Increased adult hippocampal neurogenesis is not necessary for wheel running to abolish conditioned place preference for cocaine in mice.

Recent evidence suggests that wheel running can abolish conditioned place preference (CPP) for cocaine in mice. Running significantly increases the number of new neurons in the hippocampus, and new neurons have been hypothesised to enhance plasticity and behavioral flexibility. Therefore, we tested the hypothesis that increased neurogenesis was necessary for exercise to abolish cocaine CPP. Male nestin-thymidine kinase transgenic mice were conditioned with cocaine, and then housed with or without running wheels for 32 days. Half of the mice were fed chow containing valganciclovir to induce apoptosis in newly divided neurons, and the other half were fed standard chow. For the first 10 days, mice received daily injections of bromodeoxyuridine (BrdU) to label dividing cells. On the last 4 days, mice were tested for CPP, and then euthanized for measurement of adult hippocampal neurogenesis by counting the number of BrdU-positive neurons in the dentate gyrus. Levels of running were similar in mice fed valganciclovir-containing chow and normal chow. Valganciclovir significantly reduced the numbers of neurons (BrdU-positive/NeuN-positive) in the dentate gyrus of both sedentary mice and runner mice. Valganciclovir-fed runner mice showed similar levels of neurogenesis as sedentary, normal-fed controls. However, valganciclovir-fed runner mice showed the same abolishment of CPP as runner mice with intact neurogenesis. The results demonstrate that elevated adult hippocampal neurogenesis resulting from running is not necessary for running to abolish cocaine CPP in mice.

Barriers to inclusion: Service dog handlers in science laboratories.

Despite institutional claims of the importance of diversity, equity, and inclusion in STEM, people with disabilities remain under-represented. Current policies neglect to explicitly address inclusion of the growing population of students with disabilities who rely on service dogs, specifically in accessing teaching and research laboratories. With the increase in students registering for post-secondary disability services, the science community has outgrown general policies that primarily outline steps for exclusion of student service dog handlers. Here we discuss barriers and areas in need of improvement and then outline explicit guidelines for inclusion that are currently absent from existing policies. Particular concerns arise in teaching and research laboratories where live animals are present, and we recommend further research is needed to make informed decisions. In order to realize our vision of a diverse STEM workforce, academic institutions and professionals need to recognize barriers to inclusion and consider their role in making science accessible.

Intact neurogenesis is required for benefits of exercise on spatial memory but not motor performance or contextual fear conditioning in C57BL/6J mice.

The mammalian hippocampus continues to generate new neurons throughout life. Experiences such as exercise, anti-depressants, and stress regulate levels of neurogenesis. Exercise increases adult hippocampal neurogenesis and enhances behavioral performance on rotarod, contextual fear and water maze in rodents. To directly test whether intact neurogenesis is required for gains in behavioral performance from exercise in C57BL/6J mice, neurogenesis was reduced using focal gamma irradiation (3 sessions of 5 Gy). Two months after treatment, mice (total n=42 males and 42 females) (Irradiated or Sham), were placed with or without running wheels (Runner or Sedentary) for 54 days. The first 10 days mice received daily injections of bromodeoxyuridine (BrdU) to label dividing cells. The last 14 days mice were tested on water maze (two trials per day for 5 days, then 1 h later probe test), rotarod (four trials per day for 3 days), and contextual fear conditioning (2 days), then measured for neurogenesis using immunohistochemical detection of BrdU and neuronal nuclear protein (NeuN) mature neuronal marker. Consistent with previous studies, in Sham animals, running increased neurogenesis fourfold and gains in performance were observed for the water maze (spatial learning and memory), rotarod (motor performance), and contextual fear (conditioning). These positive results provided the reference to determine whether gains in performance were blocked by irradiation. Irradiation reduced neurogenesis by 50% in both groups, Runner and Sedentary. Irradiation did not affect running or baseline performance on any task. Minimal changes in microglia associated with inflammation (using immunohistochemical detection of cd68) were detected at the time of behavioral testing. Irradiation did not reduce gains in performance on rotarod or contextual fear, however it eliminated gain in performance on the water maze. Results support the hypothesis that intact exercise-induced hippocampal neurogenesis is required for improved spatial memory, but not motor performance or contextual fear in C57BL/6J mice.

