Neuromuscular responses of the plantar flexors to whole-body vibration

Enhanced physical performance following whole-body vibration (WBV) has been attributed to increased muscle activity; however, few studies have measured the mechanisms underlying these changes. The objective of this study was to measure the responsiveness of the Ia pathway as well as contractile properties in 16 young adults (24±2 years, eight men, eight women) following repeated bouts of acute WBV (45 Hz, 2 mm). Hoffman reflexes (H-reflex), compound muscle action potentials (M-wave), and twitch contractile properties were measured prior to and immediately following five 1-minute WBV exposures, and at 3, 5, 10, and 20 minute post-WBV. M-wave and H-reflex amplitudes decreased by 8% (P<.001) and by 46% (P<.05), respectively, whereas peak twitch torque decreased by 9% (P<.01) and rate of twitch torque development slowed 8% (P<.05). Percent voluntary activation and maximal plantar flexor torque were unchanged as a consequence of WBV (P>.05). In response to acute WBV, the root mean square of the soleus electromyography signal (EMG_RMS ) increased by 8%, while the EMG_RMS of the lateral gastrocnemius increased by 3% (P<.05). These data indicate that the responsiveness of the Ia pathway is diminished and contractile function is impaired immediately following WBV, and that the neural mechanisms underlying improved performance following WBV lie in alternative hypotheses possibly involving spindle disfacilitation or Golgi afferent modulation.

In vivo, large-scale preparation of uniformly (15)N- and site-specifically (13)C-labeled homogeneous, recombinant RNA for NMR studies

Knowledge of how ribonucleic acid (RNA) structures fold to form intricate, three-dimensional structures has provided fundamental insights into understanding the biological functions of RNA. Nuclear magnetic resonance (NMR) spectroscopy is a particularly useful high-resolution technique to investigate the dynamic structure of RNA. Effective study of RNA by NMR requires enrichment with isotopes of (13)C or (15)N or both. Here, we present a method to produce milligram quantities of uniformly (15)N- and site-specifically (13)C-labeled RNAs using wild-type K12 and mutant tktA Escherichia coli in combination with a tRNA-scaffold approach. The method includes a double selection protocol to obtain an E. coli clone with consistently high expression of the recombinant tRNA-scaffold. We also present protocols for the purification of the tRNA-scaffold from a total cellular RNA extract and the excision of the RNA of interest from the tRNA-scaffold using DNAzymes. Finally, we showcase NMR applications to demonstrate the benefit of using in vivo site-specifically (13)C-labeled RNA.

Minicircle DNA Provides Enhanced and Prolonged Transgene Expression Following Airway Gene Transfer

Gene therapy for cystic fibrosis using non-viral, plasmid-based formulations has been the subject of intensive research for over two decades but a clinically viable product has yet to materialise in large part due to inefficient transgene expression. Minicircle DNA give enhanced and more persistent transgene expression compared to plasmid DNA in a number of organ systems but has not been assessed in the lung. In this study we compared minicircle DNA with plasmid DNA in transfections of airway epithelial cells. In vitro, luciferase gene expression from minicircles was 5–10-fold higher than with plasmid DNA. In eGFP transfections in vitro both the mean fluorescence intensity and percentage of cells transfected was 2–4-fold higher with minicircle DNA. Administration of equimolar amounts of DNA to mouse lungs resulted in a reduced inflammatory response and more persistent transgene expression, with luciferase activity persisting for 2 weeks from minicircle DNA compared to plasmid formulations. Transfection of equal mass amounts of DNA in mouse lungs resulted in a 6-fold increase in transgene expression in addition to more persistent transgene expression. Our findings have clear implications for gene therapy of airway disorders where plasmid DNA transfections have so far proven inefficient in clinical trials.

