The role of the central nucleus of the amygdala in nociception and aversion

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Abstract
The role of the central nucleus of the amygdala in nociception - conditioned and unconditioned aversion - was studied. Rats received microinjection of vehicle or the N-type Ca2+ channel blocker Ω-conotoxin GVIA (0.2 μg/250 nl) into the central amygdaloid nucleus prior to intra-plantar injection of formalin, ultrasound exposure or immediately prior to the acquisition phase of an aversive conditioning trial. Intra-amygdala Ω-conotoxin GVIA resulted in an earlier onset of nociceptive response to formalin and increased nociceptive behaviour during the first 5min. Ω-Conotoxin GVIA significantly reduced conditioned freezing behaviour with no effect on ultrasound-induced unconditioned aversive behaviour. These data indicate that N-type Ca2+ channels in the central amygdaloid nucleus play a role in mediating behavioural responses to nociceptive and conditioned aversive stimuli. NeuroReport 14:981–984 © 2003 Lippincott Williams & Wilkins.