Genetic loss of diazepam binding inhibitor in mice impairs social interest.

Neuropsychiatric disorders in which reduced social interest is a common symptom, such as autism, depression, and anxiety, are frequently associated with genetic mutations affecting γ-aminobutyric acid (GABA)ergic transmission. Benzodiazepine treatment, acting via GABA type-A receptors, improves social interaction in male mouse models with autism-like features. The protein diazepam binding inhibitor (DBI) can act as an endogenous benzodiazepine, but a role for DBI in social behavior has not been described. Here, we investigated the role of DBI in the social interest and recognition behavior of mice. The responses of DBI wild-type and knockout male and female mice to ovariectomized female wild-type mice (a neutral social stimulus) were evaluated in a habituation/dishabituation task. Both male and female knockout mice exhibited reduced social interest, and DBI knockout mice lacked the sex difference in social interest levels observed in wild-type mice, in which males showed higher social interest levels than females. The ability to discriminate between familiar and novel stimulus mice (social recognition) was not impaired in DBI-deficient mice of either sex. DBI knockouts could learn a rotarod motor task, and could discriminate between social and nonsocial odors. Both sexes of DBI knockout mice showed increased repetitive grooming behavior, but not in a manner that would account for the decrease in social investigation time. Genetic loss of DBI did not alter seminal vesicle weight, indicating that the social interest phenotype of males lacking DBI is not due to reduced circulating testosterone. Together, these studies show a novel role of DBI in driving social interest and motivation.

Mouse inbred strain differences in ethanol drinking to intoxication.

Recently, we described a simple procedure, Drinking in the Dark (DID), in which C57BL/6J mice self-administer ethanol to a blood ethanol concentration (BEC) above 1 mg/ml. The test consists of replacing the water with 20% ethanol in the home cage for 4 h early during the dark phase of the light/dark cycle. Three experiments were conducted to explore this high ethanol drinking model further. In experiment 1, a microanalysis of C57BL/6J behavior showed that the pattern of ethanol drinking was different from routine water intake. In experiment 2, drinking impaired performance of C57BL/6J on the accelerating rotarod and balance beam. In experiment 3, 12 inbred strains were screened to estimate genetic influences on DID and correlations with other traits. Large, reliable differences in intake and BEC were detected among the strains, with C57BL/6J showing the highest values. Strain means were positively correlated with intake and BEC in the standard (24 h) and a limited (4 h) two-bottle ethanol vs. water test, but BECs reached higher levels for DID. Strain mean correlations with other traits in the Mouse Phenome Project database supported previously reported genetic relationships of high ethanol drinking with low chronic ethanol withdrawal severity and low ethanol-conditioned taste aversion. We extend these findings by showing that the correlation estimates remain relatively unchanged even after correcting for phylogenetic relatedness among the strains, thus relaxing the assumption that the strain means are statistically independent. We discuss applications of the model for finding genes that predispose pharmacologically significant drinking in mice.

Acute effects of naltrexone and GBR 12909 on ethanol drinking-in-the-dark in C57BL/6J mice.

