Does the destruction of the catecholaminergic neurons in newborn rat pups influence the modulatory function of the cholinergic system?]

On outbred ratlings aged 21-31 days the influence was studied of the destruction of catecholaminergic (CA) system on the reactions of the neurones of the cortical somatosensory zone, elicited by the stimulation of the ischiatic nerve and modulation of these reactions after stimulation of the basal nuclei area (the source of the neocortex cholinergic innervation) and acetylcholine (ACh) microiontophoretic application. It is shown that destruction of CA system in newborn ratlings increases the reactivity of the somatosensory cortical neurones in 21-31 days old animals to sensory stimulation; it does not influence the efficiency of modulating action of the cholinergic system of the forebrain and leads to the increase of modulating influence of the applicated ACh. It is postulated that as the result of perinatal destruction of CA brain system, in the neocortex a specific morpho-functional organization is formed of structures and processes at which the modulating function of the forebrain cholinergic system turns out, by quantitative criterion, at least, to be compensated.     

Neurotransmitters and neuropeptides in the developing human central nervous system. A review

This is a review on the ontogenesis of major neurotransmitters and neuropeptides in the developing human central nervous system. In general, the molecules under study appeared early in development, usually in the first trimester. Cholinergic neurons were found to be present around the time of neuropeptide formation. The newly formed neuropeptidergic fibers extended towards the cholinergic centers where both might interact. In the major centers of the central nervous system, neuropeptides were also noted to colocalize with various neurotransmitters. For example, in the facial nucleus, enkepahlin and substance P fibers coexisted with cholinergic and catecholaminergic neurons, suggesting complex interactions. In the interpeduncular nucleus, peptidergic neurons acting as interneurons clearly modulated the afferent input to this nucleus. In the hippocampus and in sensory organs such as the retina, there were indications that neuropeptides and gamma-amino butyric acid coexisted. We hypothesize that interactions of neurotransmitters and peptides in neurons and fibers early in development play an indispensable role in the morphogenesis of the human central nervous system.     

Constitutive expression of p21H-ras(Val12) in pyramidal neurons results in reorganization of mouse neocortical afferents

The effect of constitutive expression of p21H-ras(Val12) in pyramidal neurons upon the establishment of afferent input has been investigated in the primary somatosensory cortex of transgenic mice. In these animals, relevant transgene expression is confined to cortical pyramidal neurons and starts postnatally at a period when neuronal morphogenesis has been largely completed. We have shown recently that overexpression of p21H-ras(Val12) in these cells results in considerable enlargement of their size and consequently in expansion of the cortex. In the present study we demonstrate that the density of terminals representing intra- or interhemispheric afferents within cortical layers II/III, however, is only slightly decreased. The density of thalamocortical boutons within layer IV is even higher and the number of afferent contacts to transgenic pyramidal neurons is significantly increased compared to the wild-type. The number of catecholaminergic and cholinergic terminals is augmented proportionally to cortical size or even overproportionally, respectively. Along intercortical and striatal fibers arising from p21H-ras(Val12)-expressing pyramidal neurons, frequency of varicosities is significantly increased, but remains unchanged on cortical cholinergic and catecholaminergic axons originating from "nontransgenic" neurons. Additionally, a higher number of multiple synaptic bodies are found in transgenic mice, suggesting subtle effects on synaptic plasticity. It is concluded that the enlargement of pyramidal neurons due to transgenic expression of p21H-ras(Val12) is paralleled by significant changes in the quantity and pattern of afferent connections. Moreover, expression of p21H-ras(Val12) in pyramidal cells induces an enhanced establishment of efferent boutons.     

Nerve growth factor increases stimulus-evoked metabolic activity in acetylcholine-depleted barrel cortex

Lesions of the basal forebrain deplete the neocortex of cholinergic fibers. Acetylcholine depletion in the somatosensory cortex of rats results in reduced stimulus-evoked activity in response to whisker stimulation. Previous studies demonstrate that embryonic basal forebrain transplants improve functional activity toward normal. It is not clear if the activity increase is due to cholinergic replacement or other factors present in the graft. In this study, we examined the possibility that nerve growth factor (NGF), a neurotrophin known as a survival factor and a specific protectant for cholinergic basal forebrain neurons, can preserve basal forebrain cells after a lesion and restore functional activity in the somatosensory cortex. We report that NGF alone is capable of restoring functional activity in the barrel cortex of animals with basal forebrain lesions, while vehicle injections of saline do not alter activity. Both high (10 mug) and low (5 mug) doses of NGF unilaterally injected into the lateral ventricle improved stimulus-evoked functional activity during bilateral whisker stimulation. The mechanism of NGF action is not clear since the restoration of functional activity in cortex was not accompanied by increased cholinergic activity as detected by acetylcholinesterase fiber staining. NGF may act directly on cortical neurons, although its site of action is not well defined.     

