Very slow rhythmic variations in the potential of the nuclei of the hypothalamus and the thalamus

Summary Infraslow oscillations (8 cycles per minute, 0.5–1 mv) formerly revealed in the rabbit's brain cortex, were also registered in the premammillary hypothalamus. This infraslow rhythm was absent in the thalamic nuclei of intact animal, but could be revealed after acting upon the brain metabolism by strichnine or atropine.Electric stimulation of hypothalamic dorsal-medial and ventral-medial nuclei increases the amplitude and the regularity of the infraslow rhythm in the sensomotor brain cortex and the hypothalamus proper.After strychnine injection the intensification of the infraslow fluctuations appears in the hypothalamus 10–30 minutes earlier than in the brain cortex.Prolonged stimulation of hypothalamus may cause generalized infraslow oscillations synchronic in different protions of the brain. Creating a definite gradient of electric field in the brain cortex the infraslow potential affects the excitalility of neurons, reflecting the association between the neuroendocrine function and the electric activity of the brain. Infraslow oscillations are one of the links in the integrative brain activity.Presented by Active Member of the AMN SSSR V. N. Chernigovskii     

Changes in the blood cholesterol concentration during electrical stimulation of the hypothalamus

Summary Hypothalamus takes part in blood cholesterol control. Electrical stimulation of hypothalamus provokes changes in the blood cholesterol level. The character of these changes depends on localization of the stimulation. Electrical stimulation of the anterior part of the hypothalamus causes a fall, and of the posterior part—a rise in the blood cholesterol level. The change of blood cholesterol caused by electrical stimulation of the mid portion, of the hypothalamus depends on the initial blood cholesterol level. Stimulation of the mid portion of the hypothalamus raises an initially low, and lowers an initially high, cholesterol level.(Presented by Active Member AMN SSSR A. V. Lebedinskii) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 57, No. 4, pp. 34–37, April, 1964     

电刺激VSA对IL-1β作用下兔POAH温敏神经元放电的影响关

目的和方法:本实验采用微电极细胞外记录,在32只新西兰兔下丘脑视前区(POAH)记录温敏神经元单位放电,观察电刺激腹中膈区(VSA)对致热原IL-1_β作用下兔POAH温敏神经元放电的影响。结果:(1)侧脑室注射白介素-1_β(IL-1_β)能使POAH热敏神经元放电减少,冷敏神经元放电增加;而侧脑室注射人工脑脊液(ACSF)对热敏神经元和冷敏神经元的放电均无明显影响。(2)电刺激VSA可反转IL-1_β对POAH热敏神经元和冷敏神经元的上述作用。结论:VSA可能作为负调节中枢参与致热原作用下的体温调节。     

Medial hypothalamic electrical stimulation is ineffective in suppressing septal lesion induced hyperreactivity

Animals made hyperreactive by lesions in the septal forebrain had bipolar electrodes implanted unilaterally in the medial hypothalamus while animals made hyperreactive by lesions in the medial hypothalamus had electrodes implanted unilaterally ventral to the anterior septum. Postoperatively, the animals' reactivity level was scored 5 min before, during, and 5 min following stimulation at 20 μA (60 Hz). Over 3 test days, unilateral electrical stimulation ventral to the anterior septum caused a mean decrease in reactivity of 42% while stimulation in the medial hypothalamus had no effect over a range of intensities (5–20 μA). Electrical recordings revealed no poststimulus afterdischarges associated with the suppression of reactivity. Stimulation in the medial hypothalamus was slightly rewarding. It is suggested that the failure to suppress reactivity by electrical stimulation of the medial hypothalamus may be due to an organization of neural circuitry in that region which makes it difficult for a single behavior to be elicited by electrical stimulation.     