RATIONALE: Recently, a simple procedure was described, drinking in the dark (DID), in which C57BL/6J mice self-administer ethanol to the point of intoxication. The test consists of replacing the water with 20% ethanol in the home cage for 2 or 4 h early during the dark phase of the light/dark cycle. OBJECTIVES: To determine whether the model displays predictive validity with naltrexone, and whether opioid or dopaminergic mechanisms mediate excessive drinking in the model. MATERIALS AND METHODS: Naltrexone or GBR 12909 were administered via intraperitoneal injections immediately before offering ethanol solutions, plain tap water, or 10% sugar water to male C57BL/6J mice, and consumption was monitored over a 2- or 4-h period using the DID procedure. RESULTS: Naltrexone (0.5, 1, or 2 mg/kg) dose dependently decreased ethanol drinking but these same doses had no significant effect on the consumption of plain water or 10% sugar water. GBR 12909 (5, 10, and 20 mg/kg) dose dependently reduced the consumption of ethanol and sugar water but had no effect on plain water drinking. CONCLUSIONS: The DID model demonstrates predictive validity. Both opioid and dopamine signaling are involved in ethanol drinking to intoxication. Different physiological pathways mediate high ethanol drinking as compared to water or sugar water drinking in DID. DID may be a useful screening tool to find new alcoholism medications and to discover genetic and neurobiological mechanisms relevant to the human disorder.

High motivation for exercise is associated with altered chromatin regulators of monoamine receptor gene expression in the striatum of selectively bred mice.

Although exercise is critical for health, many lack the motivation to exercise, and it is unclear how motivation might be increased. To uncover the molecular underpinnings of increased motivation for exercise, we analyzed the transcriptome of the striatum in four mouse lines selectively bred for high voluntary wheel running and four non-selected control lines. The striatum was dissected and RNA was extracted and sequenced from four individuals of each line. We found multiple genes and gene systems with strong relationships to both selection and running history over the previous 6 days. Among these genes were Htr1b, a serotonin receptor subunit and Slc38a2, a marker for both glutamatergic and γ-aminobutyric acid (GABA)-ergic signaling. System analysis of the raw results found enrichment of transcriptional regulation and kinase genes. Further, we identified a splice variant affecting the Wnt-related Golgi signaling gene Tmed5. Using coexpression network analysis, we found a cluster of interrelated coexpression modules with relationships to running behavior. From these modules, we built a network correlated with running that predicts a mechanistic relationship between transcriptional regulation by nucleosome structure and Htr1b expression. The Library of Integrated Network-Based Cellular Signatures identified the protein kinase C δ inhibitor, rottlerin, the tyrosine kinase inhibitor, Linifanib and the delta-opioid receptor antagonist 7-benzylidenenaltrexone as potential compounds for increasing the motivation to run. Taken together, our findings support a neurobiological framework of exercise motivation where chromatin state leads to differences in dopamine signaling through modulation of both the primary neurotransmitters glutamate and GABA, and by neuromodulators such as serotonin.

Neonatal alcohol exposure reduces number of parvalbumin-positive interneurons in the medial prefrontal cortex and impairs passive avoidance acquisition in mice deficits not rescued from exercise.

Developmental alcohol exposure causes a host of cognitive and neuroanatomical abnormalities, one of which is impaired executive functioning resulting from medial prefrontal cortex (mPFC) damage. This study determined whether third-trimester equivalent alcohol exposure reduced the number of mPFC GABAergic parvalbumin-positive (PV+) interneurons, hypothesized to play an important role in local inhibition of the mPFC. The impact on passive avoidance learning and the therapeutic role of aerobic exercise in adulthood was also explored. Male C57BL/6J mice received either saline or 5g/kg ethanol (two doses, two hours apart) on PD 5, 7, and 9. On PD 35, animals received a running wheel or remained sedentary for 48days before behavioral testing and perfusion on PD 83. The number of PV+ interneurons was stereologically measured in three separate mPFC subregions: infralimbic, prelimbic and anterior cingulate cortices (ACC). Neonatal alcohol exposure decreased number of PV+ interneurons and volume of the ACC, but the other regions of the mPFC were spared. Alcohol impaired acquisition, but not retrieval of passive avoidance, and had no effect on motor performance on the rotarod. Exercise had no impact on PV+ cell number, mPFC volume, or acquisition of passive avoidance, but enhanced retrieval in both control and alcohol-exposed groups, and enhanced rotarod performance in the control mice. Results support the hypothesis that part of the behavioral deficits associated with developmental alcohol exposure are due to reduced PV+ interneurons in the ACC, but unfortunately exercise does not appear to be able to reverse any of these deficits.

