Trophic effect of the sympathetic nervous system on vascular smooth muscle

While the vasomotor effect of the sympathetic nervous system (SNS) on the arterial wall is well recognized, its trophic function is not. It is the aim of these studies to demonstrate this all-important function as it relates to the vascular muscle. Although the exact mechanism by which sympathetic nerve impulses influence the metabolism of the vessel wall is unknown, effects of sympathectomy can be demonstrated. Several lines of evidence indicate that chronic absence of sympathetic innervation in rabbits increases collagen synthesis and decreases activity of tricarboxylic acid cycle enzymes in the vascular wall. When chemically sympathectomized rabbits were fed a 1% cholesterol dietary supplement for 80 days, the aortas of these rabbits contained significantly more cholesterol and total lipids than those from fully innervated controls in spite of insignificant differences in plasma lipids. In a subsequent series of experiments we analyzed the efficacy of the SNS in two strains of pigeons. White Carneau (WC) pigeons are known by their susceptibility to atherosclerosis of the aorta while Show Racer (SR) pigeons are not. Our results demonstrate that the abdominal aorta of WC pigeons has less sympathetic innervation and it declines faster with age than that of SR pigeons. The results of the described studies documenting the direct trophic influence of the SNS on the arterial wall are reinforced by the similarity to the vessel wall changes induced by partial sympathectomy and natural aging. Various phases of this work were done in collaboration with Drs. N. Alexander, D. Amiel, C.M. Bloor, M. Chvapil, J.D. Turner and T. Zemplenyi.     

Receptive field properties of visual neurons in the avian nucleus lentiformis mesencephali

The receptive field (RF) properties of visual neurons extracellularly recorded from the nucleus lentiformis mesencephali (nLM) in pigeons (Columba livia) were quantitatively analyzed using a workstation computer. These cells were actively spontaneous, and direction- and velocity-selective. Using spatial gratings as visual stimuli, these cells could be divided into three groups: uni- (74%), bi- (17%), and omnidirectional (9%) cells in terms of their directionality. On the basis of their velocity selectivity, they could be named slow cells (84%), preferring low velocity (0.1–11°/s), and fast cells (14%), preferring rapid motion (34–67°/s), with one cell (2%) responding maximally to an intermediate velocity of 18°/s. These two properties were correlated in the way that all unidirectionals were slow cells, omnidirectionals were fast cells, and bidirectionals were either slow or fast cells including the intermediate cell. Using small targets as visual stimuli, it was found that the majority of cells examined had RFs that each consisted of an excitatory RF (ERF) and an inhibitory RF (IRF) that overlapped. The unidirectionals were mainly of this type of RF structure, whereas the omnidirectionals apparently had ERFs alone. The direction preference of ERF was opposite to that of IRF for unidirectional cells tested, whereas they were perpendicular to each other for one bidirectional cell. The overall responses of these cells resulted from interaction between excitation and inhibition induced by directionally different motion. Under certain conditions, visual responses of a particular cells to a small target moving through its ERF were equal in responsive strength to those to whole-field gratings swept over the screen. It was suggested that optokinetic nystagmus produced by whole-field gratings results from population activity of large group(s) of neurons in some optokinetic nuclei, at least one of which is nLM. Received: 5 March 1997 / Accepted: 5 August 1997     

Techniques to prevent olfactory nerve reconstitution in the pigeon

Transectioned olfactory nerves in birds can reestablish structural and functional connections with the olfactory bulbs in comparatively short time spans, thereby hampering long-range studies of avian olfaction and behavior. Accordingly, techniques are described that are suitable for impeding the reconstitution of the olfactory nerve after its transection in the pigeon. These involve the use of inexpensive and easily obtainable materials including cotton pellets, glass beads, and polyethylene tubing.     

Grouping of artificial objects in pigeons: an inquiry into the cognitive architecture of an avian mind

How does a pigeon see the world? Although pigeons are known to be adept at learning large numbers of figures, colors, and natural images, various experiments show that their visual cognitive specialization is more geared towards seeing colors and textures instead of shapes. They also excel in the analysis of local features instead of shapes that can only be differentiated by their outline. We therefore embarked into a detailed analysis of the relative weight of colors versus shapes in an object grouping task. At the same time we used a design that gave us information on the question of the relative importance of the S+ and S? in cognitive tests. Our strategy was to use the classic matching to sample task in which pigeons have to associate a sample with another stimulus (S+), which belongs to the same arbitrary group while at the same time avoiding choosing another stimulus (S?), which is part of another arbitrary group. Our results clearly reveal that color is, relative to shape, the primary cue that pigeons use to guide their decisions. Although they are in principle able to use shape information, they utilize shape as the last cognitive resort. Our data further reveal that pigeons guide their decisions in a matching to sample task primarily by focusing on the S+, although they also utilize information from the S?, albeit to a smaller extent. They are flexibly able to use cognitive match- or nonmatch-strategies depending on the presence or absence of color- or shape-cues.     

