Prolonged 5-HT_IA/5-HT_2A receptor cross-talk is absent prior to adulthood in rats

In adult rats, serotonin IA (5-HT_Ia) receptor activation produces heterologous desensitization of serotonin 2A (5-HT_2a) neuroendocrine function at I h that persists up to 72 h. This study determined whether proloinfnged 5-HT_Ia/5-HT_2a cross-talk exists before sexual maturation. Adolescent male rats (postnatal day 39) received an injection with saline or ( + )- 8-hydroxy-2-(di-n-propyl-amino)tetralin hydrobromide [( + )8-OH-DPAT] 24 h before receiving a challenge injection of saline, ( + )-8-hydroxy-2-(di-n-propylamino)tetralin hydrobromide, or (-)-l-(2,5-dimethoxy-4- iodophenyl)-2-aminopropane HCl [(-)DOI] o assess changes in basal, 5-HT_Ia, and 5-HT_2A receptor-mediated hormone responses. Although homologous desensitization of 5-HT_IA neuroendocrine responses was present at 24 h, heterologous desensitization of 5-HT_2A neuroendocrine responses was not.These data suggest that 5-HT_IA heterologous desensitization of 5-HT_2A receptor function does not develop until adulthood, is more transient, or follows a different time course before maturation.