Table 1.
Summary of GABAB receptor-induced effects on gastrointestinal motility.
| Region | Species | Baclofen induced-effect | Reference |
|---|---|---|---|
| Duodenum/jejunum | Human | TTX sensitive inhibition of spontaneous and DMPP-induced contraction | Gentilini et al. (1992) |
| Rat | Reduction in electrically evoked cholinergic contraction | Krantis and Harding (1987) | |
| Disruption of migrating motor complex activity (i.v. administration) | Fargeas et al. (1988) | ||
| Atropine-sensitive increase in migrating motor complex activity (i.c.v. administration) | |||
| Ileum | Guinea-pig | Decrease in electrically evoked (cholinergic) twitch response | Ong and Kerr (1982) and Marcoli et al. (2000) |
| Relaxation (all levels of the intestine) Inhibition of somatostatin inhibitory activity on cholocystokinin-induced contraction (cholinergic) | Ong and Kerr (1987) Roberts et al. (1993) | ||
| TTX- and hyoscine-sensitive relaxation (basal) and hyoscine-sensitive relaxation following histamine and prostaglandin F2α stimulation | Giotti et al. (1983) | ||
| Inhibition of electrically stimulated NO-mediated relaxation | Kilbinger et al. (1999) | ||
| Mouse | Inhibition of electrically evoked contraction (GABAB1+/+) Loss of baclofen-induced relaxation (GABAB1−/−) | Sanger et al. (2002) | |
| Cat | Contraction of longitudinal muscle (distal and terminal ileum; modest if any sensitivity to atropine and TTX) and no effect on circular muscle activity | Pencheva et al. (1999) | |
| No effect (proximal ileum) on longitudinal or circular muscle activity | |||
| Intestine | Dog | Reduction of circular muscle motor activity coupled with a decrease in ACh release (intra arterial administration) | Kawakami et al. (2004) |
| Colon | Human | No effect | Gentilini et al. (1992) |
| Guinea-pig | Decrease in fecal pellet expulsion and TTX-sensitive relaxation | Ong and Kerr (1982) | |
| Decrease in basal and physostigmine-induced tone (i.v. administration) | Giotti et al. (1985) | ||
| TTX and scopolamine-sensitive relaxation | Giotti et al. (1985) and Minocha and Galligan (1993) | ||
| Rat | Increase in electrically evoked cholinergic and non-cholinergic circular muscle contraction that is sensitive to nicotinic receptor blockade | Bayer et al. (2003) | |
| Rabbit | Modest decrease in resting tone and inhibition of electrically-induced (cholinergic) contraction. Inhibition of NANC neurotransmission and decreased transit | Tonini et al. (1989) |
ACh, acetylcholine; DMPP, dimethylphenylpiperazinium; i.v. intravenous; i.c.v. intracerbroventricular; NANC, non-adrenergic non-cholinergic; NO, nitric oxide; TTX, tetrodotoxin. Unless otherwise noted in italicize, all drug additions were to in vitro preparations.