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. 2014 Jun 27;592(Pt 16):3611–3624. doi: 10.1113/jphysiol.2013.266494

Figure 7. Blockade of spinal α-2 adrenoceptors reveals a rapid inhibitory control on withdrawal reflexes to A- and C-nociceptor activation during acute inflammation.

Figure 7

A, the loss of acute sensitization to A-nociceptor stimulation 3 h after complete Freund's adjuvant (CFA) injection was partially reversed by the intrathecal injection of the noradrenergic α-2 receptor antagonist yohimbine [Mann–Whitney U test, *P < 0.05; n = 7 CFA (3 h), n = 5 yoh]. B, the loss of acute sensitization to C-nociceptor stimulation 3 h after CFA injection was reversed by yohimbine [Mann–Whitney U test, *P < 0.05; n = 8 CFA (3 h), n = 5 yoh]. C, D, systemic administration of the pan-opioid antagonist, naloxone, had no effect on either A-nociceptor evoked withdrawals (CFA, n = 5; CFA + nal, n = 6) (C) or C-nociceptor evoked withdrawals (CFA, n = 5; CFA + nal, n = 6) (D).