en Experimental research article Experimental research article <span style="FONT-SIZE: 12pt FONT-FAMILY: "Palatino Linotype" mso-fareast-font-family: 'Times New Roman' mso-bidi-font-family: 'Times New Roman' mso-ansi-language: EN-US mso-fareast-language: EN-US mso-bidi-language: AR-SA">Recently, vast studies have been focused on the antinociceptive and anesthetic effects of α₂<i> </i>adrenergic receptors, using specific drugs such as medetomidine and dexmedetomidine. In the present study, we tried to assess the peripheral and central effects of dexmedetomidine in phasic and tonic pain, on rats, using tail flick and formalin tests. Dexmedetomidine, administered intraperitoneally (25, 50 and 100 </span><span style="FONT-SIZE: 12pt FONT-FAMILY: "Palatino Linotype" mso-fareast-font-family: 'Times New Roman' mso-bidi-font-family: 'Levenim MT' mso-ansi-language: EN-US mso-fareast-language: EN-US mso-bidi-language: AR-SA">µ</span><span style="FONT-SIZE: 12pt FONT-FAMILY: "Palatino Linotype" mso-fareast-font-family: 'Times New Roman' mso-bidi-font-family: 'Times New Roman' mso-ansi-language: EN-US mso-fareast-language: EN-US mso-bidi-language: AR-SA">g/kg, i.p.) or intracerebroventrically (7.5, 10 and 20 </span><span style="FONT-SIZE: 12pt FONT-FAMILY: "Palatino Linotype" mso-fareast-font-family: 'Times New Roman' mso-bidi-font-family: 'Levenim MT' mso-ansi-language: EN-US mso-fareast-language: EN-US mso-bidi-language: AR-SA">µ</span><span style="FONT-SIZE: 12pt FONT-FAMILY: "Palatino Linotype" mso-fareast-font-family: 'Times New Roman' mso-bidi-font-family: 'Times New Roman' mso-ansi-language: EN-US mso-fareast-language: EN-US mso-bidi-language: AR-SA">g, i.c.v.) induced total anesthesia. This effect could be seen by 10 and 20 </span><span style="FONT-SIZE: 12pt FONT-FAMILY: "Palatino Linotype" mso-fareast-font-family: 'Times New Roman' mso-bidi-font-family: 'Levenim MT' mso-ansi-language: EN-US mso-fareast-language: EN-US mso-bidi-language: AR-SA">µ</span><span style="FONT-SIZE: 12pt FONT-FAMILY: "Palatino Linotype" mso-fareast-font-family: 'Times New Roman' mso-bidi-font-family: 'Times New Roman' mso-ansi-language: EN-US mso-fareast-language: EN-US mso-bidi-language: AR-SA">g, i.c.v. doses of the drug in spinal animals, too, which was reversed by 5 </span><span style="FONT-SIZE: 12pt FONT-FAMILY: "Palatino Linotype" mso-fareast-font-family: 'Times New Roman' mso-bidi-font-family: 'Levenim MT' mso-ansi-language: EN-US mso-fareast-language: EN-US mso-bidi-language: AR-SA">µ</span><span style="FONT-SIZE: 12pt FONT-FAMILY: "Palatino Linotype" mso-fareast-font-family: 'Times New Roman' mso-bidi-font-family: 'Times New Roman' mso-ansi-language: EN-US mso-fareast-language: EN-US mso-bidi-language: AR-SA">g, i.c.v. of yohimbine. Dexmedetomidine (6.5 </span><span style="FONT-SIZE: 12pt FONT-FAMILY: "Palatino Linotype" mso-fareast-font-family: 'Times New Roman' mso-bidi-font-family: 'Levenim MT' mso-ansi-language: EN-US mso-fareast-language: EN-US mso-bidi-language: AR-SA">µ</span><span style="FONT-SIZE: 12pt FONT-FAMILY: "Palatino Linotype" mso-fareast-font-family: 'Times New Roman' mso-bidi-font-family: 'Times New Roman' mso-ansi-language: EN-US mso-fareast-language: EN-US mso-bidi-language: AR-SA">g, i.c.v. or 20 </span><span style="FONT-SIZE: 12pt FONT-FAMILY: "Palatino Linotype" mso-fareast-font-family: 'Times New Roman' mso-bidi-font-family: 'Levenim MT' mso-ansi-language: EN-US mso-fareast-language: EN-US mso-bidi-language: AR-SA">µ</span><span