腺苷A1受体在双相呼气和吸气神经元电活动中的作用

目的探讨腺苷A1受体对双相呼气神经元和吸气神经元电活动的影响。方法制作新生大鼠体外延髓脑片标本，主要包含面神经后核内侧区(the medialregion of the nucleus retrofacialis，mNRF)，并保留舌下神经根的完整，以改良Kreb’s液灌流脑片，同步记录舌下神经根和双相呼气神经元/吸气神经元的放电活动。在灌流液中分别单独给予腺苷A1受体的特异性拮抗剂8-环戊-1，3-二丙基黄嘌呤(8-cyclopentyl-1，3-dipropylxa nthine，DPCPX)和特异性激动剂R-苯异丙基-腺苷(R—phenylisoprpyl—adeno sine，R-PIA)观察对神经元放电的影响。结果给予腺苷A1受体拮抗剂DPCPX后，双相呼气神经元/吸气神经元的呼吸周期和呼气时程明显缩短，单位放电峰频率显著性增大；给予相应激动剂R-PIA后，双相呼气神经元的呼气时程明显延长，放电频率和积分幅度显著降低，吸气神经元的放电时程和中期放电的频率和峰频率显著性降低，而早期和晚期的放电频率无明显改变。结论腺苷A1受体可能通过影响双相呼气神经元的电活动参与了呼吸时相的转换，并可能介导了吸气神经元的抑制性突触输入。     

Multifocal atrial arrhythmia—A frequent misdiagnosis? A correlative study using the computerized ECG

All computerized ECGs taken over a 17-week study period were reviewed for the detection of multifocal atrial arrhythmia (MAA)--tachycardia or rhythm--and correlated with the diagnostic statement of the ECG computer system. MAA was identified by the authors in 96 of 11,610 (0.8%) computerized ECGs. In all instances, this specific arrhythmia was misclassified by the computer system as atrial fibrillation. Moreover, during the over-read, only 27.1% of ECGs were correctly diagnosed by the assigned electrocardiographers blinded to this study. MAA is not an uncommon atrial arrhythmia since it was identified in 14% of computerized ECGs interpreted as atrial fibrillation. This study supports the inference that MAA is indeed frequently misdiagnosed by most physicians and the need for improved ECG computer analysis programs for reliable detection of MAA.     

Dipole sources of the human alpha rhythm

Summary Dipole sources were investigated in 22 normal subjects with a variety of strategies available through the BESA program. When all the data were summed one regional source, located near the midline in the basal portions of the occipital lobe, explained 92% of the variance. Two regional sources, initially constrained for symmetry but subsequently freed from constraint placed them also in the occipital regions near the midline and reduced the residual variance to 4%. Pooled data obscure, however, the marked individual differences especially in regard to lateralization. In the individual case the major source was also always in one occipital area but its location, especially the degree of separation from the midline depended upon alpha distribution and the strategy used in the workup of the data. The orientation of the major components of the regional sources was usually in the posterior-anterior direction, fairly parallel to the midline and while the other one pointed to the upper convexity. Because of the considerable variability of the alpha rhythm in given subjects and even within the same individual a model which requires symmetry constraints is not optimal for all instances, even when constraints are lifted thereafter. The study demonstrated the feasibility of distinguishing predominantly mesial sources from those which are bihemipheric with more lateral origins but several different models may have to be used to reach the most realistic conclusions.The authors would like to express their appreciation to Dr. Michael Scherg for his help and advice.     

Paradoxical sympathetic nerve response to baroreceptor reflex activation

Spectral analysis revealed an enhancement of cardiac-related postganglionic sympathetic nerve discharge (SND) in response to elevated blood pressure in cats. Most of the enhancement occurred at blood-pressure levels above which coherence of SND to the arterial pulse at the frequency of the heart beat became maximal. This raises the possibility that the enhancement is due to mechanisms other than improved phase locking of SND to pulse-synchronous baroreceptor afferent nerve activity.     

Morning bright light therapy for sleep and behavior disorders in elderly patients with dementia

Fourteen inpatients with dementia showing sleep and behavior disorders (average age = 75 years), and 10 control elderly people (average age = 75 years) were carefully observed for 2 months. Four weeks of morning light therapy markedly improved sleep and behavior disorders in the dementia group. The measurement of sleep time and the serum melatonin values suggests that sleep and behavior disorders in the dementia group are related to decreases in the amplitude of the sleep-wake rhythm and decreases in the levels of melatonin secretions. Morning light therapy significantly increased total and nocturnal sleep time and significantly decreased daytime sleep time. These results indicate that morning bright light is a powerful synchronizer that can normalize disturbed sleep and substantially reduce the frequency of behavior disorders in elderly people with dementia.     

GENERATION AND ENTRAINMENT OF ORCADIAN RHYTHMS

1. The present brief review examines some of the new developments in the area of circadian rhythm research. 2. The discovery of the mouse clock and m-per genes and their similarity to other clock genes like per and tint has provided new insight into the control of rhythms in vertebrates. In mice, these genes are expressed in the site of the biological clock, the suprachiasmatic nucleus (SCN), and so will now become a focus of research into the generation of rhythmicity. 3. Because SCN cells expressing endogenous rhythms have a periodicity different from 24 h, there must be mechanisms in place to reset the rhythms on a daily basis. This is achieved in mammals by retinal light perception and neural transmission through several discrete pathways to the SCN. 4. The nature of the neurotransmitters involved in this transfer of environmental information to the timing system is controversial and may even vary between similar species but, in the rat, there is compelling evidence that a serotonergic pathway is pre-eminent in mediating the effects of light. How the re-setting is achieved at the cellular level is not known.     

