Effect of fluoxetine on blood concentrations of serotonin, cortisol and dehydroepiandrosterone in canine aggression

Abstract

Canine aggression directed towards people is the most frequent reason for referral to behaviour practices. The serotonergic system and the hypothalamic-pituitary-adrenal (HPA) axis are believed to play an important role in controlling aggression. The selective serotonin reuptake inhibitor fluoxetine is the most commonly used drug in canine aggression. The aim of the present study was to assess the effect of a 30-day-long fluoxetine treatment on the peripheral serotonergic system and the HPA axis in canine aggression. To this end, the concentrations of serum serotonin (5-HT) and plasma cortisol and dehydroepiandrosterone (DHEA) were analysed in a group of aggressive (n = 22) and nonaggressive dogs (n = 9) during pre- (day 0) and posttreatment (day 30) conditions. Treatment caused a significant decrease in 5-HT concentrations (46% in the aggressive group and 32% in the control group). There was a trend towards a rise of DHEA/cortisol ratio values after treatment both in the aggressive and the control group. The determination of blood 5-HT and the DHEA/cortisol ratio could have important clinical applications in the future for deciding which animals might benefit from a given treatment as well as for monitoring the response. Further large-scale studies with this aim should be carried out to obtain sound conclusions.

Acute Exposure to Fluoxetine Alters Aggressive Behavior of Zebrafish and Expression of Genes Involved in Serotonergic System Regulation

“…In addition, we observed that acute exposure to a high dose fluoxetine concentration resulted in increased whole-body cortisol in males of both coping styles, compared to the respective non-treated individuals. This observation is contrary with the function of fluoxetine as a common anti-stress drug, and with several publications on zebrafish (Egan et al, 2009; de Abreu et al, 2014) and other species (Rosado et al, 2011; Piwowarska et al, 2012), showing a significant decrease in cortisol concentrations following fluoxetine treatment. However, it has to be noted that the majority of these studies deals with chronic fluoxetine treatment.…”

Behavior in dogs with spontaneous hypothyroidism during treatment with levothyroxine

“…Thyroid status also affects the turnover of monoamines, specifically serotonin, in several centers of the central nervous system . Serotonin has been associated with what has previously been called “dominance aggression” in dogs, and the serotonin 2A receptor has been demonstrated to be a valid biomarker for aggressive and anxious behavior in dogs . In our study, the serum concentration of serotonin during thyroid supplementation was not significantly different from baseline.…”

“…Involvement of the serotonergic system in dogs with aggression has been established in several reports based on the measurement of serotonin concentrations in blood or cerebrospinal fluid (CSF), functional brain imaging, or by the successful use of drugs influencing serotonergic neurotransmission, namely selective serotonin reuptake inhibitors . Thyroid hormones appear to affect the concentrations of serotonin in blood and different brain regions and modulate serotonin turnover in the brain .…”

Making the Case for Multi-Axis Assessment of Behavioural Problems

“…Firstly, traits may reflect underlying relatively stable individual differences in biological systems, which could be the target of biological therapies, including drugs, synthetic pheromones, and dietary modification or supplementation. An example of this is the use of fluoxetine to treat problems of aggression in dogs where there is also a lack of impulse control; the individual's inability to withhold the aggressive response is the primary target of the drug [8]. Secondly, trait assessment could enable us to make predictions about the animal's likely behaviour in a wide range of situations; for example, when it is faced with a novel or potentially stressful situation.…”