Neuropharmacological Analysis of Mechanisms Controlling Larval Behaviour in the Sea Urchin; 1. Effects of carbamylcholine and acetylcholine

The effect of carbamylcholine (carbachol) on the muscular, intestinal, and ciliar activities of the sea urchin pluteus larva (Psammechinus miliaris) show a complicated relation between the concentrations used, the length of exposure, and the physiological responses. Two main patterns of stimulated activity emerged upon carbachol treatment. In pattern I there is a reciprocal “antagonism” between swallowing and celomic movements, i.e. stimulation of one type of movement is attended by a decrease of the other type and even its complete paralysis. Paralysis of the celomic movements is attended by intestinal paralysis. In pattern II marked swallowing and celomic activity coexist. The fluctuations in these activities are strong, their maxima as well as their minima coincide, and intestinal cycling occurs. In pattern I low concentrations favour the celomic activity and counteract swallowing. At higher concentrations the initial effects are qualitatively similar but more intense and of short duration. They are quickly followed by the opposite effects (intense swallowing and celomic paralysis) together with intestinal paralysis. The effects are to a great extent quickly reversible after transfer of the larva to sea water. During prolonged or repeated exposure to the agent the system “adapts”, i.e. a pattern II activity may appear. If the concentration is not too high, this may be preceded or admixed by a renewed pattern I activity. The responses described suggest that two main control systems are involved in the regulation of the larval activities. The effects of acetylcholine are similar to those of carbachol but not identical. The question if the control mechanisms are related to regionally separated structures is discussed in a preliminary way.     

Effects of chemical transmitters on function of isolated canine parietal cells

In view of the complexity of the regulation of gastric acid secretion, isolated parietal cells offer the appealing prospect of studying the receptors and mechanisms activating this cell after it has been removed from the confusing milieu of the intact mucosa. Histamine and cholinergic agents stimulate the function of canine parietal cells by interacting with typical H2 and muscarinic receptors. Gastrin produces only a small stimulation, interacting with a third, presumably specific, receptor. Combinations of histamine and carbachol and of histamine and gastrin produce potentiating interactions. When isolated parietal cells are treated with these combinations of agents, cimetidine and atropine display and apparent lack of specificity, reminiscent of that found in vivo, and probably resulting from interference with the histamine and cholinergic components of these potentiating interactions. The action of histamine, but not of carbachol or gastrin, is linked to stimulation of cyclic AMP production by parietal cells. Two potential inhibitors of acid secretion, secretin and prostaglandin E2, also stimulate cyclic AMP production, but these later effects appeared to occur largely in nonparietal cells. PGE2 however specifically inhibits histamine-stimulated parietal cell function, apparently by blocking activation of adenylate cyclase. Cholinergic action on the other hand is closely linked to enhanced influx of extracellular calcium.     

Carbachol interactions with nonsteroidal anti-inflammatory drugs

The inhibition of cyclooxygenase enzymes by nonsteroidal anti-inflammatory drugs (NSAIDs) does not completely explain the antinociceptive efficacy of these agents. It is known that cholinergic agonists are antinociceptive, and this study evaluates the interactions between carbachol and some NSAIDs. Antinociceptive activity was evaluated in mice by the acetic acid writhing test. Dose-response curves were constructed for NSAIDs and carbachol, administered either intraperitoneally (i.p.) or intrathecally (i.t.). The interactions of carbachol with NSAIDs were evaluated by isobolographic analysis after the simultaneous administration of fixed proportions of carbachol with each NSAID. All of the drugs were more potent after spinal than after systemic administration. The combinations of NSAIDs and carbachol administered i.p. were supra-additive; however, the i.t. combinations were only additive. Isobolographic analysis of the coadministration of NSAIDs and carbachol and the fact that atropine antagonized the synergistic effect suggest that carbachol may strongly modulate the antinociceptive activity of NSAIDs; thus, central cholinergic modulation would be an additional mechanism for the antinociceptive action of NSAIDs, unrelated to prostaglandin biosynthesis inhibition.     

