Rostral Basal Forebrain Research Articles

Interleukin-1 Induces Slow-Wave Sleep at the Prostaglandin D2-Sensitive Sleep-Promoting Zone in the Rat Brain

To determine the site of action of the sleep-promoting effect of interleukin-1 (IL-1), we continuously infused (between 11 P.M. and 5 A.M.) murine recombinant IL-1beta into seven different locations in the ventricular and subarachnoid systems of the brain in freely moving rats. When IL-1 was infused at 10 ng/6 hr into the subarachnoid space underlying the ventral surface of the rostral basal forebrain, which previously was defined as the "prostaglandin (PG) D2-sensitive sleep-promoting zone" (PGD2-SZ), the total amount of slow-wave sleep (SWS) increased by 110.7 min (IL-1 was 208.1 +/- 14.3 min vs control at 97.4 +/- 9.3 min; n = 8; p < 0.01 by paired Student's t test) from the baseline control level obtained under continuous infusion of saline vehicle. The hourly SWS during the infusion period reached the level of daytime SWS, the physiological maximum, whereas paradoxical sleep (PS) was decreased transiently. This site of action for the SWS promotion was dissociated from the site in the third ventricle sensitive to the IL-1-mediated PS suppression, fever, and anorexia. The SWS increase caused by IL-1 infusion into the PGD2-SZ was blocked completely by coadministered diclofenac, a nonselective cyclooxygenase (COX) inhibitor. Pretreatment of rats with NS-398 or piroxicam (3 mg/kg of body weight, i.p.), which are said, respectively, to possess high and relative specificity for the COX-2 enzyme, also blocked the SWS-promoting effect of IL-1. We present a hypothesis that IL-1 induces SWS, at least in part, via COX-2-mediated PG production in the PGD2-SZ.

Activation of ventrolateral preoptic neurons by the somnogen prostaglandin D2.

Prostaglandin D2 (PGD2) is an extensively studied sleep-promoting substance, but the neuroanatomical basis of PGD2-induced sleep is only partially understood. To determine potential regions involved in this response, we used Fos immunohistochemistry to identify neurons activated by infusion of PGD2 into the subarachnoid space below the rostral basal forebrain. PGD2 increased nonrapid eye movement sleep and induced striking expression of Fos in the ventrolateral preoptic area (VLPO), a cluster of neurons that may promote sleep by inhibiting the tuberomammillary nucleus, the source of the ascending histaminergic arousal system. Fos expression in the VLPO was positively correlated with the preceding amount of sleep and negatively correlated with Fos expression in the tuberomammillary nucleus. PGD2 also increased Fos immunoreactivity in the basal leptomeninges and several regions implicated in autonomic regulation. These observations suggest that PGD2 may induce sleep via leptomeningeal PGD2 receptors with subsequent activation of the VLPO.

Involvement of adenosine A 2A receptor in sleep promotion

We examined the sleep-modulatory effects of four adenosine agonists, namely, (1) 2-(4-(2-carboxyethyl)phenylethylamino)adenosine-5′- N-ethylcarboxamideadenosine (CGS21680), a highly selective adenosine A 2A receptor agonist; (2) 2-(4-(2-(2-aminoethylaminocarbonyl)ethyl)phenylethylamino)-5′- N-ethylcarboxamidoadenosine (APEC), a selective adenosine A 2A receptor agonist; (3) 5′- N-ethylcarboxamidoadenosine (NECA), a nonselective adenosine A 1/A 2 receptor agonist, and (4) N 6-cyclopentyladenosine (CPA), a selective adenosine A 1 receptor agonist. Each agonist was administered in the subarachnoid space underlying the rostral basal forebrain of rats through chronically implanted cannulae at the rate of 0.02, 0.2, 2.0, 12.0, or 20.0 pmol/min over a 6-h period starting from 2300 h, which period is the active phase of the animals. CGS21680, APEC, and NECA produced significant increases in the total amounts of non-rapid-eye-movement (NREM) sleep and rapid-eye-movement (REM) sleep after at least one dose within the range of administration rates. CPA did not produce any significant increase in the total amount of either type of sleep at any of the above administration rates, but instead suppressed REM sleep at the administration rates of 12.0 and 20.0 pmol/min. These results indicate that the activities of adenosine A 2A receptors are crucially involved in the promotion of sleep.

