title: Histamine restores hemorrhage induced hypotension by activating cholinergic neurons in nucleus tractus solitarius.
abstract: The purpose of the current study is to investigate the functional connections between the central histaminergic and cholinergic systems at NTS level in hypotensive condition. Experiments were carried out in male Wistar Albino rats. The hypotension was achieved by withdrawing a total volume of 1.5ml blood/100g bodyweight over a period of 10min. A microdialysis study was performed in NTS area to measure extracellular ACh and Ch levels. The hemorrhage produced a severe and long-lasting decrease in mean arterial blood pressure (MAP) and increase in extracellular ACh and Ch levels in NTS. Administration of histamine intracerebroventricularly (i.c.v.) or into the NTS reversed the hemorrhagic hypotension by increasing MAP and heart rate. I.c.v. injection of histamine also caused the additional increase in extracellular ACh and Ch levels. Moreover, central histamine injection augmented intracytoplasmic AChE immunoreactivity in NTS. These changes were completely blocked by histaminergic H1 receptor antagonist chlorpheniramine, but histaminergic H2 receptor blocker ranitidine and histaminergic H3/H4 receptor antagonist thioperamide failed to produce these effects. In conclusion, these findings are interpreted that brain histaminergic H1 receptor activation by central histamine injection may promote cholinergic stimulation in the NTS and subsequently reverses the hypotension.
authors.affiliation: Department of Physiology, Faculty of Veterinary Medicine, Uludag University, Bursa 16059, Turkey.
authors.forename: Burcin
authors.initials: B
authors.lastname: Altinbas
authors.affiliation: Department of Physiology, Faculty of Veterinary Medicine, Uludag University, Bursa 16059, Turkey.
authors.forename: Gokcen
authors.initials: G
authors.lastname: Guvenc
authors.affiliation: Department of Physiology, Faculty of Veterinary Medicine, Uludag University, Bursa 16059, Turkey.
authors.forename: Leman G
authors.initials: LG
authors.lastname: Erkan
authors.affiliation: Department of Histology and Embryology, Faculty of Veterinary Medicine, Uludag University, Bursa 16059, Turkey.
authors.forename: Tuncay
authors.initials: T
authors.lastname: Ilhan
authors.affiliation: Department of Physiology, Faculty of Veterinary Medicine, Uludag University, Bursa 16059, Turkey.
authors.forename: Nasir
authors.initials: N
authors.lastname: Niaz
authors.affiliation: Department of Physiology, Faculty of Veterinary Medicine, Uludag University, Bursa 16059, Turkey. Electronic address: muraty@uludag.edu.tr.
authors.forename: Murat
authors.initials: M
authors.lastname: Yalcin
keywords: Cardiovascular system; Central cholinergic system; Hemorrhagic hypotension; Histamine; Nucleus tractus solitarius