Behavioral investigation of the coexistence of substance P,corticotropin releasing factor,and acetylcholinesterase in lateral dorsal tegmental neurons projecting to the medial frontal cortex of the rat

Colocalization of substance P (SP), corticotropin releasing factor (CRF), and acetylcholinesterase (AChE) was detected by retrograde tracing and immunocytochemical staining in the nucleus tegmentalis dorsalis lateralis (ntdl) projecting to the medial frontal cortex (MFC), septum, and thalamus of the rat. The histochemical results suggest that SP and CRF coexist within a subpopulation of ntdl cholinergic neurons that project to a number of forebrain regions including the MFC. Behavioral studies of the effects of SP, CRF, and the cholinergic agonist, carbachol, employed microinjections into the MFC of rats. SP and CRF did not elicit any behavioral effects when administered alone. Carbachol (1–5 μg/side) produced a stereotyped motor behavior, consisting of rapid forepaw treading while in an upright posture, resembling “boxing.” SP (1 μg/side) increased carbachol-induced “boxing.” CRF (1–10 ng/side) decreased carbachol-induced “boxing.” One possible functional significance of the coexistence of SP, CRF, and acetylcholinesterase, in neurons projecting to the medial frontal cortex in rats, appears to be a modulatory potentiation of cholinergic response by SP, and a modulatory inhibition of the cholinergic response by CRF.     

Effects of increased intracellular cAMP on carbachol-stimulated zymogen activation, secretion, and injury in the pancreatic acinar cell

A characteristic of acute pancreatitis is the premature activation and retention of enzymes within the pancreatic acinar cell. Because ligands linked to cAMP production may prevent some forms of pancreatitis, we evaluated the effects of increased intracellular cAMP in the rat pancreatic acinar cell. Specifically, this study examined the effects of the cholinergic agonist carbachol and agents that increase cAMP [secretin and 8-bromoadenosine 3',5'-cyclic monophosphate (8-Br-cAMP)] on zymogen activation (trypsin and chymotrypsin), enzyme secretion, and cellular injury in isolated pancreatic acini. Although cAMP agonists affected the responses to physiological concentrations of carbachol (1 microM), their most prominent effects were observed with supraphysiological concentrations (1 mM). When secretin was added to 1 mM carbachol, there was a slight increase in zymogen activation, but no change in the secretion of amylase or chymotrypsin. Furthermore, coaddition of secretin increased parameters of cell injury (trypan blue exclusion, lactic dehydrogenase release, and morphological markers) compared with carbachol (1 mM) alone. Although directly increasing cellular cAMP by 8-Br-cAMP caused much greater zymogen activation than carbachol (1 mM) alone or with secretin, 8-Br-cAMP cotreatment reduced all parameters of injury to the level of unstimulated acini. Furthermore, 8-Br-cAMP dramatically enhanced the secretion of amylase and chymotrypsin from the acinar cell. This study demonstrates that increasing acinar cell cAMP can overcome the inhibition of enzyme secretion caused by high concentrations of carbachol and eliminate acinar cell injury.     

Logical-Semantic Analysis and the Development of L.S. Vygotsky's Ideas About “Units” and “Elements” of Psychological Systems

Based on an analysis of L.S. Vygotsky's concepts of “units” and “elements” of psychological systems, this article highlights five of their attributes. It shows that these attributes are logically symmetrical, since in their wording they can be converted into one another by negation or by replacing some words with their opposites. This suggests that the concepts of the “unit” and “element” of a system are different poles of one theoretical construct of the activity of human psychology. Thus methods for the study of psychological systems by breaking them down into elements or by separating them into units can be seen as complementary. The article describes differences among the concepts of “unit,” “minimal unit,” and “cell” of a psychological system. It reviews several problems that are solvable using the “method of units,” as well as some concepts of the theory of psychological systems that are understood as holistic, conceptual, and active processes and/or results of human interaction with the world. Among the examples of such systems are “systems of psychological functions” (according to Vygotsky), as well as separate activities (according to A.N. Leontiev), human actions and operations (interactions with the world on the level of objects and mental or physical means). The “component” of a psychological system is defined as any “something” that in some sense belongs to or is included in human interaction with the world. A component that belongs to the system is called an “element” of it, but a component that is included in the functioning and development of the system is called a “part” of it. The article presents the mathematical and psychological foundation of these definitions. It identifies and discusses the substantial (independently existing) components of psychological systems and their attributes (properties and conditions). It describes the relationships between them using the bipolar theoretical constructs “part-element” and “substantial-attributive” component of a system.     

