Oleamide modulates memory in rats

Oleamide is a recently described lipid, obtained from the cerebrospinal fluid of sleep-deprived cats. It has been observed that oleamide possesses several biological effects, such as sleep induction, and immunological suppression as well as serotonin and gamma-aminobutyric acid receptors activation. In addition, oleamide also binds to the cannabinoid receptors. In this study, we have observed that oleamide facilitates memory extinction in a passive avoidance paradigm, reduces core temperature and pain perception, but does not affect significantly locomotion. These results suggest that oleamide modulates memory processes. However, we do not know if oleamide impairs the retrieval of the memory associated to the "not go" behavior, or facilitates the fast re-learning of the "go" behavior. In addition, since these effects are also induced by marijuana and anandamide, it is very likely that oleamide may be affecting the cerebral cannabinoid system to induce its effects.

Highly activated CD8(+) T cells in the brain correlate with early central nervous system dysfunction in simian immunodeficiency virus infection

One of the consequences of HIV infection is damage to the CNS. To characterize the virologic, immunologic, and functional factors involved in HIV-induced CNS disease, we analyzed the viral loads and T cell infiltrates in the brains of SIV-infected rhesus monkeys whose CNS function (sensory evoked potential) was impaired. Following infection, CNS evoked potentials were abnormal, indicating early CNS disease. Upon autopsy at 11 wk post-SIV inoculation, the brains of infected animals contained over 5-fold more CD8(+) T cells than did uninfected controls. In both infected and uninfected groups, these CD8(+) T cells presented distinct levels of activation markers (CD11a and CD95) at different sites: brain > CSF > spleen = blood > lymph nodes. The CD8(+) cells obtained from the brains of infected monkeys expressed mRNA for cytolytic and proinflammatory molecules, such as granzymes A and B, perforin, and IFN-gamma. Therefore, the neurological dysfunctions correlated with increased numbers of CD8(+) T cells of an activated phenotype in the brain, suggesting that virus-host interactions contributed to the related CNS functional defects.

Effect of oleamide on sleep and its relationship to blood pressure, body temperature, and locomotor activity in rats

Oleamide (cis-9,10-octadecenoamide) is a brain lipid that has recently been isolated from the cerebral fluid of sleep-deprived cats. Intracerebroventricular and intraperitoneal administration of oleamide induces sleep in rats. However, it is unclear whether oleamide's hypnogenic effects are mediated, in part, by its actions on blood pressure and core body temperature. Here we show that systemic administration of oleamide (10 and 20 mg/kg) in rats increased slow-wave sleep 2, without affecting blood pressure and heart rate. In addition, oleamide decreased body temperature and locomotor activity in a dose-dependent manner. These latter effects were not correlated in time with the observed increases in slow-wave sleep. These data suggest that the hypnogenic effects of oleamide are not related to changes in blood pressure, heart rate, or body temperature.

Responses of ventral tegmental area GABA neurons to brain stimulation reward

Dopamine neurons in the ventral tegmental area (VTA) have been implicated in rewarded behaviors, including intracranial self-stimulation (ICSS). We demonstrate, in unrestrained rats, that the discharge activity of a homogeneous population of presumed VTA GABA neurons, implicated in cortical arousal, increases before ICSS of the medial forebrain bundle (MFB). These findings suggest that VTA GABA neurons may be involved in the attentive processes related to brain stimulation reward (BSR).

Methamphetamine and HIV-1: potential interactions and the use of the FIV/cat model

The interaction of methamphetamine with human immunodeficiency virus (HIV), the aetiologic agent of Acquired Immune Deficiency Syndrome (AIDS), has not been thoroughly investigated. However, increasingly, a larger proportion of HIV infected individuals acquire the virus through methamphetamine use or are exposed to this drug during their disease course. In certain populations, there is a convergence of methamphetamine use and HIV-1 infection; yet our understanding of the potential effects that simultaneous exposure to these two agents have on disease progression is extremely limited. Studying the interactions between methamphetamine and lentivirus in people is difficult. To thoroughly understand methamphetamine's effects on lentivirus disease progression, an animal model that is both clinically relevant and easily manipulated is essential. In this report, we identified potential problems with methamphetamine abuse in individuals with a concurrent HIV-1 infection, described the Feline Immunodeficiency Virus (FIV)/cat model for HIV-1, and reported our early findings using this modelling system to study the interaction of methamphetamine and lentivirus infections.

Functional consequences of repeated (+/-)3,4-methylenedioxymethamphetamine (MDMA) treatment in rhesus monkeys

Six rhesus monkeys were trained to stable performance on neuropsychological tests of memory, reinforcer efficacy, reaction time and bimanual motor coordination. Three monkeys were then exposed to a high-dose, short course regimen of (+/-)3,4-Methylenedioxymethamphetamine (MDMA, "Ecstasy") (4 days, 10 mg/kg i.m., b.i.d.). Following treatment, concentrations of 5-hydroxyindoleacetic acid (5-HIAA) in cerebrospinal fluid (CSF) were reduced by approximately 50% in the treated animals, and this effect persisted for approximately three months post-MDMA. Behavioral performance was disrupted during acute MDMA treatment but returned to baseline within one week following treatment. MDMA also produced persistent alterations in late peak latencies of brainstem auditory evoked potentials (BSAEP), lasting three months post-MDMA. Both CSF 5-HIAA concentrations and evoked potential latencies were normalized four months after treatment. These findings indicate that serotonergic alterations associated with MDMA use may result in persisting changes in brain function.

Discharge profiles of ventral tegmental area GABA neurons during movement, anesthesia, and the sleep-wake cycle

Although mesolimbic dopamine (DA) transmission has been implicated in behavioral and cortical arousal, DA neurons in the ventral tegmental area (VTA) and substantia nigra pars compacta (SNc) are not significantly modulated by anesthetics or the sleep-wake cycle. However, VTA and SN non-DA neurons evince increased firing rates during active wakefulness (AW) and rapid eye movement (REM) sleep, relative to quiet wakefulness. Here we describe the effects of movement, select anesthetics, and the sleep-wake cycle on the activity of a homogeneous population of VTA GABA-containing neurons during normal sleep and after 24 hr sleep deprivation. In freely behaving rats, VTA GABA neurons were relatively fast firing (29 +/- 6 Hz during AW), nonbursting neurons that exhibited markedly increased activity during the onset of discrete movements. Adequate anesthesia produced by administration of chloral hydrate, ketamine, or halothane significantly reduced VTA GABA neuron firing rate and converted their activity into phasic 0.5-2.0 sec ON/OFF periods. VTA GABA neuron firing rate decreased 53% during slow-wave sleep (SWS) and increased 79% during REM, relative to AW; however, the discharging was not synchronous with electrocortical alpha wave activity during AW, delta wave activity during SWS, or gamma wave activity during REM. During deprived SWS, there was a direct correlation between increased VTA GABA neuron slowing and increased delta wave power. These findings indicate that the discharging of VTA GABA neurons correlates with psychomotor behavior and that these neurons may be an integral part of the extrathalamic cortical activating system.