Parameters for abolishing conditioned place preference for cocaine from running and environmental enrichment in male C57BL/6J mice.

RATIONALE: Evidence suggests that 4 weeks of voluntary wheel running abolishes conditioned place preference (CPP) for cocaine in male C57BL/6J mice. OBJECTIVES: To determine the duration and timing of exposure to running wheels necessary to reduce CPP, and the extent to which the running per se influences CPP as compared to environmental enrichment without running. METHODS: A total of 239 males were conditioned for 4days twice daily with cocaine (10mg/kg) and then split into 7 intervention groups prior to 4days of CPP testing. Experiment 1 consisted of two groups housed as follows: short sedentary group (SS; n=20) in normal cages for 1 week; the short running group (SR; n=20) with running wheels for 1 week. Experiment 2 consisted of five groups housed as follows; short 1 week of running followed by a 3 week sedentary period (SRS; n=20); a 3 week sedentary period followed by 1 week of running (SSR; n=20); long sedentary group (LS; n=66) in normal cages for 4 weeks; long running group (LR; n=66) with running wheels for 4 weeks; and long environmental enrichment group (EE; n=27) with toys for 4 weeks. RESULTS: Levels of running were similar in all running groups. Both running and environmental enrichment reduced CPP relative to sedentary groups. CONCLUSIONS: Results suggest that the abolishment of cocaine CPP from running is robust and occurs with as low as 1 week of intervention but may be related to enrichment component of running rather than physical activity.

Behavioral deficits induced by third-trimester equivalent alcohol exposure in male C57BL/6J mice are not associated with reduced adult hippocampal neurogenesis but are still rescued with voluntary exercise.

Prenatal alcohol exposure can produce permanent alterations in brain structure and profound behavioral deficits. Mouse models can help discover mechanisms and identify potentially useful interventions. This study examined long-term influences of either a single or repeated alcohol exposure during the third-trimester equivalent on survival of new neurons in the hippocampus, behavioral performance on the Passive avoidance and Rotarod tasks, and the potential role of exercise as a therapeutic intervention. C57BL/6J male mice received either saline or 5g/kg ethanol split into two s.c. injections, two hours apart, on postnatal day (PD)7 (Experiment 1) or on PD5, 7 and 9 (Experiment 2). All mice were weaned on PD21 and received either a running wheel or remained sedentary from PD35-PD80/81. From PD36-45, mice received i.p. injections of 50mg/kg bromodeoxyuridine (BrdU) to label dividing cells. Behavioral testing occurred between PD72-79. Number of surviving BrdU+ cells and immature neurons (doublecortin; DCX+) was measured at PD80-81. Alcohol did not affect number of BrdU+ or DCX+ cells in either experiment. Running significantly increased number of BrdU+ and DCX+ cells in both treatment groups. Alcohol-induced deficits on Rotarod performance and acquisition of the Passive avoidance task (Day 1) were evident only in Experiment 2 and running rescued these deficits. These data suggest neonatal alcohol exposure does not result in long-term impairments in adult hippocampal neurogenesis in the mouse model. Three doses of ethanol were necessary to induce behavioral deficits. Finally, the mechanisms by which exercise ameliorated the neonatal alcohol induced behavioral deficits remain unknown.

Evaluation of a C57BL/6J × 129S1/SvImJ Hybrid Nestin-Thymidine Kinase Transgenic Mouse Model for Studying the Functional Significance of Exercise-Induced Adult Hippocampal Neurogenesis.

