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Results for “Locus Coeruleus”

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At least 19 recordsLinked to original sources

PubMed1989

The effect of amygdala kindled seizures on locus coeruleus activity.

Locus coeruleus (LC) neuronal activity was recorded in anesthetized and in awake behaving rats during the production of amygdala afterdischarges (AD's) using kindling protocol. Both LC multiple and single unit discharges were temporally correlated with the appearance of AD's in the amygdala. Seizures were manifested in single unit activity as significant increases in firing rate. In awake animals, a bursting pattern of discharges was observed. We postulate that the observed changes in the LC activity pattern may have a modulatory role in the development of kindled seizures.

Action Potentials↗

PubMed1991

Mechanisms of opioid actions on neurons of the locus coeruleus.

The locus coeruleus (LC) has provided a useful model for pioneering studies of the mechanisms underlying the acute and chronic actions of opioid drugs. Acutely, opioids inhibit the electrical activity of single neurons in the rat and guinea pig LC. Inhibition is due to a membrane hyperpolarisation. In these cells, opioids act on mu-receptors to increase the opening of inwardly rectifying potassium channels, thus leading to hyperpolarisation. The mu-receptors are coupled to potassium channels via G-proteins which are sensitive to inactivation by pertussis toxin. This coupling process is quite direct, in that it does not involve freely diffusible intracellular second messengers. Agonists specific for other receptors, such as alpha 2- and somatostatin-receptors, are capable of opening the same population of potassium channels on LC neurons. Following chronic treatment of animals with morphine, a specific deficit develops in the ability of mu-receptors to open potassium channels, producing reduced sensitivity of LC neurons to inhibition by opioids.

Action Potentials↗

PubMed1991

Angiotensin II and the locus coeruleus.

The locus coeruleus (LC) is a putative site of action for angiotensin II in the brain. Immunocytochemical studies have identified angiotensin II-like immunoreactive material in nerve terminals innervating the LC, and the LC contains one of the highest densities of angiotensin II receptor binding sites in the rat brain. Recent studies using selective neurotoxins suggest that the binding sites for angiotensin II in the LC are present on noradrenergic perikarya. Angiotensin II receptors are now known to exist as two subtypes that are distinguishable both pharmacologically and biochemically. Radioligand binding studies using agonists and antagonists selective for these angiotensin II receptor subtypes indicate that the rat LC contains a mixture of the two known angiotensin II receptor subtypes, but that the PD123177-sensitive AII beta receptor subtype is predominant. Comparisons of spontaneously hypertensive rats with normotensive rats indicates that angiotensin II and its receptors in the LC are elevated in the hypertensive rat strain. Studies of the biochemical and physiological actions of angiotensin II in the LC have not yet established an agreed-upon function for angiotensin II in this nucleus.

Angiotensin II↗

PubMed1979

Studies on the dense-core vesicles in the ontogenesis of locus coeruleus. III. Statistical reconstruction of the diameter distribution of the dense-core vesicles in locus coeruleus during rat ontogenesis.

The method for statistical reconstruction of the diameters of dence-core vesicles, described in the previous work, is applied for studying the changes of these vesicles in the perikarya, the axonal boutons and the neuropile of the rat locus coeruleus during ontogenesis. The data obtained show the presence of the population during the embryonal development and of two populations of dense-core vesicles after birth in the structures studied. This finding is interpreted in connection with the different function of the dense-core vesicles and of the transmitters, respectively, in the development and function of the main noradrenergic nucleus in the brain of mammals -- locus coeruleus.

Age Factors↗

PubMed1978

Studies on the dense-core vesicles in the ontogenesis of locus coeruleus. I. Localization, type and density of the dense-core vesicles in locus coeruleus during rat ontogenesis.

In an attempt to clarify the function of dense-core vesicles quantitative estimation is made of their density and localization in the perikarya, axonal boutons and neuropil of rat locus coeruleus during different ontogenetic stages. The results obtained, compared with the fluorescence- and electronmicroscopic data, suggest participation of the dense-core vesicles in the neuronal development and differentiation: presence in the earliest embryonal periods, statistically significant increase in the density in the period of most intensified growth and maturing of the neuropil and axonal boutons, and change in the density of the perikarya in connection with intensified axonal transport. Quantitative data are also presented about the participation of the dense-core vesicles in synaptic transmission.

