The effect of serotonin 5HT1B receptor ligands on amphetamine self-administration in rats

A number of data indicate that serotonin (5-HT) 5-HT(1B) receptor ligands affect the behavioral effects of psychostimulants. In the present study we examined effects of the selective 5-HT(1B) receptor antagonist N-[3-[3-(dimethylamino)ethoxy]-4-methoxyphenyl]-2'-methyl-4'-(5-methyl-1,2,4-oxadiazol-3-yl)-[1,1'-biphenyl]-4-carboxamide hydrochloride (SB 216641) and the agonist 5-propoxy-3-(1,2,3,6-tetrahydro-4-pyridinyl)-1H-pyrrolo[3,2-b]pyridine hydrochloride (CP 94253) on amphetamine self-administration in rats. SB 216641 administered in doses of 2.5-7.5 mg/kg did not affect the self-administration of amphetamine injected in unit doses of 0.06 or 0.12 mg/kg/infusion. On the other hand, CP 94253 administered in doses of 2.5 or 5 mg/kg attenuated amphetamine self-administration, yet the effect of 2.5 mg/kg of the agonist was fairly weak and significant only in case of a higher unit dose of the psychostimulant. The inhibitory effect of CP 94253 administered in a dose of 5mg/kg on the self-administration of amphetamine injected in a unit dose of 0.06 mg/kg/infusion was significantly reduced by SB 216641 administrated in a dose of 7.5 mg/kg. These results indicate that tonic activation of 5-HT(1B) receptors is not involved in the self-administration of amphetamine, while pharmacological stimulation of these receptors attenuates this behavioral phenomenon.