RATIONALE:

5-HT(1B) receptors are thought to be one of the receptor subtypes that mediate the inhibitory control of serotonin on food intake and satiety.

OBJECTIVE:

To use the selective 5-HT(1B) receptor agonist, CP-94,253 as a probe of 5-HT(1B) receptor function in feeding behaviour, and to confirm the pharmacological selectivity of CP-94,253-induced hypophagia with a range of antagonists.

METHODS:

Dose-response functions for CP-94,253 (0, 1.25, 2.5, 5.0 mg/kg; IP) were determined in animals consuming wet mash in a 40-min test session during which time-sampled behavioural observations were collected to evaluate satiety sequences. A meal patterning study was carried out in a separate group of rats. The 5-HT(1A) antagonist WAY 100,635 (0, 1.0, 3.0 mg/kg; SC), the 5-HT(1B/1D)antagonist GR 127,935 (0, 3 mg/kg; IP), and the 5-HT(1B) antagonist SB 224289 (0, 2.5, 5.0 mg/kg; IP) were used to confirm that 5-HT(1B) receptor subtypes were responsible for the action of CP-94,253 on feeding behaviour.

RESULTS:

CP-94,253 (2.5 mg/kg) reduced food intake and preserved the satiety sequence in animals consuming a diet of mash. GR 127,935 (3.0 mg/kg) and SB 224289 (2.5 mg/kg), but not WAY 100,635, attenuated the hypophagic effect of the 5-HT(1B) agonist, and returned the changes in satiety sequence to control patterns. Meal patterning analyses indicated that CP-94,253 (2.5 mg/kg) reduced food intake through a decrease in meal size and duration in the absence of any alteration in the rate of eating. A hypodipsic action of CP-94,253 was also observed (2.5 and 5.0 mg/kg).

CONCLUSION:

These findings imply that 5-HT(1B) receptors regulate discrete elements of satiety. We discuss the potential role of 5-HT(1B) agonists for the treatment of obesity.