Early detection of cerebral glucose uptake changes in the 5XFAD mouse

Brain glucose hypometabolism has been observed in Alzheimer’s disease (AD) patients, and is detected with ¹⁸F radiolabelled glucose, using positron emission tomography. A pathological hallmark of AD is deposition of brain β-amyloid plaques that may influence cerebral glucose metabolism. The five times familial AD (5XFAD) mouse is a model of brain amyloidosis exhibiting AD-like phenotypes. This study examines brain β-amyloid plaque deposition and ¹⁸FDG uptake, to search for an early biomarker distinguishing 5XFAD from wild-type mice. Thus, brain ¹⁸FDG uptake and plaque deposition was studied in these mice at age 2, 5 and 13 months. The 5XFAD mice demonstrated significantly reduced brain ¹⁸FDG uptake at 13 months relative to wild-type controls but not in younger mice, despite substantial β-amyloid plaque deposition. However, by comparing the ratio of uptake values for glucose in different regions in the same brain, 5XFAD mice could be distinguished from controls at age 2 months. This method of measuring altered glucose metabolism may represent an early biomarker for the progression of amyloid deposition in the brain. We conclude that brain ¹⁸FDG uptake can be a sensitive biomarker for early detection of abnormal metabolism in the 5XFAD mouse when alternative relative uptake values are utilized.

Consequences of obesity and weight loss: a devil's advocate position

Obesity is associated with multiple negative health consequences and current weight management guidelines recommend all obese persons to lose weight. However, recent evidence suggests that not all obese persons are negatively affected by their weight and that weight loss does not necessarily always improve health. The purpose of this review is not to trivialize the significant health risks associated with obesity, but to discuss subpopulations of obese people who are not adversely affected, or may even benefit from higher adiposity, and in who weight loss per se may not always be the most appropriate recommendation. More specifically, this review will take a devil's advocate position when discussing the consequences of obesity and weight loss for adults with established cardiovascular disease and type 2 diabetes, weight cyclers, metabolically healthy obese adults, youth, older adults and obese individuals who are highly fit.

Combating child obesity: impact of HENRY on parenting and family lifestyle

BACKGROUND

One-quarter of children in England are overweight/obese at school entry. We investigated the impact of a programme designed to provide parents of infants and preschool children with the skills required for a healthier family lifestyle.

METHOD

A cohort of families was followed across the 8-week HENRY (Health Exercise Nutrition for the Really Young) parent course at nine locations in England. Seventy-seven parents enrolled on the course, of which 71 agreed to complete questionnaires addressing eating behaviours, dietary intake and parental self-efficacy. Pre- and post-course data was available from 60 (84.5%) parents (8-week follow-up data from 58 parents) and was analysed using repeated measures analyses.

RESULTS

Significant changes were observed, with most sustained at follow-up. Parents reported increased self-efficacy and ability to encourage good behaviour (P < 0.001). Increased consumption of fruits and vegetables was reported in both children and adults, together with reduced consumption of sweets, cakes and fizzy drinks in adults (all P < 0.01). There were also positive changes in eating behaviours (e.g., frequency of family mealtimes and eating while watching television or in response to negative emotion [P < 0.01] ) and reduced screen time in adults (P < 0.001).

DISCUSSION

The results build upon earlier evaluation, indicating that the HENRY intervention has a beneficial impact upon the families of infants and preschool children. Furthermore, the findings suggest that positive changes inspired by the programme can be maintained beyond its completion. Such changes may serve to protect against later obesity.

The cholinergic agonist carbachol increases the frequency of spontaneous GABAergic synaptic currents in dorsal raphe serotonergic neurons in the mouse