Origin of the neurotensinergic innervation of the rat basal forebrain studied by retrograde transport of cholera toxin

Basal forebrain cholinergic neurons project to the hippocampus and cerebral cortex where they play an important role in cortical activation, attention, and memory. These neurons have been shown to express functional neurotensin receptors and to receive a dense neurotensinergic innervation. In the present study, we investigated the origin of this innervation by combining retrograde transport of cholera toxin with immunohistochemical detection of neurotensin. After injection of cholera toxin in the anterior substantia innominata and diagonal band of Broca, retrogradely labelled cells were widely distributed throughout forebrain limbic structures. Only a small proportion of these cells, located (by decreasing order of frequency) in the lateral septum, medial preoptic area, rostral hypothalamus, nucleus accumbens, and rostral basal forebrain, were dually labelled for neurotensin. After injection of cholera toxin in the posterior substantia innominata and magnocellular preoptic nucleus, retrogradely labelled cells were detected throughout the limbic forebrain and pontomesencephalic tegmentum. Here again, only a small proportion of these cells, located (by decreasing order of frequency) in the nucleus accumbens, lateral septum, rostral basal forebrain, hypothalamus, bed nucleus of the stria terminalis, supramammilliary nucleus, ventral tegmental area, and raphe complex co-localized neurotensin. In view of the burst generating properties of neurotensin on basal forebrain cholinergic neurons, our results suggest that neurotensin projections may be part of the septo-hippocampo-septal loop regulating hippocampal theta activity. More caudally, neurotensin axons originating from the lateral hypothalamus and pontomesencephalic tegmentum may contribute to the contingent of ascending reticular formation fibers involved in the regulation of the sleep-wake cycle.

Molecular and neuroanatomical mechanisms of sleep-wakefulness regulation by prostaglandins D2 and E2

Prostaglandin (PG) s D2 and E2 are the major arachidonic acid metabolites in the mammalian brain. PGD synthase, the enzyme that produces PGD2 in the brain, is mainly localized in the arachnoid membrane and choroid plexus. It is secreted into the cerebrospinal fluid and circulates in the brain through the ventricular system. PGD2 induces sleep by acting on the surface of the ventro-medial region of the rostral basal forebrain, the signal of which is probably transmitted into the brain parenchyma by adenosine via adenosine A2a receptors. Fos expression experiments suggest that PGD2 inhibits histaminergic arousal neurons of the tuberomammillary nucleus (TMN) in the posterior hypothalamus by activating inhibitory neurons in the ventrolateral preoptic area (VLPO). However, PGE2 causes wakefulness by activating arousal neurons in the TMN via AMPA type excitatory amino acid receptors. Therefore, PGD2, acting as a sleep-inducer, and PGE2, acting as a wakefulness-promoter, jointly regulate the generation of sleep and wakefulness in the mammalian brain.

CSF levels of prostaglandins, especially the level of prostaglandin D 2, are correlated with increasing propensity towards sleep in rats