Animals↗

PubMed1991

Effects of locus coeruleus lesions on parkinsonian signs, striatal dopamine and substantia nigra cell loss after 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine in monkeys: a possible role for the locus coeruleus in the progression of Parkinson's disease.

Six pairs of female squirrel monkeys were given a daily intraperitoneal injection of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) for 9-14 days, beginning the same day on which they received either a bilateral 6-hydroxydopamine lesion or a sham lesion of the locus coeruleus. Sham animals developed typical parkinsonian signs (i.e. tremor, bradykinesia, hypokinesia and reduced blink rate) which largely recovered by six to nine weeks after the start of MPTP treatment. At nine weeks, post mortem levels of striatal dopamine in these same animals were partially reduced (by 45%), and this only in the putamen, compared to values obtained from three non-operated, normal control animals. Additionally, histological examination revealed a moderate loss of neuronal cell bodies in the substantia nigra, pars compacta. In marked contrast, the locus coeruleus-lesioned monkeys exhibited little or no recovery from the parkinsonian signs induced by MPTP. Post mortem examination of these animals revealed profound decreases in caudate (by 84%) and putamen (by 91%) dopamine content, and severe neuronal cell loss in the substantia nigra pars compacta of all animals. These neurological, biochemical and histological assessments indicate that lesioning of the locus coeruleus impairs the recovery which usually occurs from the parkinsonian manifestations induced by MPTP in squirrel monkeys. The results support the hypothesis that deficient locus coeruleus noradrenergic mechanisms underlie the progression of Parkinson's disease.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗

PubMed1991

Noradrenergic and locus coeruleus modulation of the perforant path-evoked potential in rat dentate gyrus supports a role for the locus coeruleus in attentional and memorial processes.

The perforant path-dentate gyrus synapse has provided a model system for functional neural plasticity in adult mammalian brain. NMDA-dependent long-term changes in neural connectivity occur at this synapse in response to high-frequency input. Norepinephrine (NE) applied exogenously or released endogenously can initiate both a short- and a long-term potentiation (LTP) of the dentate gyrus response to perforant path input. Triggering of the potentiated response depends on beta-receptor activation and does not require a high-frequency stimulus. An increase in locus coeruleus (LC) activity can initiate both short and LTP of the perforant path response, although a reduction in LC activity does not alter baseline perforant path responses. This chapter considers differences between NE modulation in vitro and in vivo, differences and similarities between NE-LTP and frequency-induced LTP, and the surprising specificity of NE effects at the perforant path synapse. Studies of NE in the dentate gyrus support a role for the LC in promoting both short- and long-term enhancement of responses to complex sensory inputs and are consistent with a role for the LC in memorial as well as attentional processes.

Animals↗

PubMed1987

Anomalous rectification in rat locus coeruleus neurons.

Rat locus coeruleus neurons recorded under current clamp conditions show anomalous rectification (AR) as indicated by a progressive decrease in slope resistance measured with hyperpolarizing current pulses of increasing amplitude. AR was most prominent at potentials more negative than the K+ equilibrium potential. AR was strongly dependent on external K+ concentration and was blocked by external Ba2+ and Cs+, and intracellular injection of acetate.

Animals↗

PubMed1990

Chronic stress-induced changes in locus coeruleus neuronal activity.

Locus coeruleus (LC) activity was assessed in rats exposed to either acute or chronic stress. After one immobilization session, the number of spontaneously active LC neurons dramatically decreased. On the other hand, repeated restraint sessions enhanced noradrenergic (NA) transmission and the inhibitory effect of clonidine (CLON) was greater on these cells than in those of controls. These results bear on the adaptive changes in the NA system following acute or chronic stress.

Action Potentials↗

PubMedDate not supplied

[The dynamic behavioral changes in rats after destruction of the locus coeruleus].

