EurekaMag.com logo
+ Site Statistics
References:
48,253,228
Abstracts:
22,798,842
+ Resolve Accession
+ Subscribe to Site Feeds
EurekaMag Most Shared ContentMost Shared
EurekaMag PDF Full Text ContentPDF Full Text
+ PDF Full Text
Request PDF Full TextRequest PDF Full Text
Submit PDF Full TextSubmit PDF Full Text
+ Follow Us
Follow on FacebookFollow on Facebook
Follow on TwitterFollow on Twitter
Follow on Google+Follow on Google+
Follow on LinkedInFollow on LinkedIn

+ Translate

Electrophysiological actions of norepinephrine in rat lateral hypothalamus ii. an in vitro study of the effects of iontophoretically applied norepinephrine on lh neuronal responses to gamma aminobutyric acid gaba


, : Electrophysiological actions of norepinephrine in rat lateral hypothalamus ii. an in vitro study of the effects of iontophoretically applied norepinephrine on lh neuronal responses to gamma aminobutyric acid gaba. Brain Research 446(1): 90-105

The preceding studies demonstrated that norepinephrine (NE) can consistently augment synaptically mediated (70%) and .gamma.-amino-butyric acid (GABA)-induced (69%) inhibitory responses of lateral hypothalamic (LH) neurons in vivo. The present experiments further characterized the interactions of NE with LH neuronal responses to GABA in terms of .alpha.- and .beta.-receptor mechanisms and demonstrated the utility of the in vitro LH tissue slice preparation as a model for future extra- and intracellular studies of NE modulatory phenomena. Extracellular activity of LH cells was recorded from diencephalic slices (450 .mu.m) incubated in artificial cerebrospinal fluid at 33.degree. C. Interactions between iontophoretically applied NE, isoproterenol (ISO) or phenylephrine (PE) and responses of LH neurons (n = 64) to GABA microiontophoresis were quantitated and characterized using computer-generated ratemeter and histogram records. This analysis revealed two distinct actions of NE on GABA-induced responses of LH neurons. In 8 of 32 cells tested (25%), locally applied NE markedly enhanced inhibitory responses to GABA iontophoresis in a manner identical to that observed in vivo. However, in 20 cells (62.5%), iontophoretic application of NE produced a clear antagonism of GABA responses. NE also exerted dual effects on the background firing rate of LH neurons, causing both inhibition and excitation. Overall, in those cells where NE administration increased spontaneous discharge, it either antagonized or had no effect on GABA-mediated inhibition. In contrast, spontaneous firing rate was never elevated above control levels in those cases where NE potentiated GABA responses. Additional experiments demonstrated that the GABA potentiating actions of the benzodiazepine, flurazepam, were preserved in LH tissue slice preparations. In addition, iontophoretic application of the .beta.-agonist, ISO, routinely suppressed the spontaneous activity of LH neurons and mimicked the facilitating action of NE on GABA. Likewise, microiontophoretic application of 8-bromo cyclic adenosine monophosphate (AMP) enhanced GABA-induced inhibition of LH firing rate in each of 11 cells tested. On the other hand, local administration of the alpha agonist, PE, routinely produced NE-like antagonism of GABA inhibition along with increases in spontaneous firing rate. Taken together these findings indicate that the commonly observed in vivo phenomena of NE augmentation of GABA and suppression of LH neuron spontaneous firing can be demonstrated in vitro, and most likely result from activation of beta adrenoceptors and subsequent elevation of cyclic AMP levels. As such these results suggest that the in vitro preparation will be a useful tool for further investigation of the transmembrane and intracellular events associated with noradrenergically mediated enhancement of GABA. However, in contrast to results obtained in vivo, NE antagonisms of GABA inhibition and excitatory effects on spontaneous activity were more frequently observed in LH slices and appear to be mediated by alpha receptor activation. The reduced capacity of NE to augment GABA in vitro might be related to changes in the balance between .alpha. and .beta.-mediated effects rather than deficits in GABA-facilitating mechanisms, since ISO, cyclic AMP and the benzodiazepine were all routinely capable of enhancing GABAergic responses.

(PDF 0-2 workdays service)

Order PDF Full Text

Close
Close

Click here to order any other PDF Full Text


Accession: 005349383

PDF Full Text: Submit


Submit PDF Full Text

No spam - Every submission is manually reviewed

Due to poor quality, we do not accept files from Researchgate

Submitted PDF Full Texts will always be free for everyone
(We only charge for PDFs that we need to acquire)

Select a PDF file:
Close
Close

Other references

Langmeier, J.; Langmeierová, D., 1977: Formation of the mother-child relationship. Ceskoslovenska Pediatrie 32(6): 345-349

Rambani, R.; Elnaggar, M.; Sturdee, S., 2011: Syndactyly with hallux valgus: a case report. Foot & Ankle International 32(6): 641-643

Bratt, E.; Ekblad, H.; Nycetlius, H.; Aperia, A.; Larsson, S.H., 1992: Transforming growth factor beta-1 inhibits proliferation but does not induce differentiation in infant renal epithelial cells. Pediatric Research 32(5): 626

Wu, R.S.S.; Lau, T.C., 1996: Polymer-ligands: A novel chemical device for monitoring heavy metals in the aquatic environment?. Major problems involved in using bio-indicators to monitor heavy metals in the marine environment include standardizing a great variety of physical and biological factors which have a significant effect on metal accumulation. The fact that differe...

Chalasani, N., 2005: Statins and hepatotoxicity: focus on patients with fatty liver. Hepatology 41(4): 690-695

Stead, N.; Kaplan, A.P.; Rosenberg, R.D., 1976: Inhibition of activated factor XII by antithrombin-heparin cofactor. The activation of Factor XII occurs via fragmentation of this zymogen into a diverse spectrum of enzymatically potent molecular species. To study the interaction of antithrombin-heparin cofactor and heparin with activated Factor XII, we have emplo...

Kachur, S.P.; Khatib, R.A.; Kaizer, E.; Fox, S.S.; Abdulla, S.M.; Bloland, P.B., 2004: Adherence to antimalarial combination therapy with sulfadoxine-pyrimethamine and artesunate in rural Tanzania. Artemisinin-containing antimalarial combination therapies are recommended to confront drug-resistant Plasmodium falciparum malaria. Among the questions surrounding whether these complex multidose treatments will be practical is to what extent pati...

Becker, W., 1971: Problem of female criminality. Therapie der Gegenwart 110(10): 1526-1538

Gasilin V.S.; Anikin V.V.; Lupanov V.P.; Mazaev V.P., 1982: Comparative evaluation of the results of bicycle ergometry and coronarography in patients with angina pectoris depending on the s t segment reaction on the electro cardiogram during physical exercise. A comparative study of the results of bicycle ergometry and angiocardiography was undertaken in 2 clinically homogeneous groups of patients with angina pectoris. One group was without ischemic displacement (group 1, 83 patients) and the other had...

Diener H.C.; Dichgans J.; Bruzek W.; Selinka H., 1982: Stabilization of human posture during induced oscillations of the body. Displacements of the center of foot pressure, the hip and the head were recorded in 6 subjects standing on a platform, sinusoidally tilting in pitch (anterior-posterior). Stimulus frequencies ranged between 0.01 and 1 Hz. Stimulus amplitudes were...