The concentration of PGD 2, PGE 2, and of PGF 2 α was measured in the cerebrospinal fluid (CSF) collected from the cisterna magna of conscious rats ( n=29), which, chronically implanted with a catheter for the CSF sampling, underwent deprivation of daytime sleep. Significant elevation of the CSF level of PGD 2 was observed following 2.5-h sleep deprivation (SD), and the elevation became more marked following 5- and 10-h SD, apparently reaching the maximum at 5-h SD (703±140 pg/ml (mean±S.E.M.) for baseline vs. 1734±363 pg/ml for SD, n=10). The levels of PGE 2 and PGF 2 α also significantly increased following 5- and 10-h SD, but not following 2.5-h SD. It is unlikely that these changes were simply caused by some responses of the animals to stress stimuli, because stress stimuli derived from restraint of the animal at the supine position to a board for 1 h did not produce any acute responses in the CSF levels of prostaglandins ( n=13). In a different group of animals ( n=11) implanted with electrodes for recording electroencephalogram (EEG) and electromyogram (EMG) in addition to the catheter, the levels of the prostaglandins in CSF were determined for slow-wave sleep (SWS) and wakefulness in the day and for SWS and wakefulness in the night. The highest PGD 2 value was obtained at daytime SWS, whereas the lowest was at night wakefulness; furthermore, a significant difference was observed between SWS and wakefulness rather than between day and night. The CSF level of PGE 2 also showed a similar tendency. In an additional group of animals ( n=6), not only PGD 2 but also PGE 2 and PGF 2 α significantly increased the sleeping time of the animal when applied into the subarachnoid space underlying the ventral surface area of the rostral basal forebrain, the previously defined site of action for the sleep-promoting effect of PGD 2. The promotion of sleep by PGE 2 applied to the subarachnoid space was an effect completely opposite to the well-established awaking effect of the same prostaglandin demonstrated in the hypothalamic region in a series of previous studies. Based on these results, we conclude that increases in CSF levels of prostaglandins, especially that of PGD 2, are correlated in rats with heightened propensity towards sleep and further with the depth of sleep under normal as well as SD conditions. © 1997 Elsevier Science B.V. All rights reserved.

Molecular mechanism of sleep regulation by prostaglandin D 2

Recent biochemical, molecular biological, and pharmacological experiments revealed that prostaglandin D synthase as well as prostaglandin D 2 circulated in the ventricular system, subarachnoidal space, and extracellular space in the brain. Prostaglandin D 2 then interacts with chemosensors or receptors on the ventro-medial surface of the rostral basal forebrain to initiate the signal to promote sleep. Prostaglandin D 2 is, therefore, not a typical neurotransmitter but rather a ‘neurohormone’ or an ‘informational substance’ that circulates through the cerebrospinal fluid and transmits certain chemical messages to promote sleep. The mode of communication through the cerebrospinal fluid in the ventricular system and the extracellular space has advantages for global regulation of the brain to induce sleep.

Promotion of sleep mediated by the A2a-adenosine receptor and possible involvement of this receptor in the sleep induced by prostaglandin D2 in rats.

A 6-hr continuous infusion of 2-[p-(2-carboxyethyl)phenylethylamino]-5'-N-ethylcarboxamidoadenos ine (CGS21680), a selective A2a-adenosine agonist, into the subarachnoid space underlying the ventral surface region of the rostral basal forebrain, which has been defined as the prostaglandin (PG) D2-sensitive sleep-promoting zone, at rates of 0.02, 0.2, 2.0, and 12 pmol/min increased slow-wave sleep (SWS) and paradoxical sleep (PS) in a dose-dependent manner up to 183% and 202% of their respective baseline levels. The increments produced by the infusion of CGS21680 at 0.2 and 2.0 pmol/min were totally diminished when the rats had been pretreated with an i.p. injection of (E)-1,3-dipropyl-7-methyl-8-(3,4-dimethoxystyryl)xanthine (KF17837; 30 mg/kg of body weight), a selective A2-adenosine antagonist. In contrast, the infusion of N6-cyclohexyladenosine (CHA), a selective A1-adenosine agonist, at 2 pmol/min significantly suppressed SWS before causing an increase in SWS, and a decrease in PS was also markedly visible. Essentially the same effects of CGS21680 and CHA were observed when these compounds were administered to the parenchymal region of the rostral basal forebrain through chronically implanted microdialysis probes. Thus, we clearly showed that stimulation of A2a-adenosine receptors in the rostral basal forebrain promotes SWS and PS. Furthermore, i.p. injections of KF17837 at 30 and 100 mg/kg of body weight dose-dependently attenuated the magnitude of the SWS increase produced by the infusion of PGD2 into the subarachnoid space of the sleep-promoting zone, thus indicating that the A2a-adenosine receptors are crucial in the sleep-promoting process triggered by PGD2.

Continuous recordings of brain regional circulation during sleep/wake state transitions in rats.

