The Effects of Electrolytic Lesions of the Median Raphe Nucleus on Fixed Interval Responding in Rats

2002 ◽  
Author(s):  
Chris Jones ◽  
David Wirtshafter
Keyword(s):  
Fixed Interval ◽  
Raphe Nucleus ◽  
Median Raphe ◽  
Median Raphe Nucleus ◽  
Electrolytic Lesions ◽  
Median Raphé

Does serotonin play a role in entrance into hibernation?

1986 ◽  
Vol 251 (4) ◽  
pp. R755-R761 ◽  
Author(s):  
B. Canguilhem ◽  
J. L. Miro ◽  
E. Kempf ◽  
P. Schmitt
Keyword(s):  
Anterior Part ◽  
Raphe Nucleus ◽  
Median Raphe ◽  
Median Raphe Nucleus ◽  
Serotonergic Neurons ◽  
Electrolytic Lesions ◽  
Small Parts ◽  
The Brain ◽  
Median Raphé

To study the role of brain serotonin in entrance into hibernation, intraventricular injections of 5,7-dihydroxytryptamine, electrolytic lesions of small parts of the median raphe nucleus, and chemical lesions of the same nucleus were undertaken on the European hamster in winter. All the lesions led to a variable decrease of serotonin levels in all parts of the brain areas examined. However, hibernation was suppressed only in those animals whose serotonergic neurons were destroyed in a small anterior part of the median raphe nucleus. Electrolytic lesions as well as chemical lesions in the other parts of the median raphe nucleus or the 5,7-dihydroxytryptamine injections into lateral ventricles do not prevent hibernation. These data suggest that in the European hamster only a specific group of serotonergic neurons of the median raphe nucleus are involved in the process of entrance into hibernation.

scholarly journals Distinct Contributions of Median Raphe Nucleus to Contextual Fear Conditioning and Fear-Potentiated Startle

2002 ◽  
Vol 9 (4) ◽  
pp. 233-247 ◽  
Author(s):  
R. C. B. Silva ◽  
A. P. M. Cruz ◽  
V. Avanzi ◽  
J. Landeira-Fernandez ◽  
M. L. Brandão
Keyword(s):  
Fear Conditioning ◽  
Conditioned Fear ◽  
Raphe Nucleus ◽  
Contextual Fear Conditioning ◽  
Median Raphe ◽  
Median Raphe Nucleus ◽  
Contextual Fear ◽  
Electrolytic Lesions ◽  
Fear Potentiated Startle ◽  
Median Raphé

Ascending 5-HT projections from the median raphe nucleus (MRN), probably to the hippocampus, are implicated in the acquisition of contextual fear (background stimuli), as assessed by freezing behavior. Foreground cues like light, used as a conditioned stimulus (CS) in classical fear conditioning, also cause freezing through thalamic transmission to the amygdala. As the MRN projects to the hippocampus and amygdala, the role of this raphe nucleus in fear conditioning to explicit cues remains to be explained. Here we analyzed the behavior of rats with MRN electrolytic lesions in a contextual conditioning situation and in a fear-potentiated startle procedure. The animals received MRN electrolytic lesions either before or on the day after two consecutive training sessions in which they were submitted to 10 conditioning trials, each in an experimental chamber (same context) where they. received foot-shocks (0.6 mA, 1 sec) paired to a 4-sec light CS. Seven to ten days later, the animals were submitted to testing sessions for assessing conditioned fear when they were placed for five shocks, and the duration of contextual freezing was recorded. The animals were then submitted to a fear-potentiated startle in response to a 4-sec light-CS, followed by white noise (100 dB, 50 ms). Control rats (sham) tested in the same context showed more freezing than did rats with pre- or post-training MRN lesions. Startle was clearly potentiated in the presence of light CS in the sham-lesioned animals. Whereas pretraining lesions reduced both freezing and fear-potentiated startle, the post-training lesions reduced only freezing to context, without changing the fear-potentiated startle. In a second experiment, neurotoxic lesions of the MRN with local injections of N-methyl-D-aspartate or the activation of5-HT1Asomatodendritic auto-receptors of the MRN by microinjections of the5-HT1Areceptor agonist 8-hydroxy- 2-(di-n-propylamino)tetralin (8-OH-DPAT) before the training sessions also reduced the amount of freezing and the fear-potentiated startle. Freezing is a prominent response of contextual fear conditioning, but does not seem to be crucial for the enhancement of the startle reflex by explicit aversive cues. As fear-potentiated startle may be produced in posttraining lesioned rats that are unable to freeze to fear contextual stimuli, dissociable systems seem to be recruited in each condition. Thus, contextual fear and fear-potentiated startle are conveyed by distinct 5-HT-mediated circuits of the MRN.

Intra-median raphe nucleus (MRN) infusions of muscimol, a GABA-A receptor agonist, reinstate alcohol seeking in rats: role of impulsivity and reward

2007 ◽  
Vol 195 (4) ◽  
pp. 605-615 ◽  
Author(s):  
Anh Lê Dzung ◽  
Douglas Funk ◽  
Stephen Harding ◽  
Walter Juzytsch ◽  
Zhaoxia Li ◽  
...  
Keyword(s):  
Receptor Agonist ◽  
Raphe Nucleus ◽  
Median Raphe ◽  
Median Raphe Nucleus ◽  
Gaba A ◽  
Median Raphé ◽  
Alcohol Seeking

Early postnatal stress affects the 5-HTergic and GABAergic function of the median raphe nucleus in adult rats

2010 ◽  
Vol 68 ◽  
pp. e396
Author(s):  
Kohtarou Konno ◽  
Machiko Matsumoto ◽  
Takeshi Izumi ◽  
Hiroko Togashi ◽  
Takayuki Yoshida ◽  
...  
Keyword(s):  
Raphe Nucleus ◽  
Median Raphe ◽  
Median Raphe Nucleus ◽  
Adult Rats ◽  
Postnatal Stress ◽  
Gabaergic Function ◽  
Median Raphé
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