Effects of clonazepam and ethosuximide on the responding of pigeons under a fixed-consecutive-number schedule with and without an external discriminative stimulus

Abstract

The effects of the anticonvulsant drugs clonazepam and ethosuximide were examined in pigeons performing under a fixed-consecutive-number schedule with and without an added external discriminative stimulus. Under these schedules, food was delivered whenever subjects responded between and 8 and 12 times on one response key (work key), and then responded once on a second response key (reinforcement key). For one group, an external discriminative stimulus signalled completion of the response requirement on the work key, while no stimulus change was programmed for the other group. Clonazepam (0.06-0.75 mg/kg) produced dose-dependent decreases in percentage of reinforced runs and rate of responding for both groups. The magnitude of the accuracy-decreasing effect was generally greater in the group without the external discriminative stimulus. For this group, the higher doses of clonazepam produced pronounced increases in switching to the reinforcement key before completing the minimum requirement of eight consecutive responses on the work key. No consistent patterns of errors were evident for the subjects with the added external discriminative stimulus. Although ethosuximide (20-160 mg/kg) produced dose-dependent decreases in rate of responding, it had little effect on the percentage of reinforced runs or the run length distributions. These findings are consistent with previous reports indicating that clonazepam, but not ethosuximide, substantially disrupts performance under operant tasks requiring conditional discriminations. These data also suggest that the addition of an external discrimination stimulus attenuates the disruptive behavioral effects of clonazepam.

Effects of methsuximide and mephenytoin on the responding of pigeons under a fixed-consecutive-number schedule with and without an external discriminative stimulus

“…In addition, Picker and associates have reported similar effects under the FCN procedure for different benzodiazepines (Picker et al 1986a, b). Taken together, these results suggest that antiepilepsy drugs from the same chemical class often share behavioral actions.…”

“…Under this assay, mephenytoin, phenytoin, and methsuximide substantially increased errors (impaired learning), but ethosuximide failed to do so. No comparison of the effects of these agents under other assays has appeared.The design of the present study differed from that used by Picker et al (1986a, b) in that the two FCN schedules (with and without stimulus change) were programmed within each session in the present study. Thus, all subjects were exposed to both schedules during each session.…”

“…The design of the present study differed from that used by Picker et al (1986a, b) in that the two FCN schedules (with and without stimulus change) were programmed within each session in the present study. Thus, all subjects were exposed to both schedules during each session.…”

“…Moreover, the extent to which a particular anficonvulsant disrupts behavior at a given dose depends on how the behavior in question is maintained. For example, Picker et al (1986a, b) demonstrated that the presence or absence of an external discriminative stimulus influences the degree of behavioral disrupfion produced in pigeons by several anficonvulsant drugs.The procedure used to demonstrate this effect was the FCN schedule. Under this schedule, subjects were required to respond a fixed number of times on one operandum (work operandum) and then respond once on a second operandum (reinforcement operandum).…”

“…Moreover, the extent to which a particular anficonvulsant disrupts behavior at a given dose depends on how the behavior in question is maintained. For example, Picker et al (1986a, b) demonstrated that the presence or absence of an external discriminative stimulus influences the degree of behavioral disrupfion produced in pigeons by several anficonvulsant drugs.…”