Firing Type Research Articles

Tactile input to the facial lobe of the carp, Cyprinus carpio L.

Summary Single unitary discharges in the facial lobe and trigeminofacial nerve trunks of the carp,Cyprinus carpio L., were studied electrophysiologically in response to electrical stimulation of the trigeminofacial nerve complex and the facial skin, and to chemical and tactile stimulation of the facial skin. Recording bimodal responses to chemical and tactile stimulation after sectioning the cranial Vth or VIIth (communis) nerves, and microelectrode recordings of trigeminal and facial (communis) nerve trunks revealed that taste messages are transmitted to the brain by the communis fibers and tactile ones by the trigeminus. Latencies measured in the facial lobe by electrical stimulation of the trigeminofacial nerve complex or the facial skin surface ranged from 6 to 59 msec, most firing between 10 and 29 msec in both cases. The receptive field sizes of the lobe neurons were larger than those of the primary ones. Of 84 neurons recorded from the facial lobe, 96.5% were facilitated by press and gliding movements with a glass rod on the facial skin and 3.5% by changing barbel's position. The glide group was classified into three types which were tonically firing (52.4% of total neurons), adaptive firing (39.3%) and after firing (4.8%) types. Twelve out of 84 tactile neurons responded to chemical solution, as well. The latencies of taste neurons were not centered at a certain range. The facial lobe of the carp is not only a primary gustatory center, but also a tactile one, and might play an important role for the purpose of effecting a correlation of the two diverse modalities.

Characteristics of rat aortic baroreceptors with nonmedullated afferent nerve fibers.

Nervous activity was recorded from nonmedullated afferent baroreceptor fibers in the left aortic nerve of normotensive rats. The aortic arch was perfused in vitro with oxygenated Krebs-Henseleit solution. Two different patterns of aortic C fiber discharge were found. One type (5 of 29 fibers) had a regular discharge at constant pressure whereas the other type had an irregular discharge. The differences between the two types were independent of the mean steady state rates of discharge. The average threshold pressure for the receptors with the regular discharge was 87 mm Hg (range, 65-125); it was 152 mm Hg (range, 85-260) for the irregularly discharging receptors. During a pressure step the receptors in either group normally showed an initial high frequency burst of activity and a sustained discharge which had a lower frequency. Furthermore, the peak discharge and the sustained discharge were lower on the average in the receptors with the irregular type of firing. We also found that addition of norepinephrine to the perfusate lowered threshold. Since unmyelinated axons are the predominant fiber type in the rat aortic nerve and since some receptors are activated at physiological pressures they may contribute to the tonic control of blood pressure. Their effects should be particularly important when the blood pressure is increased.

A quantitative correlation between single unit activity and fluorescence intensity of dopamine neurones in zona compacta of substantia nigra, as demonstrated under the influence of nicotine and physostigmine

In order to investigate the possible relationship between neuronal activity and cellular fluorescence intensity, extracellular recordings of single unit activity and determinations of fluorescence intensity of dopamine (DA) neurones by histochemical microfluorimetry were performed in the same (rostral) part of zona compacta of substantia nigra in male rats. In urethane anaesthesia, zona compacta neurones characteristically showed a slow and fairly regular type of firing. Nicotine (1 mg/kg s.c.) induced a transient decrease in unit activity for 1 min followed by a sustained increase in firing rate. During that stage, 4–5 neurones/rat were recorded at different anteroposterior levels, each during 200 sec. Microfluorimetric examination of the fluorescence intensity developed at the end of the 30-min observation period by the DA neurones of the same area revealed a marked rise in cellular fluorescence intensity. Similar results were obtained with a lower dose of nicotine and/or a shorter observation period. Additional microiontophoretic experiments supported the view that extracellular recordings of the correlative electrophysiological-microfluorimetric investigation belonged to DA neurones. Release of DA from terminals was indicated by an increase in HVA concentration of caudate-putamen in rats subjected to the same nicotine treatment. When tested on one cell during a prolonged period of time, physostigmine (0.25 mg/kg i.p.) caused an initial increase in firing rate of zona compacta neurones (5–10) min) followed by a decrease of unit activity (15–23 min). In agreement with previous observations in mice, fluorescence intensity of nigral DA neurones likewise showed a biphasic change with an initial rise and subsequent decrease (examined at 9.5 and 22–23.5 min, respectively). When mean unit activity and mean fluorescence intensity of individual rats out of the various experimental groups were related to each other, a highly significant positive correlation between neuronal fluorescence intensity and firing rate was found. The results obtained with physostigmine demonstrate that mean intensity closely paralleled mean unit activity in time, so that this correlation was maintained. These findings indicate that cellular fluorescence intensity of DA neurone groups can be used as an index of the level of neuronal activity, except for cases where a drug treatment interferes directly with catecholamine synthesis or storage mechanisms.