鸽脑磷脂软胶囊改善人体记忆的研究

目的研究鸽脑磷脂软胶囊对记忆的改善作用。方法选择104名战士志愿者作为受试对象，用中国科学院心理研究所编制的临床记忆量表检测。将受试者按记忆商高低分成均衡的两组，每组52人。随机选择一组为实验组口服试样（每日3次，每次2粒），另一组为对照组服用等量的安慰荆，连续服用30d。结果试验后实验组MQ为95．5±9．8，比服用前的84．2±11．8有明显提高，也与对照组MQ85．8±11．6比较，差异也均有显著性（P〈0．01）。结论鸽脑磷脂软胶囊对改善人体记忆有一定效果。     

5-HT receptors as targets for the development of novel anxiolytic drugs: models,mechanisms and future directions

The introduction of buspirone for the treatment of anxiety, together with the eventual suggestion of a mode of action involving the serotonin (5-HT)_1A receptor subtype, has generated considerable research activity and renewed interest in the potential role of 5-HT in anxiety. The further identification of multiple 5-HT₁ receptors, coupled with the possibility that these subtypes potentially are involved in discrete biobehavioral regulation and pathophysiological conditions, has greatly expanded the search for tools capable of probing these receptors and has raised hopes for a new generation of more specific compounds to treat other disorders associated with the 5-HT system such as depression, aggression, and sleep and eating disturbances. The involvement of 5-HT in anxiety has prompted a careful reevaluation of several traditional areas of research. This has included those methods used in the in vivo evaluation of drugs in preclinical animal test procedures used to assess potential anxiolytic activity, as well as the mechanisms associated with adaptive changes occurring during long-term drug administration. The proliferation of various procedures for studying the anxiolytic effects of 5-HT drugs has not always been accompanied by systematic behavioral and pharmacological validation. At the present time, this area of research is characterized by numerous inconsistent findings. Procedures that are objective and impartial to the behavioral effects of drugs provide distinct advantages for addressing some of these issues, as will the results from carefully controlled clinical studies. The main objective of this article is to provide an overview of the recent developments in research involving the 5-HT system and anxiety. The emphasis will be on the 5-HT₁ receptor system and a review of the results in the predominant animal models used to evaluate these drugs, as well as an overview of the mechanisms currently believed to be responsible for the therapeutic activity of this class of compounds. Studies with the pigeon are reviewed, since this species appears distinctly sensitive to the anxiolytic-like effects of 5-HT_1A drugs in conflict procedures. Although chronic administration of 5-HT_1A drugs appears necessary for clinical anxiolytic and antidepressant activity, the most noteworthy neuropharmacological effects in animals seem to occur in 5-HT₂ and, perhaps, 5-HT₃ receptors which are downregulated. Studies summarizing the activity of drugs interacting with 5-HT_1C/2 and 5-HT₃ receptor sites are also discussed as they too may be involved in anxiety or the actions of anxiolytic drugs. The growing evidence suggesting an interaction between 5-HT receptor types, particularly between 5-HT_1A and 5-HT_1C/2 receptors, is reviewed, since drugs with these combined properties appear to be particularly efficacious in animal models of anxiety and warrant further detailed analyses. The development of drugs targeted specifically at multiple receptors may provide distinct therapeutic advantages for disorders such as anxiety and depression that appear to involve multiple neurotransmitter systems.     

Long-term potentiation in the avian hippocampus does not require activation of the N-methyl-D-aspartate (NMDA) receptor

Evoked potentials recorded from slices of pigeon hippocampus were reversibly attenuated by 2 mM kynurenic acid. High frequency stimulation (3 × 200 Hz for 1 sec, with 1 sec intervals) evoked a persistent increase in the evoked potential, lasting in a nondecremental form for at least 2 hr. This increase in the magnitude of the potential was not blocked by antagonists of the NMDA receptor (APV and MK-801). These data suggest that the synaptic facilitation observed in the pigeon hippocampus, which appears to be a form of long-term potentiation, does not depend on the activation of NMDA receptors. © 1993 Wiley-Liss, Inc.     

A selective serotonin reuptake inhibitor reduces REM sleep in the homing pigeon

Avian and mammalian 'rapid eye movement' sleep (REM sleep) resemble each other in several aspects. However, the question of whether REM sleep has a shared evolutionary ancestry in birds and mammals has yet to be thoroughly explored. The brain regions and neurotransmitter systems involved in the generation of mammalian REM sleep are phylogenetically ancient, and are also found in extant birds and reptiles. Several pharmacological experiments in birds indicate that similar neural substrates are involved in the regulation of avian and mammalian sleep. However, because the drugs used in these studies generally resulted in non-specific sleep loss, the neurochemical regulation of avian REM sleep in particular remains uncertain. The selective serotonin reuptake inhibitor (SSRI) zimelidine is known to reduce REM sleep in mammals. If avian REM sleep is similarly regulated by serotonin, it would be expected that an acute dose of a SSRI should also reduce avian REM sleep. To investigate a putative role of serotonin in the regulation of avian REM sleep, changes in sleep electroencephalogram (EEG) and behavior were recorded in five pigeons (Columba livia) after the administration of an acute dose of zimelidine. Our results demonstrate that the effects of zimelidine on avian REM sleep are comparable to those observed in mammals, indicating that serotonin may serve a similar function in the control of avian and mammalian REM sleep.     

Effects of clozapine, chlorpromazine and haloperidol on schedule-controlled behavior

The effects of clozapine, chlorpromazine, and haloperidol were determined in mice and pigeons responding under a multiple fixed-ratio 30, fixed-interval 600 sec schedule of food presentation. In both species, low doses were without effect and moderate to high doses of all three antipsychotics decreased responding. In contrast to other behavioral tests used to predict antipsychotic activity, clozapine was equipotent or more potent than chlorpromazine in decreasing responding under the multiple fixed-ratio 30, fixed-interval 600 sec schedule. The order of potency observed in the mouse was: haloperidol greater than chlorpromazine greater than or equal to clozapine. The order of potency in the pigeon was: haloperidol greater than clozapine greater than chlorpromazine. In mice and pigeons, the rate of responding under the fixed-ratio component was decreased at lower than, or the same doses of clozapine as that required to decrease fixed-interval responding. However, in both species, chlorpromazine and haloperidol decreased fixed-interval responding at lower doses or the same dose as that required to decrease fixed-ratio responding.