Hypocretin-1 modulates rapid eye movement sleep through activation of locus coeruleus neurons

The hypocretins (hcrts), also known as orexins, are two recently identified excitatory neuropeptides that in rat are produced by approximately 1200 neurons whose cell bodies are located in the lateral hypothalamus. The hypocretins/orexins have been implicated in the regulation of rapid eye movement (REM) sleep and the pathophysiology of narcolepsy. In the present study, we investigated whether the locus coeruleus (LC), a structure receiving dense hcrtergic innervation, which is quiescent during REM sleep, might be a target for hcrt to regulate REM sleep. Local administration of hcrt1 but not hcrt2 in the LC suppressed REM sleep in a dose-dependent manner and increased wakefulness at the expense of deep, slow-wave sleep. These effects were blocked with an antibody that neutralizes hcrt binding to hcrt receptor 1. In situ hybridization and immunocytochemistry showed the presence of hcrt receptor 1 but not the presence of hcrt receptor 2 in the LC. Iontophoretic application of hcrt1 enhanced the firing rate of LC neurons in vivo, and local injection of hcrt1 into the LC induced the expression of c-fos in the LC area. We propose that hcrt receptor 1 in the LC is a key target for REM sleep regulation and might be involved in the pathophysiological mechanisms of narcolepsy.

Effects of multiple acute morphine exposures on feline immunodeficiency virus disease progression

Drug abuse is a common method of human immunodeficiency virus type 1 transmission, but the role of opiates on lentivirus disease progression is not well understood. The feline immunodeficiency virus (FIV)/cat system was used to model the weekend opiate abuser: the nondependent, nonaddicted, and nontolerant person. Sixteen cats were placed into 4 groups: FIV only, morphine only, morphine/FIV, and controls. Multiple acute morphine exposure did not increase the severity of early lentivirus infection. On the contrary, it delayed or moderated the FIV-induced disease progression. Although the animals were exposed to only 1 injection of morphine per day for 2 consecutive days per week, the morphine-treated FIV-infected animals had a delayed onset of the FIV-induced lymphadenopathy, did not develop or had a significant delay in the FIV-induced effects on brain stem auditory evoked potentials, and demonstrated a trend toward decreased virus load.

HIV- and FIV-derived gp120 alter spatial memory, LTP, and sleep in rats

Human immunodeficiency virus (HIV)-associated dementia (HAD) has been detected in 20-30% of patients suffering AIDS. The envelope glycoprotein 120 (gp120) derived from HIV seems to play a critical role in the pathophysiology of this dementia. Likewise, the feline immunodeficiency virus (FIV)-derived gp120 causes neurological and electrophysiological abnormalitites in cats. We have studied the effects of gp120 derived from HIV or FIV on learning and memory processing, hippocampal long-term potentiation (LTP), hippocampal neuronal cAMP production, the sleep-waking cycle, and locomotor activity and equilibrium in rats. Results showed that while both HIV- and FIV-gp120 impaired the rat's performance in the Barnes maze task, only HIVgp120 impaired the induction and maintenance of LTP. However, both glycoproteins induced a significant decrease in the posttetanic potentiation. HIVgp120 also caused a significant reduction in cAMP production in the hippocampus. Regarding the sleep-waking cycle, HIV- and FIV-gp120 increased the waking state and slow-wave sleep 1 (SWS1), while decreasing both SWS2 and REM sleep. Locomotor activity and equilibrium were significantly altered by these glycoproteins. These results suggest that HIVgp120 causes neurophysiological abnormalities and therefore may facilitate HAD development in AIDS patients.

Antiviral treatment normalizes neurophysiological but not movement abnormalities in simian immunodeficiency virus-infected monkeys

Simian immunodeficiency virus (SIV) infection of rhesus monkeys provides an excellent model of the central nervous system (CNS) consequences of HIV infection. To discern the relationship between viral load and abnormalities induced in the CNS by the virus, we infected animals with SIV and later instituted antiviral treatment to lower peripheral viral load. Measurement of sensory-evoked potentials, assessing CNS neuronal circuitry, revealed delayed latencies after infection that could be reversed by lowering viral load. Cessation of treatment led to the reappearance of these abnormalities. In contrast, the decline in general motor activity induced by SIV infection was unaffected by antiviral treatment. An acute increase in the level of the chemokine monocyte chemoattractant protein-1 (MCP-1) was found in the cerebrospinal fluid (CSF) relative to plasma in the infected animals at the peak of acute viremia, likely contributing to an early influx of immune cells into the CNS. Examination of the brains of the infected animals after return of the electrophysiological abnormalities revealed diverse viral and inflammatory findings. Although some of the physiological abnormalities resulting from SIV infection can be at least temporarily reversed by lowering viral load, the viral-host interactions initiated by infection may result in long-lasting changes in CNS-mediated functions.

Exogenous glucocorticoids alter parameters of early feline immunodeficiency virus infection

Feline immunodeficiency virus (FIV), a lentivirus, causes progressive immunosuppression and neurologic dysfunction in cats. Glucocorticoids are common therapeutic agents that are also immunosuppressive, and their use might enhance the pathogenic effects of lentivirus infections. Methylprednisolone acetate, a long-acting glucocorticoid, was administered to cats before FIV inoculation, and the course of early infection was monitored. The humoral immune response to FIV was not affected by corticosteroid treatment, but CD8+ cell-mediated antiviral activity was poor in cultures from FIV-infected cats treated with methylprednisolone. Steroid-treated cats had higher plasma viral RNA levels than untreated cats during acute viremia. In contrast, FIV-associated changes in brain stem auditory-evoked potentials were slow to develop in the methylprednisolone-treated cats. Methylprednisolone treatment of cats with established FIV infections appeared to reverse these neurophysiologic changes. These results emphasize the complexity of host-lentivirus interactions and suggest potential advantages and drawbacks of using glucocorticoids in lentivirus infections.