Analyse statistique de l'activite des cellules pyramidales de l'hippocampe dorsal du lapin

The spontaneous activity of CA 1 pyramidal cells was recorded with microelectrodes from the hippocampus of curarized adult rabbits under painless fixation. A statistical analysis of the data was made by a computer, using a program developed to process time interval series. 1. 1. Various temporal patterns of discharge were observed. A classification into 5 distinct patterns could be disclosed, based on statistical parameters, particularly expectation density, joint interval histogram and interspike interval histogram. 2. 2. The recorded neurones were distributed unequally in these groups, the distribution varying with sleep and wakefulness. 3. 3. Some firing patterns prevailed during wakefulness and some during sleep, but all of them were observed in both states and no one was considered specific to one state. 4. 4. The variability in neuronal discharge was estimated. “Stable” cells (60%) exhibited only one firing pattern. “Unstable” cells (40%) exhibited either two (82%) or three (18%) types of firing. 5. 5. 65% of the cells recorded during waking and then during sleep shifted their firing pattern. The majority of the other units (35%), which kept the same pattern of discharge, were already stable during waking. Hence, they exhibited only one firing pattern and did not appear to be affected by sleep or waking.

Hypothalamic supraoptic neurones: rates and patterns of action potential firing during water deprivation in the unanaesthetized monkey

Extracellulary recorded action potentials were obtained from hypothalamic supraoptic neurones in unanaesthetized rhesus monkeys. Rates and patterns of firing were studied during an initial control period, during 5 successive days of water deprivation and during 4 further days when drinking water was again available. During water deprivation, plasma osmolarity increased progressively from about 300 mOsmoles/kg to about 340 mOsmoles/kg; control values were again reached after 3 days of rehydration. Systematic changes in action potential firing accompanied the changes in plasma osmolarity. Under control conditions, the majority of cells fire slowly and irregularly (type i), whilst a few cells exhibited phases of alternating activity and silence (type p). As dehydration progresses, the frequency of neuronal firing increase and the pattern of firing changes. By the third day the majority of cells are type p with few type i cells being found. By the fourth day, the population consists of type p cells with some others showing a high continuous rate of firing (type c). By the fifth day, these two cell types are found in approximately equal proportions. Rehydration of the animal reverses the situation. We propose that type i cells contribute little, if at all, to hormone secretion, while type p and type c cells would be in a more actively secreting state. According to this view, the three firing patterns would represent different activity states of the same functional population stimulated by the unspecific stimulus of water deprivation rather than functionally different neurones. However, the use of stimuli which selectively release their oxytocin or vasopressin may be needed to answer this problem.

Systolic and diastolic pacemaker induced repetitive firing in the human heart: Analysis of 23 cases

Twenty-three tracings obtained from patients showing pacemaker-induced repetitive firing were reviewed. This complication was manifested as single extra beats, ventricular tachycardia and ventricular fibrillation. Cases in which a definite relation between pacemaker stimuli and multiple responses could not be established were excluded from this series. Systolic repetition was observed in 17 patients. This phenomenon, which was attributed to ventricular vulnerability occurred during chronic block (12 cases) as well as during acute myocardial infarction (5 cases). There were 5 instances of diastolic repetitive firing in patients with digitalis intoxication and recent myocardial infarction. It was postulated that a Wedensky-effect best explained the genesis of diastolic repetition. Knowledge regarding the types and possible mechanisms of the different types of repetitive firing can be applied for the safer use of continuous, demand and ventriculo-synchronized pacemakers.

Responses of neurones in cat's abducens nuclei to horizontal angular acceleration.