style="FONT-SIZE: 12pt FONT-FAMILY: "Palatino Linotype" mso-fareast-font-family: 'Times New Roman' mso-bidi-font-family: 'Times New Roman' mso-ansi-language: EN-US mso-fareast-language: EN-US mso-bidi-language: AR-SA">g, i.p.) showed antinociceptive effects in formalin test which was reversed by yohimbine (5 </span><span style="FONT-SIZE: 12pt FONT-FAMILY: "Palatino Linotype" mso-fareast-font-family: 'Times New Roman' mso-bidi-font-family: 'Levenim MT' mso-ansi-language: EN-US mso-fareast-language: EN-US mso-bidi-language: AR-SA">µ</span><span style="FONT-SIZE: 12pt FONT-FAMILY: "Palatino Linotype" mso-fareast-font-family: 'Times New Roman' mso-bidi-font-family: 'Times New Roman' mso-ansi-language: EN-US mso-fareast-language: EN-US mso-bidi-language: AR-SA">g, i.c.v.). Dexmedetomidine (5, 6.5, 7.5, 10 and 20 </span><span style="FONT-SIZE: 12pt FONT-FAMILY: "Palatino Linotype" mso-fareast-font-family: 'Times New Roman' mso-bidi-font-family: 'Levenim MT' mso-ansi-language: EN-US mso-fareast-language: EN-US mso-bidi-language: AR-SA">µ</span><span style="FONT-SIZE: 12pt FONT-FAMILY: "Palatino Linotype" mso-fareast-font-family: 'Times New Roman' mso-bidi-font-family: 'Times New Roman' mso-ansi-language: EN-US mso-fareast-language: EN-US mso-bidi-language: AR-SA">g, i.c.v. or 20, 25, 50 and 100 </span><span style="FONT-SIZE: 12pt FONT-FAMILY: "Palatino Linotype" mso-fareast-font-family: 'Times New Roman' mso-bidi-font-family: 'Levenim MT' mso-ansi-language: EN-US mso-fareast-language: EN-US mso-bidi-language: AR-SA">µ</span><span style="FONT-SIZE: 12pt FONT-FAMILY: "Palatino Linotype" mso-fareast-font-family: 'Times New Roman' mso-bidi-font-family: 'Times New Roman' mso-ansi-language: EN-US mso-fareast-language: EN-US mso-bidi-language: AR-SA">g/kg, i.p.) had significant antinociceptive effects in tail flick test, which could be reversed by 5 </span><span style="FONT-SIZE: 12pt FONT-FAMILY: "Palatino Linotype" mso-fareast-font-family: 'Times New Roman' mso-bidi-font-family: 'Levenim MT' mso-ansi-language: EN-US mso-fareast-language: EN-US mso-bidi-language: AR-SA">µ</span><span style="FONT-SIZE: 12pt FONT-FAMILY: "Palatino Linotype" mso-fareast-font-family: 'Times New Roman' mso-bidi-font-family: 'Times New Roman' mso-ansi-language: EN-US mso-fareast-language: EN-US mso-bidi-language: AR-SA">g, i.c.v. administration of yohimbine. The results of tail flick test in the spinal animals, shows that dexmedetomidine (6 </span><span style="FONT-SIZE: 12pt FONT-FAMILY: "Palatino Linotype" mso-fareast-font-family: 'Times New Roman' mso-bidi-font-family: 'Levenim MT' mso-ansi-language: EN-US mso-fareast-language: EN-US mso-bidi-language: AR-SA">µ</span><span style="FONT-SIZE: 12pt FONT-FAMILY: "Palatino Linotype" mso-fareast-font-family: 'Times New Roman' mso-bidi-font-family: 'Times New Roman' mso-ansi-language: EN-US mso-fareast-language: EN-US mso-bidi-language: AR-SA">g, i.c.v.) in these animals induces antinociception, which was reversed by yohimbine pretreatment (1 mg/kg, i.p.). These results indicate that, dexmedetomidine probably exerts, its antinociceptive effect, through spinal α_2<i> </i>adrenergic receptors. </span> Dexmedetomidine; Antinociception; α2 adrenergic receptors; Yohimbine 74 81 http://ppj.phypha.ir/browse.php?a_code=A-10-62-5&slc_lang=en&sid=1 Saeed Semnanian 320031947532846001677 320031947532846001677 Yes Ghasem Attarzadeh 320031947532846001678 320031947532846001678 No Mohammad Hossein Pourgholami 320031947532846001679 320031947532846001679 No