Inhibition of vestibulospinal reflexes following cholinergic activation of the dorsal pontine reticular formation

1. The multiunit EMG activity of the forelimb extensor muscle triceps brachii was recorded in precollicular decerebrate cats, either at rest or during roll tilt of the animal at 0.15Hz, +/- 10 degrees leading to sinusoidal stimulation of labyrinth receptors. Both the spontaneous EMG activity as well as the labyrinthine-induced EMG responses were tested before and after pontine microinjection of a cholinergic agonist. 2. Local injection of the cholinergic agonist carbachol into the dorsal aspect of the pontine tegmentum (usually 0.25 microliter, 0.01-0.2 microgram/microliter) produced a state of postural atonia, and abolished both the spontaneous EMG activity as well as the EMG responses of the triceps brachii to sinusoidal stimulation of labyrinth receptors. This suppression was generally ipsilateral to the side of the injection and persisted throughout the episode of postural atonia, but sometimes it involved also the contralateral limbs. In these instances it could be accompanied by a spontaneous nystagmus, interspersed at regular intervals with bursts of rapid eye movements. 3. Similar effects were also obtained following injection of carbachol in the gigantocellular tegmental field (FTG) (0.25 microliter, 0.5-1.0 microgram/microliter). However, this structure was not critically responsible for the phenomena reported above, which persisted unaltered after kainic acid lesion of the FTG performed ipsilaterally to the side of the pontine injection. 4. Local infusion of the muscarinic blocker atropine sulphate reversed the effects of carbachol injection into the dorsal aspect of the pontine tegmentum, thus indicating that muscarinic receptors were involved. 5. It is postulated that the postural atonia as well as the tonic depression of vestibulospinal reflexes, which occur in the decerebrate cat after local injection of a cholinergic agonist depends, at least in part, on the activation of cholinoceptive neurons located in dorsal pontine reticular structures. These may in turn excite medullary reticulospinal neurons, which are finally responsible for the inhibition of extensor motoneurons.     

Pigeon oesophageal EMG activity: analysis of intramural neural control

The effects of agonist and antagonist cholinergic and adrenergic drugs on spontaneous electrical activity of transverse muscular strips of pigeon cervical oesophagus were examined. Tetrodotoxin failed to affect EMG activity. Cholinomimetics produced excitatory effects. The response to carbachol was enhanced by hexamethonium and reversed into an inhibitory effect by atropine. Noradrenaline evoked a concentration-dependent, biphasic effect (inhibition at low and excitation at high concentrations). Isoproterenol induced inhibitory response unaffected by tetrodotoxin. Phenylephrine induced excitatory response completely antagonized by tetrodotoxin and partially opposed by atropine. It is concluded that: i) the oesophageal spontaneous EMG activity is myogenic; ii) the intramural neurons have no tonic influence on the spontaneous EMG activity; iii) in the intramural plexuses there are cholinergic excitatory-, non-cholinergic excitatory- and inhibitory neurons, with unknown neurotransmitter; iv) excitatory alpha-adrenoceptors, located on the nervous elements and inhibitory beta-adrenoceptors, located on the smooth-muscle cells, are present.     