Continuous measurement of regional blood flow (RBF) in the brain of a freely behaving rat was attained by a combination of laser-Doppler (LD) flowmetry and our originally devised apparatus, which had been developed for the automatic releasing of the twisting of lines connected between experimental apparatus and the freely behaving animal. RBF changes were studied in a ventral region of the rostral basal forebrain along with sleep-wake states. When compared with the RBF level during slow-wave sleep (SWS), levels of RBF during paradoxical sleep (PS) and wakefulness were higher by 24 (P = 0.0001) and 9% (P < 0.05), respectively. The LD signals suggested that the RBF elevation during PS was produced by dilation of both the large brain arteries and small vessels, whereas the elevation during wakefulness was caused by dilation of small vessels that was counteracted by contraction of large arteries. It was noticed that the original circulation tended to begin changing before the onset of SWS. A circadian rhythm was also demonstrated for the RBF, which largely decreased around the onset of the light period and returned to the high level before the beginning of the dark period. Thus continuous and real-time recordings of regional circulation were performed with satisfactorily precision in freely behaving rats.

1004 Sleep-promoting effect of interleukin- 1 β in the rostral basal forebrain

We established a capillary electrophoretic method with high sensitivity and specificity for testing hair taken from addicts. After pretreatment of hair sample, the cation-selective exhaustive injection and sweeping micellar electrokinetic chromatography (CSEI-Sweep-MEKC) was used to test for the presence of abused drugs in human hair. These drugs include morphine (M), codeine (C), ketamine (K) and methamphetamine (MA). First, an uncoated fused-silica capillary (40 cm, 50 μm I.D.) was filled with phosphate buffer (50 mM, pH 2.5) containing 30% methanol, followed by high conductivity buffer (100 mM phosphate, 6.9 kPa for 99.9 s). Electrokinetic injection (10 kV, 600 s) was used to load samples and to enhance sensitivity. Stacking steps and separations were performed at −20 kV with detection at 200 nm, using phosphate buffer (25 mM, pH 2.5) containing 20% methanol and 100 mM sodium dodecyl sulfate. Using CSEI-Sweep-MEKC, the analytes could be simultaneously analyzed and have a detection limit down to the level of picogram per milligram hair. During method validation, calibration plots were linear (r ≥ 0.999) over a range of 0.15–80 ng/mg hair for MA and K, 0.3–30 ng/mg hair for C and 0.5–50 ng/mg hair for M. The limits of detection were 50 pg/mg hair for MA and K, 100 pg/mg hair for C and 200 pg/mg hair for M (S/N = 3, sampling 600 s at 10 kV). Our method was applied for analysis of real hair samples taken from addicts. The addicts’ specimens were also analyzed by LC–MS, and showed good coincidence of results. This method has proven feasible for application in detecting trace levels of abused drugs in forensic analysis.

Prostaglandin D2-sensitive, sleep-promoting zone defined in the ventral surface of the rostral basal forebrain.

The site of action for the sleep-promoting effect of prostaglandin (PG) D2 was extensively examined in the brain of adult male rats (n = 231). PGD2 was administered at 100 pmol/0.2 microliter per min for 6 hr (2300-0500 hr) through chronically implanted microdialysis probes or infusion cannulae. Among the administrations of PDG2 by dialysis probes (n = 176), only those (n = 8) to a ventro-rostral part of the basal forebrain by the probes implanted on the midline consistently increased slow-wave sleep (SWS), by 51 +/- 6 min (mean +/- SEM) above the baseline value (111 +/- 11 min). Since this area is separated by a cleft into right and left regions, the results were interpreted to mean that, through this cleft, PGD2 diffused in the subarachnoid space over the adjacent ventral surface, where it had the effect of promoting sleep. When PGD2 was directly infused into the subarachnoid space (n = 55), extraordinary increases exceeding 90 min were consistently attained for the SWS at sites located between 0.5 and 2 mm rostral to the bregma and between 0 and 1.2 mm lateral to the midline defined according to the stereotaxic coordinates adopted from the brain atlas of Paxinos and Watson [Paxinos, G. & Watson, C. (1986) The Rat Brain in Stereotaxic Coordinates (Academic, San Diego)]. Thus, we demarcated a "PGD2-sensitive, sleep-promoting zone" within this region in the ventral surface of the rostral basal forebrain. During the bilateral infusion of PGD2 into the subarachnoid space of this zone, the hourly mean SWS level of the nocturnal animals (n = 6) in the night reached the maximum at the second hour of the infusion period; this maximum hourly SWS level, corresponding to the daytime level of the same animals, lasted until the end of PGD2 infusion.