Responses of neurons in the vibrissae projection area of the cat somatosensory cortex to afferent activation

Responses of 375 primary somatosensory cortical neurons located in the projection area of the vibrissae to electrical stimulation of the infraorbital nerve and also to adequate stimulation of the vibrissae were investigated in unanesthetized cats immobilized with tubocurarine. Stimulation of the nerve and vibrissae most frequently evoked synaptic responses in the neurons, in the form of a short EPSP followed by an IPSP or, less frequently, as a primary IPSP; during extracellular recordings corresponding changes were observed in spike activity. In response to stimulation of the vibrissae, initial inhibition was found more often than to stimulation of the nerve (in 45 and 16% of neurons respectively). The difference between the minimal values of latent periods of IPSP and EPSP evoked by stimulation of the infraorbital nerve was 0.8 msec in different neurons, and the difference between the mean values 1.4 msec. Directional sensitivity of the cortical neurons was demonstrated (to a change in the direction of deflection of the vibrissae). Neurons located close together could differ in the character of their directional sensitivity during stimulation of the same vibrissae. It is concluded that short-latency inhibition arising in the primary projection area of the cat somatosensory cortex is predominantly afferent and not recurrent. The probable mechanisms of directional sensitivity of the neurons studied are discussed.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSSR, Kiev. Translated from Neirofiziologia, Vol. 11, No. 6, pp. 550–559, November, 1979.     

Effects of cholinergic drugs on growth hormone release

Acetylcholine and the cholinergic agonists, pilocarpine and physostigmine, increased GH release $\text{in}$$\text{vivo}$. The increase in GH release by pilocarpine was reversed by concurrent administration of the cholinergic receptor blocker, atropine, whereas atropine alone did not alter serum GH concentrations. Cholinergic stimulation of GH release appears to be partially mediated through a catecholaminergic system since the response was partially inhibited by pimozide, a dopamine receptor blocker, or phentolamine, an α-adrenergic receptor blocker. The cholinergic system may function physiologically to help regulate GH release.     

Bee venom acupoint stimulation increases Fos expression in catecholaminergic neurons in the rat brain

Fos immunocytochemistry was combined with tyrosine hydroxylase (TH) or dopamine-beta-hydroxylase (DBH) immunolabeling to examine brainstem catecholaminergic neuronal activation resulting from bee venom (BV) stimulation of the Zusanli acupoint (ST36) in Sprague-Dawley rats. BV injection into the Zusanli acupoint caused increased Fos expression in catecholaminergic neurons located in the hypothalamic arcuate nucleus (Arc), the dorsal raphe (DR), the A5 cell group (A5) and the locus coeruleus (LC). BV acupoint stimulation significantly increased Fos-TH double-labeled neurons in the Arc, LC and DR. Fos-DBH positive neurons were also increased by BV acupoint stimulation in the LC and A5. In contrast BV stimulation of a non-acupoint only increased Fos expression and Fos-TH double-labeled neurons in the Arc. These data indicate that BV acupoint stimulation activates brainstem catecholaminergic neurons and that this activation underlies BV acupoint-induced antinociception.     

Cholinergic and catecholaminergic neurons relay striatal information to the optic tectum in amphibians.

In the amphibians Rana perezi and Xenopus laevis, the involvement of cholinergic and catecholaminergic neurons in the relay of basal ganglia inputs to the tectum was investigated. Tract-tracing experiments, in which anterograde tracers were applied to the basal ganglia and retrograde tracers to the optic tectum, were combined with immunohistochemistry for choline acetyltransferase and tyrosine hydroxylase. The results of these experiments suggest that dopaminergic neurons of the suprachiasmatic nucleus and pretectal region, noradrenergic cells of the locus coeruleus and the cholinergic neurons of the pedunculopontine and laterodorsal tegmental nuclei mediate at least part of the basal ganglia input to the tectum in anurans.     