Effects of electrical stimulation in the lower brainstem on temperature regulation in the unanaesthetized guinea-pig

Summary Electrical stimulation in lower brainstem areas presumed to be parts of the ascending noradrenergic system was carried out in the unanaesthetized guinea-pig. In the same animals noradrenaline (NA) was also injected into the anterior hypothalamus. Certain points in the lower brainstem were found, the stimulation of which resulted in a rise of oxygen uptake (more than 60% over the resting level), of body temperature and of electrical muscle activity at an ambient temperature of 29–30°C. Respiratory rate also rose on stimulation, while heart rate did not show a consistent change. All these changes were found to be very similar to those obtained after an intrahypothalamic injection of NA. When the electrical stimulations at the same sites were repeated several times the extent of rise in oxygen uptake became gradually smaller, amounting to only half of the initial response after four periods of stimulation. An intrahypothalamic injection of NA restored the effectiveness of electrical stimulation in the lower brainstem to the original extent.These results suggest that the thermogenesis evoked by the electrical stimulation of these lower brainstem areas may be ascribed to the activation of ascending noradrenergic pathways terminating in the hypothalamus.This study was supported by the Deutsche Forschungsgemeinschaft (SFB 122, Projekt B1).     

Bloodflow measurements of the neuromuscular apparatus of the internal carotid arteries made by a photometric method. Communication II. Control of the sympathetic nervous system

Summary Experiments were made on the internal carotid arteries of dogs and rabbits using Cybulski and Klisiecki's method of photohemotachometry. A considerable constriction of the ipsilateral internal carotid artery followed electrical stimulation (2 v) of the superior cervical sympathetic ganglion; a stronger stimulation (6 v) caused complete closure of the arterial lumen. Ergotamine blocked this effect. Simultaneous recordings of the bloodflow in both internal carotid arteries revealed periodical vasomotor fluctuations of the lumen. The effect appeared to be exerted by sympathetic control over these arteries.Presented by Active Member AMN SSSR I. S. Beritashvili Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 55, No. 2, pp. 17–22, February, 1963.     

Alteration of EEG activity of the hypothalamus by thermal stimulation of the spinal cord

Summary EEG activity of various parts of the hypothalamus was recorded in unanaesthetized guinea pigs during thermal stimulation of the spinal cord. In the anterior hypothalamus fast waves became more prominent when the spinal cord temperature (T _sc ) was raised from 40° to 42° C, resulting in an increase of the mean frequency by about 50%. The electrical activity remained unaffected whenT _sc was raised from 38° to 40° C. In the posterior hypothalamus, spinal cord heating from 39.5° to 42° C led to a decrease of the mean frequency by about 30%, while temperature changes from 38° to 39.5° C were less effective.Corresponding studies in cold-adapted animals showed that the EEG response to spinal cord heating is modified by thermal adaptation. In this group of animals electrical activity of the posterior hypothalamus could be influenced clearly by heating the spinal cord from 38° to 39.5° C, while a temperature change in this range was nearly ineffective in animals reared at 20° C.     

Hypothalamic map of stimulation current thresholds for inhibition of feeding in rats.

The rat hypothalamus was mapped for the purpose of identifying regions at which electrical stimulation caused the feeding behavior of a hungry animal to be inhibited. At each inhibitory site a determination was also made of the minimal stimulation current necessary for the inhibition of feeding. The results indicated that the inhibitory sites with the lowest current thresholds tended to form a discrete cluster in the lateral part of the ventromedial nucleus and the adjacent neuropil bordering it ventrolaterally. A few low thresholds were also found in the anterior hypothalamic area. The higher thresholds formed an orderly ascending gradient radiating away from the ventromedial nucleus and its ventrolaterally situated anatomical projections. In areas related to ascending monoamine pathways, including the lateral hypothalamus, preoptic region, and arcuate nucleus, as well as in the mammillary bodies, stimulation usually failed to suppress feeding behavior. Implications bearing on neuroregulatory models of feeding behavior are discussed.     

Recording of spontaneous oscillations in the procerebrum of the terrestrial snail <Emphasis Type="Italic">Helix</Emphasis> during free behavior

