A study of the reciprocal relationship between the thermal and behavioral effects mediated by anandamide.
The endocannabinoid system plays an important role in thermal control and modulates several behaviors, such as locomotion and food intake (FI) that may affect the body temperature (Tb). To test whether the changes in Tb induced by anandamide (AEA) are related to behavioral changes, adult Wistar rats received an intracerebroventricular injection of AEA (0.1, 1.0 and 10.0 μg) and vehicle. Total FI was weighted daily, and Tb and spontaneous locomotor activity (SLA) were simultaneously and continuously recorded. AEA induced an increase in Tb without changing SLA and FI. For all doses tested, the Tb average in the post-injection period was higher than in the pre-injection period. The higher thermal effect was verified using a dose of 10.0 μg AEA, starting within the first hour post-injection, and was maintained for 8h after treatment. A dose-dependent thermal effect was observed (r=0.953; p<0.05) at 1h post-injection. Hypoactivity was verified only at a dose of 1.0 μg AEA. As expected, both the Tb and SLA values during the dark phase were always higher than during the light phase and were positively correlated (r=0.834, p<0.001); however, this correlation was inverted (r=-0.852, p<0.01) after the rats received 10.0 μg AEA. In summary, our results suggest that brain AEA induces an increase in Tb, and that this effect may occur independently of changes in both locomotion and FI. Moreover, it is possible that the hypolocomotion induced by AEA could be an adaptive response to the increased Tb.
Departamento de Fisiologia e Biofísica, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais 31270-901, Brazil.
Paulo Marcelo Andrade
PM
Lima
Departamento de Fisiologia e Biofísica, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais 31270-901, Brazil.
Frederico S M
FS
Machado
Departamento de Fisiologia e Biofísica, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais 31270-901, Brazil. Electronic address: coimbrac@icb.ufmg.br.
Cândido C
CC
Coimbra
D000818:Animals; D001095:Arachidonic Acids / Q000494:pharmacology*; D001831:Body Temperature / Q000187:drug effects*; D063385:Cannabinoid Receptor Modulators / Q000494:pharmacology*; D002940:Circadian Rhythm / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D063388:Endocannabinoids / Q000494:pharmacology*; D008297:Male; D009043:Motor Activity / Q000187:drug effects*; D053284:Polyunsaturated Alkamides / Q000494:pharmacology*; D017208:Rats, Wistar; D013997:Time Factors
D001095:Arachidonic Acids; D063385:Cannabinoid Receptor Modulators; D063388:Endocannabinoids; D053284:Polyunsaturated Alkamides; C078814:anandamide
Endocannabinoid; Food intake; Locomotor activity; Temperature