Carbachol models of REM sleep: recent developments and new directions

Since the early '60s, injections of a broad-spectrum muscarinic cholinergic agonist, carbachol, into the medial pontine reticular formation (mPRF) of cats have been extensively used as a tool with which to study the neural mechanisms of rapid eye movement (REM) sleep. During the last decade, new carbachol models of REM sleep were introduced, including chronically instrumented/behaving rats and "reduced" preparations such as decerebrate or anesthetized cats and rats. The combined results from these distinct models show interspecies similarities and differences. The dual nature, both REM sleep-promoting and wakefulness (or arousal)-promoting, of the cholinergic effects exerted within the mPRF is more strongly expressed in rats than in cats. This strengthens the possibility suggested by earlier central neuronal recordings that active wakefulness and REM sleep have extensive common neuronal substrates, and may have evolved from a common behavioral state. Carbachol studies using different intact and reduced models also suggest that powerful REM sleep episode-terminating effects originate in suprapontine structures. In contrast, the timing of REM sleep-like episodes in decerebrate models is determined by a pontomedullary neuronal network responsible for the generation of an ultradian cycle similar to the basic rest-activity cycle of N. Kleitman. Other presumed species differences, such as the more widespread distribution of carbachol-sensitive sites or the relative failure of carbachol to increase the duration of REM sleep episodes in rats when compared to cats, may be of a quantitative or technical nature. While carbachol and many other neurotransmitters and peptides microinjected into the mPRF evoke, enhance or suppress REM sleep, the most sensitive site(s) of their actions have not been fully mapped, and the nature of the cellular and neurochemical interactions taking place at the sites where carbachol triggers the REM sleep-like state remain largely unknown. Similarly, little is known about the pathways between the mPRF and medial medullary reticular formation, but the existing evidence suggests that they are reciprocal and essential for the generation of both natural and carbachol-induced REM sleep. Studies of the mesopontine cholinergic neurons, which are hypothesized to be the main source of endogenous acetylcholine for the mPRF, need to be extended to neurons of the mPRF and cells located functionally downstream from this important site for REM sleep, or both REM sleep and active wakefulness.     

The “High Irradiance Responses” of plant photomorphogenesis

Plants growing in the natural environment are exposed daily to prolonged periods of high intensity irradiation. Many plant photomorphogenic responses are fully expressed only under prolonged exposures to high irradiances of light. The intensive study of these responses, the “High Irradiance Responses” (HIR) of plant photomorphogenesis, which started about 20 years ago, has been essentially directed—so far—toward the identification of the HIR photoreceptor, or photoreceptors, a problem that has not been satisfactorily and definitively solved, as yet. There is a great deal of evidence in support of the hypothesis that phytochrome, the pigment mediating the redfar red reversible plant photo-responses to low fluences of light, is involved in the photocontrol of the HIR. It seems likely that phytochrome may be the only photomorphogenic receptor responsible for the photocontrol of HIR responses brought about by irradiation at wavelengths longer than 600 nm. Phytochrome is probably also involved in the photocontrol of the HIR effects brought about by irradiation in the 350 to 500 nm region of the spectrum, but it cannot be excluded that other photochemical systems may also be involved. From a theoretical point of view, it does not seem unreasonable that the final expression of an HIR response may involve an interaction between phytochrome and other photochemical systems, with phytochrome probably playing the primary role and being responsible for the control of the activity of the other systems. Numerous “phytochrome only” interpretations (models) of the HIR have been proposed. Some of them have been developed to a fairly high degree of elaboration and have allowed the prediction of at least some of the features of the HIR. These “models,” although not rigorously and completely tested yet, seem to provide a reasonable interpretation for the HIR effects displayed under prolonged far red irradiation and for those HIR responses for which far red is the most effective spectral region. However, they do not provide a satisfactory explanation for the HIR responses for which blue is the most or the only effective spectral region, nor for the high effectiveness of white light. But, in spite of these problems, the “phytochrome only” interpretations of the HIR can be considered more satisfactory than those based on an interaction between phytochrome and other photochemical systems, especially in relation to the fact that the identity of these other photochemical systems has not been defined yet.     

Evidence for the Interaction of Nucleotides with Immobilized Amino-acids and its Significance for the Origin of the Genetic Code

ONE of the essential relationships between nucleic acids and amino-acids in present biological systems and perhaps in evolutionary precursors to these systems is expressed in binding and recognition interactions. Such interactions depend on the size, composition and conformation of the interacting species^1–8. When the two reacting species are simple (that is, when neither is polymeric) one cannot expect to observe “specificity” of the sort implied in the biological use of the term. Working with monomeric species in aqueous media permits the effects of individual factors to be assessed so that more complex interactions between these molecules can be understood and their evolutionary potential evaluated.     

Testosterone Cytosol “Receptor” in the Rat Levator Ani Muscle

IT is not known whether the “anabolic” action of the androgenic hormone testosterone¹, especially on muscular growth and metabolism, can be explained by the presence and the possible metabolism and “receptors” of the hormone in muscles. There are indeed several categories of muscles which, when dependent on androgens, may or may not respond directly to testosterone. It is conceivable that the hormone affects certain muscles through an increased (sexual or general) activity by way of the central nervous system, or because of the release of another hormone, or secondarily through some change of general metabolism.     

