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J F Defrance

Publications and source records attributed to J F Defrance.

5 recordsLinked to original sources
PubMed1996

Topographical analysis of adolescent affective disorders.

This study evaluated the EEG spectral content and the components of the cognitive ERPs evoked by a visual sustained-selective attention task from adolescents diagnosed as having an affective disorder and those who did not (nonreferred controls, CON) to determine if there were different electrophysiological profiles associated with major subtypes of affective disorders; i.e., Dysthymic Disorder (DysD) and Cyclothymic Disorder (CycD). Distinctive ERP and EEG profiles were found to be associated with the DysD and CycD groups. While both groups of depressives presented diminished P3b amplitudes, the DysD group showed a relatively greater suppression over the right temporal regions, whereas the CycD group exhibited relatively greater suppression over the left temporal region. In addition, there were differences with respect to the earlier components associated with information processing. For instance, the P1 was found deficient in the DysD group as compared to the other groups, whereas the N2 component was deficient in the CycD groups as compared to CON and DysD groups. In contrast to these amplitude differences, no significant latency differences were seen with respect to any component elicited by this paradigm. With respect to the EEG spectra, the CON group showed greater relative power in the Beta range than either the CycD or the DysD group, with the depressives featuring more midline frontal Theta activity. Characteristically, both depressant groups showed a greater anterior distribution of Alpha activity. In addition, the foci of the various spectral bands for the DysD subjects were shifted away from the right hemisphere as was the case for the P3b. Overall, the profiles suggested that those who fit the diagnostic classification of DysD have deficit function in right post-Rolandic zones, along with anomalous frontal function. It was also suggested that there may be a core disturbance of physiological arousal in unipolar depression. The CycD subjects, on the other hand, featured no hemispheric bias with respect to the P3b components or spectral foci, but did not show similar features of being cortically "hypoaroused" so that actively depressed adolescent CycD subjects did share certain physiological features with unipolar subjects.

Adolescent↗
PubMed1985

Cholinergic modulation of mediodorsal thalamic input into cingulate cortex.

Field potentials in cingulate cortex (area 24) produced by electrical stimulation of the mediodorsal thalamic nucleus were diminished by iontophoretic ejection of the cholinergic agonist, carbachol. The effect was frequency dependent: field potentials produced by 7.0 Hz stimulation were reduced by 34%. Potentials produced by 0.5 Hz stimulation were not significantly changed. This reduction was blocked by muscarinic but not nicotinic antagonists.

Afferent Pathways↗
PubMed1982

Histamine: correlative studies in nucleus accumbens.

The role of histamine as a neurotransmitter has been the subject of considerable controversy. Recent evidence suggests it to be involved in such complex activities as arousal and affect. The purpose of the present study is to examine the possible source, function, and pharmacology of histamine in the nucleus accumbens, an area of the brain also implicated in complex activities such as affect. The anatomical studies suggest that the most probable source of the histamine in nucleus accumbens is the complex region lateral to the mammillary nuclei. These areas are the intercalated nucleus and the tuberomammillary nucleus (nuclei gemini hypothalami). To a lesser degree, the supramammillary complex may also contribute histamine-containing axons to the accumbens area. Adenylate cyclase in the rabbit nucleus accumbens displayed activation in response to histamine agonists (histamine, 2-Me-histamine, and 4-Me-histamine). The action of the H1 antagonist promethazine was greater than the H2 antagonist metiamide in reducing enzyme activation by histamine and 2-Me-histamine. In contrast, metiamide was more potent than promethazine toward antagonism of the action of 4-Me-histamine. However, no additive effects were noted when agonists were added in combination. Based upon these data, it is suggested that activation of adenylate cyclase in the rabbit nucleus accumbens is mediated in part by mixed H1 and H2 receptors or cellular disruption reflects the loss of receptor specificity. Physiological studies demonstrated that the H2 agonist 4-Me-histamine had an inhibitory effect on the activity of neurons driven by stimulation of the fimbria. The magnitude of the effect was frequency dependent. The H1 agonist 2-Me-histamine had no significant effect. Iontophoretic application of 4-Me-histamine had minimal effect upon low frequency volleys (0.5 Hz) but had a pronounced effect upon higher frequency volleys (6.0 Hz). These effects were antagonized by metiamide. Iontophoretic application of metiamide alone produced an effect only upon the P component of the field response, which is also bicuculline sensitive. Bicuculline coadministration was also effective in antagonizing the 4-Me-histamine effect. The physiological data suggest that histamine works through H2 receptors in nucleus accumbens, perhaps by potentiating the effects of gamma-aminobutyric acid (GABA). Thus, histamine in nucleus accumbens appears to function as a modulatory substance whose effect is dependent upon the activity of other transmitter and afferent systems.

Adenylyl Cyclases↗
PubMed1977

Cholinergic mechanisms and short-term potentiation.

Acutely prepared rabbits were used to study, electrophysiologically, tetanic and post-tetanic potentiation of the pathway from the medial septal region to hippocampal field CA1. It was found that tetanic potentiation, evoked by short stimulus trains, was maximal at 6--8 Hz. Responses recovered from post-tetanic potentiation in 5--35 seconds. Acetylcholine, physostigmine, and cyclic GMP each had an excitatory effect on pyramidal cell responses when applied in stratum radiatum. The time course studies showed that these effects outlasted the duration of the injection current by many minutes. Phosphodiesterase inhibitors (e.g., isobutyl methyl xanthine) prolonged the time course of recovery with test responses which were post-tetanically potentiated. K+, on the other hand, selectively enhanced tetanic potentiation. It is suggested, with respect to the potentiation phenomena, that K+ acted primarily presynaptically to facilitate transmitter release, whereas cyclic GMP acted primarily postsynaptically for the enhancement of pyramidal cell excitability.

Acetylcholine↗