Differential expression of GAP-43 mRNA in adult central cholinergic neuronal populations

The present study addresses a question of differential expression for a ‘plasticity’ gene within neurons identified by neurotransmitter type. A method combining immunohistochemical localization of choline acetyltransferase (ChAT) with in situ hybridization histochemistry (ISHH) in the same brain sections was used to quantitate the levels of mRNA for the growth-associated protein GAP-43 (neuromodulin) in rat central cholinergic neuronal populations. We found that many cholinergic neurons in the adult rat brain express levels of GAP-43 mRNA comparable to other brain regions noted for their expression of this plasticity gene. GAP-43 expression in cholinergic cell groups appeared to be highly heterogeneous; this was often true even for cholinergic neurons within the same brain region. A dorsal-ventral gradient in GAP-43 mRNA levels was evident in the rostral basal forebrain cholinergic groups; i.e., medial septum, nucleus basalis magnocellularis and the vertical limb of the diagonal band expressed intermediate levels, while the horizontal limb of the diagonal band and the substantia innominata expressed higher levels of GAP-43 mRNA. Cholinergic interneurons of the striatum were grouped in several populations according to mRNA levels, from very low to very high expression. Similarly, GAP-43 mRNA levels in the cholinergic neurons of the nucleus basalis magnocellularis/ substantia innominata were quite variable. The expression of GAP-43 mRNA in brainstem cholinergic groups (laterodorsal tegmental and pedunculopontine nuclei) was in nearly uniform populations of somewhat lower levels. While the expression of GAP-43 mRNA in cholinergic neurons was heterogeneous, virtually every ChAT-positive neuron sampled contained GAP-43 mRNA at levels significantly over background. The highly heterogeneous expression of neuromodulin/GAP-43 in central cholinergic neurons may relate to the differential survival of these cells in brain disease or injury, or may reflect on differential involvement of GAP-43 in regulation of neurotransmitter release.

Topographic projections to the visual cortex from the basal forebrain in the rat

Recent studies have shown that cholinergic neurons within the basal forebrain give rise to a projection that terminates throughout the neocortex. The purpose of the present study is to determine the topographic organization of the basal forebrain projection to a single cortical region: the visual cortex. Injections of wheat germ agglutinin-horseradish peroxidase were placed within the infragranular layers of areas 17, 18a or 18b in Long-Evans hooded rats. Following injections placed within area 18a, retrogradely labeled neurons were located primarily within the caudal components of the basal forebrain including the basal nucleus of Meynert. Injections placed within area 18b, on the other hand, resulted in retrograde labeling of numerous neurons within rostral basal forebrain nuclei, including the horizontal limb of the diagonal band of Broca, whereas only a few labeled cells were located within the basal nucleus. Two patterns of labeled cells were evident following injections placed within area 17 and they resembled the results from injections within the adjacent extrastriate area; i.e. either area 18a or area 18b. Thus, injections restricted to the lateral portions of area 17 resulted in retrograde labeling of neurons located within the caudal levels of the basal forebrain, whereas injections within the medial portions of area 17 were followed by retrograde labeling of neurons within the rostral levels of the basal forebrain. Based on these results we suggest that the cholinergic corticopetal projection terminates within the visual cortex in a medial to lateral pattern.

