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PubMedDate not supplied

Spatial-temporal organization of subcortical brain functions during immune responses.

In the course of long-term experiments on rabbits, functional dynamics of subcortical structures were studied by recording background (DC) and evoked potentials (EP) during immune responses elicited to various antigens. During the first day of the immune response process to the different antigens, changes in hypothalamus functioning were similar and occurred with a latency of 9 to 31 min. Inductive and productive primary immune responses were accompanied by successive phasic changes in the functioning of a number of subcortical structures.

Action Potentials↗
PubMedDate not supplied

Dynamic characteristics of central auditory neurons and their relation to selective-combination mechanisms of organization of brain functions.

Unit responses of the torus and caudal neostriatum of hens to stimuli of differing ecological significance (pure tones, white noise, species-specific stimuli) were investigated. The range of frequencies receivable by central auditory neurons was shown to correspond to the frequency composition of the stimuli emitted by the animals. Neurons selectively responding to species-specific stimuli (song, alarm signals) were found in the forebrain. The specific character of the functional organization at different levels of the auditory system is examined in the light of the selective-combination principle of stimulus integration, which may lie at the basis of the mechanism of both inborn and acquired memory.

Acoustic Stimulation↗
PubMed1989

Quantitative monitoring of brain function, vital signs, and hormonal response during acute insulin-induced hypoglycemia.

Acute insulin-induced hypoglycemia provokes changes in central nervous system activity and release of counterregulatory hormones. The clinical relationship between central nervous system activity, hormone secretion, and vital signs has not to our knowledge been previously reported. We used computerized electroencephalographic (CEEG) analysis to monitor 5 nondiabetic subjects during acute insulin-induced hypoglycemia (0.75 U/kg intravenous push). Their glucose nadir was 38 +/- 6 mg/dl (mean +/- 1 SD). A three-phase pattern of change in CEEG power in response to hypoglycemia was observed: phase 1 was characterized by an increase in total CEEG power (natural log of activity = 9.1 +/- 1.3 microV2) over baseline (8.7 +/- 1.2 microV2) in the theta, delta, and beta frequency bands. This phase preceded and coincided with the glucose nadir. During phase 2, power in all frequency bands fell significantly below baseline. A nadir in CEEG power (8.0 +/- 1.6 microV2) occurred 40 to 55 minutes after insulin injection as glucose levels were rising. During phase 3 there was a return to baseline in CEEG power and frequency spectra. Heart rate increase just before phase 1; peak heart rate (91 +/- 8 beats/min) coincided with peak CEEG power and was significantly higher than basal rate (71 +/- 11, P less than 0.05). A significant increase in respiratory rate occurred during phase 1 of the CEEG and persisted through phase 2. A significant decrease in mean blood pressure (nadir = 73 +/- 6 mm Hg) below preinsulin blood pressure (81 +/- 8 mm Hg, P less than 0.05) coincided with the nadir of CEEG power in phase 2.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1998

A method for direct patch-clamp recording from smooth muscle cells embedded in functional brain microvessels.

The aim of this project was to develop a method to enable routine application of all patch-clamp configurations to smooth muscle cells while they remain embedded in blood vessels. Small blood vessels were isolated from rabbit brain using an enzymatic and mechanical procedure. Vessels were identified under a microscope and the majority were small arterioles with a mean external diameter, in Ca2+-containing (1.5 mM) solution, of 29 microm and variable lengths of 100 microm or more. Arterioles excluded trypan blue, constricted in response to 60 mM K+ and dilated in response to levcromakalim. Patch-clamp gigaOhm seals were made regularly on smooth muscle cells embedded in arterioles. The membrane potential recorded using amphotericin-B-containing patch pipettes averaged -72 mV. Short arteriolar segments could be voltage-clamped. Injection of depolarising current or bath application of 10 mM Ba2+ induced constriction of the entire arteriolar segment. Cell-attached patch, inside-out patch and outside-out patch recordings were made readily and K+ channel unitary currents were studied. The method is readily applied and has several advantages over previous methods for the study of ion channels in smooth muscle cells. Notably, avoidance of single-cell isolation means that enzymatic treatment is minimised and cells can be studied within their normal environment of the blood vessel wall.

Animals↗
PubMed2005

Functional brain imaging in hemicrania continua: implications for nosology and pathophysiology.

Hemicrania continua is a strictly unilateral, continuous headache of mild to moderate intensity, with superimposed exacerbations of moderate to severe intensity that are accompanied by trigeminal autonomic features and migrainous symptoms. The syndrome is exquisitely responsive to indomethacin. Its clinical phenotype overlaps with that of the trigeminal autonomic cephalalgias and migraine, in which the hypothalamus and the brain stem, respectively, have been postulated to play central pathophysiologic roles. A recent positron-emission tomography study of a cohort of patients with hemicrania continua demonstrated significant activation of the contralateral posterior hypothalamus and ipsilateral dorsal rostral pons in association with the headache of hemicrania continua. In addition, there was activation of the ipsilateral ventrolateral midbrain, which extended over the red nucleus and the substantia nigra and bilateral pontomedullary junction. No intracranial vessel dilatation was obvious.

Brain↗
PubMed1990

Hypofrontality and cognitive impairment in schizophrenia: dynamic single-photon tomography and neuropsychological assessment of schizophrenic brain function.

Regional cerebral blood flow (rCBF) was assessed in 40 chronic male schizophrenic patients (20 medicated, 20 unmedicated) and 31 matched normal controls with Dynamic Single-photon Emission Computed Tomography (D-SPECT). Blind analyses of normalized color-coded tomograms revealed significant bifrontal and bitemporal rCBF deficits in the patient group. Frontal flow deficits were most prominent in paranoid patients (n = 21) and right temporal deficits were most prominent in nonparanoid patients (n = 19). These relative regional declines were observed within the context of significantly elevated hemispheric blood flow in schizophrenics compared with controls. Reduced left frontal rCBF was associated with neuropsychological impairment on the Wisconsin Card Sorting Test and Luria-Nebraska Battery. Increased hemispheric CBF was correlated with the presence of positive schizophrenic symptoms. Medication status was unrelated to rCBF. These findings demonstrate that hypofrontality has important implications for cognitive function in some schizophrenic individuals.

Adult↗
PubMed1987

Thermosensitivity of anterior hypothalamic-preoptic neurons during the waking-sleeping cycle: a study in brain functional states.

The thermosensitivity of anterior hypothalamic-preoptic neurons was studied in cats during the waking-sleeping cycle. Direct cooling and warming of the anterior hypothalamic-preoptic region was accomplished with water-perfused thermodes. Neuronal thermosensitivity was determined by means of the linear regression analysis of firing rate changes vs anterior hypothalamic-preoptic temperature changes. A total of 117 neurons were classified as thermosensitive during wakefulness and synchronized sleep (20.1% of the studied neurons). Cold-sensitive neurons outnumbered warm-sensitive neurons by 3.7:1. The homeothermic states, wakefulness and synchronized sleep, are characterized by similar frequency distributions of neuronal thermosensitivity, although variable changes in single neuron thermosensitivity are state-dependent. Such changes underlie the quantitative differences in homeothermic regulation between these states. The impairment of thermoregulation during desynchronized sleep is characterized by a different frequency distribution of neuronal thermosensitivity resulting from both a drop in the responsiveness to thermal stimulation of a majority of neurons and a reversal in the sensitivity to cooling and warming of a minority of neurons. In conclusion, only the frequency distribution of thermosensitivity in the neuronal population is indicative of changes in the thermoregulation paradigm across behavioral states.

Action Potentials↗