Dorsal raphe nucleus (DRN) serotonin (5-HT) neurons play an important role in feeding, mood control and stress responses. One important feature of their activity across the sleep-wake cycle is their reduced firing during rapid-eye-movement (REM) sleep which stands in stark contrast to the wake/REM-on discharge pattern of brainstem cholinergic neurons. A prominent model of REM sleep control posits a reciprocal interaction between these cell groups. 5-HT inhibits cholinergic neurons, and activation of nicotinic receptors can excite DRN 5-HT neurons but the cholinergic effect on inhibitory inputs is incompletely understood. Here, in vitro, in DRN brain slices prepared from GAD67-GFP knock-in mice, a brief (3 min) bath application of carbachol (50 μM) increased the frequency of spontaneous inhibitory postsynaptic currents (sIPSCs) in GFP-negative, putative 5-HT neurons but did not affect miniature (tetrodotoxin-insensitive) IPSCs. Carbachol had no direct postsynaptic effect. Thus, carbachol likely increases the activity of local GABAergic neurons which synapse on 5-HT neurons. Removal of dorsal regions of the slice including the ventrolateral periaqueductal gray (vlPAG) region where GABAergic neurons projecting to the DRN have been identified, abolished the effect of carbachol on sIPSCs whereas the removal of ventral regions containing the oral region of the pontine reticular nucleus (PnO) did not. In addition, carbachol directly excited GFP-positive, GABAergic vlPAG neurons. Antagonism of both muscarinic and nicotinic receptors completely abolished the effects of carbachol. We suggest cholinergic neurons inhibit DRN 5-HT neurons when acetylcholine levels are lower i.e. during quiet wakefulness and the beginning of REM sleep periods, in part via excitation of muscarinic and nicotinic receptors located on local vlPAG and DRN GABAergic neurons. Higher firing rates or burst firing of cholinergic neurons associated with attentive wakefulness or phasic REM sleep periods leads to excitation of 5-HT neurons via the activation of nicotinic receptors located postsynaptically and presynaptically on excitatory afferents.

Use of a sestamibi-only approach to routine minimally invasive parathyroidectomy

We performed this study to compare a sestamibi-only radio-guided approach (MIBI) versus using intraoperative parathyroid hormone monitoring (IOPTH) in the performance of minimally invasive parathyroidectomy (MIP) in patients with a clearly positive preoperative sestamibi scan from January 2000 to June 2010. Five of 81 patients in the MIBI group required additional surgery, three at the time of MIP when the intraoperative findings were in conflict with the preoperative sestamibi scan and two required a second operation as a result of an undiscovered second adenoma. In the IOPTH group, five patients had an unnecessary bilateral neck exploration as a result of an inadequate drop in PTH levels, whereas six had their disease cured because the PTH levels predicted additional pathology. One patient in the IOPTH group remains hypercalcemic and represents the only surgical failure in this study. The MIBI group had a shortened operating room time and less cost (P < 0.001). No deaths or complications, including recurrent laryngeal nerve injuries, occurred in this study. Although both strategies are effective in managing hyperparathyroidism, a MIBI-only approach is less expensive and has shorter operative times with an occasional need for reoperation, whereas the IOPTH group results in more extensive surgery that will occasionally be unnecessary.

Abstract P3-06-06: Lactate dehydrogenase B in breast cancer contributes to glycolytic phenotype and predicts response to neoadjuvant chemotherapy

Purpose: Although breast cancers are known to be molecularly heterogeneous, their metabolic heterogeneity is less well understood. This study aimed to identify and evaluate metabolic biomarkers in breast cancers and determine their ability to predict outcomes.

Methods: mRNA microarray data from breast cancer cell lines were used to identify bimodal genes, those with the highest potential for robust high/low classification in a clinical setting. Using a panel of breast cancer cell lines, expression and activity of the highest scoring bimodal metabolism gene, lactate dehydrogenase B (LDHB), was quantified and associated with glycolytic phenotype. The contribution of LDHB to glycolysis was evaluated using MDA-MB-231 and HCC1937 cell lines with stable lentiviral knockdown of LDHB. mRNA expression of LDHB was evaluated for association with neoadjuvant chemotherapy response within clinical and PAM50-derived subtypes.

