title: The location of pacemakers in the uteri of pregnant guinea pigs and rats.
abstract: The pregnant uterus is a smooth muscle organ whose pattern of contraction is dictated by the propagation of electrical impulses. Such electrical activity may originate from one or more pacemakers, but the location of these sites has not yet been determined. To detect the location of the pacemaker in the gravid uterus, two approaches were used: 1) determine the site from where the contraction started using isolated uteri from the pregnant guinea pig, and videotape their contractions; and 2) record, in isolated uteri from pregnant term rats, with 240 extracellular electrodes simultaneously, and determine where the electrical bursts started. In both the contractile and electrophysiological experiments, there was not a single, specific pacemaker area. However, most contractions (guinea pig 87%) and bursts (rat 76%) started close to the mesometrial border (mean 2.7 ± 4.0 mm SD in guinea pigs and 1.3 ± 1.4 mm in rats). In addition, in the rat, most sites of initiations were located closer to the ovarial end of the horn (mean distance from the ovarial end 6.0 ± 6.2 mm SD), whereas such an orientation was not seen in the guinea pig. In both guinea pig and rat uteri at term, there is not one specific pacemaker area. Rather, contractile and electrical activity may arise from any site, with the majority starting close to the mesometrial border. Furthermore, in the rat, most activities started at the ovarial end of the horn. This may suggest a slightly different pattern of contraction in both species.
authors.affiliation: Department of Physiology, College of Medicine and Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates; and wlammers@smoothmap.org.
authors.forename: Wim J E P
authors.initials: WJ
authors.lastname: Lammers
authors.affiliation: Department of Physiology, College of Medicine and Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates; and.
authors.forename: Betty
authors.initials: B
authors.lastname: Stephen
authors.affiliation: Department of Physiology, College of Medicine and Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates; and.
authors.forename: Mahmood Ahmed
authors.initials: MA
authors.lastname: Al-Sultan
authors.affiliation: Department of Physiology, College of Medicine and Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates; and.
authors.forename: Sandeep B
authors.initials: SB
authors.lastname: Subramanya
authors.affiliation: Division of Translational and Systems Medicine, Warwick Medical School, Clinical Sciences Research Laboratory, Coventry, United Kingdom.
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Blanks
mesh_terms: D000200:Action Potentials; D000818:Animals; D001683:Biological Clocks / Q000502:physiology*; D004576:Electromyography; D005260:Female; D006168:Guinea Pigs; D066298:In Vitro Techniques; D011247:Pregnancy; D017208:Rats, Wistar; D013045:Species Specificity; D013997:Time Factors; D014590:Uterine Contraction; D014599:Uterus / Q000033:anatomy & histology / Q000502:physiology*; D014741:Video Recording
keywords: electrical activity; high-resolution electrical mapping; pregnant uterus