Interaction of hypothalamic GABA\u3csub\u3eA\u3c/sub\u3e and excitatory amino acid receptors controlling heart rate in rats

We have previously shown that microinjection of drugs that impair gamma-aminobutyric acid (GABA)-mediated synaptic inhibition into the dorsomedial hypothalamus (DMH) of rats generates cardiovascular and behavioral changes that mimic the response to stress. The purpose of this study was to examine the role of excitatory amino acid (EAA) receptors in the DMH in generating the cardiovascular changes caused by withdrawal of local GABAergic inhibition in urethan-anesthetized rats. Local treatment of the DMH with the nonselective EAA antagonist kynurenic acid blocked or reversed the increases in heart rate and blood pressure caused by microinjection of the GABAA antagonists bicuculline methiodide (BMI) or picrotoxin into the same region. Conversely, similar injection of xanthurenic acid, a structural analogue of kynurenic acid without significant effects on EAA receptors, did not significantly alter the cardiovascular changes produced by either GABAA antagonist. The tachycardic effects of BMI were also attenuated by injection of either the N-methyl-D-aspartate (NMDA) receptor antagonist 2-amino-5-phosphonopentanoic acid or the non-NMDA EAA receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione. When the two EAA receptor antagonists were combined, their effects to suppress the BMI-induced tachycardia were additive. These findings suggest that the cardiovascular effects caused by blockade of GABAergic inhibition in the DMH of the rat are dependent on activation of local NMDA and non-NMDA EAA receptors

Hypothalamic excitatory amino acid receptors mediate stress-induced tachycardia in rats

The role of hypothalamic excitatory amino acid (EAA) receptors in mediating the cardiovascular response to stress was examined using conscious chronically instrumented rats. Microinjection of the EAA agonists N-methyl-D-aspartic acid (NMDA; 1-10 pmol), alpha-amino-3-hydroxy-5-methyl-4-isooxazolepropionic acid (AMPA; 0.3-3.0 pmol), or kainic acid (0.1-1.0 pmol) into the dorsomedial hypothalamus (DMH) elicited dose-related increases in heart rate and modest elevations in arterial pressure. Local microinjection of the NMDA antagonist 2-amino-5-phosphonopentanoic acid (AP5; 100 pmol) selectively blocked NMDA-induced cardiovascular changes, whereas the non-NMDA EAA antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX; 50 pmol) selectively blocked the responses to AMPA and kainic acid. In the stress trials, microinjection of the nonselective EAA antagonist kynurenic acid (1-10 nmol) into the DMH blocked air stress-induced tachycardia in a dose-related manner. Similar injection of kynurenic acid at sites lateral or posterior to the DMH or injection of xanthurenic acid (a structural analogue of kynurenic acid with no antagonistic properties at EAA receptors) into the DMH failed to influence air stress-induced cardiovascular changes. Injection of either AP5 or CNQX into the DMH at doses shown to be selective for their respective EAA receptor subtypes also attenuated air stress-induced tachycardia. Thus activity at EAA receptors in the DMH appears to be necessary for the generation of stress-induced changes in heart rate

GABA\u3csub\u3eA\u3c/sub\u3e and excitatory amino acid receptors in dorsomedial hypothalamus and heart rate in rats

We have previously shown that microinjection of drugs that interfere with the function of the inhibitory neurotransmitter gamma-aminobutyric acid (GABA) into the hypothalamus produces cardiorespiratory and behavioral changes resembling those seen in emotional stress. The purpose of this study was to determine whether excitatory amino acids (EAAs) can produce a cardiovascular response similar to that caused by the GABAA receptor antagonist bicuculline methiodide (BMI) when microinjected at the same hypothalamic site in urethan-anesthetized rats and to clarify the precise locus of action of these agents. N-methyl-D-aspartic acid (NMDA, 0.68-6.8 pmol/50 nl) and kainic acid (KA, 0.47-4.7 pmol/50 nl) produced dose-related increases in heart rate and blood pressure when injected at sites in the dorsomedial hypothalamus reactive to BMI (20 pmol/50 nl). Higher doses of NMDA (68 pmol), however, failed to elicit consistent increases in heart rate and blood pressure when injected at these same sites. The effects of NMDA were selectively blocked by the NMDA receptor antagonist 2-amino-5-phosphonopentanoic acid, whereas the effects of KA were selectively blocked by the non-NMDA EAA receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione. These results demonstrate that 1) blockade of inhibitory amino acid receptors or stimulation of EAA receptors in the dorsomedial nucleus of the hypothalamus produces tachycardic and pressor responses in urethan-anesthetized rats and 2) use of high doses of EAAs may be an unreliable method of evoking local neuronal excitation in certain regions of the central nervous system

Characterization of the relationship between spontaneous locomotor activity and cardiovascular parameters in conscious freely moving rats

In freely behaving rats, variations in heart rate (HR) and blood pressure (BP) are coupled closely with changes in locomotor activity (Act). We have attempted to characterize this relationship mathematically. In 10- and 16-week-old rats, HR, BP and Act were recorded telemetrically every minute for 2 days under 12h:12h light-dark cycling. After examining data for individual rats, we found that the relationship between Act and HR could be approximated by the negative exponential function HR(Act)=HRmax-(HRmax-HRmin)∗exp(-Act/Acte), where HRmax, HRmin, and Acte are constants. These constants were calculated separately for light and dark periods by non-linear curve fitting. HR corresponding to maximal locomotion was similar during the light and dark phases, while HR at rest during the dark phase was higher than during the light phase. The range of HR variability associated with Act during the dark phase was similar in young and older animals, but minimal HR was significantly lower in older rats. The relationship between Act and BP was approximated with a similar function. We have found no differences between BP at rest and at maximal locomotion between light and dark and between 10-week and 16-week-old rats. Our results indicate that in rats, cardiovascular parameters are coupled to locomotion to a high degree; however both the HR and the BP reach maximal values when locomotor activity is relatively low. We also found that the phase of daily cycle affects HR in conscious rats independent of locomotor activity