Adaptive responses of gamma-aminobutyric acid neurons in the ventral tegmental area to chronic ethanol

We have recently identified a homogeneous population of gamma-aminobutyric acid (GABA)-containing neurons in the ventral tegmental area (VTA), an area implicated in the reinforcing properties of alcohol. We evaluated the effects of local and systemic ethanol on VTA GABA neuron spontaneous activity in ethanol naive and chronically treated freely behaving rats and in anesthetized rats. In freely behaving animals, acute i.p. administration of 0.2 to 2.0 g/kg ethanol reduced the firing rate of VTA GABA neurons. Chronic administration of 2.0 g/kg i.p. ethanol enhanced baseline activity of VTA GABA neurons and induced tolerance to ethanol inhibition of their firing rate. In a separate group of freely behaving animals, tolerance to 0.4 to 2.0 g/kg i.p. ethanol-induced inhibition of VTA GABA neuron firing rate was observed following 2 weeks of chronic exposure to ethanol vapors producing intermittent blood alcohol levels of 158 mg/100 ml. In acute studies in halothane-anesthetized animals, ethanol applied locally into the VTA decreased the spontaneous firing rate of VTA GABA neurons, whereas systemic ethanol produced an early inhibition followed by a late excitation at 30 to 60 min after the ethanol injection, suggesting that ethanol modulation of an extrinsic input may excite VTA GABA neurons. Tolerance to local ethanol inhibition of VTA GABA neuron firing rate was produced by 2 weeks of chronic exposure to intermittent ethanol vapors. These results demonstrate the marked sensitivity of these neurons to ethanol and suggest that chronic ethanol administration produces selective adaptive circuit responses within the VTA or in extrategmental structures that regulate VTA GABA neuron activity.

Transgenic rescue of SNAP-25 restores dopamine-modulated synaptic transmission in the coloboma mutant

Many of the molecular components constituting the exocytotic machinery responsible for neurotransmitter release have been identified, yet the precise role played by these proteins in synaptic transmission, and their impact on neural function, has not been resolved. The mouse mutation coloboma is a contiguous gene defect that leads to electrophysiological and behavioral deficits and includes the gene-encoding SNAP-25, an integral component of the synaptic vesicle-docking/fusion core complex. The involvement of SNAP-25 in the hyperactive behavior of coloboma mice, which can be ameliorated by the indirect dopaminergic agonist, amphetamine, has been demonstrated by genetic rescue using a SNAP-25 transgene. Coloboma mice also exhibit increased recurrent inhibition, reduced theta rhythm by tail-pinch and reduced long-term potentiation in the hippocampal dentate gyrus that, as the hyperkinesis seen in these mutants suggests, may reflect impaired monoaminergic modulation. We sought to identify neurophysiological correlates of the rescued hyperactivity within hippocampal synaptic circuitry of SNAP-25 transgenic coloboma mutant mice. In contrast to the differences between coloboma and wild-type mice, there was no significant difference in the duration or amplitude of theta rhythmic activity (4-6 Hz) induced by tail-pinch (10 s), afferent-evoked field potentials, or paired-pulse responses recorded in the dentate gyrus of SNAP-25 transgenic coloboma and wild-type mice. Amphetamine (3.0 mg/kg, i.p.) produced disinhibition of dentate paired-pulse responses in both SNAP-25 transgenic and wild-type mice but increased inhibition in non-transgenic coloboma mice. These findings support the hypothesis that alteration of monoaminergic neurotransmission, which can be reversed by the indirect agonist, amphetamine, is particularly sensitive to alterations in the expression of SNAP-25.

Feline immunodeficiency virus envelope protein (FIVgp120) causes electrophysiological alterations in rats

Close to 20% of the patients infected with the AIDS virus develops neurological deficit; eventhough HIV does not invade neurons. Consistently with the neurological deficit, HIV(+) subjects show abnormalities in brainstem auditory and visual evoked potentials (BSAEP and VEP) and in sleep patterns. The HIV-derived glycoprotein 120 has been postulated as a neurotoxic; therefore, it may be playing a crucial role in the generation of BSAEP and VEP, as well as in sleep disturbances. To study the role of the virus-derived proteins on the development of these electrophysiological signals' alterations, we have used the feline immunodeficiency virus (FIV)-derived gp120 and evaluated the changes in these electrophysiological signals. We employed 15 adult male Sprague-Dawley rats (250-350 g), chronically implanted for evoked potential and sleep recordings. Results showed that the i.c.v. administration of FIVgp120 (5 ng/10 microliter) produces changes in the latency of both cortical auditory evoked potentials (CAEPs) and VEPs and a decrease in both REM sleep and SWS. These data support the notion that FIVgp120 is neurotoxic to the central nervous system of cats and rats and that this protein suffices to cause electrophysiological alterations. In addition, it suggests that a similar effect may be occurring in humans as a result of HIVgp120's neurotoxic effects.

Structural and functional neuropathology in transgenic mice with CNS expression of IFN-alpha

Cytokines belonging to the type I interferon (e.g. interferon-alpha) family are important in the host response to infection and may have complex and broad ranging actions in the central nervous system (CNS) that may be beneficial or harmful. To better understand the impact of the CNS expression of the type I interferons (IFN), transgenic mice were developed that produce IFN-alpha(1) chronically from astrocytes. In two independent transgenic lines with moderate and low levels of astrocyte IFN-alpha mRNA expression respectively, a spectrum of transgene dose- and age-dependent structural and functional neurological alterations are induced. Structural changes include neurodegeneration with loss of cholinergic neurons, gliosis, angiopathy with mononuclear cell cuffing, progressive calcification affecting basal ganglia and cerebellum and the up-regulation of a number of IFN-alpha-regulated genes. At a functional level, in vivo and in vitro electrophysiological studies revealed impaired neuronal function and disturbed synaptic plasticity with pronounced hippocampal hyperexcitability. Severe behavioral alterations were also evident in higher expressor GFAP-IFNalpha mice which developed fatal seizures around 13 weeks of age precluding their further behavioral assessment. Modest impairments in discrimination learning were measured in lower expressor GFAP-IFNalpha mice at various ages (7-42 weeks). The behavioral and electrophysiological findings suggest regional changes in hippocampal excitability which may be linked to abnormal calcium metabolism and loss of cholinergic neurons in the GIFN mice. Thus, these transgenic mice provide a novel animal model in which to further evaluate the mechanisms that underlie the diverse actions of type I interferons in the intact CNS and to link specific structural changes with functional impairments.

Cellular responses of nucleus accumbens neurons to opiate-seeking behavior: I. Sustained responding during heroin self-administration

The nucleus accumbens (NAcc) has been hypothesized to be a critical component of the circuit mediating opiate-seeking behaviors. To further explore the electrophysiological correlates of opiate-seeking behavior, we recorded neurons in the NAcc and in the medial prefrontal cortex (mPFC) of rats trained to self-administer heroin for at least 2 weeks. Rats were trained to lever press (FR-1 schedule) for an intravenous (i.v.) infusion of heroin (0.06 mg/kg/injection) in an operant chamber. Spontaneous single unit activity in the NAcc and the mPFC was then recorded while animals were allowed to self-administer heroin. Our data suggest that about 20% (8/42) of the NAcc neurons studied exhibited an inhibitory response immediately after heroin self-administration. However, most of the NAcc neurons studied (76%; 32/42) were not affected during heroin self-administration. In contrast, noncontingent injection of a similar dose of heroin (0.06 mg/kg/injection) had no effect on NAcc spontaneous activity (0/6). On the other hand, passive administration of higher doses of heroin (0.2-0.6/mg/kg/injection) markedly suppressed the firing rate in 46% (6/13) of the neurons studied. These effects of heroin on NAcc activity were antagonized by systemic administration ofnaloxone (4-6 mg/kg, i.v.). Studies characterizing the responses of mPFC neurons during heroin self-administration showed that 40% (2/5) of the neurons tested exhibited an inhibitory effect immediately after heroin self-administration. These data suggest that in animals well-trained to self-administer heroin, only a small number (20%) of the NAcc neurons studied responded to heroin self-administration. Further research is necessary to determine whether these responses are a function of the opiate-seeking state of the animal and the mechanism(s) responsible for these effects of heroin.