The procerebrum is the central component of the olfactory analyzer in terrestrial snails and slugs; spontaneous rhythmic oscillations have been recorded in this structure, but their role in the mechanisms of odor perception and recognition has yet to be clarified. The present report describes a method for recording total electrical activity from the procerebrum in vivo and demonstrates changes in spontaneous rhythmic oscillations in the procerebrum of the snail Helix in response to olfactory stimulation. Recording of total electrical activity from the snail procerebrum in conditions of free behavior demonstrated a significant reduction in the frequency and an increase in the amplitude of spontaneous oscillations in the procerebrum in the first 10 sec after presentation of the odor of cineole at low concentration, which corresponds to the time required for performance of the olfactory tentacle withdrawal reaction. Presentation of the odor at high concentration resulted in a significant increase in the amplitude of spontaneous oscillations in the procerebrum over the time interval 11–20 sec after odor presentation and a tendency to a decrease in the frequency, which correlates with an increase in the time required for the olfactory tentacle withdrawal reaction. These data suggest an implicit relationship between the amplitude and frequency of oscillations in odor recognition. __________ Translated from Zhurnal Vysshei Nervnoi Deyatel’nosti imeni I. P. Pavlova, Vol. 56, No. 6, pp. 725–730, November–December, 2006.     

Evoked responses of pyramidal tract neurons to stimulation of the lateral hypothalamus

The evoked responses of identified pyramidal tract neurons of the pericruciate region of the cortex arising on stimulation of the posterior, tuberal, and anterior sections of the lateral hypothalamus were investigated in acute experiments on cats anesthetized with chloralose. The pyramidal tract neurons recorded were situated at a depth of 0.75–2.5 mm and on stimulation of the hypothalamus discharged with a latent period of 1.6–52.5 msec. They discharged most efficiently in the case of stimulation of the caudal half of the lateral hypothalamus. The pyramidal tract neurons activated by the hypothalamus were also tested by electrocutaneous stimulation of the four limbs. Of the neurons 75% responded to stimulation of several limbs, i.e., they had a broad bilateral receptive field, while 15% reacted to stimulation of one contralateral limb (either the anterior limb or the posterior limb), i.e., they had a small contralateral receptive field. Comparison of the latent periods of the anti- and orthodromic responses of the pyramidal tract neurons did not reveal any relationship between the magnitude of the latent period of the orthodromic response (on hypothalamic or electrocutaneous stimulation) and the type of pyramidal tract neuron (according to the axonal transmission velocity). No relationship between the latent period of hypothalamic stimulation and the magnitude of the latent period of the response to a peripheral stimulus was detected either.Translated from Fiziologicheskii Zhurnal SSSR, imeni I. M. Sechenova, Vol. 65, No. 5, pp. 661–667, May, 1979.     

Effect of posterior hypothalamic stimulation on neocortical electrical activity in the chronic premesencephalic cat

Chronic experiments were carried out on 19 adult cats after preliminary division of the brain stem at the level of the anterior border of the superior colliculus. High-frequency electrical stimulation of the posterior hypothalamus of these animals caused desynchronization of electrical activity in different parts of the neocortex. The influence of the posterior hypothalamus was predominantly on activity in the frontal zones of the neocortex. It is postulated on the basis of these results that the posterior hypothalamus has an activating effect on the neocortex through the thalamic nuclei.Translated from Neirofiziologiya, Vol. 8, No. 1, pp. 47–53, January–February, 1976.     

Secretory reactions of the salivary glands during stimulation of the hypothalamus in relation to the frequency,strength, and duration of stimulation

Summary Chronic experiments were staged on 9 dogs with multipolar electrodes implanted into the hypothalamus. The amount of saliva secreted and the rate of its secretion in hypothalamic stimulation depends on the frequency and the stimulating current. The maximum amount of saliva secretion is observed at 40 pulses per sec (pulse duratio— 0.2 millisec, 0.7–0.8 and the sinusoid current of 0.5–0.6 mA (frequency 40–50 cycles per sec). Prolonged stimulation of hypothalamus by rectangular current pulses provokes saliva secretion during the whole course of stimulation. Prolonged stimulation by a sinusoidal current causes the greatest secretory effect only during the first minute, after which in decreases considerably and is completely arrested in the 10th minute of stimulation. Salivary secretion also depends on the portion of hypothalamus stimulated.(Presented by Active Member AMN SSSR A. V. Lebedinskii) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 57, No. 2, pp. 16–20, February, 1964     

Hypothalamic, midbrain and bulbar areas involved in the defense reaction in rabbits