New neurons are continuously generated in the adult hippocampus but their function remains a mystery. The nestin thymidine kinase (nestin-TK) transgenic method has been used for selective and conditional reduction of neurogenesis for the purpose of testing the functional significance of new neurons in learning, memory and motor performance. Here we explored the nestin-TK model on a hybrid genetic background (to increase heterozygosity, and "hybrid vigor"). Transgenic C57BL/6J (B6) were crossed with 129S1/SvImJ (129) producing hybrid offspring (F1) with the B6 half of the genome carrying a herpes simplex virus thymidine kinase (TK) transgene regulated by a modified nestin promoter. In the presence of exogenously administered valganciclovir, new neurons expressing TK undergo apoptosis. Female B6 nestin-TK mice (n = 80) were evaluated for neurogenesis reduction as a positive control. Male and female F1 nestin-TK mice (n = 223) were used to determine the impact of neurogenesis reduction on the Morris water maze (MWM) and rotarod. All mice received BrdU injections to label dividing cells and either valganciclovir or control chow, with or without a running wheel for 30 days. Both the F1 and B6 background displayed approximately 50% reduction in neurogenesis, a difference that did not impair learning and memory on the MWM or rotarod performance. Running enhanced neurogenesis and performance on the rotarod but not MWM suggesting the F1 background may not be suitable for studying pro-cognitive effects of exercise on MWM. Greater reduction of neurogenesis may be required to observe behavioral impacts. Alternatively, new neurons may not play a critical role in learning, or compensatory mechanisms in pre-existing neurons could have masked the deficits. Further work using these and other models for selectively reducing neurogenesis are needed to establish the functional significance of adult hippocampal neurogenesis in behavior.

Strain differences in three measures of ethanol intoxication in mice: the screen, dowel and grip strength tests.

Mice from 8 to 21 inbred strains were tested for sensitivity to ethanol intoxication using a range of doses and three different measures: the screen test, the dowel test and a test of grip strength. Strains differed under nearly all conditions. For the dowel test, two dowel widths were employed, and mice were tested immediately or 30 min after ethanol. For the dowel and screen tests, low doses failed to affect some strains, and the highest doses failed to discriminate among mice, maximally affecting nearly all. For grip strength, a single ethanol dose was used, and mice of all strains were affected. Pharmacokinetic differences among strains were significant, but these could not account for strain differences in intoxication. For doses and test conditions in the middle range, there were only modest correlations among strain means within a test. In addition, genotypic correlations across tests were modest to quite low. These results suggest that different specific versions of a test reflect the influence of different genes, and that genetic influences on different tests were also distinct.

The evolution of gene expression in mouse hippocampus in response to selective breeding for increased locomotor activity.

The evolution of behavior has been notoriously difficult to study at the molecular level, but mouse genetic technology offers new promise. We applied selective breeding to increase voluntary wheel running in four replicate lines of Mus domesticus (S mice) while maintaining four additional lines through random breeding to serve as controls (C mice). The goal of the study was to identify the gene expression profile of the hippocampus that may have evolved to facilitate the increased voluntary running. The hippocampus was of interest because it is known to display marked physiological responses in association with wheel running itself. We used high-density oligonucleotide arrays representing 11,904 genes. To control for the confounding influence of physical activity itself on gene expression, animals were housed individually without access to running wheels, and were sampled during the day when they are normally inactive. Two-month-old female mice in estrus were used (n = 16 total; two per line; 8 S and 8 C). After correcting for an acceptable false discovery rate (10%), 30 genes, primarily involved in transcription and translation, significantly increased expression whereas 23 genes, distributed among many categories including immune function and neuronal signaling, decreased expression in S versus C mice. These changes were relatively small in magnitude relative to the changes in gene expression that occur in the hippocampus in response to wheel running itself. A priori tests of dopamine receptor expression levels demonstrated an increase of approximately 20% in the expression of D2 and D4 receptors. These results suggest that relatively small changes in the expression patterns of hippocampal genes underlie large changes in phenotypic response to selection, and that the genetic architecture of running motivation likely involves the dopaminergic system as well as CNS signaling machinery.

Hippocampal brain-derived neurotrophic factor but not neurotrophin-3 increases more in mice selected for increased voluntary wheel running.

