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Electrophysiological and iontophoretic aspects of the habenular influence on hippocampal neurones.
- Source :
-
Archives of physiology and biochemistry [Arch Physiol Biochem] 1995 Apr; Vol. 103 (1), pp. 59-63. - Publication Year :
- 1995
-
Abstract
- In previous experimental studies, carried out on cats, we demonstrated that electrical stimulation of lateral habenula (LH) at 0.5-3.0 Hz or 5-20 Hz had a double effect (low frequency-excitation; high frequency-inhibition) on the spontaneous firing rate of single hippocampal neurones. Our results, in agreement with similar case studies, allowed us to hypothesise that in the habenular modulation of the hippocampus the raphe nucleus is probably involved. In fact, all the effects of LH stimulation were antagonised by the iontophoretic intrahippocampal application of methysergide. In the present series of experiments, performed on rats, it was possible to demonstrate that LH stimulation at 1-10 Hz causes an excitation of a progressively major number of hippocampal neurones depending upon the increase of frequency stimulation. The absence of habenulo-induced effects after a iontophoretic application of methysergide on single hippocampal units suggests the involvement of the raphe nucleus. Furthermore, in consideration of recent anatomical evidences demonstrating an excitatory projection between LH and raphe nucleus, intraraphal N-methyl-D-aspartate (NMDA) application, performed through a Hamilton microsyringe, induces an inhibitory effect. All the results suggest that in the raphe context it is possible to hypothesise the presence of an intrinsic interneurone, directly activated by the excitatory projection arising from the LH; this interneurone is likely inhibitory on the serotonergic raphe-hippocampus efferent neurone. This functional organization is responsible for the effect of LH stimulation at different frequencies as well as for the effects of intraraphal NMDA application.
- Subjects :
- Animals
Electric Stimulation
Electrophysiology
Hippocampus drug effects
Iontophoresis
Male
Methysergide administration & dosage
Methysergide pharmacology
N-Methylaspartate pharmacology
Raphe Nuclei drug effects
Raphe Nuclei physiology
Rats
Rats, Wistar
Serotonin physiology
Cochlea physiology
Hippocampus physiology
Neurons physiology
Subjects
Details
- Language :
- English
- ISSN :
- 1381-3455
- Volume :
- 103
- Issue :
- 1
- Database :
- MEDLINE
- Journal :
- Archives of physiology and biochemistry
- Publication Type :
- Academic Journal
- Accession number :
- 8574779
- Full Text :
- https://doi.org/10.3109/13813459509007565