Neurons containing messenger RNA encoding glutamate decarboxylase in rat hypothalamus demonstrated by in situ hybridization, with special emphasis on cell groups in medial preoptic area, anterior hypothalamic area and dorsomedial hypothalamic nucleus.

Previous deafferentation studies have suggested that most hypothalamic GABAergic innervation originates from neurons within the hypothalamus. We have investigated the distribution of GABAergic cell groups in the rat hypothalamus by means of the in situ hybridization technique, using a cDNA probe for messenger RNA encoding glutamate decarboxylase. Several major GABAergic cell groups were demonstrated, including cells of the tuberomammillary nucleus, arcuate nucleus, suprachiasmatic nucleus, medial preoptic area, anterior hypothalamic area, the dorsomedial hypothalamic nucleus, perifornical area, and lateral hypothalamic area. The most prominent glutamate decarboxylase mRNA-containing cell groups were located in the medial preoptic area, anterior hypothalamic area and dorsomedial hypothalamic nucleus, and were composed of small- to medium-sized neurons. Compared to previously well-characterized GABAergic cell groups in the tuberomammillary nucleus, reticular thalamic nucleus, and non-pyramidal cells of cerebral cortex, the cells of these GABAergic groups demonstrated only weak cDNA labelling, indicating that they contain lower levels of glutamate decarboxylase mRNA. Several types of control experiments supported the specificity of this cDNA labelling, and the GABAergic nature of these cell populations was further supported by detection of glutamate decarboxylase and GABA immunoreactivity. Abundance of GABAergic cells in many hypothalamic nuclei indicates that GABA represents quantitatively the most important transmitter of hypothalamic neurons, and may be involved in neuroendocrine and autonomic regulatory functions.

Progressive increases of protein synthesis in the circumventricular organs during chronic dehydration in rats.

The quantitative autoradiographic method with L-(35S)methionine was applied to investigate the effect of chronic dehydration on rates of protein synthesis in circumventricular organs (CVOs). Water deprivation for 1, 2 and 3 days causes progressive increases of protein synthesis in the subfornical organ (SFO), the area postrema, the organum vasculosum laminae terminalis and the neurohypophysis. Chronic salt ingestion with 2% NaCl in drinking water for 3 days resulted in increases of protein synthesis in the CVOs similar to those found after 3 days water deprivation, with only one exception, the SFO, in which the rise in protein synthesis was of lower amplitude after 3 days salt ingestion as compared to 3 days water deprivation. These results suggest that several circulating factors related to intracellular dehydration and the high plasma levels of the neurohormones vasopressin and oxytocin are probably important determinants of the rise of protein synthesis in circumventricular organs. Alternatively, the elevated level of blood-borne angiotensin II may well explain the higher metabolic response of the SFO following water deprivation compared to salt ingestion.

Effects of an acute immobilization stress upon proopiomelanocortin (POMC) mRNA levels in the mediobasal hypothalamus: a quantitative in situ hybridization study.

The aim of this study was to examine by quantitative in situ hybridization the effects of an acute stress on the expression of the POMC gene in the mediobasal hypothalamus (MBH) of the rat. In control animals, the highest levels of POMC mRNA were observed in the posterior periventricular region of the MBH. Lower levels were found in the anterior and posterior arcuate nucleus. At the end of a one hour immobilization, a small decrease (-8%) was observed in the periventricular region only. Four hours after the end of immobilization, increases in POMC mRNA levels were detected in the anterior part (7%), in the posterior part (25%) and in the periventricular region (13%) of the MBH. These results suggest that MBH POMC-derived peptides might be an important component in the central response to stress.

Retrograde axonal transport specificity in the locus coeruleus neurons after [(3)H]noradrenaline injection into the rat olfactory bulb.

