Disruption of Temporally Organized Behavior by Morphine

Abstract

Four pigeons pecked keys in two different procedures commonly used in the study of timing, or temporal discrimination. Sessions consisted of 40 trials. During half of the trials, two keys were presented for 50 s. Left-key pecks were reinforced according to a variable-interval 67.86-s schedule during the first 25 s of the trial, and right-key pecks were not reinforced. During the second 25 s of the trial, right-key pecks were reinforced according to the same schedule, and left-key pecks were not reinforced. In the other half of the 40-trial session, the center key was presented. The majority of these trials arranged fixed-interval 2.5-s schedules. Occasionally a probe, or peak-interval, trial was presented. These trials were 100 s in duration and terminated without reinforcement. These two procedures were used to examine the effects of morphine on indexes of timing and on patterns of responding. Morphine altered behavior in a race-dependent manner in both procedures. Low baseline (saline) response rates were increased following morphine administration, and high baseline rates were either unaffected or decreased slightly. Rate-dependent effects appeared as leftward shifts in the timing index for two-key trials and decreases in the index of curvature for fixed-interval trials. Despite large changes in response rates, no consistent shift of the peak time was observed during peak-interval trials. These results are discussed primarily in terms of rate dependency; that is, rates of responding following drug administration tend to be determined in large part by rates of responding under baseline conditions.

The Effects of Morphine on the Production and Discrimination of Interresponse Times

“…Morphine produced generalized disruption of the production of IRTs when the effects were assessed about 10 to 45 min after administration. Other experiments, however, have reported results consistent with Meck's (1996) model of the neuropharmacology of timing with relatively short session durations with morphine (e.g., Knealing & Schaal, 2002;Popke et al, 2000;Schulze & Paule, 1991), d-amphetamine (e.g., Bizot, 1997;Chiang et al, 2000;Spetch & Treit, 1984) and the dopamine antagonist haloperidol (Bizot, 1997). Furthermore, results inconsistent with the model have been reported with relatively long session durations with the dopamine antagonist pimozide (Ohyama et al, 2000).…”

“…Popke, Mayorga, Fogle, and Paule (2000) had separate groups of rats respond under either a differential-reinforcement-of-low-rate-limited-hold (DRL-LH) schedule, in which lever presses produced food if the latency since the last response was between 10 and 14 s, or a temporal response differentiation (TRD) schedule, in which releasing the lever produced food if it had been held down between 10 and 14 s. Morphine tended to increase IRTs on the DRL-LH, but decreased response duration on the TRD schedule. Similarly, morphine produced different effects on two measures of timing with pigeons (Knealing & Schaal, 2002), and d-amphetamine (Chiang et al, 2000) and amineptine (Lejeune et al, 1995) produced different effects on two measures of timing with rats.…”

Effects of D‐amphetamine in a Temporal Discrimination Procedure: Selective Changes in Timing or Rate Dependency?

“…The peaked function relating the rate of response to time in the interval is flatter. With higher doses of drugs, higher rates near the usual time of food availability are decreased, resulting in flattening of the function (e.g., Knealing & Schaal, 2002). For the interval bisection task, which is a discrete-trial procedure, the subject has one opportunity to make a response per trial.…”

Oxycodone lengthens reproductions of suprasecond time intervals in human research volunteers

“…Similarly, heroin-dependent volunteers in the first few days of withdrawal made short reproductions of a 12-s interval compared to normal, healthy volunteers (Aleksandrov 2005), suggesting a shortening of the perception of time when heroin is withheld. Some studies with pigeons suggest that time may be overestimated in response to morphine administration, but alternative accounts based on the ability of morphine to change response rates and discrimination accuracy complicate the interpretation of these studies (Knealing and Schaal 2002, Odum and Ward 2004, Ward and Odum 2005). Thus more work needs be done to clarify the impact, if any, that opiates have in interval timing.…”