The effects of opiate agonists on growth hormone and prolactin release in rats

Various opioid receptor agonists, including Met5-enkephalin amide, Leu5-enkephalin amide, [D-Ala]2-Met5-enkephalin amide, [D-Ala]2-Leu5-enkephalin amide, morphine sulfate, d-methadone hydrochloride, and l-methadone hydrochloride were administered to adult male rats by subcutaneous injection. All opioid receptor agonists except Leu5-enkephalin amide significantly stimulated growth hormone and prolactin release. Naloxone and naltrexone blocked the hormone stimulatory effects of the opioids and both naloxone and naltrexone, when administered alone, significantly reduced serum growth hormone and prolactin concentrations. The dopaminergic agonist apomorphine, but not the alpha-adrenergic agonist clonidine, blocked opiate stimulation of prolactin. Morphine sulfate caused growth hormone release in rats pretreated with alpha-methyl-p-tryosine, a catecholamine synthesis inhibitor. Cholinergic agonists, physostigmine and pilocarpine, antagonized the growth hormone and prolactin release induced by morphine sulfate. The data suggest that the opiates stimulate prolactin via an interaction with catecholaminergic neurons controlling prolactin release and stimulate growth hormone via a mechanism independent of alpha-adrenergic or general catecholaminergic influence. The mechanism through which cholinergic agonists act to inhibit opiate agonist stimulation of growth hormone is presently unknown.     

Brainstem in Multiple System Atrophy: Clinicopathological Correlations

1. Multiple system atrophy (MSA) is a sporadic neurodegenerative disorder that manifests with parkinsonism, cerebellar ataxia, and autonomic failure in various combinations.2. Orthostatic hypotension, neurogenic bladder, laryngeal stridor and sleep apnea, and rapid eye movement (REM) sleep behavior disorder are prominent manifestations of MSA.3. In MSA, there is severe depletion of catecholaminergic neurons of the C1 and A1 areas in the ventrolateral medulla, and this may contribute to orthostatic hypotension and endocrine disturbances in this disorder, respectively.4. Loss of corticotrophin-releasing factor (CRF) neurons in the pontine micturition area may contribute to neurogenic bladder dysfunction.5. Respiratory abnormalities may reflect loss of cholinergic neurons in the arcuate nucleus of the ventral medulla.6. Loss of cholinergic mesopontine neurons, in the setting of loss of locus ceruleus neurons and preservation of rostral raphe neurons, may contribute to REM sleep abnormalities in MSA.     

Neuromediator shifts in the peripheral blood of dogs resulting from negative emotiogenic exposure

The analysis of negative emotiogenic influence in dogs carried out according to dynamics of levels of acetylcholine and catecholamine content in peripheral blood and concomitant changes of the higher nervous activity, allows to conclude about the participation of both cholinergic and catecholaminergic neurotransmitter systems in reactions to this influence with a relative predominance of the first one. In animals with decreased reactivity and with compensatory abilities of the cholinergic system, the same influence leads to enhancement of the specific significance of the reaction of the catecholaminergic system, and especially of its transmitter, noradrenergic component.     

Catecholaminergic, cholinergic and peptidergic innervation of gut-associated lymphoid tissue in porcine jejunum and ileum

With its abundance of neurons and immunocytes, the gut is a potentially important site for the study of the interaction between the nervous and immune systems. Using immunohistochemical techniques, we tested the hypothesis that gut-associated lymphoid tissue in the porcine small intestine might receive catecholaminergic, cholinergic and peptidergic innervation. Antibodies against protein gene product (PGP) 9.5 were employed to detect neuronal membranes; antibodies against tyrosine hydroxylase (TH), type 2 vesicular monoamine transporter (VMAT-2) and choline acetyltransferase (ChAT) were used to detect catecholaminergic and cholinergic neurons; and antibodies to neuromedin U-8 (NMU-8), substance P (SP) and vasoactive intestinal peptide (VIP) were also used. PGP9.5-immunoreactive nerve fibers were observed between jejunal Peyer's patch (PP) follicles and in submucosal ganglia localized at the base of continuous ileal PP. Many ChAT-positive and a few TH-/VMAT-2-immunoreactive neurons or axons adjacent to jejunal and ileal PP were observed. Neurons and fibers from ganglia situated between or at the base of PP follicles manifested robust immunoreactivities to VIP and NMU-8; relatively less SP immunoreactivity was observed at these locations. All neuromedin-U 8-positive neurons observed exhibited immunoreactivity to ChAT as did some VIP-positive neurons. The specific chemical coding of enteric neurons in close apposition to jejunal and ileal PP and the differential localization of neuropeptides within the jejunal and ileal PP are indicative of neuroimmunomodulation at these sites.     