Structural and compositional determinants of cortistatin activity

Cortistatin-14 (CST-14) is a putative novel neuropeptide that shares 11 of its 14 residues with somatostatin-14 (SRIF-14), yet its effects on sleep physiology, locomotor behavior and hippocampal function are different from those of somatostatin. We studied the structural basis for cortistatin's distinct biological activities. As with SRIF-14, CST-14 does not show any preferred conformation in solution, as determined by circular dichroism and nuclear magnetic resonance. Synthetic cortistatin analogs were designed and synthesized based on the cyclic structure of octreotide. Biological assays were carried out to determine their binding affinities to five somatostatin receptors (sstl-5) and their ability to produce changes in locomotor activity and to modulate hippocampal physiology and sleep. The results show that the compound with N-terminal proline and C-terminal lysine amide exhibits cortistatin-like biological activities, including reduction of population spike amplitudes in the hippocampal CA1 region, decrease in locomotor activity and enhancement of slow-wave sleep 2. These findings suggest that both proline and lysine are necessary for cortistatin binding to its specific receptor.

C10 is a novel chemokine expressed in experimental inflammatory demyelinating disorders that promotes recruitment of macrophages to the central nervous system

Chemokines may be important in the control of leukocytosis in inflammatory disorders of the central nervous system. We studied cerebral chemokine expression during the evolution of diverse neuroinflammatory disorders in transgenic mice with astrocyte glial fibrillary acidic protein-targeted expression of the cytokines IL-3, IL-6, or IFN-alpha and in mice with experimental autoimmune encephalomyelitis. Distinct chemokine gene expression patterns were observed in the different central nervous system inflammatory models that may determine the phenotype and perhaps the functions of the leukocytes that traffic into the brain. Notably, high expression of C10 and C10-related genes was found in the cerebellum and spinal cord of GFAP-IL3 mice with inflammatory demyelinating disease and in mice with experimental autoimmune encephalomyelitis. In both these neuroinflammatory models, C10 RNA and protein expressing cells were predominantly macrophage/microglia and foamy macrophages present within demyelinating lesions as well as in perivascular infiltrates and meninges. Intracerebroventricular injection of recombinant C10 protein promoted the recruitment of large numbers of Mac-1(+) cells and, to a much lesser extent, CD4(+) lymphocytes into the meninges, choroid plexus, ventricles, and parenchyma of the brain. Thus, C10 is a prominent chemokine expressed in the central nervous system in experimental inflammatory demyelinating disease that, we show, also acts as a potent chemotactic factor for the migration of these leukocytes to the brain.

Early physiological abnormalities after simian immunodeficiency virus infection

Central nervous system (CNS) damage and dysfunction are devastating consequences of HIV infection. Although the CNS is one of the initial targets for HIV infection, little is known about early viral-induced abnormalities that can affect CNS function. Here we report the detection of early physiological abnormalities in simian immunodeficiency virus-infected monkeys. The acute infection caused a disruption of the circadian rhythm manifested by rises in body temperature, observed in all five individuals between 1 and 2 weeks postinoculation (p.i.), accompanied by a reduction in daily motor activity to 50% of control levels. Animals remained hyperthermic at 1 and 2 months p.i. and returned to preinoculation temperatures at 3 months after viral inoculation. Although motor activity recovered to baseline values at 1 month p.i., activity levels then decreased to approximately 50% of preinoculation values over the next 2 months. Analysis of sensory-evoked responses 1 month p.i. revealed distinct infection-induced changes in auditory-evoked potential peak latencies that persisted at 3 months after viral inoculation. These early physiological abnormalities may precede the development of observable cognitive or motor deficiencies and can provide an assay to evaluate agents to prevent or alleviate neuronal dysfunction.

Opioid effects on activation of neurons in the medial prefrontal cortex

1. The effects of opioids have been characterized in portions of the neural circuitry proposed to underly the development and maintenance of addiction. One possible mechanism is modulation of function of endogenous transmitters. 2. Cells in the prefrontal cortex, a brain area involved in cognitive function and processes relevant to addiction, are described that exhibit morphine-associated attenuation of activation response to glutamate but not acetylcholine. 3. The predominantly excitatory response of prefrontal cortical cells to local application of glutamate and acetylcholine were differentially modified by systemic and local application of opioids. 4. Local mu opioid effects mimic those of systemic morphine to a more limited degree. 5. Morphine attenuates the response of prefrontal cortical cells to activation of excitatory afferents from the mediodorsal thalamus, and to a lesser degree, from the basolateral amygdala and the hippocampus. 6. Morphine modulation of prefrontal excitatory activation is naloxone-reversible.

Electrophysiological characterization of GABAergic neurons in the ventral tegmental area

GABAergic neurons in the ventral tegmental area (VTA) play a primary role in local inhibition of mesocorticolimbic dopamine (DA) neurons but are not physiologically or anatomically well characterized. We used in vivo extracellular and intracellular recordings in the rat VTA to identify a homogeneous population of neurons that were distinguished from DA neurons by their rapid-firing, nonbursting activity (19.1 +/- 1.4 Hz), short-duration action potentials (310 +/- 10 microseconds), EPSP-dependent spontaneous spikes, and lack of spike accommodation to depolarizing current pulses. These non-DA neurons were activated both antidromically and orthodromically by stimulation of the internal capsule (IC; conduction velocity, 2.4 +/- 0.2 m/sec; refractory period, 0.6 +/- 0.1 msec) and were inhibited by stimulation of the nucleus accumbens septi (NAcc). Their firing rate was moderately reduced, and their IC-driven activity was suppressed by microelectrophoretic application or systemic administration of NMDA receptor antagonists. VTA non-DA neurons were recorded intracellularly and showed relatively depolarized resting membrane potentials (-61.9 +/- 1.8 mV) and small action potentials (68.3 +/- 2.1 mV). They were injected with neurobiotin and shown by light microscopic immunocytochemistry to be multipolar cells and by electron microscopy to contain GABA but not the catecholamine-synthesizing enzyme tyrosine hydroxylase (TH). Neurobiotin-filled dendrites containing GABA received asymmetric excitatory-type synapses from unlabeled terminals and symmetric synapses from terminals that also contained GABA. These findings indicate that VTA non-DA neurons are GABAergic, project to the cortex, and are controlled, in part, by a physiologically relevant NMDA receptor-mediated input from cortical structures and by GABAergic inhibition.

