Different effects on the responses of functional pre- and postsynaptic 5-HT1A receptors by repeated treatment of rats with the 5-HT1A receptor agonist 8-OH-DPAT

Adult mice with reduced Nurr1 expression: an animal model for schizophrenia

“…The tissue concentrations of DA, homovanillic acid (HVA), 4-dihydroxyphenylacetic acid (DOPAC); serotonin (5-HT); 5-hydroxyindoleacetic acid (5-HIAA), and noradrenaline (NA) were determined in each brain region by high-performance liquid chromatography (HPLC) with electrochemical detection according to a method previously described. 28 The ratio of 5-HIAA/5-HT, DOPAC/DA and HVA/DA were calculated as an index of transmitter turnover. The mobile phase (pH 2.59) used was phosphate/phosphoric acid buffer (0.1 M NaH 2 PO 4 / 30 mM H 3 PO 4 ), sodium octylsulphate (0.29 g/l) and 12.5% methanol.…”

Effect of Chronic Serotonin-2 Receptor Agonist or Antagonist Administration on Serotonin-1A Receptor Sensitivity

“…Chronic treatment of rats with the 5-HT 1A receptor agonist 8-OH-DPAT (Larsson et al 1990) or with a variety of antidepressants, including monoamine oxidase inhibitors, tricyclic antidepressants, and selective serotonin reuptake inhibitors (Goodwin et al 1987a;Hensler et al 1991) results in the attenuation of 8-OH-DPAT-induced hypothermia. The serotonin syndrome, of which forepaw treading is a component, is also attenuated by chronic antidepressant treatment (Lucki and Frazer 1982;Goodwin et al 1987a;Maj et al 1996) or chronic 5-HT 1A receptor agonist administration (Kennett et al 1987;Larsson et al;Wieland et al 1993).…”

“…5 Modulation of 5-HT 1A Receptor Sensitivity 355 1985 responses mediated by the 5-HT 1A receptor is decreased after chronic administration of 5-HT 1A receptor agonists or antidepressants drugs. The desensitization of 5-HT 1A receptor-mediated responses has also been reported to occur after acute or short-term agonist administration (Kennett et al 1987;Larsson et al 1990). Although some investigators have reported changes in 5-HT 1A receptor number following agonist or antidepressant treatments (Welner et al 1989;Fanelli and McMonagle-Strucko 1992), in many cases desensitization of 5-HT 1A receptor-mediated responses has not been found to be accompanied by a decrease 5-HT 1A receptor number (Larsson et al 1990;Schecter et al 1990;Hensler et al 1991;Wieland et al 1993).…”

“…The desensitization of 5-HT 1A receptor-mediated responses has also been reported to occur after acute or short-term agonist administration (Kennett et al 1987;Larsson et al 1990). Although some investigators have reported changes in 5-HT 1A receptor number following agonist or antidepressant treatments (Welner et al 1989;Fanelli and McMonagle-Strucko 1992), in many cases desensitization of 5-HT 1A receptor-mediated responses has not been found to be accompanied by a decrease 5-HT 1A receptor number (Larsson et al 1990;Schecter et al 1990;Hensler et al 1991;Wieland et al 1993). Changes in 5-HT 1A receptor second messenger function have not been consistently reported to follow administration of antidepressants or 5-HT 1A receptor agonists (Sleight et al 1988;Varrault et al 1991;Newman et al 1992).…”

“…Although this may be caused by the presence of residual drug in the binding assay, perhaps a more likely explanation in view of the ample wash-out period (i.e., cortical homogenates were prepared from animals sacrificed 48 hours after the last injection of antagonist), is that chronic antagonist administration alters the affinity of the receptor. Our data indicate that the sensitivity of 5-HT 1A receptor-mediated forepaw treading or hypothermia is not altered by 5-HT 2A receptor antagonist treatments, suggesting that the downregulation of 5-HT 2A receptors is insufficient to alter postsynaptic 5-HT 1A receptor-mediated responses.Chronic treatment of rats with the 5-HT 1A receptor agonist 8-OH-DPAT (Larsson et al 1990) or with a variety of antidepressants, including monoamine oxidase inhibitors, tricyclic antidepressants, and selective serotonin reuptake inhibitors (Goodwin et al 1987a;Hensler et al 1991) results in the attenuation of 8-OH-DPAT-induced hypothermia. The serotonin syndrome, of which forepaw treading is a component, is also attenuated by chronic antidepressant treatment (Lucki and Frazer 1982;Goodwin et al 1987a;Maj et al 1996) or chronic 5-HT 1A receptor agonist administration (Kennett et al 1987;Larsson et al;Wieland et al 1993).…”