A circadian rhythm in neural activity can be recorded from the central nervous system of the cockroach

Summary Evidence presented in this paper indicates that a robust circadian rhythm in the frequency of neural activity can be recorded from the central nervous system of intact cockroaches, Leucophaea maderae. This rhythmicity was abolished by optic lobe removal. Spontaneous neural activity was then used as an assay to demonstrate that the optic lobe is able to generate circadian oscillations in vitro. These results provide direct evidence that the cockroach optic lobe is a self-sustained circadian oscillator capable of generating daily rhythms in the absence of neural or hormonal communications with the rest of the organism.Abbreviations CNS central nervous system - DD constant dark - LD light/dark cycle - SCN suprachiasmatic nucleus - ZT Zeitgeber time     

Therapeutic electrical stimulation of the central nervous system

The electrical effects on the nervous system have been known for long. The excitatory effect has been used for diagnostic purposes or even for therapeutic applications, like in pain using low-frequency stimulation of the spinal cord or of the thalamus. The discovery that High-Frequency Stimulation (HFS) mimics the effect of lesioning has opened a new field of therapeutic application of electrical stimulation in all places where lesion of neuronal structures, such as nuclei of the basal ganglia, had proven some therapeutic efficiency. This was first applied to the thalamus to mimic thalamotomy for the treatment of tremor, then to the subthalamic nucleus and the pallidum to treat some advanced forms of Parkinson's disease and control not only the tremor but also akinesia, rigidity and dyskinesias. The field of application is increasingly growing, currently encompassing dystonias, epilepsy, obsessive compulsive disease, cluster headaches, and experimental approaches are being made in the field of obesity and food intake control. Although the effects of stimulation are clear-cut and the therapeutic benefit is clearly recognized, the mechanism of action of HFS is not yet understood. The similarity between HFS and the effect of lesions in several places of the brain suggests that this might induce an inhibition-like process, which is difficult to explain with the classical concept of physiology where electrical stimulation means excitation of neural elements. The current data coming from either clinical or experimental observations are providing elements to shape a beginning of an understanding. Intra-cerebral recordings in human patients with artefact suppression tend to show the arrest of electrical firing in the recorded places. Animal experiments, either in vitro or in vivo, show complex patterns mixing inhibitory effects and frequency stimulation induced bursting activity, which would suggest that the mechanism is based upon the jamming of the neuronal message, which is by this way functionally suppressed. More recent data from in vitro biological studies show that HFS profoundly affects the cellular functioning and particularly the protein synthesis, suggesting that it could alter the synaptic transmission by reducing the production of neurotransmitters. It is now clear that this method has a larger field of application than currently known and that its therapeutical applications will benefit to several diseases of the nervous system. The understanding of the mechanism has opened a new field of research, which will call for reappraisal of the basic effects of electricity on the living tissues.     

Spontaneous regeneration of the central nervous system in gastropods

Of all organs in mammals including humans, the brain has the most limited regenerative capacity after injury or damage. In spite of extensive efforts to treat ischemic/stroke injury of the brain, thus far no reliable therapeutic method has been developed. However, some molluscan species show remarkable brain regenerative ability and can achieve full functional recovery following injury. The terrestrial pulmonates are equipped with a highly developed olfactory center, called the procerebrum, which is involved in olfactory discrimination and odor-aversion learning. Recent studies revealed that the procerebrum of the land slug can spontaneously recover structurally and functionally relatively soon after injury. Surprisingly, no exogenous interventions are required for this reconstitutive repair. The neurogenesis continues in the procerebrum in adult slugs as in the hippocampus and the olfactory bulb of mammals, and the reconstitutive regeneration seems to be mediated by enhanced neurogenesis. In this review, we discuss the relationship between neurogenesis and the regenerative ability of the brain, and also the evolutionary origin of the brain structures in which adult neurogenesis has been observed.     

Pyridine alkaloids with activity in the central nervous system

This review discusses all pyridine alkaloids with CNS activity, their therapeutic potential, and the interesting array of sources whence they originate.     

CCD imaging of the electrical activity in the leech nervous system

A single ganglion of the nervous system of the leechHirudo medicinalis was isolated. One or both roots emerging from each side of the ganglion were sucked into suction pipettes used either for extracellular stimulation or for recording the gross electrical activity. The ganglion was stained with the fluorescence voltage sensitive dye Di-4-Anepps. The fluorescence was measured with a nitrogen cooled CCD camera. Our recording system allowed us to measure in real time slow optical signals corresponding to changes in light intensity of at least 5. These signals were caused by the direct polarization of neuronal structures, the afterhyperpolarization or the afterdischarge induced by a prolonged stimulation. When images were acquired at fixed times, several of them could be averaged and optical signals of at least 2 could be reliably measured. These optical signals originated from well identified neurons, such as T, P and N sensory neurons. By taking images at different times and at different focal planes, electrical events could be followed at a temporal resolution of 50 Hz. The three dimensional dynamics of electrical events, initiated by a specific stimulation, was imaged and the spread of excitation among leech neurons was followed. When two roots were selectively stimulated, their neuronal interactions could be imaged and the linear and non-linear terms of the interaction could be characterized.     

