Possible Interaction: Amphetamine and Naloxone

“Thus, the lowest dose of naloxone , having no effects alone in place conditioning was still able to block the reinforcing effects of amphetamine.”

“In addition, an ineffective dose of amphetamine (0.5 mg/kg), given either pre-or post-training together with the lower dose of naloxone (0.1 mg/kg), produced a significant enhancement of acquisition or consolidation, respectively.”

“Pretreatment with the higher dose of naloxone (3 mg/kg) blocked the facilitative effect of amphetamine on acquisition.”

“The higher doses of amphetamine or nicotine, however, when given together with a dose of naloxone which is ineffective alone (0.2 mg/kg), markedly enhance consolidation.”

“The finding that an enantiomer of naloxone , with no opiate antagonist activity, is able to block the excitatory action of amphetamine , suggests the existence of a hitherto unknown mechanism of counteracting some of the effects of stimulants and euphoriants like amphetamine and cocaine.”

“When treated simultaneously with amphetamine and l-naloxone , these subjects showed low motility.”

“However, the exact nature of the NX induced alteration of AMPH induced behaviors is controversial, with some studies using high (5-40 mg/kg) doses of NX reporting an inhibition, and others using low (< or = 1-2 mg/kg) doses observing a potentiation.”

“ NX pretreatment (0.8 mg/kg) … by a higher dose of AMPH (3.0 mg/kg) produced a significantly greater cumulative effect on DA release than saline pretreatment over the last … combined intervals (30-90 min) and over two grouped intervals (30-50 min and 40-60 min inclusive).”

“On the other hand, the same dose of NX significantly enhanced AMPH induced striatal DA release relative to saline pretreated animals during each of four separate intervals, from 30 to 70 minutes following AMPH (1.5 mg/kg), and across all nine intervals combined.”

“The opiate antagonist naloxone NX ) alters amphetamine (AMPH) induced behaviors including locomotor activity, rearing and stereotypy.”

“The present results suggest that NX potentiates AMPH induced striatal DA release when lower doses of NX are used.”

“These results combined with those of previous studies also suggest that NX exerts a biphasic effect on AMPH induced DA release, with lower doses potentiating release and higher doses inhibiting release.”

“ Naloxone and naltrindole attenuate the locomotor response to amphetamine , implicating delta-opioid receptors in the opioid-antagonist/amphetamine interaction.”

“ Naloxone , the opioid receptor antagonist, attenuates the effects of amphetamine in a wide range of behavioral paradigms.”

“Gross locomotor counts following AMPH administration were significantly lower for rats pretreated with NX than for rats pretreated with saline.”

“However, compared to pretreatment with saline pretreatment with NX significantly decreased the dopaminergic response to AMPH in the STR.”

“These findings suggest that a decrease in the dopaminergic response to AMPH is the mechanism by which NX attenuates behavioral stimulant effects of AMPH.”

“In contrast, amphetamine , a DA-releasing agent, significantly increased DA release in the presence of naloxone.”

“Naloxone (0-2 mg/kg) had no significant effect of DA-stimulated locomotion; the lowest dose of naloxone tested (0.5 mg/kg) was shown to significantly disrupt the locomotor activation produced by amphetamine (0.5 mg/kg).”