Retrograde axonal transport process was investigated in the afferent systems to the rat olfactory bulb, after [(3)H]noradrenaline ([(3)H]NA) injection into the olfactory bulb, in order to provide evidence regarding its specificity and the biochemical basis supporting this specificity. Radioautographs showed that [(3)H]NA unilaterally injected into the olfactory bulb at a concentration of 10(?3) M, resulted in labeling of the structures afferent to the olfactory bulb, mainly on the injected side: locus coeruleus (LC), dorsal and central raphes, nucleus of the lateral olfactory tract and piriform cortex. Heavy labeling was observed on the noradrenergic LC cell bodies, whereas the radioautographic reaction was less intense on the other structures. After 10(?4) M injection, the labeling intensity of the LC cell bodies was lower while very rare weakly labeled cell bodies persisted in the dorsal raphe, nucleus of the lateral olfactory tract and piriform cortex. The LC cell bodies were exclusively labeled when the concentration of [(3)H]NA injection was 10(?5) M. All the other structures were devoid of labeling. It was still possible to detect labeled cell bodies in the LC for a 10(?6) M concentration. Following bilateral injections of [(3)H]NA (10(?3) M) the total radioactivity retrogradely transported to the LC represented about 4 times the total radioactivity measured in the periaqueductal gray substance (as control tissue of the tracer diffusion). Fractional study by ethanol of LC tissue homogenate and liquid scintillation counting of each fraction showed that 60% of the total radioactivity (about 2.5 times the control value) was in the supernatant and 40% (about 20 times the control value) was associated with the precipitate. In the other regions such as the dorsal and central raphes and periaqueductal gray substance, radioactivity was mainly found in the supernatant, except for the dorsal raphe whose precipitate contained a low amount of radioactivity (about 4 times the control value). Colchicine (an axonal transport inhibitor) bilaterally injected into the medial forebrain bundle and systemic administration of desipramine (a noradrenaline uptake inhibitor) decreased the radioactivity associated with the LC precipitate by 90 and 85% and the LC supernatant radioactivity by 55 and 35%, respectively. These pretreatments did not significantly affect the radioactivity amounts measured in the different fractions of dorsal and central raphes and periaqueductal gray substance. Radioautographic study after colchicine treatment showed a large decrease in the labeling intensity of the LC cell bodies as compared to the non-treated side. Therefore, we suggest that low concentrations (10(?5) M) of [(3)H]NA injected in the olfactory bulb determine specific conditions of noradrenergic pathway labeling. This specific labeling after migration could be supported by the radioactive ethanol precipitate which would appear to contain [(3)H]NA- and/or (3)H-derivatives-binding protein. Such a (3)H-macromolecular complex, which could represent the specific carrier, may well undergo retrograde transport from the nerve terminals towards the cell bodies.

Retrograde axonal transport after radioactive serotonin injections into the olfactory bulb: a biochemical analysis of transported radioactive material.

A biochemical analysis of radioactive compounds was performed in the olfactory bulb (OB) and raphe dorsalis (RD) after injection of radioactive [(3)H] or [(14)C]serotonin (5-HT ranging from 10(?2) M to 10(?7) M) into the OB of rats treated or not with a monoamine-oxidase inhibitor (MAOI). In the OB of untreated rats, radioactivity was associated with precipitated protein and soluble perchloric acid (PCA) fractions. High performance liquid chromatography (HPLC) analysis of the PCA-supernatant gave 4 radioactive peaks: one associated with endogenous 5-HT, another with endogenous 5-hydroxyindole acetic acid (5-HIAA) and two without any relationship with endogenous hydroxyindoles: a '5-HT derivative A' and a '5-HT derivative B'. The presence of these '5-HT derivatives' was significantly reduced after treatment with 5,6-dihydroxytryptamine. In the RD, radioactivity was associated with the protein fraction and with '5-HT derivative A'. The kinetic analysis (from 30 min to 46 h) of the '5-HT derivative A' was characterized by a disappearance in the OB and an accumulation in the RD corresponding to a rate of migration in a range of 0.7 to 2 mm/h. This compound was absent or negligible in other non-serotoninergic neurons (such as the Locus Coeruleus, Amygdala and Cortex piriformis). No clear evidence for retrograde transport of radioactive 5-hydroxytryptophan (5-HTP) or 5-HIAA was found. At lower concentration of 5-HT injected into the OB, the half lives and the times of maximal accumulation for 5-HIAA, '5-HT derivative A' and '5-HT derivative B' were increased. The specific activity of 5-HT and 5-HIAA was also increased. The selective radioactive accumulation in the cell bodies of RD neurons after injection of radioactive 5-HT into the OB is discussed as resulting from a selectivity in (a) the uptake by 5-HT nerve terminals; (b) the metabolism of 5-HT into '5-HT derivative A' in the OB; (c) the retrograde axonal transport of '5-HT derivative A'. This '5-HT derivative A' could represent a messenger between nerve terminals and cell bodies and could be involved in homeostatic mechanisms that maintain cellular dynamics. When a MAOI was used, '5-HT-derivative A' and [(3)H]5-HT were found in the OB and also in the RD cell bodies, and to a lesser extent, in the non-serotoninergic cell bodies. These results indicate that MAO inhibition produces a relative non-selectivity in the 'uptake-metabolism and retrograde axonal transport' systems.

