Involvement of pertussis toxin sensitive G-proteins in conditioned fear-potentiated startle: possible involvement of the amygdala.
The present study evaluated the effects of intraventricular or intracerebral administration of pertussis toxin on fear-potentiated startle (a measure of conditioned fear) and shock sensitization (a measure of unconditioned fear). In Experiment 1 all animals were unilaterally implanted with cannulae into the lateral ventricle 1 week prior to 2 days of fear conditioning (ten light-shock pairings on each of 2 days). Five days later, animals were infused with either 1 microgram pertussis toxin or saline and tested for fear-potentiated startle 24 h after infusion and tested for shock sensitization 26 or 50 h after infusion. Pertussis toxin blocked the ability of a light conditioned stimulus to facilitate startle but did not alter the ability of acute footshock to increase startle amplitude in the same animals. In Experiment 2 bilateral infusion of 1 microgram pertussis toxin into the basolateral nuclei of the amygdala, but not the interpositus nuclei of the cerebellum, also blocked fear-potentiated startle when animals were tested 6 h after infusion. These findings suggest a role for pertussis toxin sensitive G-proteins, perhaps within the amygdala, in the expression of conditioned but not unconditioned fear.
Melia
K R
KR
Department of Psychology, Yale University, New Haven, CT 06508.
Falls
W A
WA
Davis
M
M
D000161:Acoustic Stimulation; D000679:Amygdala / Q000033:anatomy & histology / Q000187:drug effects*; D000818:Animals; D002529:Cerebellar Nuclei; D003213:Conditioning, Psychological / Q000187:drug effects*; D004597:Electroshock; D005239:Fear / Q000187:drug effects*; D019204:GTP-Binding Proteins / Q000502:physiology*; D007267:Injections; D007276:Injections, Intraventricular; D008297:Male; D037342:Pertussis Toxin; D051381:Rats; D011919:Rats, Inbred Strains; D013216:Reflex, Startle / Q000187:drug effects*; D010566:Virulence Factors, Bordetella / Q000008:administration & dosage / Q000494:pharmacology*
D010566:Virulence Factors, Bordetella; D037342:Pertussis Toxin; D019204:GTP-Binding Proteins