Oleamide: an endogenous sleep-inducing lipid and prototypical member of a new class of biological signaling molecules

Oleamide is an endogenous fatty acid primary amide that accumulates in the cerebrospinal fluid under conditions of sleep deprivation and induces physiological sleep in animals. A review covering its discovery, its implications, and the emerging biology surrounding its discovery is presented. Consistent with its role as a prototypical member of a new class of biological signaling molecules, enzymatic regulation of endogenous concentrations of oleamide have been characterized or proposed. Fatty acid amide hydrolase (FAAH) is an integral membrane protein that degrades oleamide and potent inhibitors with physiological sleep-inducing properties have been disclosed. The characterization, cloning, and neuronal distribution of FAAH have been detailed and the enzyme was found to possess the ability to hydrolyze a range of fatty acid amides including anandamide which serves as the endogenous ligand for the cannabinoid receptor. An additional endogenous substance with REM sleep-inducing properties, 2-octyl gamma-bromoacetoacetate, was characterized as a potent FAAH inhibitor. Oleamide has been shown to modulate serotonergic neurotransmission and inhibit intercellular gap junction communication and detailed studies of its well defined and selective structural features required for activity have been disclosed.

Endogenous protein kinase A inhibitor (PKIalpha) modulates synaptic activity

Protein kinase A (PKA) has long been known to be involved in major regulatory mechanisms underlying synaptic plasticity and complex behaviors such as learning and memory. The endogenous PKA inhibitor, PKIalpha, has been extensively studied for its effects on PKA and PKA-mediated signal transduction. Clear functions for PKIalpha in vivo, however, remain to be established. Here we describe that several forms of synaptic stimulation in the rat hippocampus cause a dramatic decrease in the concentration of PKIalpha in dentate granule cells. Furthermore, chronic infusion of antisense oligonucleotides against PKIalpha into the rat brain results in a dramatic reduction of the excitability of these neurons and elimination of their ability to exhibit long-term potentiation (LTP) and long-term depression (LTD), suggesting a stimulus-dependent regulatory role for PKIalpha in PKA signal transduction.

Electrophysiological responses of nucleus accumbens neurons to novelty stimuli and exploratory behavior in the awake, unrestrained rat

To establish a physiological correlate of goal-directed and reward-seeking non-operant behaviors, we studied the electrophysiological activity of NAcc neurons in unrestrained, naive Sprague-Dawley rats. Our results showed an inhibitory response in 21% (7/34) of the recorded NAcc neurons during spontaneous nosepoking behavior and in 16% (4/25) of the NAcc neurons when rats were fed with a favorite novel food morsel (popcorn). These data suggest that a subgroup of NAcc neurons is actively modulated during motivated behavior and during consummatory events resulting in a suppression of neuronal activity.

Acute ethanol induces c-fos immunoreactivity in GABAergic neurons of the central nucleus of the amygdala

The central nucleus of the amygdala (CNA) is a component of the brain reward pathway which is believed to represent an anatomical substrate for drugs of abuse. Previous studies have shown that acute ethanol administration induces the expression of c-fos in the CNA of rat brains. We report here, that over 70% of these c-fos immunoreactive neurons are GABAergic. This observation provides the first anatomical evidence that GABAergic neurons of the CNA are responsive to acute ethanol exposure and suggest that the GABAergic system of the CNA is a key neuronal substrate for ethanol actions on the central nervous system.

Measurements of behavior in the naked mole-rat after intraperitoneal implantation of a radio-telemetry system

The naked mole-rat (Heterocephalus glaber) is a unique fossorial mammal that is eusocial, object blind, and virtually poikilothermic. This animal is an ideal model to examine questions pertaining to the thermoregulatory aspects of sleep/wake cycles and other circadian events. However, the monitoring of mammalian sleep usually involves implanting permanent electrodes into the skull which are linked to a counter-weighted cable apparatus. This is not a viable option for H. glaber because of the tunneled environments and sensitive social milieu. Instead, to monitor sleep, core temperature, and activity we have utilized intraperitoneal telemetry, a technique that transmits biopotential signals by radio waves. Here we describe the surgical procedure used to implant the device, the anesthesia technique developed, and the social reintroduction method devised for this novel animal model.

Longitudinal analysis of behavioral, neurophysiological, viral and immunological effects of SIV infection in rhesus monkeys

A model is proposed in which a neurovirulent, microglial-passaged, simian immunodeficiency virus (SIV) is used to produce central nervous system (CNS) pathology and behavioral deficits in rhesus monkeys reminiscent of those seen in humans infected with human immunodeficiency virus (HIV). The time course of disease progression was characterized by using functional measures of cognition and motor skill, as well as neurophysiologic monitoring. Concomitant assessment of immunological and virological parameters illustrated correspondence between impaired behavioral performance and viral pathogenesis. Convergent results were obtained from neuropathological findings indicative of significant CNS disease. In ongoing studies, this SIV model is being used to explore the behavioral sequelae of immunodeficiency virus infection, the viral and host factors leading to neurologic dysfunction, and to begin testing potential therapeutic agents.

Simian immunodeficiency virus: a model for neuroAIDS

In addition to its profound effects on the immune system, HIV also infects the CNS and can cause abnormalities in infected individuals ranging from mild cognitive and motor disorders to frank dementia. We have been actively investigating the molecular and cellular mechanisms underlying the CNS manifestations of lentivirus infection through the comparative evaluation of brain pathophysiology under a number of parallel interrelated strategies. Here we describe our ongoing studies with the SIV/rhesus macaque system. We have applied an interdisciplinary multistep approach, utilizing viral, immunological, pathological, behavioral, and electrophysiological techniques to assess disease and study CNS dysfunction induced by SIV. The profile of the infection and the host response, and the resulting cognitive, motor, and neurophysiological abnormalities in SIV-infected monkeys, recapitulates many aspects of the functional impairments associated with HIV-induced CNS disease in humans. Consequently, the SIV model is ideal for examining the mechanisms underlying these functional abnormalities and for testing potential therapeutic agents.

