Effects of (2R)‐(3‐amino‐2‐fluoropropyl)sulphinic acid (AFPSiA) on transient lower oesophageal sphincter relaxation in dogs and mechanism of hypothermic effects in mice

• Published in: British journal of pharmacology 2005-09, Vol.146 (1), p.89-97
• Main Authors: Lehmann, Anders, Holmberg, Ann Aurell, Bhatt, Ulhas, Bremner‐Danielsen, Marianne, Brändén, Lena, Elg, Susanne, Elebring, Thomas, Fitzpatrick, Kevin, Geiss, William B, Guzzo, Peter, Jensen, Jorgen, Jerndal, Gunilla, Mattsson, Jan P, Nilsson, Karolina, Olsson, Britt‐Marie
• Format: Article
• Language: English
• Subjects: Animals; Biological and medical sciences; Body Temperature - drug effects; Brain - drug effects; Brain - metabolism; Calcium - metabolism; CHO Cells; Cricetinae; Cricetulus; Deglutition - drug effects; Dogs; Esophageal Sphincter, Lower - drug effects; Esophageal Sphincter, Lower - physiology; Esophagus; Female; GABA Agonists - pharmacology; GABA-A Receptor Agonists; GABA-B Receptor Agonists; GABA-B Receptor Antagonists; GABAA; GABAB; Gastroenterology. Liver. Pancreas. Abdomen; gastrointestinal motility; Gastro‐oesophageal reflux disease; Hypothermia - chemically induced; Medical sciences; Mice; Muscle Relaxation - drug effects; Other diseases. Semiology; Pharmacology. Drug treatments; Rats; Rats, Sprague-Dawley; Rats, Wistar; Receptors, GABA-A - metabolism; Receptors, GABA-B - metabolism; Sulfinic Acids - adverse effects; Sulfinic Acids - pharmacology; Synaptic Vesicles - drug effects; Synaptic Vesicles - metabolism; transient lower oesophageal sphincter relaxation
• ISSN: 0007-1188; 1476-5381
• DOI: 10.1038/sj.bjp.0706299

The effects of the novel GABA analogue (2R)‐(3‐amino‐2‐fluoropropyl)sulphinic acid (AFPSiA) on transient lower oesophageal sphincter relaxations (TLOSRs) were studied in the dog. In addition, the GABAA/GABAB selectivity was determined in vitro and in vivo, and the pharmacokinetics and the metabolism of the compound were studied in the dog and rat. TLOSRs were reduced by 55±8% after intragastric administration of AFPSiA at 14 μmol kg−1 and did not decrease further at higher doses. When evaluated 2 and 4 h after administration, the effect declined to 37±6 and 16±9%, respectively. Spontaneous swallowing was only significantly inhibited at 100 μmol kg−1. The oral availability of AFPSiA was 52±17 and 71±4% in the dog and rat, respectively. A fraction of AFPSiA was oxidised to the corresponding sulphonate, (2R)‐(3‐amino‐2‐fluoropropyl)sulphonic acid (AFPSoA) after oral administration to the rat and dog. In rat brain membranes, AFPSiA was found to have ten times higher affinity for rat brain GABAB (Ki=47±4.4 nM) compared to GABAA (Ki=430±46 nM) binding sites. The compound was a full agonist at human recombinant GABAB(1a,2) receptors (EC50=130±10 nM). In contrast, the metabolite AFPSoA was considerably more selective for binding to rat brain GABAA (Ki=37±3.1 nM) vs GABAB (Ki=6800±280 nM) receptors. In the mouse, high doses (1–8 mmol kg−1) of AFPSiA induced a rapid and mild hypothermia followed by a profound and sustained hypothermia at the higher doses tested (6 and 8 mmol kg−1). This effect was unaffected by the selective GABAB receptor antagonist CGP62349. AFPSoA (1 and 2 mmol kg−1) produced transient and moderate hypothermia while the hypothermic response was considerably larger at 4 mmol kg−1. It is concluded that AFPSiA inhibits but does not abolish TLOSRs in the dog. High doses of the compound induce hypothermia in the mouse, which probably is attributable to activation of the GABAA receptor. The latter effect may be caused both by AFPSiA and its oxidised sulphonic acid metabolite AFPSoA. British Journal of Pharmacology (2005) 146, 89–97. doi:10.1038/sj.bjp.0706299