Results: LDHB was highly expressed in cell lines with glycolytic, basal-like phenotypes. Knockdown of LDHB in cell lines reduced glycolytic dependence, linking LDHB expression directly to metabolic function. Using four independent patient datasets, LDHB mRNA expression was positively associated with basal subtype and negatively associated with luminal and HER2 subtypes. Furthermore, LDHB predicted basal phenotype independently of hormone-receptor (HR) clinical status (OR = 21.6 for HR-positive/HER2-negative and OR = 18.2 for triple-negative). While LDHB expression could predict basal phenotype, high LDHB expression identified aggressive breast cancer tumors that were primarily but not exclusively basal. Importantly, high LDHB expression predicted pathological complete response to neoadjuvant chemotherapy for both hormone receptor (HR) positive/HER2-negative (OR = 4.0, P = .0002) and triple-negative (OR = 3.0, P = .003) cancers. Consistent with increased response to chemotherapy, LDHB expression in basal cancers within the triple-negative group was associated with the proliferative marker CCNB1 (P &lt; .0001).

Conclusion: mRNA expression of LDHB as a single marker predicted glycolytic phenotype in cell lines and response to neoadjuvant chemotherapy in breast cancers independently of HR status. These observations support prospective clinical evaluation of LDHB as a predictive marker of response for breast cancer patients treated with neoadjuvant chemotherapy.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P3-06-06.

The cost of managing genital warts in the UK

The national cost of managing genital warts (GWs) in the UK has not been fully estimated, yet is required to inform decisions on vaccination against human papillomavirus. This study estimated the 2010 UK costs based on secondary genitourinary (GU) medicine clinic data from the Health Protection Agency (HPA) and primary care data from the Health Improvement Network database. Extrapolating data to 2010 resulted in 173,077 GU medicine clinic and 16,782 primary care GW episodes. Using treatment patterns obtained from key opinion leaders and tariffs from National Health Service Payment by Results (NHS PbR), the national costs were estimated at £52.4 million: £276 per treated GW episode.

Complex receptor mediation of acute ketamine application on in vitro gamma oscillations in mouse prefrontal cortex: modeling gamma band oscillation abnormalities in schizophrenia

Schizophrenia (Sz), along with other neuropsychiatric disorders, is associated clinically with abnormalities in neocortical gamma frequency (30-80 Hz) oscillations. In Sz patients, these abnormalities include both increased and decreased gamma activity, and show a strong association with Sz symptoms. For several decades, administration of sub-anesthetic levels of ketamine has provided the most comprehensive experimental model of Sz-symptoms. While acute application of ketamine precipitates a psychotic-like state in a number of animal models, as well as humans, the underlying mechanisms behind this effect, including alteration of neuronal network properties, are incompletely understood, making an in vitro level analysis particularly important. Previous in vitro studies have had difficulty inducing gamma oscillations in neocortical slices maintained in submerged-type recording chambers necessary for visually guided whole-cell recordings from identified neurons. Consequently, here, we validated a modified method to evoke gamma oscillations using brief, focal application of the glutamate receptor agonist kainate (KA), in slices prepared from mice expressing green fluorescent protein in GABAergic interneurons (GAD67-GFP knock-in mice). Using this method, gamma oscillations dependent on activation of AMPA and GABA(A) receptors were reliably elicited in slices containing mouse prelimbic cortex, the rodent analogue of the human dorsolateral prefrontal cortex. Examining the effects of ketamine on this model, we found that bath application of ketamine significantly potentiated KA-elicited gamma power, an effect mimicked by selective NMDAR antagonists including a selective antagonist of NMDARs containing the NR2B subunit. Importantly, ketamine, unlike more specific NMDAR antagonists, also reduced the peak frequency of KA-elicited oscillatory activity. Our findings indicate that this effect is mediated not through NMDAR, but through slowing the decay kinetics of GABA(A) receptor-mediated inhibitory postsynaptic currents in identified GABAergic interneurons. These in vitro findings may help explain the complexities of gamma findings in clinical studies of Sz and prove useful in developing new therapeutic strategies.

