328
P. Janssen et al
5-HT receptors in dog proximal stomach
that the dog 5-HT
2
Overall, the obtained anities strongly point to 5-HT7
receptor involvement.
7
receptor expresses higher anity for SB-
contraction in the canine distal stomach (antropyloric tissue)
(Prins et al., 2001b). This ®rmly establishes the pharmacolo-
gical impact of 5-HT7 receptor stimulation in the dog
stomach in vitro. It remains to be determined as to whether
7
69970 than the human or guinea-pig 5-HT receptor.
The pK
B
for mesulergine against 5-CT agrees well with the
anity estimates obtained in 5-HT receptor bioassays of the
7
this is translated into a signi®cant role of 5-HT receptor
stimulation as a trigger for dog gastric relaxation in vivo.
7
guinea-pig ileum (7.8; Carter et al., 1995), rat jejunum (8.1;
McLean & Coupar, 1996) and human colon (8.3; Prins et al.,
Conclusion
1
5
999). Thus, the antagonism by mesulergine emphasizes that
-HT7 receptors mediate relaxation in this bioassay of dog
5-HT elicits both contraction and relaxation in canine
proximal stomach longitudinal muscle strips via 5-HT
receptors located on the smooth muscle cells. The receptor
mediating contraction has the characteristics of a 5-HT2A
stomach.
In the presence of ketanserin (0.3 mM), the 5-HT-induced
relaxation could be competitively antagonized by SB-269970
and mesulergine. The estimates obtained are in good
receptor, while the receptor mediating relaxation is a 5-HT
receptor.
7
7
agreement with literature anities at 5-HT receptors and
thus strongly point to 5-HT receptors mediating relaxation
7
in this bioassay of canine proximal stomach. This ®nding is
not surprising since we recently reported smooth muscle 5-
HT7 receptors mediating inhibition of electrically induced
The authors wish to thank Marcel Sysmans for his technical
assistance.
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British Journal of Pharmacology vol 136 (2)