The discriminative stimulus properties of LY233708, a selective serotonin reuptake inhibitor, in the pigeon.

RATIONALE

Understanding the contribution of the various serotonin (5-HT) receptor subtypes to the behavioral effects of selective serotonin reuptake inhibitors (SSRIs) may contribute to the discovery of increasingly effective drugs for the treatment of conditions such as depression, panic and obsessive-compulsive disorders.

OBJECTIVES

A drug discrimination procedure was used to determine whether the administration of an SSRI was associated with a specific interoceptive stimulus cue and to what extent that cue was related to activation of the 5-HT(1A) receptor.

METHOD

Pigeons were trained to discriminate 20 mg/kg of the short acting, SSRI, LY233708 dihydrochloride dihydrate [(-)-cis-1-(6-chloro-1,2,3,4- tetrahydro-1-methyl-2-naphthalenyl)piperazine] from saline.

RESULTS

LY233708 induced a specific, dose-related stimulus cue. The SSRIs, fluoxetine and citalopram, induced dose-related responding on the LY233708-associated key. In contrast, nisoxetine, a selective norepinephrine uptake inhibitor, induced responding on the saline-associated key. The prototypical 5-HT(1A) agonist, 8-OH-DPAT [8-hydroxy-(2-di-n-propylamino)tetralin] substituted for LY233708. This generalization was blocked by the selective 5-HT(1A) antagonist, WAY-100635 [N-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-N-(2-pyridinyl) cyclohexanecarboxamide].

CONCLUSION

These data demonstrate that an SSRI can induce a specific, stable discriminative stimulus that appears to involve activation of the 5-HT(1A) receptor in the pigeon.