Correlational Imaging of Thalamocortical Coupling in the Primary Visual Pathway of the Human Brain

While the anatomy of the human brain is well defined, the functional connectivity of its structures is far less understood. Modern neuroimaging techniques offer the unique opportunity of visualizing physiologic activation in central nervous structures and of identifying the elements underlying distributed networks for information processing. Following improved spatial resolution of deoxyhemoglobin-sensitive magnetic resonance imaging, we were able to detect simultaneous signal changes in the lateral geniculate nucleus and primary visual cortex during periodic photic stimulation. Visualization of coupled activation by cross-correlation analysis resulted in the first demonstration of thalamocortical interaction in the primary visual pathway of the intact human brain.

[14C]deoxyglucose incorporation into rat brain regions during hypothalamic or peripheral thermal stimulation

The central nervous structures involved in thermoregulatory responses induced by hypothalamic or peripheral thermal stimulation were investigated in conscious rats by means of the 2-deoxy-D-[14C]glucose ([14C]-DG) autoradiographic technique. According to autoradiographs, many brain regions with significant increases or decreases in [14C]-DG incorporation were observed during thermoregulatory responses. Based on the present changes in [14C]-DG incorporation of brain regions obtained from two kinds of thermal stimulation, the following conclusions were drawn. 1) The medial preoptic area and the medial forebrain bundle are common sites for development of thermoregulatory responses being activated during cooling and warming. 2) The anterior hypothalamic area is activated during hypothalamic or peripheral warming and not during cooling. 3) The ventromedial hypothalamus, dorsomedial thalamus, caudate-putamen, globus pallidus, pars compacta of the substantia nigra, red nucleus, and the midbrain reticular formation are activated with hypothalamic or peripheral cooling. 4) The lateral preoptic area, suprachiasmatic nucleus, ventroposteromedial thalamus, pars reticulata of the substantia nigra, and the hippocampus change their activities only during peripheral cooling and warming.

Circadian rhythm of TSH in adult men and women

The circadian rhythm of TSH secretion and its typical pattern were investigated during the spring of two successive years in a group of 12 adult women, and then in a group of 12 adult men, both having normal thyroid function. Blood samples were obtained from each individual every two h for 24 h. TSH was measured by RIA. Data were processed by inferential analysis and represented using the cosinor method. The chronobiological rhythm of TSH is in good agreement with the typical function of circadian rhythms both in men and in women, significance averaging ‰. The typical parameters of the rhythm (M = mesor, i.e. the mean level of the rhythm; A = amplitude of the sinusoidal function approximating the rhythm; Ø = acrofase, i.e. the lag from a reference timepoint of the crest time in the function) under the conditions used in our investigation were shown to be: Male subjects: mean ± se = 3.72 ± 0.21 mU/l, A (95% C.I.) = 1.15 (0.93–1.47) mU/l; Ø (95% C.I.) = 3.9° (−8.6° + 23.8°). Female subjects: mean ± SE = 5 ± 0.13 mU/l; A (95% C.I.) = 0.96 (0.86–1.11) mU/l; Ø (95% C.I.) = 8.8° (−0.2° + 20.5°). The patterns of TSH biorhythm are practically identical in both sexes. Taking into account the methods used and the results obtained we think that the circadian rhythm of TSH secretion is programmed in both sexes in order to meet the cyclic requirements of the target gland, while several other factors which mark the course of the day at the level of central nervous structures function as rhythm harmonizers.

PHARMACOLOGICAL INHIBITION OF ADRENALINE SECRETION FOLLOWING INSULIN INDUCED HYPOGLYCAEMIA IN MAN: THE EFFECT OF CATAPRESAN®

ABSTRACT In untreated subjects insulin induced hypoglycaemia was followed by a marked increase in urinary adrenaline excretion without any significant change in noradrenaline, thus confirming previous observations. This stimulating effect of hypoglycaemia on adrenaline production could be markedly inhibited by treatment with the antihypertensive agent Catapresan® (2-(2,6-dichlorphenylamine)-2-imidazoline hydrochloride). The basal urinary noradrenaline excretion was markedly suppressed under medication with Catapresan® and again there was no significant change in connection with hypoglycaemia. Infusion studies demonstrated that Catapresan® did not influence the urinary recovery of adrenaline and noradrenaline. Thus, the diminished adrenaline excretion following Catapresan® represented a reduced secretion of the hormone. This inhibitory effect of Catapresan® might be due to an action of the compound on central nervous structures.