Basic and Clinical Neuroscience Journal
مجله علوم اعصاب پایه و بالینی
BCN
Medical Sciences
http://bcn.iums.ac.ir
137
journal137
2008-126X
2228-7442
10.32598/bcn
en
jalali
1392
11
1
gregorian
2014
2
1
5
1
online
1
fulltext
en
Termination of Nociceptive Bahaviour at the End of Phase 2 of Formalin Test is Attributable to Endogenous Inhibitory Mechanisms, but not by Opioid Receptors Activation
Behavioral Neuroscience
Behavioral Neuroscience
Original
Original
<p><b>Introduction:</b> Formalin injection induces nociceptive bahaviour in phase I and II, with a quiescent phase between them. While active inhibitory mechanisms are proposed to be responsible for initiation of interphase, the exact mechanisms which lead to termination of nociceptive response in phase II are not clear yet. Phase II is a consequence of peripheral and central sensitization processes, which can lead to termination of the noxious stimuli responses 45-60 minutes after formalin injection via possible recruitment of active inhibitory mechanisms which we have investigated in this study. </p>
<div><b>Methods:</b> To test our hypothesis, in the first set of experiments, we evaluated nociceptive response after two consecutive injection of formalin (50&muL, 2%), with intervals of 5 or 60 minutes. In the next set, formalin tests were carried out in companion with injection of Naloxone Hydrochloride, a non-selective antagonist of opioid receptors, pre-formalin injection and 30 and 45 minutes post formalin injection.
<div><b>Results:</b> While normal nociceptive behaviour was observed in the group receiving one injection of formalin, a diminished response was observed in phases I and II of those receiving consequent injection of formalin, 60 minute after first injection. While second injection of formalin, 5 minute after first injection, had no effect. Administration of naloxone (1mg/kg) decreased nociception in phase 2A but had no effect on delayed termination of formalin test. </div>
<div><b>Discussion:</b> The results of this study suggest the existence of an active inhibitory mechanism, other than the endogenous opioids, that is responsible for termination of nociceptive behaviour at the end of formalin test.</div>
</div>
Formalin Test, Nociception, Naloxone
48
54
http://bcn.iums.ac.ir/browse.php?a_code=A-10-1-195&slc_lang=en&sid=1
Hassan
Azhdari-Zarmehri
1370031947532846006441
1370031947532846006441
No
Department of Basic Sciences, Torbat heydariyeh University of Medical Sciences, Torbat heydariyeh, Iran.
Mohammad
Mohammad-Zadeh
1370031947532846006442
1370031947532846006442
Yes
Department of Physiology & Cellular and Molecular Research Center, Sabzevar University Of medical Sciences, Sabzevar, Iran.
Masoud
Feridoni
1370031947532846006443
1370031947532846006443
No
Department of Biology, Faculty of Sciences, Ferdowsi University of Mashhad, Mashhad, Iran.
Masoud
Nazeri
1370031947532846006444
1370031947532846006444
No
Medical Students Research Committee, Kerman Medical University, Kerman, Iran.