Dose-finding study of fluoxetine and venlafaxine for the treatment of self-injurious and stereotypic behavior in rhesus macaques (Macaca mulatta)

The short-term effects on rates and durations of self-injurious behavior and self-directed stereotypies associated with various doses of fluoxetine (FLX) and venlafaxine (VEN) were examined in rhesus macaques. Adult male macaques (Macaca mulatta; n = 17; age, 7 to 15 y) with at least 1 episode of severe SIB within the past 5 y were randomized to treatment with FLX (n = 6), VEN (n = 6), or placebo (PLC, n = 5), administered by voluntary consumption of medication provided in fruit-flavored tablets. After 4-wk baseline and 4-wk placebo lead-in phases, doses were increased monthly for 4 mo (FLX: 0.5, 2.0, 4.0, and 8.0 mg/kg; VEN: 2.0, 4.0, 8.0, and 16.0 mg/kg). Animals in the PLC condition received similar nonmedicated fruit-flavored tablets. Focal behavioral observations, plasma drug levels, and neurochemical data were obtained. Results indicated that rates and percentage time spent self-biting declined at all doses of FLX, with the greatest effect seen at 2.0 mg/kg. For VEN, percentage time spent self-biting was significantly lower only at the 4.0 mg/kg dose. Treatment-induced reductions in platelet serotonin and cerebrospinal fluid 5-hydroxyindoleacetic acid (CSF 5HIAA) concentrations were substantially greater in the FLX-treated condition than in the VEN-treated condition. Plasma FLX and norfluoxetine levels increased with FLX dose; plasma levels of VEN were low and not dose-related. Fluoxetine at a dose of 2.0 mg/kg daily was most efficacious in reducing SIB, and the observed reductions in platelet serotonin and CSF 5HIAA levels indicated substantial bioeffect at this dose. Treatment with VEN was marked by noncompliance, low bioeffect, and low efficacy.

Interactions in predicting mood from extraversion and neuroticism

Many researchers have found evidence that, when only marginal distributions are examined, extraversion is related primarily to positive affect, whereas neuroticism is related primarily to negative affect. Recent findings have suggested that extraversion and neuroticism interact in predicting mood so that marginal relations could be misleading. The present study used extraversion (and its components, sociability and impulsivity) along with neuroticism in regression equations including interactive and curvilinear components to predict measures of positive and negative affect. Results confirm earlier findings that extraversion and neuroticism interact in predicting both positive and negative affect. The interaction pattern was similar to previous findings. Both positive and negative affect were strongly related to extraversion only among neurotic subjects.

Interactions in predicting mood from extraversion and neuroticism

Many researchers have found evidence that, when only marginal distributions are examined, extraversion is related primarily to positive affect, whereas neuroticism is related primarily to negative affect. Recent findings have suggested that extraversion and neuroticism interact in predicting mood so that marginal relations could be misleading. The present study used extraversion (and its components, sociability and impulsivity) along with neuroticism in regression equations including interactive and curvilinear components to predict measures of positive and negative affect. Results confirm earlier findings that extraversion and neuroticism interact in predicting both positive and negative affect. The interaction pattern was similar to previous findings. Both positive and negative affect were strongly related to extraversion only among neurotic subjects.