Substance P and Luteinizing Hormone-Releasing Hormone Levels in the Brain of the Male Golden Hamster Are Both Altered by Castration and Testosterone Replacement

The effects of castration and testosterone (T) replacement on levels of substance P (SP) and luteinizing hormone-releasing hormone (LHRH) were assessed in discrete areas of the male hamster brain. The animals were either castrated, castrated and given a chronically low or high dose of T by Silastic implant, or sham-operated. Brain tissues and trunk blood were collected 3 weeks after surgery. Plasma T levels were maintained within the normal range by the implants but at significantly lower or higher levels than the mean for sham-operated males. Levels of SP and LHRH were quantified in the olfactory bulbs, rostral basal forebrain, anterior hypothalamic and preoptic area, medial basal hypothalamic area, medial basal hypothalamic area and median eminence, and brain stem. In general, castration and T replacement effected opposite changes in levels of SP and LHRH. In the medial basal hypothalamic area and median eminence SP levels were found to be inversely related to the chronic T levels, whereas the LHRH levels were directly correlated. In the anterior hypothalamic and preoptic area, castration reduced levels of SP. Conversely, castration elevated levels of LHRH in this area. This inverse dynamic relationship between changing peptide levels was also observed in the rostral basal forebrain but not in the olfactory bulbs. In most of these forebrain regions, the dose-response curves for the experimental groups could not incorporate the peptide levels in the sham-operated control group. SP levels in the brain stem showed a monotonic inverse relationship to circulating T levels which did include the control group values.(ABSTRACT TRUNCATED AT 250 WORDS)

Spinal neuronal inhibition and EEG synchrony by electrical stimulation in subcortical forebrain regions of the cat.

In cats anaesthetized with sodium pentobarbital and 70% N2O, single lumbar dorsal horn neurons were excited by controlled noxious radiant heating of glabrous hindpaw skin. The EEG was recorded from the pericruciate cortex and posterior lateral gyrus. Subcortical forebrain sites where electrical stimulation inhibited dorsal horn neuronal heat-evoked responses contralaterally were identified by mapping the caudate nucleus, internal capsule, septum, nucleus accumbens and basal forebrain regions. Inhibitory sites were mainly located in the ventral forebrain (ventral septum, diagonal band, basal forebrain). The caudate nucleus and internal capsule had a low incidence and effectiveness of inhibitory sites. In the basal forebrain, the incidence and effectiveness of inhibitory sites decreased from caudal to rostral regions. There was a rostral limit of inhibitory sites, both medially and laterally. The magnitude of inhibition increased with graded increases in brain stimulation intensity. The mean incremental increase in inhibition was greater for caudal than for rostral basal forebrain sites. Mean stimulus currents for threshold of inhibition and for inhibition to 50% of control heat responses were lower for caudal than for rostral sites. Responses of the dorsal horn neurons to increasing temperatures of noxious skin heating were monotonic linear functions over the temperature range studied (48-53 degrees C). Stimulation in both rostral and caudal basal forebrain decreased the slope of this stimulus-response function, with a greater decrease for caudal sites. Cortical EEG synchronization was evoked by stimulation in the caudate nucleus and rostral basal forebrain. For both regions, most synchronogenic sites did not produce descending inhibition of dorsal horn neurons. The significance of these findings in relation to descending inhibition from other brain regions and stimulation-produced analgesia is discussed.

Fiber projections from rostral basal forebrain structures in the cat

Rostral basal forebrain structures, such as preoptic and rhinencephalic regions, are known to receive direct projections from the orbital cortex, and thus may participate in descending influences on brain stem and spinal structures. Projections from these preoptic and rhinencephalic sites were traced in the present study by means of the Nauta method. The medial forebrain bundle was followed from the olfactory tubercle to the mamillary body, and from the preoptic area to the subthalamus, the central gray matter of rostral midbrain and the midbrain tegmentum. Projections to the amygdaloid complex were chiefly confined to the anterior amygdaloid region. Three projection pathways to the thalamus were observed. The first coursed in the stria medullaris via the inferior thalamic peduncle to terminate in nuclei reticularis, ventralis anterior, anterior ventralis, anterior dorsalis, parataenialis, medialis dorsalis, and habenularis lateralis. The second pathway entered the internal medullary lamina via the inferior thalamic peduncle to distribute in nucleus medialis dorsalis and in the intralaminar nuclei. The third pathway to the thalamus ascended through medial hypothalamic areas to distribute fibers to nucleus ventralis medialis and the midline nuclei. Ascending fibers from the preoptic area were traced to the olfactory tubercle and the septal region. Based on these findings, possible modulating influences exerted by the orbital cortex through the medial forebrain bundle on thalamocortical and brain stem-hippocampal systems might be envisioned.