Injections of muscimol into the median raphe nucleus produce hippocampal theta rhythm in the urethane anesthetized rat

1995 ◽  
Vol 120 (3) ◽  
pp. 244-248 ◽  
Author(s):  
G. G. Kinney ◽  
B. Kocsis ◽  
R. P. Vertes
Keyword(s):  
Theta Rhythm ◽  
Raphe Nucleus ◽  
Median Raphe ◽  
Median Raphe Nucleus ◽  
Hippocampal Theta Rhythm ◽  
Hippocampal Theta ◽  
Median Raphé

scholarly journals GABAergic Control of the Ascending Input From the Median Raphe Nucleus to the Limbic System

2005 ◽  
Vol 94 (4) ◽  
pp. 2561-2574 ◽  
Author(s):  
Shaomin Li ◽  
Viktor Varga ◽  
Attila Sik ◽  
Bernat Kocsis
Keyword(s):  
Limbic System ◽  
Theta Rhythm ◽  
Raphe Nucleus ◽  
Median Raphe ◽  
Median Raphe Nucleus ◽  
Hippocampal Theta Rhythm ◽  
Theta Waves ◽  
Short Period ◽  
Hippocampal Theta ◽  
Median Raphé

The median raphe nucleus (MRN) is the primary source of serotonergic afferents to the limbic system that are generally considered to suppress hippocampal theta oscillations. GABA receptors are expressed in the MRN by serotonergic and nonserotonergic cells, including GABAergic and glutamatergic neurons. This study investigated the mechanisms by which the fluctuating GABA tone in the MRN leads to induction or suppression of hippocampal theta rhythm. We found that MRN application of the GABAA agonist muscimol (0.05–1.0 mM) or GABAB agonist baclofen (0.2 mM) by reverse microdialysis had strong theta promoting effects. The GABAA antagonist bicuculline infused in low concentrations (0.1, 0.2 mM) eliminated theta rhythm. A short period of theta activity of higher than normal frequency preceded hippocampal desynchronization in 46% of rats. Bicuculline in larger concentrations (0.5, 1.0, 2.0 mM) resulted in a biphasic response of an initial short (<10 min) hippocampal desynchronization followed by stable theta rhythm that lasted as long as the infusion continued. The frequency and amplitude of theta waves were higher than in control recordings and the oscillations showed a conspicuous intermittent character. Hippocampal theta rhythm elicited by MRN administration of bicuculline could be completely (0.5 mM bicuculline) or partially (1.0 mM bicuculline) blocked by simultaneous infusion of the GABAB antagonist CGP35348 . Our findings suggest that the GABAergic network may have two opposing functions in the MRN: relieving the theta-generators from serotonergic inhibition and regulating the activity of a theta-promoting circuitry by the fluctuating GABA tone. The two mechanisms may be involved in different functions.

Discharge properties of neurons of the median raphe nucleus during hippocampal theta rhythm in the rat

2002 ◽  
Vol 145 (3) ◽  
pp. 383-394 ◽  
Author(s):  
Gonzalo Viana Di Prisco ◽  
Zimbul Albo ◽  
Robert P. Vertes ◽  
Bernat Kocsis
Keyword(s):  
Theta Rhythm ◽  
Raphe Nucleus ◽  
Median Raphe ◽  
Median Raphe Nucleus ◽  
Hippocampal Theta Rhythm ◽  
Hippocampal Theta ◽  
Median Raphé
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