Cortical neuronal cytoskeletal changes associated with FIV infection

HIV-1 infection is often complicated by central nervous system (CNS) dysfunction. Degenerative neuronal changes as well as neuronal loss have been documented in individuals with AIDS. Feline immunodeficiency virus (FIV) infection of cats provides a model for both the immune and the central nervous system manifestations of HIV infection of humans. In this study we have examined neurons in the frontal cortex of feline immunodeficiency virus-infected cats and controls for immunoreactivity with SMI 32, an antibody recognizing a non-phosphorylated epitope on neurofilaments. We noted a significant increase in the number of immunoreactive pyramidal cells in infected animals compared to controls. The changes seen in the neuronal cytoskeleton as a consequence of the inoculation with FIV were similar to those seen in humans undergoing the normal aging process as well as those suffering from neurological diseases, including Alzheimer's and dementia pugilistica. The changes we noted in the feline brain were also similar to that reported in animals with traumatic injuries or with spontaneously occurring or induced motor neuron diseases, suggesting that the increase in reactivity represents a deleterious effect of FIV on the central nervous system.

Cortistatin is expressed in a distinct subset of cortical interneurons

Cortistatin is a presumptive neuropeptide that shares 11 of its 14 amino acids with somatostatin. In contrast to somatostatin, administration of cortistatin into the rat brain ventricles specifically enhances slow wave sleep, apparently by antagonizing the effects of acetylcholine on cortical excitability. Here we show that preprocortistatin mRNA is expressed in a subset of GABAergic cells in the cortex and hippocampus that partially overlap with those containing somatostatin. A significant percentage of cortistatin-positive neurons is also positive for parvalbumin. In contrast, no colocalization was found between cortistatin and calretinin, cholecystokinin, or vasoactive intestinal peptide. During development there is a transient increase in cortistatin-expressing cells in the second postnatal week in all cortical areas and in the dentate gyrus. A transient expression of preprocortistatin mRNA in the hilar region at P16 is paralleled by electrophysiological changes in dentate granule cells. Together, these observations suggest mechanisms by which cortistatin may regulate cortical activity.

Ethanol inhibits single-unit responses in the nucleus accumbens evoked by stimulation of the basolateral nucleus of the amygdala

We studied the actions of intoxicating doses of ethanol on excitatory inputs from the basolateral nucleus of the amygdala, a major afferent system projecting to the nucleus accumbens (NAcc). In view of the hypothesized role of opioid receptors on the effects of ethanol on NAcc physiology, we also explored whether naloxone modulates ethanol-induced suppression of NAcc excitability in halothane anesthetized and freely moving unanesthetized rats. Intraperitoneal administration of ethanol (1.2-1.4 g/kg) markedly suppressed a subgroup of amygdala-activated NAcc neurons. The ethanol-induced reduction in amygdala-activated NAcc neurons was not reversed by naloxone (5.0 mg/kg, intraperitoneally). Moreover, naloxone had no effect on the suppressive effects of ethanol on NAcc spontaneous activity in either halothane-anesthetized or unanesthetized freely moving preparations. These findings suggest that opiate mechanisms either are not participating or are not solely responsible for the inhibitory effects of acute intoxicating doses of ethanol on NAcc physiology.

Transgenic models to assess the pathogenic actions of cytokines in the central nervous system

In order to better understand the actions of proinflammatory cytokines in the mammalian CNS, a transgenic approach was employed in which the expression of IL-6, IL-3 or TNF-alpha was targeted to astrocytes in the intact CNS of mice. Transgenic mice exhibited distinct chronic-progressive neurological disorders with neurodegeneration and cognitive decline due to IL-6 expression, macrophage/microglial-mediated primary demyelination with motor impairment due to IL-3 expression and lymphocytic meningoencephalomyelitis with paralysis induced by TNF-alpha expression. Thus, expression of specific cytokines alone in the intact CNS results in unique neuropathological alterations and functional impairments, thereby directly implicating these mediators in the pathogenesis of CNS disease.

Differential sensitivity of c-Fos expression in hippocampus and other brain regions to moderate and low doses of alcohol

Alcohol consumption in humans is characterized by a wide range of behavioral effects and pathological consequences that suggest several neuroanatomical targets for this drug. To identify these targets we have mapped alcohol-induced changes in the expression of the c-Fos protein in the rat brain. Administration of a moderate dose of alcohol (1.5 g kg-1) led to a suppression of basal and novel environment-induced c-Fos expression in the hippocampus and simultaneous induction of this protein in regions important for the reinforcing as well as aversive properties of drugs. These include the extended amygdala (including the central nucleus of amygdala, bed nucleus of stria terminals and nucleus accumbens), regions processing sensory information (including the Edinger-Westphal nucleus and the paraventricular nucleus of the thalamus) and in stress-related areas (including the paraventricular nucleus of the hypothalamus, nucleus of the solitary tract and several neocortical areas). Repeated administration of the same dose of alcohol did not decrease alcohol-mediated suppression of c-Fos in the hippocampus, but decreased alcohol-induced expression of c-Fos in other areas. A lower dose of acute alcohol (0.5 g kg-1) reduced basal c-Fos expression in several areas of the neocortex, hippocampus and hypothalamus. However, while this low dose of alcohol was unable to counteract the environmental novelty-induced c-Fos expression in these areas, it increased c-Fos expression in the central nucleus of amygdala (an effect similar to the one observed previously for diazepam). Our data suggest that the effects of low doses of alcohol may be due to selective GABA-like effects of ethanol, whereas higher doses of ethanol involve effects on multiple neurotransmitter systems.

Neurologic dysfunctions caused by a molecular clone of feline immunodeficiency virus, FIV-PPR

FIV is a lentivirus of domestic cats that causes a spectrum of diseases that is remarkably similar to the clinical syndrome produced by HIV infection in people. Both HIV and FIV has been shown to cause neurologic dysfunction. Specific Pathogen-Free (SPF) cats were placed into one of three groups: FIV-PPR infected; DU-FIV-PPR (a dUTPase mutant of the FIV-PPR clone) infected; or an age-matched control group. In both infected groups, the general clinical signs of infection included lymphadenopathy, oral ulcerations, rough hair coat, and conjuntivitis. Specific neurological changes in the FIV-PPR infected cats included hind limb paresis; delayed righting and pupillary reflexes; behavioral changes; delayed visual and auditory evoked potentials; decreased spinal and peripheral nerve conduction velocities; and marked alterations in sleep patterns. Most of these changes were also observed in the DU-FIV-PPR infected cats. However, these cats tended to have a slightly less severe disease. In this study, we have demonstrated that an infectious molecular clone of FIV closely parallels the disease course of wild type FIV-infected cats. By using a knockout gene mutant of this clone, we were able to demonstrate that the dUTPase gene is not essential for neuropathogenesis. Further use of the FIV-PPR clone should prove useful in determining the essential viral elements that are important in the neuropathogenesis of lentiviral infections.

