Role of the superior colliculus in the motor effects of cannabinoids and dopamine

We studied the cellular distribution of CB1 cannabinoid receptors in the superior colliculus of the rat using an antibody raised against the N-terminal of the receptor. The effect of unilateral cannabinoid receptor stimulation in the intermediate layers of the superior colliculus on rotational behavior in rats was also explored. The antibody against CB1 receptors outlined the crossed descending system of the superior colliculus (predorsal bundle output system) as well as the collicular commisure. The potent cannabinoid agonist CP55,940 (5 microgram/0.25 microliter) induced strong contralateral turning when microinjected unilaterally into the lateral intermediate layers of the superior colliculus. The levels of turning obtained with the intracollicular administration of the cannabinoid were comparable to the highest levels obtained with dopamine agonists in the basal ganglia. The D(2) dopamine agonist quinpirole or the D(1) dopamine agonist SKF82958 reversed this contralateral rotation but failed to affect motor behavior on their own. A new motor pathway for cannabinoids is discussed.     

Influence of visual experience deprivation on the postnatal development of the microvascular bed in layer IV of the rat visual cortex

Cerebral vascular density is correlated with metabolic demands, which increase in highly active brain areas. External inputs are an essential requirement in the modeling of the visual cortex. Experience-mediated development is very active during the first postnatal month, when congruous blood supply is needed. We studied the development of visual cortex vascularization in relation to experience, comparing rats raised in darkness with rats reared in normal conditions. Vascular density, vascular area and their ratio vs. neuronal density were calculated. Conventionally stained semi-thin sections were used to measure the vascular area by computer assisted morphometry. Animals from both groups were sampled at 14, 21, and 60 days postnatal (dpn). We found a significantly lower density of vessels and neurons as well as a smaller vascular area in dark-reared adult rats while no differences were founded at the other ages. Our results also show no differences between the ratio of vessels/neuron, and vascular area/neuron, between both groups. The absence of visual experience causes decrease of cortical activity which correlates with lower vessels density and vascular area, without their ratio/neuron being affected.     

Opioid site in nucleus accumbens shell mediates eating and hedonic 'liking' for food: map based on microinjection Fos plumes

Microinjection of opioid agonists, such as morphine, into the nucleus accumbens shell produces increases in eating behavior (i.e. 'wanting' for food). This study (1) reports direct evidence that activation of accumbens opioid receptors in rats also augments food 'liking', or the hedonic impact of taste, and (2) identified a neural site that definitely contains receptors capable of increasing food intake. Morphine microinjections (0.5 microgram) into accumbens shell, which caused rats to increase eating, were found also to cause selective increases in positive hedonic patterns of behavioral affective reaction elicited by oral sucrose, using the 'taste reactivity' test of hedonic palatability. This positive shift indicated that morphine microinjections enhanced the hedonic impact of food palatability. The accumbens site mediating morphine-induced increases in food 'wanting' and 'liking' was identified using a novel method based on local expression of Fos induced directly by drug microinjections. The plume-shaped region of drug-induced increase in Fos immunoreactivity immediately surrounding a morphine microinjection site (Fos plume) was objectively mapped. A point-sampling procedure was used to measure the shape and size of 'positive' plumes of Fos expression triggered by microinjections of morphine at locations that caused increases in eating behavior. This revealed a functionally 'positive' neural region, containing receptors directly activated by behaviorally-effective drug microinjections. A subtraction mapping procedure was then used to eliminate all surrounding regions containing any 'negative' Fos plumes that failed to increase food intake. The subtraction produced a conservative map of the positive site, by eliminating regions that gave mixed effects, and leaving only a positive region that must contain receptors capable of mediating increases in food intake. The resulting mapped 'opioid eating site' was contained primarily within the medial caudal subregion of the nucleus accumbens shell, and did not substantially penetrate either into the accumbens core or into other subregions of the shell. Several other structures outside the nucleus accumbens (such as rostral ventral pallidum), immediately medial and adjacent to the shell, also appeared to be included in the functional site. Opioid receptors within this site thus are capable of mediating morphine-induced increases in eating, in part by enhancing the hedonic reward properties of food.     

Development of the mammillothalamic tract in normal and Pax-6 mutant mice

The mammillary bodies represent important relay stations for one of the major neuronal circuits in the brain: the limbic circuit. Mammillary projections traveling through the principal mammillary tract are established early during development, forming the mammillotegmental bundle, which appears fully developed by embryonic day 15 (E15). The mammillothalamic tract develops later, around E17-E18, forming a compact system of collateral fibers originating from the principal mammillary tract and reaching the thalamus by E20. The Pax-6 gene is expressed in various regions of the developing brain, among which the border separating the ventral thalamus from the dorsal thalamus, known as the zona limitans intrathalamica, is especially significant. In this report, the development of the efferent mammillary system of fibers was studied in wild type and Pax-6 mutant mice by using carbocyanine tracers and Golgi preparations. In mutant mice, the mammillotegmental bundle developed normally; however, the mammillothalamic tract was missing. By using anti-Pax-6 antibodies in wild type mice, the existence of an immunoreactive cell cluster is described surrounding the bifurcation point of the principal mammillary tract. The results of this study suggest that there is a correlation of these cells with a particular type of Golgi impregnated neuron.     

Geodesics without conjugate points and curvatures at infinity

We study the asymptotic behavior of curvature and prove that the integral of curvature along a geodesic without conjugate points is nonpositive and some generalizations of Myers theorem and Cohn-Vossen's theorem. Some applications are also given.     

Psychopathology and wisconsin card sorting test performance in young unmedicated schizophrenic patients

The relationship between psychopathology and Wisconsin Card Sorting Test (WCST) performance was evaluated in 25 unmedicated young acute schizophrenic female patients (14 neuroleptic-naive and 11 neuroleptic-free) and 15 female controls. The schizophrenic patients (especially the neuroleptic-free) performed more poorly than controls in the WCST. In addition, WCST impairment correlated with both negative and positive symptoms. The results suggest that the neuropsychological dysfunction in schizophrenia is present at the onset of the illness, and is neither secondary to previous neuroleptic treatment nor to chronicity of the illness.     

Extended cervical mediastinoscopy in the staging of bronchogenic carcinoma

BACKGROUND: Extended cervical mediastinoscopy (ECM) is a technique in the staging of bronchogenic carcinoma described first by Ginsberg in 1984. To update our experience we have prospectively evaluated our results on 106 patients who underwent the technique from 1985 to 1998. METHODS: The ECM technique is performed once the operability of the patient has been evaluated, according to the computed tomography findings. The intervention is carried out at the same time as a standard cervical mediastinoscopy through the same incision following the same technique as previously published. The ECM is considered positive when metastatic nodes or tumor involvement directly in the paraaortic or subaortic regions is detected and confirmed histologically. Negative cases of ECM and positive cases of standard cervical mediastinoscopy are excluded from this study. A false-negative ECM is defined as the presence of infiltrated adenopathies at the paraortic level detected on postoperative histologic study. RESULTS: We had performed ECM in 106 patients, and a total of 13 were subsequently excluded for the reasons stated above. Of the remaining cases, 26 were positive, 61 negative and 6 had false-negative results with no false-positive results. Sensitivity was 81.2%, specificity 100%, accuracy 93.3%, positive predictive value 100%, and negative predictive value 91%. There were no complications with the technique. CONCLUSIONS: We conclude that ECM is a useful technique for staging bronchogenic carcinoma that allows samples to be taken from paraortic and subaortic regions with minimally invasive techniques.