Analysis of sensory, motor and cognitive functions of the coloboma (C3Sn.Cg-Cm/J) mutant mouse

The coloboma mutant mouse (C3Sn.Cg-Cm/J) has been proposed as an animal model of attention-deficit hyperactivity disorder (ADHD) because of excessive locomotion in the open field, yet few studies have looked at other behavioral measures in these mice. We analyzed activity levels of male and female Cm mice and their littermate controls (C3H) in two different types of open field, as well as their hearing (acoustic startle) and sensorimotor gating (prepulse inhibition), pain responsiveness (tail flick and hot plate), motor control (balance beam), motor learning (Rotarod), hippocampal working memory (spontaneous alternation in a Y-maze) and olfactory learning and memory (conditioned odor preference). We found hyperactivity and a lack of habituation in the small and large open fields and a deficit in prepulse inhibition in these mice, as well as a learning deficit in male Cm mice in conditioned odor preference but no deficits in pain perception or spontaneous alternation. Results from the rotarod and balance beam tasks indicate that Cm mice have severe motor co-ordination and balance problems compared to their C3H littermates, suggesting that Cm mice may be a more suitable model of ataxia than ADHD.

Tissue-specific effects of valsartan on rstn and fiaf gene expression in the ob/ob mouse

The RAS is a novel target in the study of diabetes, and clinical trials have indicated that ARBs, such as valsartan, may exert some of their clinical effects through an influence on adipose tissue. We studied the effect of valsartan on adipokine genes resistin (rstn) and fasting-induced adipose factor (fiaf) using obese and diabetic ob/ob mice. In addition to visceral and subcutaneous fat, rstn and fiaf mRNA levels were also measured in several other tissues known to express these adipokines, including the pituitary, cerebral cortex and hypothalamus. The significant findings were that (a) fiaf gene expression was elevated two- to fourfold in visceral and subcutaneous fat from ob/ob mice, compared with lean controls; (b) the increase in fiaf mRNA in subcutaneous, but not visceral, fat from ob/ob mice was returned to lean control levels following 2 weeks of valsartan treatment; (c) fiaf expression was reduced in the hypothalamus, but not in the cortex or pituitary, of ob/ob mice; (d) rstn expression was greatly reduced in visceral fat from ob/ob mice, compared with lean controls, but this was unaffected by valsartan; and (e) rstn expression was unchanged in all other tissues from ob/ob mice, with or without valsartan treatment.

The effects of principal-implemented techniques on the behavior of pupils

Three investigations were conducted on the effects of various procedures initiated by a principal on the behavior of elementary school children. Seventy nine children including kindergarten, first, third, and fifth graders served as subjects. In Experiment I, when three chronically absent children attended school, the principal entered their classrooms and praised them for being present. In Experiment II, three low-achieving subjects were sent to the principal's office to receive praise contingent on meeting predetermined criteria in word-recognition and addition tutoring sessions. Experiment III assessed the effects that a procedure implemented by a principal had on the academic functioning of 74 third graders. Twice weekly in two classrooms the principal recognized both improving students and the highest performing students for their work on addition study sheets. In all three experiments, the target behaviors increased when the principal applied the treatment contingencies. The application of multiple baseline designs revealed a functional relationship between the children's behavior and the procedures implemented by the principal. Since the study was carried out in an overcrowded innercity public school, it was suggested that the treatment procedures might be widely applicable.

Issues in blood pressure control and the potential role of single-pill combination therapies

Hypertension (HTN) is a major risk factor for cardiovascular mortality, yet only a small proportion of hypertensive individuals receive appropriate therapy and achieve target blood pressure (BP) values. Factors influencing the success of antihypertensive therapy include physicians' acceptance of guideline BP targets, the efficacy and tolerability of the drug regimen, and patient compliance and persistence with therapy. It is now well recognised that most hypertensive patients require at least two antihypertensive agents to achieve their target BP. However, complicated treatment regimens are a major contributory factor to poor patient compliance. The use of combination therapy for HTN offers a number of advantages over the use of monotherapy, including improved efficacy, as drug combinations with a synergistic mechanism of action can be used. This additive effect means that lower doses of the individual components can be used, which may translate into a decreased likelihood of adverse events. The use of single-pill combination therapy, in which two or more agents are combined in a single dosage form, offers all the benefits of free combination therapy (improved efficacy and tolerability over monotherapy) together with the added benefit of improved patient compliance because of the simplified treatment regimen. The use of single-pill combination therapy may also be associated with cost savings compared with the use of free combinations for reasons of cheaper drug costs, fewer physician visits and fewer hospitalisations for uncontrolled HTN and cardiovascular events. Thus, the use of single-pill combination therapy for HTN should help improve BP goal attainment through improved patient compliance, leading to reduced costs for cardiovascular-related care.