Constitutive expression of p21H‐rasVal12 in pyramidal neurons results in reorganization of mouse neocortical afferents

The effect of constitutive expression of p21H‐ras^Val12 in pyramidal neurons upon the establishment of afferent input has been investigated in the primary somatosensory cortex of transgenic mice. In these animals, relevant transgene expression is confined to cortical pyramidal neurons and starts postnatally at a period when neuronal morphogenesis has been largely completed. We have shown recently that overexpression of p21H‐ras^Val12 in these cells results in considerable enlargement of their size and consequently in expansion of the cortex. In the present study we demonstrate that the density of terminals representing intra‐ or interhemispheric afferents within cortical layers II/III, however, is only slightly decreased. The density of thalamocortical boutons within layer IV is even higher and the number of afferent contacts to transgenic pyramidal neurons is significantly increased compared to the wild‐type. The number of catecholaminergic and cholinergic terminals is augmented proportionally to cortical size or even overproportionally, respectively. Along intercortical and striatal fibers arising from p21H‐ras^Val12‐expressing pyramidal neurons, frequency of varicosities is significantly increased, but remains unchanged on cortical cholinergic and catecholaminergic axons originating from “nontransgenic” neurons. Additionally, a higher number of multiple synaptic bodies are found in transgenic mice, suggesting subtle effects on synaptic plasticity. It is concluded that the enlargement of pyramidal neurons due to transgenic expression of p21H‐ras^Val12 is paralleled by significant changes in the quantity and pattern of afferent connections. Moreover, expression of p21H‐ras^Val12 in pyramidal cells induces an enhanced establishment of efferent boutons. © 2004 Wiley Periodicals, Inc. J Neurobiol 60: 263–274, 2004     

Characterization of a target-derived neuronal cholinergic differentiation factor

The sympathetic innervation of rat sweat glands undergoes a target-induced switch from a noradrenergic to a cholinergic and peptidergic phenotype during development. Treatment of cultured sympathetic neurons with sweat gland extracts mimics many of the changes seen in vivo. Extracts induce choline acetyltransferase activity and vasoactive intestinal peptide expression in the neurons in a dose-dependent fashion while reducing catecholaminergic properties and neuropeptide Y. The cholinergic differentiation activity appears in developing glands of postnatal day 5 rats and is maintained in adult glands. It is a heat-labile, trypsin-sensitive, acidic protein that does not bind to heparin-agarose. Immunoprecipitation experiments with an antiserum directed against an N-terminal peptide of a cholinergic differentiation factor (CDF/LIF) from heart cells suggest that the sweat gland differentiation factor is not CDF/LIF. The sweat gland activity is a likely candidate for mediating the target-directed change in sympathetic neurotransmitter function observed in vivo.     

Cholinergic regulation of the activity of somatosensory cortex neurons during early postnatal ontogeny of the cat

In 11-14 days kittens, about 20% of neurones in the somatosensory cortical zone react to stimulation of subpallidal region which is a source of cholinergic projections to the cerebral cortex. The effect of subpallidal region stimulation is reproduced in case of microiontophoretic acetylcholine application and blocked by atropine what points to its cholinergic nature. Cholinergic stimulation causes inhibition of the background and evoked activities of the cortical neurones while, as it is known, in adult cats, acetylcholine mainly stimulates a reaction of activation. It is postulated that in kittens at the end of the second week of postnatal development, cholinergic innervation of the cortex significantly differs from the definitive one by its quantitative and functional parameters.     

Raphe Stimulation-Evoked Modulation of Postsynaptic Responses by Neurons of the Cat Somatosensory Cortex Activated by Stimulation of Nociceptors

We studied the effects of electrical stimulation of the raphe nuclei (RN) of the cat brain on postsynaptic potentials developing in somatosensory cortex neurons activated by nociceptive influences. Intracellular records were obtained from 15 cells, which were either selectively excited by stimulation of nociceptors (intense electrical stimulation of the dental pulp) or activated by both the above nociceptive and non-nociceptive (moderate stimulations of the infraorbital nerve or thalamic ventroposteromedial nucleus, VPMN) influences. In neurons of both groups, stimulation of both nociceptive afferents and the VPMN evoked complex responses (EPSP–AP–IPSP; IPSPs were 200 to 300 msec long). In some studied cortical neurons, isolated electrical stimulation of the RN (which caused the release of serotonin, 5-HT, in the cortex) resulted in relatively short-latency synaptic excitation, while inhibition was observed in other cells. In the case where stimulation of the RN was used as conditioning influence, such stimulation (independently of the kind of the initial response to RN stimulation) led to long-latency and long-lasting suppression of all components of the synaptic reactions evoked by excitation of nociceptors. The maximum of inhibition was observed at test intervals of 300 to 800 msec. The mechanisms underlying modulatory influences coming from the 5-HT-ergic brainstem system to neurons of the somatosensory cortex, which are activated by excitation of high-threshold (nociceptive) afferent inputs, are discussed.     