Microglia-passaged simian immunodeficiency virus induces neurophysiological abnormalities in monkeys

Four rhesus macaques were inoculated intravenously with a cryopreserved stock of microglia obtained from a simian immunodeficiency virus (SIV)-infected rhesus macaque. Before infection, three of the four monkeys were trained and tested daily on a computerized neuropsychological test battery. After SIV infection, behavioral testing continued to monitor deficits associated with disease progression. Five additional age-matched, behaviorally trained monkeys served as controls. Neurophysiological testing for visual and auditory evoked responses was accomplished 37-52 weeks after infection in all monkeys. Subsequently, all four SIV-infected monkeys and one control subject were sacrificed, and samples of brain tissue were taken for pathological analysis. SIV-infected monkeys demonstrated abnormal responses in both auditory and visual evoked responses. In addition, around the time of electrophysiological recording, all three SIV-infected, behaviorally trained monkeys exhibited significant decreases in progressive-ratio performance, reflecting a reduction in reinforcer efficacy. One subject also demonstrated impairments in shifting of attentional set and motor ability at that time. Neuropathological evaluation revealed that all four SIV-infected monkeys exhibited numerous perivascular and parenchymal infiltrating T cells. These findings document that SIV causes electrophysiological, behavioral, and neuropathological sequelae similar to what has been observed in the human neuroAIDS syndrome. Our observations further validate the simian model for the investigation of the pathogenesis of AIDS dementia and for the investigation of drugs with potential therapeutic benefits.

A cortical neuropeptide with neuronal depressant and sleep-modulating properties

Acetylcholine (ACh) plays a key role in the transitions between the different phases of sleep: Slow-wave sleep requires low ACh concentrations in the brain, whereas rapid-eye-movement (REM) sleep is associated with high levels of ACh. Also, these phases of sleep are differentially sensitive to a number of endogenous neuropeptides and cytokines, including somatostatin, which has been shown to increase REM sleep without significantly affecting other phases. Here we report the cloning and initial characterization of cortistatin, a neuropeptide that exhibits strong structural similarity to somatostatin, although it is the product of a different gene. Administration of cortistatin depresses neuronal electrical activity but, unlike somatostatin, induces low-frequency waves in the cerebral cortex and antagonizes the effects of acetylcholine on hippocampal and cortical measures of excitability. This suggests a mechanism for cortical synchronization related to sleep.

Microelectrophoretic application of SCH-23390 into the lateral septal nucleus blocks ethanol-induced suppression of LTP, in vivo, in the adult rodent hippocampus

Ethanol intoxication produces deficits in the acquisition of new information and blocks the induction of hippocampal long-term potentiation (LTP), a candidate neurophysiological correlate for learning and memory. We report that, in adult rats, local application of the dopamine (DA) D1 receptor antagonist SCH-23390 into the lateral septum (LS) blocks ethanol-induced suppression of LTP and alterations of paired-pulse responses in the dentate gyrus. This suggests a primary role for an extra-hippocampal circuit and neurotransmitter system mediating ethanol's ability to suppress LTP.

Coloboma contiguous gene deletion encompassing Snap alters hippocampal plasticity

Mice heterozygous for the semidominant mutation coloboma (Cm/+) display several distinct pathologies including head bobbing, ophthalmic deformation, and locomotor hyperactivity. The Cm/+ mutation comprises a contiguous gene defect which encompasses deletion of the gene Snap encoding the presynaptic nerve terminal protein SNAP-25 that is an integral component of the synaptic vesicle docking and fusion complex. Indeed, SNAP-25 is required for axonal growth and for the regulated release of neurotransmitters at the synaptic cleft. As an extension of our studies on the behavioral deficits exhibited by these mutants, including evaluation of the hyperkinesis and dopamine-related behavioral pharmacology that might be related to attention-deficit hyperactivity disorder in humans, we have studied spontaneous electroencephalographic and evoked potential recordings in the dentate gyrus of halothane-anesthetized Cm/+ and normal (+/+) littermates to evaluate potential physiological abnormalities of synaptic function in these mice. While sensory activation elicited by brief (10 sec) tail-pinch produced 1-2 min of theta rhythmic activity in +/+ mice, theta induction was markedly reduced in Cm/+ mice. There were no significant differences in dentate afferent-evoked population excitatory postsynaptic potential (pEPSP) slopes, pEPSP facilitation, or population spike (PS) amplitudes; however, paired-pulse inhibition of dentate PS amplitudes was significantly increased in Cm/+ mice. Furthermore, although brief high-frequency stimulation of the perforant path produced robust long-term potentiation (LTP) of synaptic responses in the dentate gyrus of +/+ mice, LTP was attenuated in Cm /+ mice. It has been previously demonstrated that dopamine (DA) neurotransmission is essential for induction of one type of hippocampal theta rhythm and also may modulate hippocampal LTP, suggesting that alterations in DA synaptic transmission may underlie the behavioral abnormalities, in particular the hyperactivity, associated with Cm/+ mutant mice.

Systemic morphine and local opioid effects on neuronal activity in the medial prefrontal cortex

Behavioral studies support the importance of the medial prefrontal cortex in the circuitry of drug-reinforced behavior, yet the neurophysiological correlates of this phenomenon remain unclear. The present study evaluates opioid neuropharmacology in the medial prefrontal cortex of the anesthetized rat. The effects of both systemic and local application of mu agonists on individual neurons in the medial prefrontal cortex were examined. Systemic morphine was found to inhibit (63%), excite (4%) or have no effect on (33%) spontaneous firing. The inhibitory response was reversed by systemic naloxone in 77% of the cases. Electrophoretic application of a mu-selective agonist, [D-Ala2,N-Me-Phe4,Gly-ol5]enkephalin, had mixed effects on cell activity. While most cells exhibited no change in firing rate (53%), 38% showed inhibition of spontaneous activity. The [D-Ala2,N-Me-Phe4,Gly-ol5]enkephalin-evoked inhibitory responses were antagonized by electrophoresis of naloxone (86%). These results indicate that the medial prefrontal cortex might directly mediate some portion of the overall response to opiates in reinforcement or self-administration paradigms. The naloxone-reversible inhibition of firing seen following both systemic and local application of predominantly mu-selective agonists argues for a direct involvement of medial prefrontal cortical neurons in opiate-induced effects. However, the smaller percentage of cells inhibited by local versus systemic application of mu agonists also supports an influence of other brain circuitry in this response.