Effects of sepsis on neonatal thrombopoiesis

We serially evaluated the effects of sepsis and/or necrotizing enterocolitis (NEC) on neonatal thrombopoiesis, using a panel of tests that included platelet counts, thrombopoietin concentrations (Tpo), circulating megakaryocyte progenitor concentrations (CMPs), and reticulated platelets (RPs). Variables analyzed included sepsis type, time after onset of sepsis, platelet counts, and gestational (GA) and postconceptional ages (PCA). Twenty neonates were enrolled. Ten had Gram-negative, six had Gram-positive, and four had presumed sepsis. Four neonates had NEC stage II or higher, and six developed thrombocytopenia. Overall, septic neonates had significantly elevated Tpo concentrations and circulating megakaryocyte progenitors. The highest Tpo levels were associated with Gram-negative or presumed sepsis. RP percentages were increased only in neonates with low platelet counts, while RP counts (RP% x platelet count) were elevated in neonates with high platelet counts. Our findings suggest that septic neonates up-regulate Tpo production, leading to increased megakaryocytopoiesis and platelet release, although the degree of upregulation is moderate. The changes in RP% and RP count most likely reflect increased thrombopoiesis with variable degrees of platelet consumption. In addition, our findings suggest that different factors, likely including level of illness and/or specific platelet or bacterial products, can down-regulate the magnitude of the thrombopoietic response.

Neonatal thrombocytopenia: what we do and don't know

The evaluation and management of thrombocytopenia is a frequent challenge for neonatologists, as it affects 22-35% of infants admitted to the neonatal intensive care unit. Multiple disease processes can cause neonatal thrombocytopenia, and these can be classified as those inducing early thrombocytopenia (< or =72 h of life) and those inducing late-onset thrombocytopenia (>72 h). Most cases of neonatal thrombocytopenia are mild to moderate, and do not warrant intervention. In approximately 25% of affected neonates, however, the platelets count is <50 x 10(9)/L, and therapy with platelet transfusions is considered to decrease the risk of hemorrhage. The existing evidence to establish platelet transfusion triggers in neonates is very limited, but it suggests that transfusing platelets to non-bleeding neonates with platelet counts >50 x 10(9)/L does not decrease the risk of intraventricular hemorrhage (IVH), and that 30 x 10(9)/L might be an adequate threshold for stable non-bleeding neonates. However, adequately powered multi-center studies are needed to conclusively establish the safety of any given set of neonatal transfusion guidelines.

KiSS-1 mRNA in adipose tissue is regulated by sex hormones and food intake

Hypothalamic KiSS-1 gene expression is critical for the maintenance of reproductive function, and levels are attenuated by sex hormones and by food restriction, providing a link between fat mass and fertility. We hypothesized that adipose tissue (FAT) would express KiSS-1. KiSS-1 mRNA was quantified in FAT, hypothalamus (HYP) and pituitary gland (PIT) using realtime RT-PCR. FAT KiSS-1 expression was sensitive to sex steroids and to nutritional status. Gonadectomized rats given estradiol (E; females) or testosterone (T; males) revealed striking increases in KiSS-1 mRNA in FAT (E: 8-fold, p<0.01; T: 5-fold, p<0.01). In contrast, HYP KiSS-1 expression was reduced by E/T, whereas PIT expression was reduced by gonadectomy only in females, reversed by E. Food restriction (18 h) increased FAT KiSS-1 mRNA in both sexes (2.5-4.0-fold, p<0.01), but decreased levels in male PIT and female HYP. Conversely, FAT expression was reduced in rats fed a high fat diet (HFD), as well as in obese Zucker rats, whereas PIT expression was increased in Zucker rats (p<0.05) but not by HFD. In contrast HYP KiSS-1 mRNA was elevated by HFD. Experiments in which the arcuate nucleus was damaged by an excitotoxic lesion revealed that hypothalamic KiSS-1 mRNA was significantly reduced, whereas FAT levels were unaffected, suggesting that regulation of KiSS-1 in FAT is independent of the hypothalamus. In conclusion, KiSS-1 expression is differentially regulated by sex hormones, food intake and obesity in FAT, HYP and PIT. Kisspeptins of adipose tissue origin may act as adipokines or as local regulators of adipocyte function.