Voluntary wheel running in rats increases hippocampal brain-derived neurotrophic factor (BDNF) expression, a neurochemical important for neuronal survival, differentiation, connectivity and synaptic plasticity. Here, we report the effects of wheel running on BDNF and neurotrophin-3 (NT-3) protein levels in normal control mice, and in mice selectively bred (25 generations) for increased voluntary wheel running. We hypothesized that increased voluntary wheel running in selected (S) mice would increase CNS BDNF and NT-3 protein levels more than in control (C) mice. Baseline hippocampal BDNF levels (mice housed without running wheels) were similar in S and C mice. Following seven nights of running, hippocampal BDNF increased significantly more in S versus C mice, and levels were correlated with distance run (considering C and S mice together). Spinal and cerebellar BDNF and hippocampal NT-3 levels were not significantly affected by wheel running in any group, but there was a small, positive correlation between spinal C3-C6 BDNF levels and distance run (considering C and S mice together). This is the first study to demonstrate that mice which choose to run more have greater elevations in hippocampal BDNF, suggesting enhanced potential for exercise-induced hippocampal neuroplasticity.

Differential sensitivity to acute administration of Ritalin, apomorphine, SCH 23390, but not raclopride in mice selectively bred for hyperactive wheel-running behavior.

RATIONALE: Previous studies of mice ( Mus domesticus) selectively bred for high voluntary wheel running have suggested that the hyperactivity is associated with dysfunction in the dopaminergic neuromodulatory system and that high-running mice may represent a useful genetic model for attention deficit hyperactivity disorder (ADHD). OBJECTIVES: We tested the hypothesis that mice from the four replicate hyperactive lines would respond differently to methylphenidate (Ritalin), apomorphine (non-selective dopamine agonist), SCH 23390 (selective D1-like dopamine antagonist), and raclopride (selective D2-like dopamine antagonist) than individuals from the four replicate, randomly bred, control lines. METHODS: After animals were habituated (3 weeks) to their cages with attached wheels, drugs were administered via intraperitoneal injections, at night, during peak wheel-running activity. Revolutions on wheels 10-70 min post-injection were used to quantify drug responses. RESULTS: Ritalin (15 mg/kg and 30 mg/kg) increased wheel running in control lines but decreased running in selected lines. A low-dose (0.125 mg/kg) of apomorphine reduced wheel running by a similar amount in control and selected lines; however, higher doses of apomorphine (0.25 mg/kg and 0.5 mg/kg) produced greater reductions in wheel running in the control lines. SCH 23390 (0.025, 0.05, and 0.1 mg/kg) caused greater reductions in wheel running in control than in selected lines. Raclopride (0.5, 1, and 2 mg/kg) reduced wheel running by a similar amount in control and selected lines. CONCLUSIONS: These results support the interpretation that genetically determined hyperactive wheel-running behavior is associated with altered dopaminergic function in this mouse model. More specifically, results suggest that D1-like (D1 or D5), but not D2-like (D2, D3, or D4), dopamine receptors have reduced function in the high-running mice. The fact that Ritalin decreased wheel running in selected lines further supports their use as an animal model of ADHD.

Differential sensitivity to acute administration of cocaine, GBR 12909, and fluoxetine in mice selectively bred for hyperactive wheel-running behavior.

RATIONALE: To study the neural basis of genetic hyperactivity, we measured acute drug responses of mice (Mus domesticus) from four replicate lines that had been selectively bred (23-24 generations) for increased running-wheel activity. OBJECTIVES: We tested the hypothesis that the high-running lines would respond differently to cocaine, GBR 12909, and fluoxetine (Prozac) compared with four replicate, random-bred, control lines. We also tested the hypothesis that the high-running lines would display hyperactivity in cages without wheels. METHODS: Drug trials were conducted at night, during peak activity, after animals were habituated (3 weeks) to their cages with attached wheels. Revolutions on wheels 10-40 min post-injection were used to quantify drug responses. In a separate study, total photobeam breaks (produced on the first and second 24-h period of exposure) were used to quantify basal activity in animals deprived of wheels. RESULTS: Cocaine and GBR 12909 decreased wheel running in selected lines by reducing the average speed but not the duration of running, but these drugs had little effect in control lines. Fluoxetine reduced running speed and duration in both selected and control animals, and the magnitude of the reduction was proportional to baseline activity. Basal activity in animals deprived of wheels (quantified using photobeam breaks) was significantly higher in selected than control lines on the second day of testing. CONCLUSIONS: These results suggest an association between genetically determined hyperactive wheel-running behavior and dysfunction in the dopaminergic neuromodulatory system. Our selected lines may prove to be a useful genetic model for attention deficit hyperactivity disorder.