Enhancement of early human E rosette formation by cholinergic stimuli.

The effects of the cholinergic stimuli carbamylcholine (carbachol) and dibutyrl cyclic guanosine monophosphate (DBCGMP) were determined on both 'early' and 'total' E rosette formation. Ficoll-Hypaque-separated lymphocytes were preincubated with either carbachol or DBCGMP over a 10(-3) M to 10(-13) M dose range. Both agents significantly enhanced 'early', but not 'total' E rosette formation. Peak enhancement above control values occurred at 10(-7) M (72%) and 10(-9) M (69%) for carbachol and 10(-5) M (70%) and 10(-7) M (70%) for DBCGMP. Kinetic studies showed a rapid onset of enhancement (2.5 min) for carbachol, whereas DBCGMP required 15 min for significant enhancement to occur. The muscurinic nature of carbachol enhancement of E rosettes was demonstrated. Atropine at 10(-7) M completely abolished the carbachol effect while showing little inhibition of the DBCGMP effect on rosette formation. These studies indicate that the cholinergic stimuli carbachl and DBCGMP significantly enhance the 'early' E rosette former in man. Human T lymphocytes appear to have functional cholinergic receptors that can be blocked by the muscurinic antagonist atropine. The role of the cyclic nucleotides and their stimulants on the immune system is incompletely understood, but it would appear that they are extremely important in the differentiation and function of the T lymphocyte. E rosette formation may be a useful model in man for studying the effects of the cyclic nucleotides on the human T lymphocyte.     

Role of Egr-1 in Cholinergic Stimulation of Phenylethanolamine N-Methyltransferase Promoter

Abstract: The effects of the cholinergic agonist carbachol on phenylethanolamine N -methyltransferase promoter activity and Egr-1 mRNA expression in PC12-derived RS1 cells were examined to investigate the potential involvement of Egr-1 in the neural regulation of phenylethanolamine N -methyltransferase gene expression. Carbachol stimulated luciferase expression in cells transfected with a rat phenylethanolamine N -methyltransferase promoter-luciferase reporter gene construct and also elevated Egr-1 mRNA levels in untransfected cells. Maximum induction of Egr-1 mRNA by carbachol was rapid (0.5 h), whereas by comparison, peak luciferase activity was delayed (6 h). In addition, carbachol stimulation of both luciferase and Egr-1 mRNA expression could be completely inhibited by atropine but not hexamethonium. Furthermore, bethanechol but not nicotine could mimic the effects of carbachol, indicating that carbachol activation was medicated through muscarinic cholinergic receptors. Finally, carbachol failed to stimulate luciferase expression in cells transfected with a mutant construct, in which the Egr-1 binding element in the phenylethanolamine N -methyltransferase promoter was mutated. These results suggest that carbachol activates the phenylethanolamine N -methyltransferase promoter through stimulation of Egr-1 expression, and are consistent with the potential involvement of Egr-1 in the cholinergic activation of the phenylethanolamine N -methyltransferase gene.     

Cholinergic microstimulation of the peribrachial nucleus in the cat. I. Immediate and prolonged increases in ponto-geniculo-occipital waves.

The cholinergic agonist carbachol was injected into the pontine Pb area where PGO bursting cells have been recorded. When microinjections were localized to the ventrolateral aspect of the caudal Pb nucleus near aggregates of ChAT immunolabeled cholinergic neurons, carbachol produced an immediate onset of state-independent PGO waves in the ipsilateral LGB. These state-independent PGO waves persisted for 3-4 days. After the first 24 hrs PGO wave activity increasingly became associated with REM sleep and with REM transitional SP sleep as both of these PGO-related states increased in amount to 3-4 times baseline levels. The increase in amount of PGO-related states peaked on days 2-4 following one carbachol injection and persisted for 10-12 days. These results suggest a two stage process: stage one, PGO enhancement, is the direct consequence of the membrane activation of cholinoceptive PGO burst neurons by carbachol; stage two, REM enhancement, is the consequence of metabolic activation of endogenous cholinergic neurons. This experimental preparation is a useful model for the study of the electrophysiology and functional significance of PGO wave and REM sleep generation.     