Destruction of locus coeruleus (LC) was conducted in adult rats (male rats of the Wistar line, 250-300 g) electrolytically or by means of 6-hydroxydopamine (6-OHDA). Behaviour of the intact animals sham-operated and of rats with destructed LC was evaluated before and every week after the operation during 5 weeks. Statistically significant alterations in the behaviour were revealed only in the initially low-active rats. These animals were characterized firstly, by low motor and exploratory activity in all tests (open field and automated devices), disturbance of the reactivity to novelty--only in one week after the operation with subsequent compensation of shifts; secondly, by low level of investigatory activity in the open field and absence of habituation to the repetitive tests--from the 21-st day after the operation.

Animals↗

PubMedDate not supplied

The distribution of dopamine-beta-hydroxylase, neuropeptide Y and galanin in locus coeruleus neurons.

The locus coeruleus (LC) is composed of noradrenaline-producing neurons that project widely throughout the neuraxis. Subpopulations of LC neuron perikarya have been shown to contain neuropeptide Y (NPY) and galanin (GAL). In the major terminal fields of LC projections, the cerebral cortex, dorsal thalamus and cerebellar cortex, there are differing plexuses of dopamine-beta-hydroxylase (DBH), NPY and GAL immunoreactive axons. DBH immunoreactive plexuses are found in all areas which conform in appearance to previous demonstrations of noradrenaline localization by fluorescence histochemistry. In contrast, there are few NPY immunoreactive axons in thalamus and cerebellum, and the cortical plexus, while similar to the DBH immunoreactive plexus, is not affected by 6-hydroxydopamine treatment. Similarly, there are few GAL immunoreactive axons in either cerebral cortex, dorsal thalamus or cerebellar cortex. Transection of ascending LC axons results in accumulation of DBH but not NPY or GAL immunoreactivity proximal to the lesion. These observations indicate that NPY and GAL are distributed differently in LC neurons from noradrenaline and DBH.

Animals↗

PubMedDate not supplied

Labyrinthine influences on locus coeruleus neurons.

The locus coeruleus (LC) complex, located in the dorsolateral pontine tegmentum, is composed principally of noradrenergic neurons, which project to broad regions of the CNS, including the spinal cord. Experiments were performed in precollicular decerebrate cats to ascertain whether units histologically identified within the LC complex, and having the physiological characteristics of noradrenergic neurons, would respond to sinusoidal stimulation of labyrinth receptors. Among 141 LC complex neurons, 16 of which could be activated antidromically by stimulation of the spinal cord at T12-L1, 80 (i.e. 56.7%) responded to roll tilt of the animal at 0.15 Hz, +/- 10 degrees. The responses were particularly related to the extreme animal displacements, thus being attributed to stimulation of macular utricular receptors. The proportion of responsive units, and also the average gain of the responses, were higher in the LCd and the subcoerular (subLC) area than in the LCa. Moreover in the same structures the majority of units showed a beta-pattern of response (excitation during side-up tilt), which contrasted with the predominant alpha-pattern (excitation during side-down tilt) displayed by the previously recorded vestibulospinal neurons projecting to the same segments of the spinal cord. The role that the noradrenergic coeruleospinal neurons exert in the dynamic control of posture during the vestibulospinal reflexes is discussed.

Animals↗

PubMed1987

Alterations in responsiveness of noradrenergic neurons of the locus coeruleus in deoxycorticosterone acetate (DOCA)-salt hypertensive rats.

