Potential utility of rubidium 82 PET quantification in patients with 3-vessel coronary artery disease.

BACKGROUND: Standard perfusion imaging may underestimate the extent of disease in 3-vessel coronary atherosclerosis. This study determined whether positron emission tomography quantification of perfusion reserve by use of rubidium 82 net retention defined a greater extent of disease than the standard approach in patients with 3-vessel disease. METHODS AND RESULTS: Rb-82 net retention was quantified as an estimation of absolute perfusion at rest and with dipyridamole stress by use of dynamic positron emission tomography imaging. The percent of abnormal myocardial sectors, as compared with a normal database, for a standard and quantification approach was determined. Twenty-three patients were evaluated. Defect sizes were larger in patients with 3-vessel disease (n = 13) by use of quantification methods: 44% +/- 18% of the myocardial sectors were abnormal by use of the standard approach versus 69% +/- 24% of sectors when measured by quantification of the stress-rest perfusion difference (P =.008). In patients with single-vessel disease (n = 10), defect sizes were smaller with quantification methods. CONCLUSIONS: Quantification of Rb-82 net retention to measure the stress-rest perfusion difference in the myocardium defined a greater extent of disease than the standard approach in this group of patients with triple-vessel disease. More accurate measurement of the extent of coronary artery disease could facilitate better risk stratification and identify more high-risk patients in whom aggressive intervention is required.

Chlordiazepoxide, go-nogo successive discrimination and brain biogenic amines in cats.

Chlordiazepoxide (CDP; 0.4 mg/kg/day, per os) was administered to cats during either the acquisition (CDP 21-22 days) of a go-nogo successive discrimination task (SD) or the performance (CDP 10 days) of the previously learned SD task. Endogenous levels of serotonin, 5-hydroxyindoleacetic acid, noradrenaline and dopamine were assayed in 12 brain areas, in trained as well as in untrained cats. This study has shown that (1) CDP strongly impaired the acquisition but not performance of the SD task, revealing a dissociation of the effects of CDP on these two stages of training; (2) the CDP administration, as well as the SD training, produced regional changes in brain levels of biogenic amines, suggesting the involvement of particular monoaminergic neurons in the behavioral effects of CDP and in operant behavior; and (3) in particular brain areas, interactions were observed between the effects of the SD training and those of the CDP administration on monoamines, indicating that the behavioral state may interfere with the neurochemical effects of CDP.

Zona incerta and lateral hypothalamic afferents to the midbrain reticular core of cat--HRP and electrophysiological study.

The zona incerta (ZI) and lateral hypothalamic afferents to the midbrain reticular formation (MRF) of cat were investigated with the horseradish peroxidase (HRP) technique and by using antidromic identification in experiments on chronically implanted, behaving preparations. Following HRP injections restricted to the MRF territory (nucleus cuneiformis and central tegmental field), the largest number of retrogradely labeled cells appeared in the medial third of the ipsilateral ZI. Labeling extended medially to the adjacent lateral hypothalamus. The number of positive elements gradually diminished towards the lateral extremity of the ZI and continuing reticularis thalamic nucleus. Ventral lateral geniculate neurons were consistently labeled. No positive elements were found in ventrobasal, pulvinar-lateralis posterior and ventralis lateralis thalamic nuclei. The MRF-evoked antidromic invasion of ZI cells occurred with a sharp mode between 0.5 and 0.75 ms (median latency of the whole sample: 0.6 ms). The conduction velocity of the ZI leads to MRF axons is twice as high as the values found in the reciprocal MRF leads to ZI projection. In addition to the antidromically elicited discharges, MRF stimulated resulted in short-latency synaptic excitation, sometimes following the antidromic invasion of the same neuron. The difference between the discharge rates of ZI neurons during EEG-desynchronized and EEG-synchronized behavioral states was not significant. A statistically significant increase in firing rates was found in ZI neurons during waking periods with movements compared to quiet, motionless epochs of waking. The possible involvement of caudally projecting ZI cells in the preparation of postural and/or phasic motor functions is discussed.

Effects of chlordiazepoxide on acquisition and performance of a go-no go successive discrimination task, and on brain biogenic amines in cats.

1. Normal and chlordiazepoxide (0.4 mg/kg/day, per os) treated cats were trained on a symmetric go-no go successive discrimination task with positive reinforcement. 2. The treatment impaired the acquisition, but not the performance once the task was learned. 3. Serotonin, 5-hydroxyindoleacetic acid and noradrenaline were assayed in 12 brain areas in trained cats, and in normal and treated cats which did not undergo the training. 4. The treatment produced localized changes in the serotonin: 5-hydroxyindoleacetic acid ratio and the noradrenaline level; these effects were modified by the training. 5. The drug induced an acquisition deficit rather than a general behavioral disinhibition, and produced neurochemical effects which were dependent upon the brain area, the treatment duration and the behavioral state.

Immediate behavioral effects of kainic acid injections into the midbrain reticular core.

Microinjections of kainic acid into the midbrain reticular core were performed in chronically implanted, unanesthetized cats. The immediate effects of kainate excitation were studied during the first 8 h, in animals without any behavioral or EEG signs of epilepsy. Animals displayed pupillary dilatation, piloerection, accelerated respiration, a frozen attitude with a complete lack of facial expression, and no or only very slight orienting reactions. The most structural syndrome was a hallucinatory-type behavior that began in the first hour following the injection. Animals moved forward in a crouched position as if stalking a prey, vocalizing and opening their mouth in an attacking attitude, or moved back as if defending themselves against as imaginary menacer, seeming virtually terrified. The EEG desynchronization began 20-30 sec after the onset of injection and lasted for 12-14 h without any trace of alpha rhythm, spindles or slow waves. Control injections of buffer solution into the midbrain core and kainic acid in other cerebral structures were followed neither by the hallucinatory defense-attack syndrome, nor by comparably long-lasting EEG desynchronization. The hallucinatory-type behavior elicited during the waking state in the present experiments is compared to the oneiric behavior described by Jouvet and Delorme [21] during paradoxical sleep in animals with suppression of muscular atonia, and possible common mechanisms are discussed.

Excitatory-inhibitory processes in parietal association neurons during reticular activation and sleep-waking cycle.

Excitatory-inhibitory processes of parietal association neurons were studied during reticular-induced EEG activation and natural sleep-waking cycle. The probability of antidromic invasion in long-axon cells is enhanced following midbrain reticular stimulation and during both waking (W) and desynchronized sleep (D) states compared to slow-wave sleep. The thalamically elicited inhibitory phase occurs with a shorter latency following reticular stimulation and during W and D states; this is due to the reduced duration, during all these experimental conditions, of secondary excitatory processes. The duration of the inhibitory period is shorter during reticular activation; the postinhibitory rebound occurs at shorter latencies and is sharper following reticular stimulation and during W and D states. The similarity between reticular effects and changes during both W and D states is discussed.

A study of geniculate unit activity during cryogenic blockade of the primary visual cortex in the cat.

In cats under nembutal or chloralose anesthesia, unilateral temporary cryogenic blockades of the primary visual cortex were performed and their influence on unitary responses to restricted light spots was tested in the ipsilateral geniculate nucleus. No significant effect could thus be observed, at variance with previous positive results obtained by our group in structures like superior colliculus and pulvinar complex using the same experimental procedure.