Effects of naltrexone, andd-amphetamine, and their interaction on the stimulus control of choice behavior of rats

Abstract

The hypothesis that endogenous opioid peptides modulate attentional processes was tested. The effects of the opioid antagonist naltrexone (NALT), d-amphetamine (AMP), and their interaction were investigated in rats trained in a two-choice task in which the position of a short-duration light served as a cue for food-reinforced responses. NALT (0.25, 1.0, 5.0, and 10.0 mg/kg) produced no significant changes in performance (accuracy, choice latency, and food retrieval time). As predicted, AMP induced dose-dependent biphasic effects. Low doses of AMP (0.25 and 0.5 mg/kg) significantly enhanced accuracy, decreased choice latency, and lengthened food retrieval time; 1.25 mg/kg AMP disrupted accuracy, increased choice latency, and further lengthened food retrieval time. The combination of NALT (0.25, 1.0, and 10.0 mg/kg) and subthreshold doses of AMP (0.07 and 0.1 mg/kg) had no effect on performance except for an increase in food retrieval time with 10.0 mg/kg NALT, whereas the combination of NALT and moderate doses of AMP (0.5 and 1.0 mg/kg) disrupted accuracy, increased choice latencies, and lengthened food retrieval time. These results do not support the hypothesis that endogenous opioid peptides play a vital role in attentional processes or that opioid antagonists may be useful in the treatment of attentional deficit disorders.

The Pharmacological Characterization of Attentional Processes Using a Two-lever Choice Reaction Time Task in Rats.

“…6,11,21) It is known that this facilitative effect of methamphetamine on attentional processes is due to enhanced noradrenergic transmission. 22) Moreover, pharmacological studies using a 2 receptor antagonists and lesion studies suggest a role for the dorsal ascending noradrenergic projection in the processes of attentional processes. 5,23,24) Therefore additional studies were carried out using prazosin, an a 1 receptor antagonist, to gain further insight into the possible role of noradrenergic a 1 receptors in attentional processes in the two-lever CRT task.…”

α2- and β-adrenoceptors involvement in nortriptyline modulation of auditory sustained attention and impulsivity

“…A similar two-choice version of this task has also been extensively used to test the effect of other neurotransmitter systems on attention (Grilly and Gowans 1988;McGaughy and Sarter 1995). In the final phase of the sustained attention protocol, the testing session was divided into 5 blocks of 100 trials for 60 min.…”

Relevance of a neutral cue in a two-choice detection task in the rat

“…Sustained attention has been assessed through two-choice tasks and operant paradigms similar to the one used in this study (Bushnell et al, 1994;Bushnell, 1998b;Givens, 1997;Grilly and Gowans, 1988;Grilly et al, 1998;McCaughy and Sarter, 1995;McGaughy et al, 1996;Sahgal, 1988;Sarter and McCaughy, 1998). A critical factor in the assessment of sustained attention is the unpredictability of the target that has to be detected.…”

“…If the response was correct, the next trial began immediately, if incorrect the animal had a two seconds time-out in darkness before the next trial began. The signaling of each trial by a central light made the target a predictable event, which ruled out the sustained attention component of other two-choice tasks (Grilly and Gowans, 1988;Grilly et al, 1998;Sahgal, 1988) and centered the measures on the attentional shift between the two targets.…”

“…In sustained attention studies (Grilly and Gowans, 1988;Grilly et al, 1998;Sahgal, 1988), the critical parameter is the predictability of the target, which is related to the duration and variability of the intertrial interval (ITI), among other things. Stoher et al (1997) developed a visual two-choice task in order to model attentional shift and thereby isolate whether it was aging or the loss of cholinergic basal forebrain neurons that produces the difficulties of Alzheimer patients to shift visuospatial attention.…”