Genetic selection of mice for high voluntary wheel running: effect on skeletal muscle glucose uptake.

Effects of genetic selection for high wheel-running activity (17th generation) and access to running wheels on skeletal muscle glucose uptake were studied in mice with the following treatments for 8 wk: 1) access to unlocked wheels; 2) same as 1, but wheels locked 48 h before glucose uptake measurement; or 3) wheels always locked. Selected mice ran more than random-bred (nonselected) mice (8-wk mean +/- SE = 8,243 +/- 711 vs. 3,719 +/- 233 revolutions/day). Body weight was 5-13% lower for selected vs. nonselected groups. Fat pad/body weight was ~40% lower for selected vs. nonselected and unlocked vs. locked groups. Insulin-stimulated glucose uptake and fat pad/body weight were inversely correlated for isolated soleus (r = -0.333; P < 0.005) but not extensor digitorum longus (EDL) or epitrochlearis muscles. Insulin-stimulated glucose uptake was higher in EDL (P < 0.02) for selected vs. nonselected mice. Glucose uptake did not differ by wheel group, and amount of running did not correlate with glucose uptake for any muscle. Wheel running by mice did not enhance subsequent glucose uptake by isolated muscles.

Brimonidine purite 0.15% versus dorzolamide 2% each given twice daily to reduce intraocular pressure in subjects with open angle glaucoma or ocular hypertension.

BACKGROUND/AIMS: To evaluate the efficacy of brimonidine purite versus dorzolamide given twice daily in primary open angle glaucoma or ocular hypertensive subjects. METHODS: In this double masked, multicentre, prospective, crossover comparison 33 subjects were randomised to brimonidine purite or dorzolamide for the first 4 week treatment period after a 4 week washout. Subjects began the opposite treatment for the second 4 week period after another 4 week washout. Intraocular pressure (IOP) was measured at 08:00 (trough) and 10:00, 18:00, and 20:00 hours after dosing at each baseline and at the end of each treatment period. RESULTS: The baseline diurnal IOP was 22.9 (SD 2.8) for brimonidine purite and 22.2 (SD 2.4) mm Hg for dorzolamide. The trough IOP following 4 weeks of therapy was 21.0 (SD 3.7) for brimonidine purite and 21.0 (SD 3.1) mm Hg for dorzolamide (p = 0.90). The mean diurnal IOP was 19.3 (SD 3.1) for brimonidine purite and 19.8 (SD 2.4) mm Hg for dorzolamide (p = 0.46). Dorzolamide caused more ocular stinging upon instillation (n = 8) than brimonidine purite (n = 1) (p = 0.02). No statistical differences existed between groups for systemic adverse events. CONCLUSIONS: This study suggests that brimonidine purite and dorzolamide each given twice daily have similar efficacy in primary open angle glaucoma or ocular hypertensive subjects. However, a trend was observed at 10:00 of greater brimonidine purite efficacy compared with dorzolamide.

Root canal retreatment: I. Case assessment and treatment planning.

Root canal retreatment is often the preferred method of treating a tooth in which root canal treatment has failed. Part one of this two-part article discusses reasons for failure of root canal treatment, case assessment and treatment planning. Part two describes some of the practical techniques that are available to the practitioner and the rationale for root canal retreatment.

Root canal retreatment: 2. Practical solutions.

Root canal retreatment is often the preferred method of treating a tooth in which root canal treatment has failed. Part two of this two-part article discusses the rationale for root canal retreatment and practical techniques and equipment that are available to practitioners.