Infusions of alpha-2 noradrenergic agonists and antagonists into the amygdala: effects on kindling.
We reported previously that activation of alpha-2 adrenoceptors with infusions of clonidine into the amygdala/pyriform region is sufficient to retard kindling. To characterize further the involvement in kindling of alpha-2 receptors in the amygdala/pyriform, we exposed rats to unilateral intraamygdaloid infusions of a variety of noradrenergic drugs followed by either low-frequency stimulation of the amygdala, to induce rapid kindling, or conventional high-frequency stimulation. Infusions and electrical stimulation were administered once every 48 h. The prophylactic effects of clonidine were blocked by simultaneous infusion of idazoxan, an alpha-2 adrenergic antagonist, which suggests strongly that these effects were produced at an alpha-2 receptor. Intraamygdaloid infusions of xylazine, another alpha-2 agonist, also significantly retarded low-frequency kindling. Unexpectedly, intraamygdaloid infusions of the alpha-2 antagonists idazoxan, yohimbine, and SK&F 104856 failed to accelerate kindling. Infusion of the alpha-1 antagonist corynanthine also failed to affect kindling. We propose that the alpha-2 adrenoceptors in the amygdala/pyriform region contribute to the prophylactic effects of systemically administered clonidine and that the facilitation of kindling observed after systemic administration of alpha-2 antagonists may be due to blockade of alpha-2 adrenoceptors outside of the amygdala/pyriform region.
Pelletier
M R
MR
University of Victoria, Department of Psychology, BC, Canada.
Corcoran
M E
ME
D058669:Adrenergic alpha-2 Receptor Antagonists; D000316:Adrenergic alpha-Agonists / Q000008:administration & dosage / Q000494:pharmacology*; D000317:Adrenergic alpha-Antagonists / Q000008:administration & dosage / Q000494:pharmacology*; D000679:Amygdala / Q000187:drug effects / Q000502:physiology*; D000818:Animals; D001552:Benzazepines / Q000008:administration & dosage / Q000494:pharmacology; D003000:Clonidine / Q000008:administration & dosage / Q000494:pharmacology*; D004146:Dioxanes / Q000008:administration & dosage / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D007839:Functional Laterality; D019329:Idazoxan; D007263:Infusions, Parenteral; D007696:Kindling, Neurologic / Q000187:drug effects* / Q000502:physiology; D008297:Male; D051381:Rats; D018341:Receptors, Adrenergic, alpha-2 / Q000502:physiology*; D012640:Seizures / Q000503:physiopathology; D014991:Xylazine / Q000008:administration & dosage / Q000494:pharmacology*; D015016:Yohimbine / Q000008:administration & dosage / Q000494:pharmacology
D058669:Adrenergic alpha-2 Receptor Antagonists; D000316:Adrenergic alpha-Agonists; D000317:Adrenergic alpha-Antagonists; D001552:Benzazepines; D004146:Dioxanes; D018341:Receptors, Adrenergic, alpha-2; C071739:SK&F 104856; D014991:Xylazine; D015016:Yohimbine; D003000:Clonidine; D019329:Idazoxan