Muscimol acts in dorsomedial but not paraventricular hypothalamic nucleus to suppress cardiovascular effects of stress

Both the dorsomedial hypothalamic nucleus (DMH) and the paraventricular hypothalamic nucleus (PVN) have been implicated in the neural control of the cardiovascular response to stress. We used the GABAA agonist muscimol to inhibit neuronal activation and attempted to identify hypothalamic nuclei required for the cardiovascular response to air stress. Chronically instrumented rats received bilateral injections of either 80 pmol of muscimol or 100 nl of saline vehicle into the DMH, the PVN, or an intermediate area (including the rostral edge of the DMH and the region between the two nuclei) and were placed immediately in a restraining tube and subjected to 20 min of air stress. In all rats, air stress after vehicle injections caused marked increases in heart rate (137 +/- 6 beats/min) and blood pressure (26 +/- 2 mmHg). Microinjection of muscimol into the DMH suppressed the heart rate and blood pressure response by 85 and 68%, respectively. Identical microinjection of muscimol into the intermediate area between the DMH and the PVN attenuated the increases in heart rate by only 46% and in blood pressure by 52%. In contrast, similar injections into the vicinity of the PVN failed to alter the cardiovascular response to air stress. These findings demonstrate that muscimol-induced inhibition of neuronal activity in the region of the DMH blocks air stress-induced increases in heart rate and arterial pressure, whereas similar treatment in the area of the PVN has no effect

Changing small group interaction through visual reflections of social behavior

Thesis (Ph. D.)--Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 2005.Leaf 141 blank.Includes bibliographical references (leaves 135-140).People collaborating in groups have potential to produce higher-quality output than individuals working alone, due to the pooling of resources, information, and skills. Yet social psychologists have determined that groups rarely harness this potential. This thesis proposes that technology in face-to-face settings can be used to address the social factors that have damaging influence on group decision-making processes. While there is much work in the area of collaborative software and groupware, this work differentiates itself with its specific aim to influence the way a group shares information without mediating the group's communication. By presenting visualizations to the group of individual levels of participation and turn-taking behavior, the technology aims to augment the group's communication ability, by making it more aware of imbalances. A series of dynamic displays positioned peripherally to a discussion were developed and used by a variety of groups during face-to-face meetings. Both observational and experimental results indicate that these displays influence individual participation levels and the process of information sharing used during a decision-making discussion. A display revealing real-time participation levels caused those at the highest levels of participation to decrease the amount they spoke. Viewing a visualization of previous turn-taking patterns caused those who spoke the least to increase the amount they spoke in a subsequent discussion; real-time feedback did not produce this change. Additionally, after reviewing their turn-taking patterns, groups altered their information-sharing strategies.(cont.) For groups that had poor sharing strategies on an initial task, this change improved their ability to share information related to the decision; for those who did not need intervention, feedback on turn-taking was not beneficial for their subsequent information sharing. The central finding of this research is that displays of social information, viewed during or after a meeting, bring about changes in a group's communication style, highlighting the potential for such displays to improve real-world decision-making.by Joan Morris DiMicco.Ph.D

Organizational Chart Inference

Nowadays, to facilitate the communication and cooperation among employees, a new family of online social networks has been adopted in many companies, which are called the "enterprise social networks" (ESNs). ESNs can provide employees with various professional services to help them deal with daily work issues. Meanwhile, employees in companies are usually organized into different hierarchies according to the relative ranks of their positions. The company internal management structure can be outlined with the organizational chart visually, which is normally confidential to the public out of the privacy and security concerns. In this paper, we want to study the IOC (Inference of Organizational Chart) problem to identify company internal organizational chart based on the heterogeneous online ESN launched in it. IOC is very challenging to address as, to guarantee smooth operations, the internal organizational charts of companies need to meet certain structural requirements (about its depth and width). To solve the IOC problem, a novel unsupervised method Create (ChArT REcovEr) is proposed in this paper, which consists of 3 steps: (1) social stratification of ESN users into different social classes, (2) supervision link inference from managers to subordinates, and (3) consecutive social classes matching to prune the redundant supervision links. Extensive experiments conducted on real-world online ESN dataset demonstrate that Create can perform very well in addressing the IOC problem.Comment: 10 pages, 9 figures, 1 table. The paper is accepted by KDD 201

Yohimbine is a 5-HT1A agonist in rats in doses exceeding 1 mg/kg.

Yohimbine is a prototypical alpha2-adrenergic receptor antagonist. Due to its relatively high selectivity, yohimbine is often used in experiments whose purpose is to examine the role of these receptors. For example, yohimbine has been employed at doses of 1–5 mg/kg to reinstate drug-seeking behavior after extinction or to antagonize general anesthesia, an effects presumably being a consequence of blocking alpha2-adrenergic receptors. In this report we characterized dose-dependent autonomic and behavioral effects of yohimbine and its interaction with an antagonist of 5-HT1A receptors, WAY 100635. In low doses (0.5 – 2 mg/kg i.p.) yohimbine induced locomotor activation which was accompanied by a tachycardia and mild hypertension. Increasing the dose to 3–4.5 mg/kg reversed the hypertension and locomotor activation and induced profound hypothermia. The hypothermia as well as the suppression of the locomotion and the hypertension could be reversed by the blockade of 5-HT1A receptors with WAY 100635. Our data confirm that yohimbine possesses 5-HT1A properties, and demonstrated that in doses above 1 mg/kg significantly activate these receptors