The dental profession has an opportunity to demonstrate leadership in handicapped access in both the private and public professional sectors without direct governmental mandates. The American Dental Association and constituent state associations can further accomplish this by setting accessibility guidelines for the dental environment.

Cognitive scores in carriers of Huntington's disease gene compared to noncarriers.

Huntington's disease (HD) is a progressive neurodegenerative disorder recently shown to be due to an excess number of CAG trinucleotide repeats in the 5' translated region of chromosome 4. One of the cardinal features of HD is cognitive decline. While mental deterioration is obvious later in the disease course, the time of its onset is difficult to determine precisely. A sample of at-risk individuals without signs or symptoms of HD by self-report was studied. The Wechsler Adult Intelligence Test--Revised and a neurological rating scale were administered. The genotypes of 394 individuals were then determined by polymerase chain reaction testing. On all portions of the WAIS-R test, the mean score of the HD gene carriers was lower than that of the noncarriers. Scores on two of the performance subtests, the digit symbol and the picture arrangement, were significantly different in the two groups, even after the scores from all gene carriers who were diagnosed as affected based on their neurological motor examination were removed. The scores for the gene carriers on the various subtests were negatively correlated with the number of CAG repeats in the expanded HD allele. Such a relationship was not seen with the normal alleles of the noncarriers. Taken together, our results suggest that a deficit in cognitive function is an early finding of HD and that in this patient population, the degree of cognitive deficit is proportional to the number of CAG repeats in the HD allele.