Single cell activity was recorded extracellularly from neurones in cat's abducens nuclei in unanesthetized, decerebrate preparations. Two types of neurones were found. i) The motoneurones (type IIA) increased their firing linearly or exponentially to contralateral constant angular accelerations and decreased firing to ipsilateral rotation. The increased frequency was maintained at a constant level without any sign of adaptation. This constant level of maximum frequency was proportional to the logarithm of the acceleration applied. No significant differences of the frequency responses of tonic and silent motoneurones were found. The conduction velocities of the axons of spontaneously firing type IIA cells were slower than in silent neurones. Electrical stimulation of the contralateral VIIIth nerve led to activation of the type IIA cells; stimulation of the ipsilateral nerve resulted in inhibition of both spontaneous discharge and antidromic invasion of the motoneurones. ii) The type IA units increased their firing rate to ipsilateral rotation and ceased to discharge in response to contralateral rotation. They never were excited antidromically by stimulation of the VIth nerve. However, they were excited by stimulation of the ipsilateral VIIIth nerve. Their possible functional role in the vestibulo-ocular system was discussed.

A study of the action of angiogensin on the superior cervical ganglion in comparison with other ganglion stimulating agents

Angiotensin injected intra-arterially to the superior cervical ganglion of the cat in doses ranging from 0.125 μg to 1000 μg enhances the transmission, with maximum effect in the 30th–60th sec and a return to the control values in the 10th min after injection. The time course of this angiotensin-induced facilitating effect on transmission is similar to that induced by McN-A-343. The enhancement of transmission produced by nicotine appears sooner, 10 sec after injection, and reaches its maximum at the same time. With increasing doses of angiotensin the facilitation of transmission does not change into blockade even at a dose of 1000 μg. Histamine in dose of 500 μg did not block transmission. We did not observe an inhibition of transmission after doses of angiotensin ranging from 10 −15 to 10 −11 g injected to the ganglion. I.v. injected angiotensin in a dose of 50 μg/kg/2 min also produces facilitation of transmission with a similar time course to that produced by McN-A-343. Pretreatment with reserpine, guanethidine, dibenamine or pronethalol did not modify the action of angiotensin on transmission. The postganglionic firing could be induced by i.a. injection of angiotensin to the ganglion in doses ranging from 0.01 μg to 1000 μg after repetitive preganglionic stimulation. The type of firing is similar to that produced by McN-A-343 and histamine, characterized by a later onset and longer duration than the firing produced by nicotine. The angiotensin-induced postganglionic firing was not inhibited by previous injection of atropine, hexamethonium or mepyramine.

Utilization of Coal Ash through the Slag Tap Furnace

From the view point of utilization of coal ashes, the production of various by-productsash-cement, ash-wool and fused phosphate-is undertaken through a small test furnace of a slag-tap firing type. Further described here are the test results and some consideration about the industrial procedure in the future. These by-products, in their qualities, are comparatively inferior to the like products on the market. They are, however, economically valuable from the point of utilizing the very wastes-coal ashes-as raw materials. The purpose of applying both sintering and quality-control furnaces for the production of cement and wool lies in eliminating the trouble caused by the load variation unavoidable in the practical boiler operation, and also lies in improving the quality of the by-products themselves. These auxiliary-furnaces, in the present level of development in the fields of industries, are considered the very useful measures for the realization of them in their industrial scale.

Influence of Firing Conditions, Composition, and Screening Media on the Zeta Potentials of ZnS Phosphors as Related to Adherence to Glass Surfaces

Zeta potentials were determined by the streaming potential method as a function of firing conditions, flux, activator, phosphor coating, and type and concentration of screening media. The effect of these factors on adherence was determined by the jet impingement method. Positive zeta potentials were obtained in solutions and in during all stages of phosphor preparation prior to the coating operation. Either positive or negative potentials are obtained with the finished phosphor depending on the type of coating used. Firing conditions also have been found to be important in determining the sign of the zeta potential. A general trend toward enhanced wet adherence with decreasing negative zeta potential and increasing positive zeta potential has been noted.The influence of electrolyte concentration on the zeta potentials of powders was measured with solutions of the following materials: , , mixtures, , polyvinyl alcohol, and mixtures of and polyvinyl alcohol.