Effects of carbenoxolone on syncytial electrical properties and junction potentials of guinea-pig vas deferens

Abstract

The effects of the putative gap junction blocker carbenoxolone on smooth muscle syncytial properties and junction potentials were studied in guinea pig vas deferens (GPVD). Treatment with 50 muM carbenoxolone reversibly and significantly increased input resistance (R (in)) (by 682.5 +/- 326.0 %, P < 0.05) and abolished cable potentials within 6-7 mins of incubation, without disturbing resting membrane potential. Carbenoxolone reversibly and significantly increased the amplitude of spontaneous excitatory junction potentials (sEJPs) by 96.9 +/- 35.45% (P < 0.05), shifted their amplitude distribution rightwards, and reduced their frequency of occurrence by 58.17 +/- 17.7% (P < 0.05), without altering their time courses. Similarly, carbenoxolone increased the amplitude of evoked excitatory junction potentials (eEJPs) by 17.7 +/- 5.88% and tau (decay) by 19.43 +/- 8.29% (P < 0.05). Our results indicate that carbenoxolone alters the electrical properties and junctional potentials of the GPVD by a mechanism consistent with a relatively specific block of gap junctions. These results suggest that gap junction mediated cell-to-cell communication may significantly modulate the electrical properties and junctional potentials of the GPVD and consequently the physiological functioning of this tissue.

The Role of L- and T-Type Calcium Channels in Local and Remote Calcium Responses in Rat Mesenteric Terminal Arterioles

“…3). In previous studies, both palmitoleic acid and carbenoxolone were shown to inhibit gap junctional communication in a concentration-dependent manner without extra-junctional effects at the concentrations used in the present study [17,27,28,29]. The role of gap junctions for conducted vasomotor responses was originally proposed by Segal et al [2 ]and Segal and Duling [5] based on studies performed in hamster cheek pouch arterioles.…”

A computational model of urinary bladder smooth muscle syncytium

“…For instance, our studies show that for syncytia of larger sizes, the input resistance of a cell is markedly affected following changes in intercellular coupling, while the effect is limited in smaller syncytia. Experimentally, measuring the input resistance before and after the application of agents that reportedly modulate gap junctional conductance, such as carbenoxolone (Palani et al 2006;De Groot et al 2003), 18β-glycyrrhetinc acid (18β-GA) (Hashitani et al 2001) and 2-aminoethoxydiphenylborate (2-APB) (Hashitani et al 2004), could furnish information regarding the size of the syncytium in which the recorded cell is located. Simultaneous electrical and optical recordings, such as those conducted for vas deferens (Young et al 2007), could be carried out to verify the correlations our model postulates between SEJP properties and syncytial size.…”

Some Comparative Immunohistochemical Studies on the Ductus Deferens in the Donkey (Equus asinus) and Water Buffalo Bull (Bubalus bubalis).

“…The immunohistochemical findings in the present work assume that the lack of Cx43-IR, in the donkey, may be compensated by the S100immunoreactive dense network of nerves both in the lamina propria and tunica muscularis. Occurrence of gap junctions (Cx-binding sites) might reveal the reciprocal relationships between the ductal epithelium and the periductal components, necessary for regu-lation of the different functions (Segretain and Falk, 2004;Palani et al, 2006;Hejmej et al, 2007) of the duct.…”