Possible factors which may affect phase durations in the natural chewing rhythm

To study central and peripheral control mechanisms maintaining rhythmical jaw behaviors, chewing movements with different foods in texture were obtained in the freely behaving rabbit. Jaw movement trajectories and muscle activities (masseter, digastric, thyrohyoid) were recorded and the durations in total cycle, fast closing (FC), slow closing (SC), and opening (OP) phases were obtained as well as the burst duration in the muscles. Durations varied cycle-by-cycle and among the foods, however, the total cycle duration was found to have little differences among the foods tested. Regression analyses were applied to seek time relations to the change in total cycle duration with the duration in its constituent phases. Results suggested that changes in the total cycle duration may be due to those in the SC duration (power phase) with hard food (heavy load), but due to those in the OP duration (reverse phase) with soft food (light load). The duration of the FC was fairly constant for all the foods tested. In conclusion, the chewing rhythm may be controlled centrally to be independent of the load, and chewing cycles may begin at the middle of the opening phase.     

Colchicine-induced deafferentation of the hippocampus selectively disrupts cholinergic rhythmical slow wave activity

It has been proposed that hippocampal rhythmical slow wave activity (RSA or theta-rhythm) induced by sensory stimulation (atropine-sensitive theta) is generated by the cholinergic septo-hippocampal system. Although ablations of the septum or its projections to the hippocampus disrupt hippocampal RSA, such non-selective lesions damage both cholinergic and non-cholinergic septo-hippocampal inputs. The present study assesses the effects of a selective septal neurotoxic lesion on hippocampal electrical activity. Colchicine, which has been reported to be selectively toxic to cholinergic neurons in the medial septum, was injected into the right lateral ventricle, and electrodes were implanted bilaterally into the dorsal hippocampus of female Sprague-Dawley rats. Hippocampal electrical activity was recorded 10-14 days later from the ipsilateral (colchicine-treated) and contralateral (control) hemispheres during locomotor activity or immobility. RSA ranging from 6.3 to 8.7 Hz was evoked in both hippocampi during mobility. Following i.p. administration of an anesthetic dose of urethane, hippocampal RSA at a frequency of 4 Hz could be elicited in the control hemisphere (n = 12) of all animals by pinching the tail. RSA was absent in 6 of 9 animals in the colchicine-treated hemisphere. RSA from control and treated hemispheres persisting after urethane administration was abolished by 5 mg/kg of scopolamine, thus verifying its cholinergic nature. A decrease in the number of choline acetyltransferase (ChAT)-immunoreactive neurons in the medial septum and a depletion of acetylcholinesterase (AChE)-staining in the hippocampus were evident in the hemisphere ipsilateral to colchicine administration. These data support the septal pacemaker hypothesis of hippocampal theta-rhythm and further demonstrate the neurotoxic effect of colchicine on septo-hippocampal cholinergic neurons by the induction of a functional alteration. The selective disruption of cholinergic neurons in the medial septum by colchicine provides a means to dissociate the contribution of septal cholinergic and non-cholinergic components to hippocampal electrical activity.     

大鼠面神经后核内侧区传入／传出纤维投射

实验在 2 0只成年SD大鼠上进行。面神经后核内侧区 (mNRF)内微量注射辣根过氧化物酶 (HRP ,0 .5～ 1.0 μl,30 % ,13例。对照组 2例 ) /麦芽凝集素辣根过氧化物酶 (WGA HRP ,0 .0 2～ 0 .0 6 μl,5 % ,5例 ) ,逆行 /顺行追踪mNRF的传入和传出纤维联系。发现 :HRP标记神经元胞体主要位于延髓孤束核 (NTS)、疑核 (AMB)、巨细胞网状核 (Gi)、中缝核群 (raphenuclei)、脑桥臂旁核 (PB)、K F核、脊髓中间带 (intermediatezone)、延髓及脑桥网状结构 ;WGA HRP标记神经纤维主要存在于孤束核、疑核、脊髓中间带、延髓网状结构。结果提示 :mNRF神经元与脑干后部一些核团之间具有比较广泛的纤维联系 ,延髓基本呼吸节律起源过程中可能受其调控     

Colocalization of γ-aminobutyric acid with vasopressin,vasoactive intestinal peptide,and somatostatin in the rat suprachiasmatic nucleus

The seemingly contradictory observations in previous publications that γ-aminobutyric acid (GABA) is detected in all cell bodies of the suprachiasmatic nucleus (SCN) and that terminals originating from the SCN are only 20–30% GABA positive prompted us to investigate whether this might be explained by a preference of colocalization in terminals of certain peptidergic neurons in the SCN or by a day/night rhythm in GABA synthesis. At three different circadian times, animals were perfusion fixed, and their SCNs were stained for vasopressin (VP), somatostatin (SOM), or vasoactive intestinal polypeptide (VIP). Subsequently, the number of GABA peptide-positive terminals was determined using GABA postembedding staining in ultrathin sections. It appeared that the highest percentage of colocalization with GABA was detected in VIP terminals (38%) and the lowest in VP terminals (15%). No differences in colocalization percentages could be observed in any parameter at any circadian time. In the dorsomedial hypothalamus, one of the target areas of the VP and VIP fibers from the SCN, a colocalization of GABA within VP and VIP terminals was found similar to that in the SCN. In the region of the somatostatin-containing neurons in the SCN, a number of axoaxonal contacts could be observed that sometimes exhibited synaptic specializations. In nearly all cases, the axoaxonic terminals contained GABA and/or SOM. The conclusion is that the high level of intrinsic GABAergic connections in the SCN represents a putatively powerful mechanism to synchronize or shut down the activity of the SCN. We discuss the possibility that, depending on the firing frequency of the neurons, the colocalization of GABA with all peptides under investigation allows for the selection of which transmitter is released, the peptidergic one or the amino acid. © 1995 Wiley-Liss, Inc.