Spontaneous electrical activity of the claustrum

The dynamics of spontaneous electrical activity of the rostral, dorsal, ventral, and caudal parts of the claustrum were studied in chronic experiments on 12 dogs with implanted electrodes during extinction of orienting reactions and during biologically meaningful changes in the animals' functional state. In the animal at rest, electrical activity of the claustrum was similar to that of subcortical structures, but in a state of attention, its activity began to resemble that of the electrocorticogram, in agreement with the view that this nucleus occupies an intermediate position between cortical and subcortical structures. Enhancement of fast activity in the claustrum with the appearance of orienting reactions was expressed more intensively, and during extinction it was preserved for a longer time, in the dorsal and ventral parts of the claustrum than in the rostral and caudal parts, evidence of structural heterogeneity of the nucleus. Under conditions of increased food excitability the amplitude and frequency of the fast waves recorded from the rostral and caudal parts of the claustrum were selectively increased, whereas during reflexes to a rejected stimulus (acids) and in defensive reflexes they were increased in recordings from the dorsal and ventral parts, on which basis the existence of specialized efferent zones participating in biologically different types of activity can be postulated. Enhancement of fast activity in the claustrum during reflexes to food and acid differed in its genesis: The switch from the first to the second took place through a phase of suppression of the first. Differentiation of a food-conditioned stimulus was accompanied by the development of active inhibition in the "food zones" of the claustrum and by enhancement of activity in the "zones of orienting reactions."A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 12, No. 2, pp. 155–164, March–April, 1980.     

Spontaneous electrical activity and effects of noradrenaline on pregnant human myometrium recorded by the single sucrose-gap method

Spontaneous intracellular electrical activity and contraction of pregnant human myometrium were recorded by the single sucrose-gap method, and the effects of noradrenaline on the muscle were studied. Human myometrium obtained at various stages of gestation showed three types of action potentials, which were spike-, plateau- and intermediate-type in configuration. In human isthmic myometrium at full-term pregnancy dissected from the endometrial side of the uterine wall, both plateau and spike types of action potential were observed. All contractions were well synchronized with each action potential. These results indicate the possibility of the intertwinning of two different types of muscle bundles. The magnitude of contraction depended on the frequency of the spikes in spike-type or the plateau duration in plateau-type action potentials. The alpha-excitatory action of noradrenaline (2 X 10(-7) g/ml) was found to affect the configuration of the action potential; even the spike-type configuration became plateau.     

Immune-mediated clearance of virus from the central nervous system

Immune-mediated clearance of virus from the central nervous system (CNS) differs from that of the other organs. Mechanisms of virus control are largely dependent upon the target cell type. Although cytolytic T lymphocytes may mediate clearance of virus from glial cells, non-cytolytic mechanisms mediated by antibody and cytokines dominate clearance from neurons.     

Sildenafil acts on the central nervous system increasing sympathetic activity.

Sildenafil induces vasodilation and is used for treating erectile dysfunction. Although its influence on resting heart function appears to be minimal, recent studies suggest that sildenafil can increase sympathetic activity. We therefore tested whether sildenafil injected into the central nervous system alters the autonomic control of the cardiovascular system in conscious rats. The effect of sildenafil citrate injected into the lateral cerebral ventricle was evaluated in conscious rats by means of the recording of lumbar sympathetic nerve activity (LSNA), spectral analysis of systolic arterial pressure and heart rate variability, spontaneous baroreflex sensitivity, and baroreflex control of LSNA. Intracerebroventricular (ICV, 100 microg /5 microl) administration of sildenafil caused remarkable tachycardia without significant change in basal arterial pressure and was associated with a conspicuous increase (47 +/- 14%) in LSNA. Spectral analysis demonstrated that systolic arterial pressure oscillations in the low frequency (LF) range were increased (from 6.3 +/- 1.5 to 12.8 +/- 3.8 mmHg(2)), whereas the high frequency (HF) range was not affected by ICV administration of sildenafil. Sildenafil increased pulse interval oscillations at LF and decreased them at HF. The LF-HF ratio increased from 0.04 +/- 0.01 to 0.17 +/- 0.06. Spontaneous baroreflex sensitivity measured by the sequence method and the baroreflex relationship between mean arterial pressure and LSNA were not affected by ICV administration of sildenafil. In conclusion, sildenafil elicited an increase in sympathetic nerve activity that is not baroreflex mediated, suggesting that this drug is able to elicit an autonomic imbalance of central origin. This finding may have implications for understanding the cardiovascular outcomes associated with the clinical use of this drug.     

Angiotensin II increases MAO activity in rat central nervous system

The effects of angiotensin II (ANG II) and bilateral nephrectomy on monoamine oxidase (MAO) activity were studied in rat hypothalamus and medulla oblongata. ANG II increased MAO activity in both central nervous system (CNS) regions. The fall of circulating ANG II caused by 48 h bilateral nephrectomy decreased the activity of the enzyme in the mentioned areas. The results showed that ANG II stimulates catecholamine metabolism in the CNS.