TY  - JOUR
TI  - Formalin Murine Model of Pain
AU  - López-Cano, Marc  
AU  - Fernández-Dueñas, Víctor 
AU  - Llebaria, Amadeu  
AU  - Ciruela, Francisco 
VL  - 7
IS  - 23
PY  - 2017
DA  - 2017/12/05
SP  - e2628
C1  - Bio-protocol 2017;7:e2628
DO  - 10.21769/BioProtoc.2628
UR  - https://doi.org/10.21769/BioProtoc.2628
AB  - Pain research is mostly based on experimental assays that use animal models, which may allow deciphering the physiopathology of this condition and to propel drug discovery. The formalin nociception test is considered one of the most predictive approaches to study acute pain in rodents. This test permits monitoring pain-related responses (i.e., itch) caused by a subcutaneous injection of an inflammatory agent, namely 2.5% formalin solution, in the hind paw. After the injection, two distinct time periods or phases of licking/biting behaviour occur, which are separated by a quiescent period. Importantly, these phases differ in duration and underlying mechanisms. Hence, the initial acute phase (phase I), commonly recorded for 5 min just after formalin administration, reflects acute peripheral pain, probably due to direct activation of nociceptors through TRPA1 channels. On the other hand, the phase II, which starts after the quiescent period (5-15 min) and is commonly recorded for 15-30 min, is due to the ongoing inflammatory input and central nociceptive sensitization. Here, we describe in detail the protocol used to perform a reliable and reproducible formalin test in mice.
KW  - Pain
KW  - Nociception
KW  - Inflammation
KW  - Analgesia
KW  - Mice
JF  - Bio-protocol
SN  - 2331-8325
PB  - Bio-protocol LLC.
BIO101  - False