Activation of thalamic ventroposteriolateral neurons by phrenic nerve afferents in cats and rats.

It has been demonstrated that phrenic nerve afferents project to somatosensory cortex, yet the sensory pathways are still poorly understood. This study investigated the neural responses in the thalamic ventroposteriolateral (VPL) nucleus after phrenic afferent stimulation in cats and rats. Activation of VPL neurons was observed after electrical stimulation of the contralateral phrenic nerve. Direct mechanical stimulation of the diaphragm also elicited increased activity in the same VPL neurons that were activated by electrical stimulation of the phrenic nerve. Some VPL neurons responded to both phrenic afferent stimulation and shoulder probing. In rats, VPL neurons activated by inspiratory occlusion also responded to stimulation on phrenic afferents. These results demonstrate that phrenic afferents can reach the VPL thalamus under physiological conditions and support the hypothesis that the thalamic VPL nucleus functions as a relay for the conduction of proprioceptive information from the diaphragm to the contralateral somatosensory cortex.     

Parkin protects against the toxicity associated with mutant alpha-synuclein: proteasome dysfunction selectively affects catecholaminergic neurons

One hypothesis for the etiology of Parkinson's disease (PD) is that subsets of neurons are vulnerable to a failure in proteasome-mediated protein turnover. Here we show that overexpression of mutant alpha-synuclein increases sensitivity to proteasome inhibitors by decreasing proteasome function. Overexpression of parkin decreases sensitivity to proteasome inhibitors in a manner dependent on parkin's ubiquitin-protein E3 ligase activity, and antisense knockdown of parkin increases sensitivity to proteasome inhibitors. Mutant alpha-synuclein also causes selective toxicity to catecholaminergic neurons in primary midbrain cultures, an effect that can be mimicked by the application of proteasome inhibitors. Parkin is capable of rescuing the toxic effects of mutant alpha-synuclein or proteasome inhibition in these cells. Therefore, parkin and alpha-synuclein are linked by common effects on a pathway associated with selective cell death in catecholaminergic neurons.     

Neuronal regulation by which microglia enhance the production of neurotrophic factors for GABAergic, catecholaminergic, and cholinergic neurons

A phenomenon-in which microglia are activated in axotomized rat facial nucleus suggests that a certain neuronal stimulus triggers the activation of microglia. However, how the microglial characteristics are regulated by this neuronal stimulus has not previously been determined. In this study, therefore, the regulation of microglial properties by neurons was characterized in vitro from a neurotrophic perspective. To evaluate the neurotrophic effects of microglia stimulated with neurons, the effects of conditioned medium (CM) of microglia stimulated with neuronal CM (NCM) were assessed in neuronal cultures. The amounts of tyrosine hydroxylase (TH) in neuronal culture exposed to CM of microglia stimulated with NCM was much more than those in neurons exposed to CM of control microglia, suggesting that neuronal stimulus enhances the production of neurotrophic factors for catecholaminergic neurons in microglia. Therefore, the neurotrophic effects of CM of microglia stimulated with NCM were analyzed in detail. The immunocytochemical and biochemical experiments revealed that the CM of microglia stimulated with NCM enhances the survival/maturation of GABAergic and catecholaminergic neurons. The levels of choline acetyltransferase specific to cholinergic neurons also significantly increased in response to stimulation with the same microglial CM. These results allowed us to investigate the production of neurotrophic factors in the CM of microglia stimulated with NCM. The results indicated that NCM induces nerve growth factor (NGF), and enhances neurotrophin-4/5 (NT-4/5), transforming growth factor beta1 (TGFbeta1), glial cell line-derived neurotrophic factor (GDNF), fibroblast growth factor 2 (FGF2), interleukin-3 (IL-3), and IL-10 in microglia. The promoted neurotrophic effects of CM of microglia stimulated with NCM were significantly abrogated by deprivation of neurotrophic factors by means of an immunoprecipitation method. Taken together, neuronal stimulus was found to activate microglia to produce more neurotrophic factors as above, thereby changing microglia into more neurotrophic cells.