Behavioral depression induced by an amygdala seizure and the opioid fentanyl was mediated through the nucleus accumbens

Purpose:  To study the behavioral depression induced by a generalized limbic seizure and by an opioid. The hypothesis that an opioid fentanyl and an amygdala-evoked seizure induced behavioral depression through the nucleus accumbens was tested.
Methods:  The behavioral depression induced by an amygdala-kindled seizure was studied in fully kindled rats, with or without prior injection of fentanyl (0.05 mg/kg, s.c.). Local infusion of a nonspecific opioid antagonist, naloxone, or saline, was made bilaterally in the nucleus accumbens. The durations of loss of righting reflex (LORR), loss of tail-pinch response, and catalepsy were assessed.
Results:  Fentanyl induced an LORR following a generalized kindled seizure. The combination of fentanyl and a generalized seizure, as compared to fentanyl alone or a generalized seizure alone, resulted in a prolonged duration of LORR, catalepsy, and loss of tail pinch response. Infusion of naloxone as compared to saline in the nucleus accumbens reduced the duration of catalepsy and LORR induced by fentanyl, with or without a generalized seizure.
Conclusions:  Postictal depression that follows a generalized kindled seizure enhanced the behavioral effects of the opioid fentanyl. Network synaptic depression induced by the seizure acted synergistically with fentanyl to produce analgesia, catalepsy, and LORR, in part through the nucleus accumbens.