Endogenous histamine in the medial septum-diagonal band complex increases the release of acetylcholine from the hippocampus: a dual-probe microdialysis study in the freely moving rat.
The effects of histaminergic ligands on both ACh spontaneous release from the hippocampus and the expression of c-fos in the medial septum-diagonal band (MSA-DB) of freely moving rats were investigated. Because the majority of cholinergic innervation to the hippocampus is provided by MSA-DB neurons, we used the dual-probe microdialysis technique to apply drugs to the MSA-DB and record the induced effects in the projection area. Perfusion of MSA-DB with high-KCl medium strongly stimulated hippocampal ACh release which, conversely, was significantly reduced by intra-MSA-DB administration of tetrodotoxin. Histamine or the H2 receptor agonist dimaprit, applied directly to the hippocampus, failed to alter ACh release. Conversely, perfusion of MSA-DB with these two compounds increased ACh release from the hippocampus. Also, thioperamide and ciproxifan, two H3 receptor antagonists, administered into MSA-DB, increased the release of hippocampal ACh, whereas R-alpha-methylhistamine, an H3 receptor agonist, produced the opposite effect. The blockade of MSA-DB H2 receptors, caused by local perfusion with the H2 receptor antagonist cimetidine, moderated the spontaneous release of hippocampal ACh and antagonized the facilitation produced by H3 receptor antagonists. Triprolidine, an H1 receptor antagonist, was without effect. Moreover, cells expressing c-fos immunoreactivity were significantly more numerous in ciproxifan- or thioperamide-treated rats than in controls, although no colocalization of anti-c-fos and anti-ChAT immunoreactivity was observed. These results indicate a role for endogenous histamine in modulating the cholinergic tone in the hippocampus.
Bacciottini
Lucia
L
Dipartimento di Farmacologia Preclinica e Clinica, Universitá di Firenze, V.le G. Pieraccini 6, Italy.
Passani
Maria Beatrice
MB
Giovannelli
Lisa
L
Cangioli
Iacopo
I
Mannaioni
Pier Francesco
PF
Schunack
Walter
W
Blandina
Patrizio
P
D000109:Acetylcholine / Q000378:metabolism*; D000818:Animals; D006624:Hippocampus / Q000378:metabolism*; D006632:Histamine / Q000502:physiology*; D017442:Histamine Agonists / Q000008:administration & dosage / Q000494:pharmacology; D006633:Histamine Antagonists / Q000008:administration & dosage / Q000494:pharmacology; D006634:Histamine H1 Antagonists / Q000494:pharmacology; D007093:Imidazoles / Q000494:pharmacology; D008297:Male; D017551:Microdialysis; D009474:Neurons / Q000378:metabolism; D010477:Perfusion; D010880:Piperidines / Q000494:pharmacology; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D018100:Receptors, Histamine H3 / Q000187:drug effects; D012686:Septal Nuclei / Q000166:cytology / Q000378:metabolism*; D013779:Tetrodotoxin / Q000008:administration & dosage / Q000494:pharmacology; D014311:Triprolidine / Q000494:pharmacology
D017442:Histamine Agonists; D006633:Histamine Antagonists; D006634:Histamine H1 Antagonists; D007093:Imidazoles; D010880:Piperidines; D016760:Proto-Oncogene Proteins c-fos; D018100:Receptors, Histamine H3; D014311:Triprolidine; D013779:Tetrodotoxin; C115705:ciproxifan; D006632:Histamine; C052075:thioperamide; D000109:Acetylcholine