Cardiac responses of Pacific oyster Crassostrea gigas to agents modulating cholinergic function

To examine the functional effects of cholinergic modulation compounds in oyster hearts and to explore their possible use in monitoring intoxication with acetylcholine-esterase (AChE) inhibitors such as organophosphates, tests were performed with in situ oyster heart preparations. The endogenous cholinergic agonist acetylcholine (ACh), AChE-resistant synthetic agonist carbachol, and the reversible carbamate type of AChE inhibitor physostigmine, all potently depressed spontaneous cardiac contractility. The depression was reversed by extensive washout, or prevented by muscarinic cholinergic antagonist atropine. The irreversible organophosphate type AChE inhibitor parathion or its active metabolite paraoxon at concentrations up to 100 microM failed to depress cardiac contractility. While other reversible AChE inhibitors such neostigmine and pyridostigmine also depressed the contractility, organophosphate AChE inhibitors malathion, diazinon, or phenthoate did not. Despite the differential effect in depressing cardiac function between the reversible and irreversible inhibitors, both of these inhibitors effectively inhibited cardiac AChE activity. The results suggest that the activation of muscarinic cholinergic receptors is coupled to inhibitory cardiac modulation, and organophosphate AChE inhibitors may inhibit only an AChE isozyme located at sites that are not important for control of cardiac activity in oysters.     

Selective activation of cholinergic interneurons enhances accumbal phasic dopamine release: setting the tone for reward processing

Dopamine plays a critical role in motor control, addiction, and reward-seeking behaviors, and its release dynamics have traditionally been linked to changes in midbrain dopamine neuron activity. Here, we report that selective endogenous cholinergic activation achieved via in vitro optogenetic stimulation of nucleus accumbens, a terminal field of dopaminergic neurons, elicits real-time dopamine release. This mechanism occurs via direct actions on dopamine terminals, does not require changes in neuron firing within the midbrain, and is dependent on glutamatergic receptor activity. More importantly, we demonstrate that in vivo selective activation of cholinergic interneurons is sufficient to elicit dopamine release in the nucleus accumbens. Therefore, the control of accumbal extracellular dopamine levels by endogenous cholinergic activity results from a complex convergence of neurotransmitter/neuromodulator systems that may ultimately synergize to drive motivated behavior.     

Genetic rescue of lethal genotypes in the mouse

Deletions of gene sequences in chromosome 7 of the mouse are known to interfere with biochemical and cellular development differentiation with lethal effects in homozygotes. The presence of the corresponding wild-type alleles in Cattanach's translocation (chromosomes 7 to X) is able to “rescue” potentially lethal females if they are made heterozygous for the translocation-carrying X chromosome. This holds true for those chromosome 7 deletions with perinatally lethal effects, whereas “rescue” is not readily accomplished with the deletions that cause early embryonic lethality. Females homozygous for the relevant deletion sequences and heterozygous for the translocation-carrying X chromosome are mosaics of two cell types: those in which the wild-type alleles included in the translocated piece complement the depleted sequences, resulting in a normal cellular phenotype, and those with the ordinary X chromosome expressing the lethal phenotype. The developmental interactions between the two cell types and their role in the mechanisms responsible for survival of females homozygous for lethal deletions are discussed. The failure of “rescue” of embryonic lethals reflects as yet unknown temporal and functional aspects of X-inactivation early embryogenesis.     

Basal forebrain cholinergic modulation of auditory activity in the zebra finch song system

The cholinergic basis of auditory "gating" in the sensorimotor nucleus HVc and its efferent target robustus archistriatalis (RA) was investigated in anesthetized zebra finches. Injections of cholinergic agonists carbachol or muscarine into HVc strongly affected discharge rates and diminished auditory responsiveness in both HVc and its target RA, changes toward an awake-like condition. HVc nicotine injections produced similar strong effects in HVc, but weaker and inconsistent effects in RA. Stimulation of basal forebrain (BF) produced an initial transient network shutdown followed by diminished auditory responsiveness in HVc and RA. All stimulation effects were blocked when preceded by HVc injections of nicotinic or muscarinic antagonists. Thus, BF cholinergic modulation of song system auditory activity acting via functionally distinct HVc circuits can contribute to auditory gating. We hypothesize that wakeful BF activity levels block sensory input to motor systems and adaptively change during behavior to allow sensorimotor feedback such as auditory feedback during singing.