Discriminative stimulus properties of indorenate in a conditioned taste aversion paradigm.
Indorenate (5-methoxytryptamine beta-methylcarboxylate, INDO) is a serotonin (5-hydroxytryptamine, 5-HT) agonist that has affinity for 5-HT(1A/1B/2C) receptors. It possesses anxiolytic and antihypertensive actions mediated by 5-HT(1A) receptors and anorectic activity mediated by 5-HT(2C/1B) receptors. This study examined whether INDO may exert discriminative control using a conditioned taste aversion (CTA) paradigm, and whether differential participation of 5-HT receptor subtypes may be involved in its cue. Male Wistar rats trained to drink their daily water in a 30-min period were trained to discriminate INDO from saline. One group received the intraperitoneal administration of INDO (10.0 mg/kg) before saccharin-LiCl pairings; on alternate days, rats received saline before the saccharin-saline pairings (Group D(+)S(-)). The other group had the contingencies reversed (i.e., the administration of INDO preceded saccharin-saline pairings: Group D(-)S(+)). In two-bottle generalization tests (one bottle containing saccharin, the other plain water), the preference for saccharin was evaluated after different doses of INDO, [3H]-8-hydroxy-2-(di-N-propylamino)tetralin (8-OH-DPAT) (5-HT(1A)), buspirone (5-HT(1A)), RU24969 (5-HT(1A/1B)), TFMPP (5-HT(1B/2C)), MK212 (5-HT(2C)), alpha-Me-5-HT (5-HT(2C/2A)), 2-Me-5-HT (5-HT(3)) and cisapride (5-HT(4)). The results showed that INDO, RU24969, TFMPP, alpha-Me-5-HT and MK 212 produced a dose-dependent generalization; 8-OH-DPAT and buspirone produced only partial generalization, while 2-Me-5-HT and cisapride did not produce generalization. The results indicate that INDO administration may exert discriminative control over saccharin preference mediated mainly by 5-HT(1B/2C) receptors, but with an important contribution of 5-HT(1A) receptors.
Miranda
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F
ENEP-Iztacala, Facultad de Psicología, Universidad Nacional Autónoma de México, D.F., Mexico City, Mexico.
Hong
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E
Velázquez-Martínez
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DN
D008735:5-Methoxytryptamine / Q000031:analogs & derivatives* / Q000494:pharmacology*; D000818:Animals; D001362:Avoidance Learning / Q000187:drug effects*; D004192:Discrimination, Psychological / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D004326:Drinking / Q000187:drug effects; D005793:Generalization, Psychological / Q000187:drug effects; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D011985:Receptors, Serotonin / Q000187:drug effects*; D044263:Receptors, Serotonin, 5-HT1; D044406:Receptors, Serotonin, 5-HT3; D044422:Receptors, Serotonin, 5-HT4; D017366:Serotonin Receptor Agonists / Q000494:pharmacology*; D013649:Taste / Q000187:drug effects*
D011985:Receptors, Serotonin; D044263:Receptors, Serotonin, 5-HT1; D044406:Receptors, Serotonin, 5-HT3; D017366:Serotonin Receptor Agonists; D044422:Receptors, Serotonin, 5-HT4; D008735:5-Methoxytryptamine; C033600:indorenate