Biochemical and autoradiographic investigations of the retrograde axonal transport of labeled material following [(3)H]norepinephrine injection in the olfactory bulb.

Biochemical and autoradiographic methods were used to investigate the retrograde transport of labeled material after injection of [(3)H]norepinephrine ([(3)H]NE) in the olfactory bulb (OB) of rat. Mechanical obstruction of the ventricular recess prevented intraventricular diffusion. At different time intervals following bilateral [(3)H]NE injections, total radioactivity was measured in the OB, locus caeruleus (LC), raphe dorsalis and periaqueductal gray. Preferential accumulation occurred in the LC, and an approximate rate of retrograde transport of 1-6 mm/h could be calculated. Previous administration of 6-hydroxydopamine in the OB reduced this accumulation by 60%. Sixteen hours after [(3)H]NE injection, the radioactivity in LC was equally distributed between an ethanol-soluble and -insoluble fraction. A small proportion of the soluble material was recovered as [(3)H]NE and/or [(3)H]normetanephrine. Following unilateral injections of [(3)H]NE, light microscopic autoradiograms demonstrated nerve cell body labeling mainly in the ipsilateral LC and of greater intensity after 16 than 4 and 8 h. These data lead to the conclusion that the movement of radioactive material was indeed representative of retrograde axonal transport rather than of other mechanisms such as diffusion. The observation of a preferential labeling of noradrenergic perikarya in LC supports the hypothesis of a process mediated by specific binding and/or uptake of [(3)H]NE into noradrenergic axon terminals.

Retrograde axonal transport after radioactive hydroxyindole injections into the olfactory bulb-an autoradiographic study.

Light microscope autoradiography was used to study the retrograde transport of labelled material after injection of [(3)H]serotonin ([(3)H]5-HT), [(3)H]5-hydroxytryptophan ([(3)H]5-HTP) and [(14)C]5-hydroxyindoleacetic acid ([(14)C]5-HIAA) into the olfactory bulb (OB) of rat. A perikaryal labelling was clearly visualized in the Raphe Dorsalis (RD) and the Raphe Centralis (RC) 24 h after injection of [(3)H]5-HT (but not after injection of [(3)H]5-HTP or [(14)C]5-HIAA) into the OB of rats without monoamine-oxidase inhibitor (MAOI). In the OB, the labelled cells (mitral, granular, periglomerular and tufted cells) and the varicosities (dispersed in granular, plexiform and glomerular layers) were greater in number and intensity at 8 h than at 24 h after [(3)H]5-HT (10(?3) M) injection. Five hours after injection of [(14)C]5-HIAA (10(?3) M) some mitral, granular and tufted cells were labelled in the cytoplasm, nuclei and dendrites. A few varicosities were also observed. In contrast, after [(3)H]5-HTP injection no clear labelling was visualized in axonal processes. A net autoradiographic reaction was seen, however, in the capillary walls and some granular cells. After injection of [(3)H]5-HT at various concentrations (10(?2) M to 10(?5) M) into the OB of rats pretreated with MAOI, a selectivity in the pattern of labelling in the injection site and the afferent cell bodies was found at 10(?4) M and 10(?5) M. At these concentrations, the serotoninergic RD and RC neurons were clearly labelled, but the non-serotoninergic neurons such as those originating in the Locus Coeruleus, prepiriform cortex were devoid of label. In the OB, only varicosities and fiber-like structures were reactive. In the RD cell bodies, the intensity of labelling as well as the number of labelled cells were greater at higher concentrations of injected [(3)H]5-HT and when rats were pretreated with a MAOI.

