Median raphe serotonergic innervation of medial septum/diagonal band of Broca (MSDB) parvalbumin-containing neurons: Possible involvement of the MSDB in the desynchronization of the hippocampal EEG

Coronal vibratome sections of the rostral part of the medial septum (MS) and vertical limb of the diagonal band of Broca (VDB) nuclei were studied by an immunocytochemical technique using a monoclonal antibody against choline acetyltransferase (ChAT) and a double histochemical method for detection of acid phosphatase (AcPase) and nucleoside diphosphatase (NDPase) activity. The electron microscopic morphology of ChAT-immunoreactive and non-immunoreactive neurons was compared with similar neurons showing both AcPase and NDPase activity. ChAT-labeled and non-labeled neurons were well differentiated by the organization of the endomembrane system and especially by the structure of the rough endoplasmic reticulum (RER) and associated lamellar bodies. These results support the theory that the peculiar ultrastructure of the lamellar bodies in each neuron is related to the pattern of organization of the endomembrane system and its function. The significance of the lamellar bodies is discussed, and the data of the present work, together with findings described by other investigators. These data suggest that these bodies are predominant in efferent projection neurons in the basal forebrain nuclei.

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A distinctive subpopulation of medial septal slow-firing neurons promote hippocampal activation and theta oscillations

Journal of Neurophysiology ◽

10.1152/jn.00267.2011 ◽

2011 ◽

Vol 106 (5) ◽

pp. 2749-2763 ◽

Cited By ~ 26

Author(s):

Hao Zhang ◽

Shih-Chieh Lin ◽

Miguel A. L. Nicolelis

Keyword(s):

Medial Septum ◽

Theta Oscillations ◽

Short Term ◽

Neuronal Ensembles ◽

Gamma Range ◽

Diagonal Band ◽

Hippocampal Activity ◽

Diagonal Band Of Broca ◽

Hippocampal Theta ◽

Relationship Of

The medial septum-vertical limb of the diagonal band of Broca (MSvDB) is important for normal hippocampal functions and theta oscillations. Although many previous studies have focused on understanding how MSVDB neurons fire rhythmic bursts to pace hippocampal theta oscillations, a significant portion of MSVDB neurons are slow-firing and thus do not pace theta oscillations. The function of these MSVDB neurons, especially their role in modulating hippocampal activity, remains unknown. We recorded MSVDB neuronal ensembles in behaving rats, and identified a distinct physiologically homogeneous subpopulation of slow-firing neurons (overall firing <4 Hz) that shared three features: 1) much higher firing rate during rapid eye movement sleep than during slow-wave (SW) sleep; 2) temporary activation associated with transient arousals during SW sleep; 3) brief responses (latency 15∼30 ms) to auditory stimuli. Analysis of the fine temporal relationship of their spiking and theta oscillations showed that unlike the theta-pacing neurons, the firing of these “pro-arousal” neurons follows theta oscillations. However, their activity precedes short-term increases in hippocampal oscillation power in the theta and gamma range lasting for a few seconds. Together, these results suggest that these pro-arousal slow-firing MSvDB neurons may function collectively to promote hippocampal activation.

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