The present study mapped neuroanatomical sites in the hypothalamus and periaqueductal gray (PAG) of the rabbit which, when stimulated electrically, evoked the cardiorespiratory components of the defense reaction (CRDR). This included increases in heart rate, blood pressure, hindlimb blood flow and respiration rate. All of the components of the CRDR were elicited by electrical stimulation of the posterior hypothalamus, at sites dorsal and medial to the fornix. Although there were regions throughout the PAG in which electrical stimulation elicited concomitant increases in blood pressure, hindlimb blood flow and respiration rate, only stimulation of the dorsal PAG evoked tachycardia. Injection of horseradish peroxidase into the rostral ventrolateral medulla (RVLM) led to heavy retrograde and anterograde labeling in the region of the hypothalamus that yielded the CRDR when stimulated electrically. Heavy labeling was also observed in the dorsal and ventral PAG. The results of this study provide evidence that the posterior hypothalamus and the dorsal PAG are nodal structures in the mediation of the CRDR and that cells in posterior hypothalamus, dorsal PAG and ventral PAG make monosynaptic connections with the RVLM.     

Induction of slow oscillations by rhythmic acoustic stimulation

Slow oscillations are electrical potential oscillations with a spectral peak frequency of ～0.8 Hz, and hallmark the electroencephalogram during slow‐wave sleep. Recent studies have indicated a causal contribution of slow oscillations to the consolidation of memories during slow‐wave sleep, raising the question to what extent such oscillations can be induced by external stimulation. Here, we examined whether slow oscillations can be effectively induced by rhythmic acoustic stimulation. Human subjects were examined in three conditions: (i) with tones presented at a rate of 0.8 Hz (‘0.8‐Hz stimulation’); (ii) with tones presented at a random sequence (‘random stimulation’); and (iii) with no tones presented in a control condition (‘sham’). Stimulation started during wakefulness before sleep and continued for the first ～90 min of sleep. Compared with the other two conditions, 0.8‐Hz stimulation significantly delayed sleep onset. However, once sleep was established, 0.8‐Hz stimulation significantly increased and entrained endogenous slow oscillation activity. Sleep after the 90‐min period of stimulation did not differ between the conditions. Our data show that rhythmic acoustic stimulation can be used to effectively enhance slow oscillation activity. However, the effect depends on the brain state, requiring the presence of stable non‐rapid eye movement sleep.     

Electrophysiological correlates of slow periodicity of cardiac rhythm

Regular changes in frequency of cardiac contractions with a period of more than 10 sec were investigated in acute experimentation on immobilized cats. Possible conditions for the origination of decasecond periodicity of cardiac rhythm are examined. Quantitative characteristics are presented. It is shown that spontaneous galvanic skin surges can be grouped in relation to phases of slow oscillations in cardiac rhythm. In some experiments synchronous decasecond oscillations were registered in the frequency of cardiac contractions with change in amplitudes of electrical responses of the hippocampus to stimulation of the amygdaloid complex. The possible functional significance of slow modulation in the frequency of cardiac contractions and the mechanisms responsible for determining the association of observed phenomena are discussed.Translated from Fiziologicheskii Zhurnal SSSR im. I. M. Sechenova, Vol. 65, No. 4, pp. 598–605, April, 1979.     

Effect of stimulation of the hypothalamus on the activity of the cardiovascular system in long-term experiments

Summary In chronic experiments on waking unanesthetized dogs a study was made of the effect produced by stimulating various portions of the hypothalamus on the blood pressure and the frequency of cardiac contractions. Blood pressure was recorded in the coronary artery or in the subcutaneous artery of the knee joint. As demonstrated, stimulation of the posterior hypothalamus (caudal portion of the tuber cinereum and of the mamillary body) increased the blood pressure by 20–40 mm Hg, whereas stimulation of the anterior hypothalamus (the area of the supraoptic and paraventricular nuclei) decreased the pressure in a number of cases by 10–20 mm Hg. The frequency of cardiac contraction usually increased by 10–14 (at times by 60 beats) per minute; the rise in response to stimulation of the anterior hypothalamus was less pronounced. In individual cases there was an insignificant deceleration of the cardiac rhythm by 4–8 contractions per minute. Other autonomic and somatic reactions often accompanied the blood pressure and pulse changes, i.e., the pupil size changes, those of respiration, of the smelling reaction, licking, urination, defecation, general motor excitation, etc.(Presented by Active Member AMN SSSR V. V. Parin) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 57, No. 2, pp. 11–16, February, 1964     