A chronic arterial and venous cannulation method for freely moving rats.

A chronic arterial and venous cannulation method appropriate for pharmacokinetics studies in freely moving rats is described. Two catheters were implanted: one in the abdominal aorta, the other in the inferior vena cava. Passing subcutaneously, the catheters then emerged at the nape of the neck and were sealed by heating. In most cases (70%), 2-3 weeks after surgery, there were no problems of catheter patency. Twenty-four hours after surgery, all the animals were in good health as attested by normal behaviour and physiological parameters. Plasma corticosterone levels (544 +/- 219 ng/ml) determined at various times after an i.v. injection of saline, though 2.4-fold lower than in restrained rats (1330 +/- 292 ng/ml), were, however, indicative of a moderate stress. From a differential analysis of the factors involved in the relatively elevated circulating corticosterone as compared to basal levels, it is concluded that a prolonged postoperative period (7 days) and maintaining of the animals in metabolic cages are necessary conditions to obtain a minimal state of stress with this technique.

Comparison of the effects of chronic water deprivation and hypertonic saline ingestion on cerebral protein synthesis in rats.

The effects of 3 days water deprivation and 3 days with 2% (w/v) NaCl in drinking water on local rates of methionine incorporation into brain proteins were compared by means of a quantitative autoradiographic method with L-[35S]methionine. The two conditions of chronic dehydration resulted in large increases in the rate of methionine incorporation in the supraoptic (SON), magnocellular paraventricular (mPVN) and arcuate nuclei of the hypothalamus, and in the subfornical organ (SFO). Significant increases of lower amplitude occurred as a result of both treatments in the anteroventral third ventricle area, parvocellular paraventricular nucleus and locus coeruleus. Water deprivation caused larger increases of protein synthesis than hypertonic saline ingestion in the SON, mPVN and SFO. These results indicate that following chronic dehydration, increases in protein synthesis occur mainly in forebrain areas involved in the regulation of water balance, whereas no major changes in protein synthesis occur in brainstem areas involved in the control of blood volume and pressure.

The effects of melatonin and pinealectomy upon local cerebral glucose utilization in awake unrestrained rats are restricted to a few specific regions.

The effects of the infusion of melatonin (MT) and/or of pinealectomy upon glucose utilization in anatomically discrete regions of the brain of freely moving rats have been studied by the quantitative autoradiographic 2-deoxy-D-[1-14C]glucose technique. The experiments were made from 14.00 to 16.00 h, when MT is normally not secreted by the pineal gland, in order to compare the local cerebral glucose utilization (LCGU) response to MT from animals with long-term (pinealectomized) or short-term (pineal intact) absence of MT secretion. The majority of the 98 brain areas examined showed no change in LCGU after MT administration and/or pinealectomy. Pinealectomy increased the LCGU in the median mammillary nucleus only, whereas following MT administration, an increase in LCGU was observed in 3 cerebral regions of intact rats (paraventricular nucleus of the hypothalamus, nucleus of the solitary tract, choroid plexus of the third ventricle) and in 5 cerebral regions of pinealectomized rats (paraventricular nucleus of the hypothalamus, nucleus of the solitary tract, choroid plexuses of the lateral ventricles, third and fourth ventricles). Except for the choroid plexuses of the fourth ventricle, there was no difference in LCGU response to MT between pinealectomized and intact animals. This does not favor the hypothesis of receptor supersensitivity under the conditions of this experiment. Our results suggest that the hypothalamus, nucleus of the solitary tract and choroid plexuses represent a neural substrate through which MT could influence the activity of the central nervous system when administered at a low dose under near-physiological conditions.

Retrograde axonal transport following injection of [3H]serotonin in the olfactory bulb. I. Biochemical study.