Locus coeruleus may have a function in central blood pressure regulation and possibly in the pathogenesis of hypertension. In keeping with this notion, we have recently shown that deoxycorticosterone acetate (DOCA)-salt hypertensive rats demonstrate a greater increase in blood pressure induced by locus coeruleus stimulation than control animals. In an attempt to elucidate the underlying mechanisms leading to this alteration in responsiveness of the locus coeruleus, the sensitivity of noradrenergic neurons of the locus coeruleus to the transmitter candidates, epinephrine and glutamate, was investigated in DOCA-prehypertensive (3 days post-DOCA), DOCA chronic hypertensive (6-8 weeks post-DOCA) and control rats using conventional microiontophoretic and single cell recording techniques. Iontophoretically applied epinephrine produced a current-dependent decrease in spontaneous firing rate of all noradrenergic neurons in both DOCA-treated and control rats. Locus coeruleus neurons of DOCA-treated rats at 3 days and 6-8 weeks were less sensitive to epinephrine than those of control rats and the magnitude of the depression in spontaneous firing rate was less. By contrast, iontophoretic applications of glutamate produced an increase in activity of all noradrenergic locus coeruleus neurons. However, there was minimal difference in glutamate sensitivity between neurons of DOCA and control rats. Since the changes in epinephrine sensitivity are apparent not only in the chronic stage but also in the prehypertensive stage, our findings suggest a potential role of the adrenergic input to the locus coeruleus in the pathogenesis of DOCA-hypertension.

Animals↗

PubMed1987

Effect of locus coeruleus and periventricular gray substance lesions on suprachiasmatic damage-induced persistent estrous.

To assess the relation between the suprachiasmatic nucleus and the locus coeruleus, persistent estrous was induced in female rats by damage of the suprachiasmatic nucleus followed with electrolytic damage of the locus coeruleus. Locus coeruleus lesions resulted in a transient loss of persistent estrous indicated by sustained diestrous aspect of the vaginal smears. There was a direct correlation between duration of estrous loss and the amount of locus coeruleus damage. Simultaneous damage to the periventricular gray substance, adjacent to the locus coeruleus, prevented the suppression effects of locus coeruleus damage upon persistent estrous. These results suggest a physiological role of the locus coeruleus and periventricular gray substance in the modulation of the neuroendocrine control of ovarian function due to suprachiasmatic nucleus activity.

Animals↗

PubMedDate not supplied

Raphe projections to the locus coeruleus in the rat.

Afferent projections to the locus coeruleus from the various raphe nuclei, particularly of the midbrain (nuclei raphe dorsalis and medianus) and pons (nuclei raphe pontis and magnus), have been studied in the rat by retrograde transport methods using horseradish peroxidase (HRP). The locus coeruleus, in both its dorsomedial and ventrolateral divisions, and in its various anterior-posterior components, were injected with 0.05 microliters of horseradish peroxidase following which various structures of the brainstem, particularly the raphe nuclei, were examined for HRP reactive cells. It was found that injections in most components of the locus coeruleus were associated with HRP positive cells in varying degrees of density in the nuclei raphe dorsalis, medianus, pontis, and magnus, with considerably sparser labelling in the anterior aspects of the medullary raphe nuclei pallidus and obscurus. Labelled cells were also seen in the nuclei of the solitary tract, contralateral locus coeruleus. lateral reticular areas of the pons and midbrain, nuclei pontis oralis and caudalis, vestibular nuclei, mesencephalic nucleus of the trigeminal nerve, fastigial nuclei of cerebellum and medial parabrachial nuclei. These data, showing widespread innervation of the locus coeruleus from all raphe nuclei, as well as many other brainstem areas, in the rat support the general view of heavy innervation of the locus coeruleus from both extra-raphe and raphe nulcei. These latter raphe projections, probably serotonergic in nature, provide anatomical support for the various experiments indicating considerable regulation of locus coeruleus activities, such as phasic events of REM sleep, among other, by widespread projections from most raphe nuclei was well as several other regions of the brainstem.

Afferent Pathways↗

PubMed1978

Locus coeruleus fibre growth in oculo induced by trigeminotomy.

Locus coeruleus from fetal donors was homologously grafted to the anterior eye chambers of adult rats whose eyes were sympathetically denervated. After intraocular maturation, outgrowth of noradrenaline-containing fibres from the locus coeruleus neurons on the host iris was studied by Falck--Hillarp fluorescence histochemistry. In control animals locus coeruleus grafts produce a halo of noradrenaline-containing nerve fibres around the graft, covering approximately one third of the surface of the host iris. Sensory denervation of host eyes carrying maturated locus coeruleus grafts was produced by intracranial lesions of the trigeminal nerve. Such lesions induced a rapid growth response in the grafted locus coeruleus neurons, leading within three weeks to complete innervation of the host iris. It was concluded that removal of non-sympathetic, non-parasympathetic nerve fibres on the host iris elicits a strong fibre-growth response in the grafted locus coeruleus.

