Serotonin and Tryptophan Serum Concentrations in Shelter Dogs Showing Different Behavioural Responses to a Potentially Stressful Procedure.

Giacomo Riggio,Angelo Gazzano,Chiara Mariti,Silvana Diverio,Valeria Sergi

doi:10.3390/vetsci8010001

Giacomo Riggio, Angelo Gazzano + Show 3 more

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https://doi.org/10.3390/vetsci8010001

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Journal: Veterinary sciences	Publication Date: Dec 24, 2020
Citations: 6	License type: CC BY 4.0

Affiliation: University of Pisa, University of Perugia

Abstract

In mammals, serotonin (5-HT) levels depend on the availability of tryptophan (TRP). Low 5-HT concentrations have been linked to behavioural disorders in dogs. This study aimed at investigating possible differences in dogs’ serum TRP and 5-HT concentrations according to their behavioural response to a potentially stressful procedure. Thirty-nine physically healthy shelter dogs, 15 females and 24 males, mean age = 5.6 years, were categorized by a certified veterinary behaviourist according to their behavioural response to medical examination and blood collection, in: relaxation, stress signals, tension without growling, tension with growling, escape attempts, and aggression attempts. Extraction and quantification of 5-HT and TRP were performed using a HLPC method. Data were statistically analysed, applying Chi-square and Spearman tests. Results showed no significant difference in TRP (χ2 = 2.084, p = 0.555) nor 5-HT (χ2 = 0.972, p = 0.808) serum concentrations among different categories of dogs; however, some categories were underrepresented (relaxation = 20.5%, stress signals = 30.8%, tension without growling = 43.6%, tension with growling = 5.1%, escape attempts = 0%, aggression attempts = 0%). No correlation between serum TRP and 5-HT concentrations was found (ρ = 0.086, p = 0.602). Serum 5-HT levels do not seem to be associated with dogs’ behavioural response to a stressful situation nor with serum TRP concentrations. The relationship between serum TRP and 5-HT concentrations and behaviour needs further research.

Highlights

Serotonin (5-HT) is a monoamine neurotransmitter implicated in the regulation of a variety of physiological processes, cognitive functions, emotional states and behaviours in mammals [1,2,3]
No significant differences in either TRP (χ2 = 2.084, p = 0.555) nor 5-HT (χ2 = 0.972, p = 0.808) serum concentrations were found between dogs that remained relaxed (TRP: median = 99.52800, min–max = 70.385–115.660; 5-HT: median = 181.37201, min–max = 73.103–320.319), dogs that displayed signs of stress (TRP: median = 115.56432, min–max = 65.483–139.347; 5-HT: median = 156.12664, min–max = 29.928–392.737), dogs that appeared tense but did not growl (TRP: median = 108.06257, min–max = 58.335–157.304; 5-HT: median = 185.62264, min–max = 56.950–430.186), and those that were tense and did growl (TRP: median = 97.22486, min–max = 62.545–131.905; 5-HT: median = 227.85393, min–max = 14.994–314.714)
No correlation between serum TRP and 5-HT levels were found in our sample of shelter dogs

Summary

Introduction

Serotonin (5-HT) is a monoamine neurotransmitter implicated in the regulation of a variety of physiological processes, cognitive functions, emotional states and behaviours in mammals [1,2,3]. 5-HT and CSF 5-HIAA have been linked to increased aggressive behaviour [10,11,12,13] and impulsivity [14], whereas high 5-HT plasma concentrations have been linked to anxious states [15]. Alongside exerting a fundamental role in the biosynthesis of proteins, TRP is the obligatory substrate for the production of 5-HT in the gut and in the brain [17]. In the latter, the synthesis of 5-HT consists of a two-step process during which TRP is initially hydroxylated to 5-hydroxytryptophan by the enzyme

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