Amygdaloid-thalamic interactions mediate the antinociceptive action of morphine microinjected into the periaqueductal gray.
The bilateral administration of the serotonin receptor antagonist methysergide (2.5 microg, 5 microg, and 10 microg) into either the central nucleus of the amygdala (ACe) or nucleus parafascicularis thalami (nPf) produced dose-dependent inhibition of the antinociceptive action of ventrolateral periaqueductal gray (vPAG)-administered morphine. Unilateral administration of these doses of methysergide into either the ACe or nPf had no effect on morphine-induced antinociception. However, the combined unilateral administration of these doses of methysergide into the ACe and nPf produced dose-dependent inhibition of morphine antinociception that was identical to that observed after its bilateral administration into either site. This latter finding is interpreted as evidence that a functional interaction between the ACe and nPf supports the antinociceptive action of morphine administered into the vPAG.
Borszcz
G S
GS
Department of Psychology, Wayne State Unviersity, Detroit, Michigan 48202, USA. gborszcz@sun.science.wayne.edu
Streltsov
N G
NG
D000679:Amygdala / Q000187:drug effects*; D000818:Animals; D001931:Brain Mapping; D004292:Dominance, Cerebral / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D007267:Injections; D008297:Male; D008784:Methysergide / Q000494:pharmacology; D009020:Morphine / Q000494:pharmacology*; D009433:Neural Inhibition / Q000187:drug effects*; D009619:Nociceptors / Q000187:drug effects*; D017288:Pain Threshold / Q000187:drug effects*; D010487:Periaqueductal Gray / Q000187:drug effects*; D051381:Rats; D020318:Rats, Long-Evans; D013787:Thalamic Nuclei / Q000187:drug effects*
D009020:Morphine; D008784:Methysergide