Atherosclerosis induced in rabbits by prolonged electrical stimulation of the hypothalamus

The effect of prolonged electrical stimulation of emotiogenic zones of the hypothalamus in rabbits on their blood lipid level and the development of atherosclerosis was studied with the aid of a specially designed autonomous system. A negative emotional state observed during stimulation was accompanied by hyperlipemia and by the development of atherosclerosis in one third of uncastrated and two thirds of castrated animals.Department of Pathological Physiology and Central Scientific-Research Laboratory, Leningrad Sanitary Hygiene Medical Institute. (Presented by Academician of the Academy of Medical Sciences of the USSR P. N. Beselkin.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 82, No. 11, pp. 1294–1296, November, 1976.     

Hypothalamic afferent projections of the aortic nerve

Responses of neurons in the anterior, middle, and posterior hypothalamus to electrical stimulation of the aortic nerve were studied. Two groups of neurons were distinguished in the pressor zones of the hypothalamic region. Changes in the discharges of one group of neurons preceded a fall of arterial pressure in response to stimulation of the aortic nerve. Changes in activity of the other group of neurons occurred after the fall of blood pressure. It is concluded that excitation evoked by stimulation of the aortic depressor nerves and afferent influences from the baroreceptors of the blood vessels arriving during the depressor response spread to neurons of the supraoptic, paraventricular, and ventromedial nuclei of the hypothalamus, the anterior and lateral hypothalamic field, and the supramamillary region.P. K. Anokhin Institute of Normal Physiology, Academy of Medical Sciences of the USSR, Moscow. (Presented by Academician of the Academy of Medical Sciences of the USSR N. A. Yudaev.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 83, No. 6, pp. 643–646, June, 1977     

Dorsal periaqueductal gray stimulation facilitates anxiety-, but not panic-related,defensive responses in rats tested in the elevated T-maze

The escape response to electrical or chemical stimulation of the dorsal periaqueductal gray matter (DPAG) has been associated with panic attacks. In order to explore the validity of the DPAG stimulation model for the study of panic disorder, we determined if the aversive consequences of the electrical or chemical stimulation of this midbrain area can be detected subsequently in the elevated T-maze. This animal model, derived from the elevated plus-maze, permits the measurement in the same rat of a generalized anxiety- and a panic-related defensive response, i.e., inhibitory avoidance and escape, respectively. Facilitation of inhibitory avoidance, suggesting an anxiogenic effect, was detected in male Wistar rats (200-220 g) tested in the elevated T-maze 30 min after DPAG electrical stimulation (current generated by a sine-wave stimulator, frequency at 60 Hz) or after local microinjection of the GABA_A receptor antagonist bicuculline (5 pmol). Previous electrical (5, 15, 30 min, or 24 h before testing) or chemical stimulation of this midbrain area did not affect escape performance in the elevated T-maze or locomotion in an open-field. No change in the two behavioral tasks measured by the elevated T-maze was observed after repetitive (3 trials) electrical stimulation of the DPAG. The results indicate that activation of the DPAG caused a short-lived, but selective, increase in defensive behaviors associated with generalized anxiety.     

Preferential ipsilateral influence of the posterior hypothalamus on the neocortex

On the 10th-20th day after precollicular transection of the brain stem weak low-frequency electrical stimulation of the posterior hypothalamus preferentially activates the ipsilateral neocortex. After unilateral injury to the posterior hypothalamus, synchronous activity predominates in the ipsilateral neocortex. In premesencephalic animals weak single electrical stimulation of the posterior hypothalamus evokes the appearance of spindles in ipsilateral zones of the frontal cortex, whereas stronger single stimulation causes the diffuse generation of spindles in various parts of the neocortex. Besides this preferential unilateral effect, the influence of the posterior hypothalamus is found to be more strongly expressed in the frontal than in the occipital cortex. It is postulated that the posterior hypothalamus exerts its influence on the neocortex through the thalamic nuclei.Translated from Neirofiziologiya, Vol. 8, No. 2, pp. 139–145, March–April, 1976.