Baroreflex dysfunction in rats submitted to protein restriction

Earlier studies from the authors' laboratory showed that malnourishment induces alterations in the cardiovascular homeostasis increasing the basal mean arterial pressure and heart rate. In this study, the authors evaluated whether the sympathetic and parasympathetic efferent activities contribute to changes in the cardiovascular homeostasis through altered modulation of the arterial baroreflex of malnourished rats. After weaning, male Fischer rats were given 15% (Normal Protein--NP) or 6% (Low Protein--LP) protein diet for 35 d. The baroreflex gain and latency were evaluated before and after selective autonomic blockades in control and malnourished rats. It was observed that malnourishment affected the baroreflex gain in response to activation and deactivation of the arterial baroreflex. Moreover, malnourished rats showed increased baroreflex latency as compared to that of control rats. Regarding the autonomic efferent activity directed to the heart, the data showed increased sympathetic and decreased parasympathetic efferent activities in malnourished rats, and such alterations could be related to the observed changes in the arterial baroreflex gain as well as in the basal mean arterial pressure and heart rate.     

Changes in social environment induce higher emotional disturbances than changes in physical environment in quail

In intensive rearing, birds are exposed to frequent changes in both their social and physical environments, and this can have an impact on animal welfare under commercial conditions. The aim of the present study was to compare the emotional responses induced by social and non-social changes and to study the influence of the familiarity on these responses.Twenty-two female quail were first reared with a ball in 15–20-individual groups for 3 weeks from hatching. Then, each experimental subject was allocated either a familiar congener (CONG) or a familiar object (BALL). At 6 weeks of age the birds were fitted with a telemetric device to collect motor and cardiac activities. After that, each subject was exposed first to a separation from its cage-mate/familiar object, and secondly to the (re-)introduction of either the cage-mate/familiar object or of an unknown conspecific/another ball. Emotional responses were assessed through behavioural reactions and heart rate variability.Before being separated, both BALL and CONG quail showed stereotyped pacing that was more pronounced in BALL quail. BALL quail were not affected by the ball withdrawal, unlike CONG quail which reacted to the separation from their cage-mate by reducing activity and exploratory behaviour (P < 0.05). After the re-introduction, BALL quail remained closer to their ball and CONG quail spent more time with “stretched necks” than before the separation (P < 0.05). Surprisingly, CONG quail showed less stereotyped pacing when their partner was removed and recovered the initial level of stereotyped behaviour when their cage-mate was re-introduced (P < 0.01). Likewise, CONG quail also recovered the initial values of heart rate after the re-introduction of their cage-mate, indicating an increase in sympathetic activity compared to the isolation period. When the unfamiliar congener or ball was introduced in their cage, BALL quail pecked the unknown ball more than the familiar ball and had more contact with it (P < 0.05) and CONG quail had more contact with the unknown congener than with the cage-mate (P < 0.05).In conclusion, the quail appeared to experience a negative affective state before being separated, and there was no clear evidence of negative emotion in quail in response to the separation from either a social partner or an inanimate object. Nevertheless, the emotional responses of the quail in reaction to the (re-)introduction was influenced by the familiarity of the congener or the ball. Finally, changes in the quail's social environment induced more behavioural and cardiac modifications than changes in its non-social environment.     

迷走神经背核的研究进展

迷走神经背核（ＤＭＶ）是一个重要的内脏运动核团和内脏感觉核团。ＤＭＶ与中枢及外周存在广泛的纤维联系。ＤＭＶ和孤束核、最后区一起构成了“迷走感觉运动中枢”。ＤＭＶ存在神经－体液回路,使ＤＭＶ神经元可以直接感受外周血及脑脊液中的信息。ＤＭＶ含乙酰胆碱、儿茶酚胺、神经肽类等多种递质及相应受体。ＤＭＶ参与中枢调节胃肠、心血管及内分泌等生理功能。     

Effects of Muscarinic Agonists and Depolarizing Agents on Inositol Monophosphate Accumulation in the Rabbit Vagus Nerve

The effects of muscarinic agonists and depolarizing agents on inositol phospholipid hydrolysis in the rabbit vagus nerve were assessed by the measurement of [3H]inositol monophosphate production in nerves that had been preincubated with [3H]inositol. After 1 h of drug action, carbachol, oxotremorine, and arecoline increased the inositol monophosphate accumulation, though the maximal increase induced by these agonists differed. Addition of the muscarinic antagonists atropine or pirenzepine shifted the carbachol dose-response curves to the right, without decreasing the carbachol maximal stimulatory effects. The KB for pirenzepine was 35 nM, which is characteristic of muscarinic high-affinity binding sites coupled to phosphoinositide turnover and often associated with the M1 receptor subtype. On the other hand, agents known to depolarize or to increase the intracellular Ca2+ concentration, e.g., elevated extracellular K+, ouabain, Ca2+, and the Ca2+ ionophore A23187, also increased inositol monophosphate accumulation. These effects were not mediated by the release of acetylcholine, as suggested by the fact that they could not be potentiated by the addition of physostigmine nor inhibited by the addition of atropine. The Ca(2+)-channel antagonist Cd2+, also known to inhibit the Na+/Ca2+ exchanger, was able to block the effects of K+ and ouabain, but did not alter those of carbachol. These results suggest that depolarizing agents increase inositol monophosphate accumulation in part through elevation of the intracellular Ca2+ concentration and that muscarinic receptors coupled to phosphoinositide turnover are present along the trunk of the rabbit vagus nerve.     

