Shock-induced hyperalgesia: IV. Generality.
Brief-moderate shock (3, 0.75 s, 1.0 mA) has opposite effects on different measures of pain, inducing antinociception on the tail-flick test while lowering vocalization thresholds to shock and heat (hyperalgesia) and enhancing fear conditioned by a gridshock unconditioned stimulus (US). This study examined the generality of shock-induced hyperalgesia under a range of conditions and explored parallels to sensitized startle. Reduced vocalization thresholds to shock and antinociception emerged at a similar shock intensity. Severe shocks (3, 25 s, 1.0 mA or 3, 2 s, 3.0 mA) lowered vocalization threshold to shock but increased vocalization and motor thresholds to heat and undermined fear conditioned by a gridshock or a startling tone US. All shock schedules facilitated startle, but only brief-moderate shock inflated fear conditioning. The findings suggest that brief-moderate shock enhances the affective impact of aversive stimuli, whereas severe shocks attenuate pain.
Meagher
M W
MW
Department of Psychology, Texas A&M University, College Station 77843-4235, USA. m-meagler@tamu.edu
Ferguson
A R
AR
Crown
E D
ED
McLemore
S
S
King
T E
TE
Sieve
A N
AN
Grau
J W
JW
D000339:Affect; D000818:Animals; D001522:Behavior, Animal / Q000502:physiology; D003213:Conditioning, Psychological; D005239:Fear; D006930:Hyperalgesia / Q000175:diagnosis / Q000209:etiology*; D007858:Learning; D008297:Male; D009619:Nociceptors / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013216:Reflex, Startle / Q000502:physiology; D012769:Shock / Q000150:complications*; D014828:Vocalization, Animal / Q000502:physiology