A retrograde axonal transport from the serotonergic nerve terminals in the olfactory bulb (OB) to their parent cell bodies in the midbrain raphe nuclei has been demonstrated after stereotaxic injection of [2H]5-HT into the OB of rats pretreated with a monoamine oxidase (MAO) inhibitor: at various time intervals thereafter (4-92 h) there was a preferential accumulation of radioactivity mainly in the raphe dorsalis nucleus (RDN). Maximal accumulation occurred at 24 h. Of this radioactivity, 30-50% was recovered as 5-HT. The accumulation was estimated to take place at two rates: a fast one (48 mm/day) and a slower one (16 mm/day). Under the same experimental conditions there was no clear evidence for a retrograde accumulation of [3H]norepinephrine in the RDN. A passive diffusion mechanism could be excluded since the diffuson of tracer towards the cerebrospinal fluid was prevented by prior mechanical obstruction of the olfactory diverticle of the lateral ventricle. Furthermore, colchicine strongly reduced (by 80%) the radioactive accumulatin in the RDN. Destruction of serotonergic nerve terminals by 5,6-dihydroxytryptamine or inhibiton of 5-HT uptake by fluoxetine decreased this retrograde accumulation whereas destruction of catecholaminergic nerve terminals by 6-hydroxydopamine was without effect. Pretreatment with reserpine decreased the amount of radioactivity transported to the RDN by 40%. In the absence of MAO inhibition pretreatment, animals still presentd 35% of the tracer transported to the RDN. Intrabulbar injection of MAO inhibitor did not affect the accumulation rates when compared with animals which received the inhibitor by the intraperitoneal route. In conclusion, the retrograde axonal transport following [3H]5-HT injection in the serotonergic RDN-OB system occurs via an active process which depends on a colchicine-sensitive mechanism and is partially linked to a reserp ine-sensitive structure. During its transport, the amine seems to be relatively protected from metabolic inactivation.

The efferent connections of the nucleus raphe centralis superior in the rat as revealed by radioautography.

By chronically implanting a glass micropipette filled with tritiated leucine in the raphe centralis superior of the rat, the projection of this nucleus was traced by radioautography. The majority of the ascending projections were located within the ventral tegmental area and, further rostrally, the median forebrain bundle. Along the course of this bundle numerous fibers branched successively into the mammillary peduncle, the fasciculus retroflexus, the stria medullaris, the fornix and the cingulum. The most significant projections included the ones to the interpeduncular nucleus, the mammillary bodies, the habenular nuclei and the hippocampus. No projections were detected in the striatum, the cortex piriformis or the amygdala. Descending projections diffused to the pontine reticular formation and central gray through the medial and the dorsal longitudinal bundles. In addition widespread projections were also seen in nuclei located near the raphe centralis superior: raphe nuclei, dorsal and ventral tegmental nuclei.

GABA-accumulating neurons in the nucleus raphe dorsalis and periaqueductal gray in the rat: a biochemical and radioautographic study.

The possibility of a GABAergic innervation of the nucleus raphe dorsalis (NRD) has been investigated by using the following approaches: (i) the identification of the principal neuronal groups afferent to the NDR by using horseradish peroxidase retrograde transport, (ii) the determination of glutamate decarboxylase activity (GAD) in the NRD after lesioning these groups or their putative pathways, and (iii) the radioautographic identification of terminals axons and nerve cells accumulating intraventricularly injected [3H]GABA. The hypothesis of a local GABAergic network is supported by the failure to obtain important changes in GAD after lesions of NRD afferents and the presence in this nucleus of terminals, fibers and nerve cell bodies accumulating [3H]GABA. It appears that these GABA-accumulating neurons could represent a portion of aperiventricular GABAergic system in the periaqueductal gray and the pontine ventricular gray.

Regulation of expression and enzymatic activities of tyrosine and tryptophan hydroxylases in rat brain after acute electroconvulsive shock.