Fine structure of the autonomic nerves of the rabbit myometrium

Summary The fine structure of the preterminal nerve fibers of the rabbit myometrial smooth muscle was studied using potassium permanganate fixation or glutaraldehyde fixation with postosmification. The preterminal fibers were mostly formed by 2–10 axons enveloped by Schwann cells. Two kinds of axons and axon terminals were found. (1) Adrenergic axons, which contained many small, granular vesicles (diameter 300–600 Å) and large granular vesicles (diameter 700–1200 Å) which represented ca. 2% of the total count of the vesicles. (2) Nonadrenergic axons, which contained small agranular vesicles (diameter 300–600 Å) and large granular vesicles (diameter 700–1200 Å). Both types of axons formed preterminal varicosities along their course. The real terminal varicosities, representing the anatomical end of the axons, were usually larger than the preterminal ones and showed close contact to the plasma membranes of the smooth muscle cells. Both adrenergic and nonadrenergic terminals were found close to the smooth muscle cells, but a gap of at least 2000 Å was always present between the two cell membranes. The axons and preterminal varicosities of both types of nerves were in intimate contact with each other within the preterminal nerve fiber. Axo-axonal interactions between the two types of axons are possible in the rabbit myometrium. The relative proportion of the nonadrenergic axons from the total was about one fourth.     

Ectoderm removal prevents cutaneous nerve formation and perturbs sensory axon growth in the chick hindlimb

Target tissues are thought to provide important cues for growing axons, yet there is little direct evidence that they are essential for axonal pathfinding. Here we examined whether target ectoderm is necessary for the formation of cutaneous nerves, and for the normal growth and guidance of cutaneous axons as they first enter the limb plexus. To do this, we removed a patch of ectoderm from the chick hindlimb at various times during early axon outgrowth. We find there is a critical period when cutaneous nerve formation requires target ectoderm. When the ectoderm is absent during this time, axons progress into the limb more slowly and, although a few sensory axons occasionally diverge a short distance from the plexus, they do not form a discrete nerve that travels to the skin. A few days later, when the nerve pattern is mature, axons normally destined for the 'deprived' cutaneous nerve are not segregated appropriately within the plexus. Some cutaneous axons are instead misdirected along an inappropriate cutaneous nerve, while others have seemingly failed to reach their correct target, or a suitable alternative, and died. These results demonstrate that the target ectoderm is necessary for normal sensory axon growth and guidance in the hindlimb.     

Evolutionary origin of autonomic regulation of physiological activities in vertebrate phyla

Proper regulation of physiological activities is crucial for homeostasis in animals. Autonomic regulation of these activities is most developed in mammals, in which a part of peripheral nervous system, termed the autonomic nervous system plays the dominant role. Circulatory activity and digestive activity in vertebrates change in opposite phases to each other. The stage where circulatory activity is high and digestive activity is low is termed the "fight or flight stage" while the stage where circulatory activity is low and digestive activity is high is termed the "rest and digest stage". It has been thought that the autonomic nervous system originated in early vertebrate phyla and developed to its greatest extent in mammals. In this study, we compared the pattern of change of circulatory and digestive activities in several invertebrates and found that the two stages seen in mammals are also present in a wide variety of animals, including evolutionarily early-diverging invertebrate taxa. From this and other arguments we propose a novel possibility that the basic properties of the autonomic nervous system were established very early in metazoan evolution.     

Neuronal organization of the ascidian (Urochordata) branchial basket revealed by cholinesterase activity

Summary Innervation of the ascidian branchial basket and other structures is demonstrated by staining for cholinesterase. Cholinesterase activity is not restricted to synaptic sites but is present throughout the neurons. Primary and secondary axonal bundles form a bilaterally symmetric innervation pattern around the large dorsal visceral nerve. These bundles continue to split into progressively smaller bundles as they course throughout the basket. Axons are suspended in a fibrous matrix and run within the blood sinuses on the atrial side of the basket. Stigmatal ciliated cells of the branchial basket are innervated by highly branched distal portions of neurons, whose cell bodies are located in the ganglion. Synaptic boutons, containing electron-lucent vesicles, are found at nearly all stigmatal ciliated cells. NiCl₂backfills of the visceral nerve reveal a distinct population of central neurons, some of which presumably control ciliary arrest.