Persistent dentate granule cell hyperexcitability after neonatal infection with lymphocytic choriomeningitis virus

Infection of neonatal Lewis rats with lymphocytic choriomeningitis virus (LCMV) produces distinct retinal, cerebellar, and hippocampal neuropathology. To understand the neurophysiological consequences of LCMV-induced hippocampal pathology, we studied evoked monosynaptic potentials and electro-encephalographic (EEG) activity in the dentate gyrus and CA1 and CA3 subfields of the hippocampus in vivo. Lewis rats were inoculated intracerebrally with LCMV at postnatal day 4. In rats studied 84-107 d postinfection, virus was cleared from the dentate gyrus and the number of dentate granule cells was decreased by 70%. No viral antigen or cell loss was apparent in CA1 or CA3. The hippocampal EEG of LCMV-infected rats 84-102 d postinfection was dominated by continuous theta. Although evoked potentials elicited in CA1 and CA3 by monosynaptic afferent stimulation revealed no differences between sham- and LCMV-infected rats, there was a site-specific dissociation of synaptic [population excitatory postsynaptic potential (pEPSP)] and cellular (population spike) responses and a suppression of GABA-mediated recurrent inhibition in the dentate gyrus of LCMV-infected rats. These findings indicate that GABA-mediated inhibition was markedly decreased in LCMV-infected rats. In support of this, parvalbumin-immunoreactive cell bodies and neuronal processes were decreased in LCMV-infected rats, suggesting that a subpopulation of GABA interneurons was affected. These findings indicate that abnormalities in synaptic function persist after clearance of infectious virus from the central nervous system and suggest that decreased inhibition subsequent to pathological sequence in a subpopulation of GABA interneurons may be implicated in the hyperexcitability of dentate granule cells.

Increased mutation frequency of feline immunodeficiency virus lacking functional deoxyuridine-triphosphatase

Feline immunodeficiency virus (FIV) encodes the enzyme deoxyuridine-triphosphatase (DU; EC 3.6.1.23) between the coding regions for reverse transcriptase and integrase in the pol gene. Here, we report the in vivo infection of cats with a DU- variant of the PPR strain of FIV and compare its growth properties and tissue distribution with those of wild-type FIV-PPR. The results reveal several important points: (i) DU- FIV is able to infect the cat, with kinetics similar to that observed with wild-type FIV; (ii) both wild-type and DU- FIV-infected specific-pathogen free cats mount a strong humoral antibody response which is able to limit the virus burden in both groups of animals; (iii) the virus burden is reduced in the DU- FIV-infected cats, particularly in tissues such as spleen and salivary gland; and (iv) the mutation frequency in DU- FIVs integrated in the DNA of primary macrophages after 9 months of infection is approximately 5-fold greater than the frequency observed in DU- FIV DNA integrated in T lymphocytes. Mutation rate with wild-type FIV remains the same in both cell types in vivo. The dominant mutations seen in macrophages with DU- FIV are G-->A base changes, consistent with an increased misincorporation of deoxyuridine into viral DNA of DU- FIVs during reverse transcription. Because this enzyme is absent from human immunodeficiency virus type 1 and other primate lentiviruses, virus replication in cell environments with low DU activity may lead to increased mutation and contribute to the rapid expansion of the viral repertoire.

Site-selective acute desensitization following local administration of opioid in the hippocampus

Electrophoretic administration of the mu selective opioid agonist [D-Ala2, NMe-Phe4, Gly-ol]-Enkephalin (DAMGO) in the dentate gyrus of the hippocampus acutely produces a marked increase in the responsiveness of dentate granule cells to perforant path stimulation. This can be measured by an increase in the primary population spike (PS) amplitude and by disinhibition in the paired-pulse (PP) paradigm. Concomitantly, the spontaneous single unit activity of interneurons is usually inhibited. We have observed that after prolonged (usually 10-20 min) local (electrophoretic) administration of DAMGO, a second, late effect is noted, suggesting acute desensitization. There is a loss of the disinhibition seen in the PP paradigm while the primary PS shows only some increased variability in response to stimulation. Furthermore, in a time course parallel to the loss of disinhibition, single cell activity initially inhibited by DAMGO appears to lose its responsiveness. Pretreatment with kappa or delta opioid agonists, or with GABA agonists and antagonists, does not affect the development of this desensitization suggesting selective involvement of the mu receptor. We further propose a regional specificity within the hippocampus since we are unable to detect evidence of desensitization to opioid in CA1 using the same techniques.

Chemical characterization of a family of brain lipids that induce sleep

A molecule isolated from the cerebrospinal fluid of sleep-deprived cats has been chemically characterized and identified as cis-9,10-octadecenoamide. Other fatty acid primary amides in addition to cis-9,10-octadecenoamide were identified as natural constituents of the cerebrospinal fluid of cat, rat, and human, indicating that these compounds compose a distinct family of brain lipids. Synthetic cis-9,10-octadecenoamide induced physiological sleep when injected into rats. Together, these results suggest that fatty acid primary amides may represent a previously unrecognized class of biological signaling molecules.

Sensitivity of nucleus accumbens neurons in vivo to intoxicating doses of ethanol

The nucleus accumbens septi (NAcc) is considered an important component of the final common pathway involved in the reinforcing properties of ethanol. We studied the effects of intraperitoneal administration of ethanol on spontaneous, glutamate-activated, and fimbria-activated NAcc neurons in acute anesthetized and freely moving unanesthetized rats. Ethanol significantly reduced the firing rate of spontaneous and glutamate-activated NAcc neurons in both electrophysiological preparations. Stimulation of the ipsilateral fimbria evoked single-unit activity in NAcc neurons with two characteristic latencies (early, 7.21 +/- 0.74 msec; late, 18.24 +/- 0.66 msec). Intoxicating doses of ethanol inhibited the recruitment of late, but not of early, fimbria-activated NAcc neurons. These data demonstrate electrophysiological evidence for the existence of neurons in the core region of the NAcc that are sensitive and insensitive to acute systemic ethanol administration.

Lentiviral infection, immune response peptides and sleep

The aberrant sleep documented in subjects with human immunodeficiency virus (HIV) infection is uniquely important because of the contribution this poor quality sleep makes to the fatigue, disability, and eventual unemployment that befalls these patients. Especially given this importance in clinical care, the research on the prominent sleep changes described in HIV infection remains modest in quantity. The chronic asymptomatic stage of HIV infection is associated with the most intriguing and singular sleep structure changes. Especially robust is the increase in slow wave sleep, particularly in latter portions of the sleep period. This finding is rare in other primary or secondary sleep disorders. The sleep structure alterations are among the most replicable of several pathophysiological sequelae in the brain associated with early HIV infection. It is unlikely that these sleep architecture changes are psychosocial in etiology, and they occur before medical pathology is evident. They are not associated with stress, anxiety, or depression. Evidence is accumulating to support a role for the somnogenic immune peptides tumor necrosis factor (TNF)alpha and interleukin (IL-1 beta) in the sleep changes and fatigue commonly seen in HIV infection. These peptides are elevated in the blood of HIV-infected individuals, and are somnogenic in clinical use and animal models. The peripheral production of these peptides may also have a role in the regulation of normal sleep physiology. The lentivirus family contains both HIV and the feline immunodeficiency virus (FIV). The use of the FIV model of HIV infection may provide a way to further investigate the mechanism of a neurotropic, neurotoxic virus initiating the immune acute phase response and affecting sleep. Neurotropic lentivirus infection is a microbiological probe facilitating neuroimmune investigation.