Acute electroconvulsive shock (ECS) causes a significant increase of protein synthesis in depressive patients and such an increase raises the possibility that the regulation of specific proteins and enzymatic activities in the brain might be one of the mechanisms required for the induction of long-term adaptive neurochemical changes after electroconvulsive therapy. In current studies, we investigated and compared simultaneously the short- and long-term effects of an acute ECS on the expression and enzymatic activities of both tyrosine and tryptophan hydroxylases (TH and TpOH, respectively) in different rat brain areas. Our results demonstrated that an acute ECS produced: (1) a long-lasting decrease in TH and TpOH protein levels in locus ceruleus (LC), ventral tegmental area (VTA) and in TpOH protein level in the raphe centralis (RC), maximal at 72 h, with concomitant changes in mRNA levels and enzymatic activities in the LC only; (2) large increase of TpOH protein levels in the frontal cortex (Cxf) (+145%) and increase of TH protein levels in the hippocampus (Hip) (+207%), maximal at 72 h and 7 days which was not accompanied by corresponding increase of in vivo enzymatic activities. Furthermore, a second ECS increased in vivo TpOH activity in the Cxf (+19%) while decreasing K(m) value (-50%) for tetrahydrobiopterin cofactor. A stability of the observed findings on TpOH activity in the Cxf after repeated ECS might be one of the mechanisms for the antidepressant effects of electroconvulsive therapy.

Cerebral protein synthesis alterations in response to acute and chronic immobilization stress in the rat.

The quantitative autoradiographic method with L-(35S)methionine was used to determine the effects of 1-acute (4h) and 2-chronic (14 days) immobilization stress followed by one week of recovery. Acute stress induced a significant decrease in methionine incorporation into proteins in 17 of the 35 brain structures examined (mean effect: -22%), and a significant increase in the prepositus hypoglossal nucleus (+23%). Chronic stress induced a significant decrease in methionine incorporation into proteins in 8 of the 35 structures analyzed. Only 4 structures were similarly affected in both these conditions. Our results indicate that stress-induced specific molecular changes in brain are also associated with changes in more general molecular components of cellular metabolism.

Retrograde axonal transport following injection of [3H]-serotonin into the olfactory bulb. II. Radioautographic study.

Radioautography was used to study the intraneuronal distribution of [3H]-serotonin (5-HT) and/or its derivatives selectively taken up by the olfactory bulb (OB) serotonergic terminals and subsequently transported to their parent cell bodies in the midbrain raphe nuclei. This was done 24 h after injection of [3H]5-HT into the main OB of rats either pretreated or not with monoamine oxidase (MAO) inhibitor. A prior mechanical obstruction of the rostral ventricular cavities prevented diffusion of the tracer towards cerebrospinal fluid. Heavily labelled nerve cell bodies were found mainly in the ipsilateral raphe dorsalis nucleus (RDN) and to a lesser extent in the raphe centralis nucleus. The radioautographic reaction often extended to dendritic processes while sparing the nucleus. A diffuse reaction was also observed but limited to the raphe area. The supraependymal 5-HT fibers were found to be free of labelling. Neither local destruction of catecholaminergic terminals with 6-OHDA, nor absence of MAO inhibition, impaired this radioautographic pattern, while destruction of serotonergic terminals with 5,6-dihydroxytryptamine in OB resulted in the disappearance of labelled axonal varicosities and neurons in the OB and the RDN respectively. At the electron microscopy level, labelled cell bodies in the RDN were medium-sized (12-15 micrometers). Silver grains were localized mainly on mitochondria and, to a lesser extent, on lysosomes and endoplasmic reticulum but spared the nucleus and the nucleolus. Silver grains were also found near the nuclear membrane and outside the neuronal membrane. The observation of heavy metal impregnated thick sections confirmed the preferential localization of silver grains on mitochondria with or without inhibition of MAO. These results could account for the subcellular compartments involved in the retrograde axonal transport of [3H]5-HT and its subsequent degradation and/or dendritic release.

The raphe nuclei of the cat brain stem: a topographical atlas of their efferent projections as revealed by autoradiography.