Animals↗

PubMed1987

Locus coeruleus neurons projecting to the forebrain and the spinal cord in the cat.

The intranuclear organization of the cat locus coeruleus neurons was investigated anatomo-physiologically. The locus coeruleus neurons project to the forebrain through the dorsal noradrenergic bundle and to the spinal cord. Horseradish peroxidase, a retrograde tracer, was pressure-injected into either the dorsal noradrenergic bundle or the ventrolateral funiculus of the high cervical cord (C1-C2). The cats (n = 12) were killed after a 2- or 3-day survival period. The frontal sections (100 micron) throughout the locus coeruleus were observed by light microscope after carrying out the diaminobenzidine reaction. The labeled locus coeruleus neurons were located predominantly in the rostral locus coeruleus proper and locus coeruleus alpha when horseradish peroxidase was injected into the dorsal noradrenergic bundle, whereas they were predominantly located in the caudal locus coeruleus alpha and subcoeruleus when horseradish peroxidase was injected into the spinal cord. In the electrophysiological experiments, cats (n = 30) were anesthetized with alpha-chloralose and two stimulating electrodes were placed stereotaxically in the dorsal noradrenergic bundle and the ipsilateral ventrolateral funiculus of the high cervical cord (C1-C2), respectively. Monophasic square-wave pulses (2.5 Hz, 100 microsecond duration, 800 microA) were delivered. A recording glass electrode, filled with 2 M NaCl saturated with Fast Green, was placed in the locus coeruleus. Neurons with different conduction velocities, which were evoked by the antidromic stimulation of the dorsal noradrenergic bundle and spinal cord, were verified in the locus coeruleus and the adjacent areas. The slow conductive neurons with a conduction velocity of less than 1 m/s had a slow firing rate (1.6 +/- 0.9/s). They were located predominantly in the rostral locus coeruleus proper and locus coeruleus alpha by the dorsal noradrenergic bundle stimulation. From the anatomical and electrophysiological experimental results, it was concluded that the conduction velocities of the horseradish peroxidase-labeled neurons observed in locus coeruleus proper and locus coeruleus alpha were mostly slow and less than 1 m/s. Most of the slow conductive neurons were considered to be noradrenergic. Neurons evoked antidromically by both the dorsal noradrenergic bundle and spinal cord stimulation were not observed.

Action Potentials↗

PubMed1976

The roles of noradrenaline and dopamine in contraversive circling behaviour seen after unilateral electrolytic lesions of the locus coeruleus.

Unilateral electrolytic lesions of the locus coeruleus in rats result in spontaneous ipsiversive rotation, which is then replaced by contraversive rotation. One week after lesioning, when spontaneous turning ceases, apomorphine and d-amphetamine elicit contraversive circling behaviour, which was not affected by noradrenergic receptor blockade but was abolished by dopamine receptor blockade. The drug-induced contraversive circling response was also reproduced by piribedil but not clonidine. Combined unilateral electrolytic locus coeruleus and substantia nigra lesions on the same side resulted in apomorphine- and d-amphetamine-induced ipsilateral rotational behaviour which was indistinguishable from that seen with substantia nigra lesions alone. In rats with unilateral locus coeruleus lesions, the dose of intrastriatally injected apomorphine required to produce circling was less on the lesioned than the non-lesioned side. Direct injection of noradrenaline into one substantia nigra caused contraversive circling. Direct injection of phenoxybenzamine into one substantia nigra followed by apomorphine caused ipsiversive circling. The results suggest that the circling behaviour seen after unilateral locus coeruleus lesions depends on an asymmetry of striatal dopamine receptor activity and are consistent with a proposed coeruleus-nigral noradrenergic pathway, which enhances impulse flow in the dopaminergic nigrostriatal system.

Animals↗