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Parvocellular Neurons (parvocellular + neuron)

Distribution by Scientific Domains

Medical Sciences	33%

Selected Abstracts

Prokineticin 2 depolarizes paraventricular nucleus magnocellular and parvocellular neurons

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 2 2007
Erik A. Yuill
Abstract Blind whole-cell patch-clamp techniques were used to examine the effects of prokineticin 2 (PK2) on the excitability of magnocellular (MNC), parvocellular preautonomic (PA), and parvocellular neuroendocrine (NE) neurons within the hypothalamic paraventricular nucleus (PVN) of the rat. The majority of MNC neurons (76%) depolarized in response to 10 nm PK2, effects that were eliminated in the presence of tetrodotoxin (TTX). PK2 also caused an increase in excitatory postsynaptic potential (EPSP) frequency, a finding that was confirmed by voltage clamp recordings demonstrating increases in excitatory postsynaptic current (EPSC) frequency. The depolarizing effects of PK2 on MNC neurons were also abolished by kynurenic acid (KA), supporting the conclusion that the effects of PK2 are mediated by the activation of glutamate interneurons within the hypothalamic slice. PA (68%) and NE (67%) parvocellular neurons also depolarized in response to 10 nm PK2. However, in contrast to MNC neurons, these effects were maintained in TTX, indicating that PK2 directly affects PA and NE neurons. PK2-induced depolarizations observed in PA and NE neurons were found to be concentration-related and receptor mediated, as experiments performed in the presence of A1MPK1 (a PK2 receptor antagonist) abolished the effects of PK2 on these subpopulations of neurons. The depolarizing effects of PK2 on PA and NE neurons were also shown to be abolished by PD 98059 (a mitogen activated protein kinase (MAPK) inhibitor) suggesting that PK2 depolarizes PVN parvocellular neurons through a MAPK signalling mechanism. In combination, these studies have identified separate cellular mechanisms through which PK2 influences the excitability of different subpopulations of PVN neurons. [source]

Postnatal handling alters the activation of stress-related neuronal circuitries

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 8 2000
István M. Ábrahám
Abstract Postnatal handling, as a crucial early life experience, plays an essential role in the development of hypothalamo-pituitary,adrenal axis responses to stress. The impact of postnatal handling on the reactivity of stress-related neuronal circuitries was investigated in animals that were handled for the first 21 days of life and as adults they were exposed to physical (ether) or emotional (restraint) challenge. To assess neuronal activation we relied on the induction of immediate-early gene product c-Fos and analysed its spatial and temporal distribution at various time intervals after stress. Ether and restraint commonly activated parvocellular neurons in the hypothalamic paraventricular nucleus, and resulted in activation of brain areas providing stress-related information to the hypothalamic effector neurons and/or in regions governing autonomic and behavioural responses to stress. Beyond these areas, the strength and timing of c-Fos induction showed stressor specificity in olfactory and septal region, basal ganglia, hypothalamus, hippocampal formation, amygdala and brainstem. Handled rats displayed a lower number of c-Fos-positive cell nuclei and weaker staining intensity than non-handled controls in the hypothalamic paraventricular nucleus, bed nucleus of stria terminalis, central nucleus of amygdala, hippocampus, piriform cortex and posterior division of the cingulum. Significant differences were revealed in timing of c-Fos induction as a function of stressor and early life experience. Together, these data provide functional anatomical evidence that environmental enrichment in the early postnatal period attenuates the reactivity of stress-related neuronal circuitries in the adult rat brain. [source]

Gender-related changes in the avian vasotocin system during ontogeny

MICROSCOPY RESEARCH AND TECHNIQUE, Issue 1 2001
Aleksandr Jurkevich
Abstract The arginine vasotocin (AVT) system of the avian brain includes a sexually dimorphic part that extends from the caudal part of preoptic region through the medial part of the bed nucleus of stria terminalis (BSTm) to the lateral septum. It is composed of the parvocellular neurons located in the BSTm and the dense innervation of the medial preoptic region and lateral septum. In this part of the brain, AVT expression is stronger in males than in females in a few bird species investigated to date. This review focuses on the ontogeny of sexual differences in the vasotocinergic system of two gallinaceous species, domestic chicken and Japanese quail, and on the role of gonadal hormones in organizing during development and maintaining in adulthood these differences. Parvocellular AVT neurons become discernible in the BSTm of males and females during the second half of embryonic development. These cells undergo a profound and irreversible sexual differentiation during ontogenetic development. Recent findings demonstrate a dual role of estrogens in the organization and activation of sex differences in the AVT system. During the embryonic period of ontogeny, estrogens differentiate the AVT system in a sexually dimorphic manner in parallel with the differentiation of sexual behavior, while in adulthood estrogens, locally produced from testosterone in the male brain, activate AVT synthesis in the BSTm. The sexually dimorphic part of the AVT system is sensitive to a number of abiotic factors such as light, temperature, and water availability. It is suggested that sex dimorphic vasotocinergic systems could be implicated in processes of social recognition in various behavioral contexts. Microsc. Res. Tech. 55:27,36, 2001. © 2001 Wiley-Liss, Inc. [source]

Proceedings of the Australian Physiological and Pharmacological Society Symposium: The Hypothalamus HYPOTHALAMIC PARAVENTRICULAR NUCLEUS AND CARDIOVASCULAR REGULATION

CLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 1-2 2001
Emilio BadoerArticle first published online: 10 DEC 200
SUMMARY 1. The hypothalamic paraventricular nucleus (PVN) is an important integrative site within the brain composed of magnocellular and parvocellular neurons. It is known to influence sympathetic nerve activity. 2. The parvocellular PVN contains neurons that project to the intermediolateral cell column of the thoraco,lumbar spinal cord (IML). This defines the PVN as an autonomic ,premotor nucleus', one of only five present within the brain. 3. Another projection arising from the PVN is a prominent innervation of the pressor region of the rostral ventrolateral medulla (RVLM), also a premotor nucleus. The distribution of the PVN neurons projecting to the RVLM is similar to that of the PVN neurons that project to the IML. 4. It has been found that up to 30% of spinally projecting neurons in the PVN also send collaterals to the RVLM. Thus, there are neurons in the PVN that can: (i) directly influence sympathetic nerve activity (via PVN,IML connections); (ii) indirectly influence sympathetic nerve activity (via PVN,RVLM connections); and (iii) both directly and indirectly influence sympathetic nerve activity (via neurons with collaterals to the IML and RVLM). 5. In the rat, results of studies using the protein Fos to identify activated neurons in the brain suggest that neurons in the PVN with projections to the IML or RVLM may be activated by decreases in blood volume. 6. In conclusion, the PVN can influence sympathetic nerve activity. Within the PVN are neurons with anatomical connections that enable them to affect sympathetic nerve activity either directly, indirectly or via both mechanisms (via collaterals). Studies that have examined the role of specific subgroups within the PVN suggest that PVN neurons with connections to the IML or to the RVLM may play a role in the reflex changes in sympathetic nerve activity that are involved in blood volume regulation. [source]