Stereotaxic injections of [14C]leucine were made in nulei raphe centralis superior, raphe dorsalis, raphe magnus and raphe pontis of the cat. The organization of the regional connections was outlined in a stereotaxic atlas using the autoradiographic tracing method: the majority of the ascending pathways from the rostral raphe nuclei are directed mainly through a ventrolateral bundle via the ventral tegmental area of Tsai, with some lateral extensions to the substantia nigra, and then through the fields of Forel and the zona incerta. More rostrally the fibers are joined to the medial forebrain bundle through the hypothalamic region up to the preoptic area or the diagonal band of Broca. Multiple divisions leave this tract towards the epithalamic or the intralaminar thalamic nuclei, the stria terminalis, the septum, the capsula interna and the ansa lenticularis. The bulk of the rostral projections terminates in the frontal lobe, while some labeling is scarcely distributed throughout the rest of the neocortex. The projections of nucleus (n.) raphe centralis superior are specifically associated with the n. interpeduncularis, the mammillary bodies and the hippocampal formation while the n. raphe dorsalis innervates selectively the lateral geniculate bodies, striatus, piriform lobes, olfactory bulb and amygdala. The rest of the ascending fibers form the centrolateral or the dorsal ascending tracts radiating either in the reticular mesencephalic formation or in the periventricular gray matter. On the contrary there are heavy descending projections from n. raphe centralis superior which distribute to the main nuclei of the brain stem, the central gray matter and the cerebellum. The ascending projections form the caudal raphe nuclei are much less dense. They disseminate mainly in the colliculus superior, the pretectum, the nucleus of the posterior commissure, the preoculomotor complex and the intralaminar nuclei of the thalamus. From n. raphe pontis, a dense labeling is selectively localized at the n. paraventricularis hypothalami with some rostral extensions to limbic areas. Diffuse caudal and rostral projections from both nuclei are observed in the mesencephalic, pontobulbar reticular formation and the cerebellum. The main differences come from the specific localization of their descending bulbospinal tracts inside the lateroventral funiculus of the spinal cervical cord.

Early and prolonged widespread increase in brain protein synthesis following a single electroconvulsive shock in free-moving rats.

The autoradiographic method with l-[35S] methionine ([35S]Met) was used to determine the effect of a single electroconvulsive shock (ECS) on local rates of protein synthesis in the adult rat brain in free-moving conditions. We have estimated the relative contribution of methionine derived from protein breakdown to the intracellular precursor amino acid pool (tRNA pool) for protein synthesis. In steady-state conditions, we showed a large contribution (around 60%) of Met recycling into the precursor pool (lambda=0.37+/-0.11), after a single ECS. In all the 36 brain regions examined, apparent rates of protein synthesis were greatly increased (21-50%) 3 h after a single ECS indicating a generalized effect in rat brain. This ECS-induced activation of the overall rate of brain protein synthesis persisted for at least 24 h after cessation of ECS. This is consistent with the hypothesis that electroconvulsive therapy is associated with long-term molecular changes in neuronal activity.

Glucose utilization increases in choroid plexus during slow wave sleep. A [14C] deoxyglucose study in the cat.

Glucose utilization (GU) was measured during spontaneous waking and slow-wave sleep (SWS) by adaptation of the [14C]deoxyglucose method to the unrestrained cat. In sleeping animals a greater autoradiographic signal between choroid plexus (CP) and the rest of brain was noticed. Quantification provided an index of the metabolic rate of CP and confirmed that mean values for GU were significantly higher in "sleeping' than in "awake' cats.

RU 24722, a new eburnamine derivative, induces selective alterations in cerebral glucose utilization in freely moving rat.

The effect of a new eburnamine derivative, RU 24722, a putative phasic activator of catecholaminergic systems on local cerebral glucose utilization was studied in freely moving rats 15 min, 90 min and 6 h after the intraperitoneal administration of the drug (25 mg/kg). Of the 53 brain regions examined, 9 exhibited significant time-dependent increases of glucose utilization (up to 45-55%). Some changes were early and transient, as in the substantia nigra reticulata and the paraventricular nuclei. Other areas showed sustained (median septal nucleus) or delayed increases of glucose utilization (lateral septum, dorsal subiculum, hippocampal fimbria, fronto-parietal motor cortex and ventral cochlear nucleus). No significant alterations of glucose utilization could be elicited in the locus coeruleus and raphe nuclei, and none of the brain regions showed a decrease in glucose consumption. Our findings suggest that RU 24722 preferentially stimulates the activity in some brain areas involved in cognitive, vegetative and locomotor functions.