Visual detection, pattern discrimination and visual acuity in 14 strains of mice

Based on the procedure of Prusky et al. (2000, Vision Research, 40, 2201-2209), we used a computer-based, two-alternative swim task to evaluate visual detection, pattern discrimination and visual acuity in 14 strains of mice from priority groups A and B of the JAX phenome project (129S1/SvImJ, A/J, AKR/J, BALB/cByJ, BALB/cJ, C3H/HeJ, C57BL/6J, CAST/Ei, DBA/2J, FVB/NJ, MOLF/Ei, SJL/J, SM/J and SPRET/Ei). Each mouse was tested for eight trials/day for 8 days on each of the three tests. There was a significant strain difference in visual ability in all three tests. Mice with reported normal vision (129S1/SvImJ, C57BL/6J and DBA/2J) and one albino strain (AKR/J) performed very well in these tasks. The other albino strains (A/J, BALB/cByJ and BALB/cJ) took longer to learn the tasks than mice with normal vision and did not reach the criterion of 70% correct. Mice with retinal degeneration (C3H/HeJ, FVB/NJ, MOLF/Ei and SJL/J) performed only at chance levels as did the three strains with unknown visual abilities (CAST/Ei, SM/J and SPRET/Ei). Because many behavioral tasks for rodents rely on visual cues, we suggest that the visual abilities of mice should be evaluated before they are tested in commonly used visuo-spatial learning and memory tasks.

Electrophysiological characterization of neurons in the dorsolateral pontine rapid-eye-movement sleep induction zone of the rat: Intrinsic membrane properties and responses to carbachol and orexins

Pharmacological, lesion and single-unit recording techniques in several animal species have identified a region of the pontine reticular formation (subcoeruleus, SubC) just ventral to the locus coeruleus as critically involved in the generation of rapid-eye-movement (REM) sleep. However, the intrinsic membrane properties and responses of SubC neurons to neurotransmitters important in REM sleep control, such as acetylcholine and orexins/hypocretins, have not previously been examined in any animal species and thus were targeted in this study. We obtained whole-cell patch-clamp recordings from visually identified SubC neurons in rat brain slices in vitro. Two groups of large neurons (mean diameter 30 and 27 mum) were tentatively identified as cholinergic (rostral SubC) and noradrenergic (caudal SubC) neurons. SubC reticular neurons (non-cholinergic, non-noradrenergic) showed a medium-sized depolarizing sag during hyperpolarizing current pulses and often had a rebound depolarization (low-threshold spike, LTS). During depolarizing current pulses they exhibited little adaptation and fired maximally at 30-90 Hz. Those SubC reticular neurons excited by carbachol (n=27) fired spontaneously at 6 Hz, often exhibited a moderately sized LTS, and varied widely in size (17-42 mum). Carbachol-inhibited SubC reticular neurons were medium-sized (15-25 mum) and constituted two groups. The larger group (n=22) was silent at rest and possessed a prominent LTS and associated one to four action potentials. The second, smaller group (n=8) had a delayed return to baseline at the offset of hyperpolarizing pulses. Orexins excited both carbachol excited and carbachol inhibited SubC reticular neurons. SubC reticular neurons had intrinsic membrane properties and responses to carbachol similar to those described for other reticular neurons but a larger number of carbachol inhibited neurons were found (>50%), the majority of which demonstrated a prominent LTS and may correspond to pontine-geniculate-occipital burst neurons. Some or all carbachol-excited neurons are presumably REM-on neurons.