The aim of the present study was to determine whether alterations in 5- hydroxytryptamine (5-HT)(1A) receptors would be found in knockout mice lacking the serotonin transporter (5HTT). Hypothermic and neuroendocrine responses to the 5-HT(1A) agonist 8-hydroxy-2-(di-n-propylamino)tetraline (8- OHDPAT) were used to examine the function of 5-HT(1A) receptors. Initial studies evaluated the dose-response and time course of 8-OH-DPAT-induced hypothermia and hormone secretion in normal CD-1 mice (the background strain of the 5-HTT knockout mice). 8-OH-DPAT dose-dependently produced hypothermic responses that peaked at 20 min postinjection. 8-OHDPAT-induced hypothermia was blocked by the 5-HT(1A) antagonist WAY-100635. 8-OH-DPAT dose-dependently increased the concentrations of plasma oxytocin, corticotropin, and corticosterone. In the 5-HTT knockout (-/-) mice, the hypothermic response to 8-OH-DPAT (0.1 mg/kg s.c.) was completely abolished. Furthermore, 5-HTT-/- mice had significantly attenuated plasma oxytocin and corticosterone responses to 8-OH-DPAT. No significant changes in the hypothermic or hormonal responses to 8-OH-DPAT were observed in heterozygous (5-HTT+/-) mice. [3H]8- OH-DPAT- and [125I]MPPI [4-(2'-methoxyphenyl)-1-[2'-[N-(2'-pyridinyl)- iodobenzamido]ethyl]piperazine]-binding sites in the hypothalamus and [125I]MPPI-binding sites in the dorsal raphe were significantly decreased in 5-HTT-/- mice. The results indicate that lack of the 5-HTT- is associated with a functional desensitization of 5-HT(1A) receptor responses to 8-OH- DPAT, which may be a consequence, at least in part, of the decrease in density of 5-HT(1A) receptors in the hypothalamus and dorsal raphe of 5-HTT- /- mice.
|Original language||English (US)|
|Number of pages||9|
|Journal||Journal of Pharmacology and Experimental Therapeutics|
|State||Published - Dec 1999|
ASJC Scopus subject areas
- Molecular Medicine