The addition of fenfluramine to amphetamine decreased the maximum responding, at least at the highest dose ratio (1 10, amphetamine/fenfluramine), in all monkeys.
Self-administration of intermediate doses of cocaine (0.025 0.1 mg/kg per injection) was decreased when mixed with PB (0.05 0.2 mg/kg per injection); full maximum responding was re-established when cocaine dose was increased.
We compared the following measures of demand; maximum price paid; number of rewards consumed, two measures from a linear-elasticity model estimating (Pmax, cost at which maximum responding occurs; Omax, maximum work done at Pmax); and a measure (alpha value) from an exponential demand model as sheep worked to obtain food.
This was achieved by measuring six silver fox males' maximum operant responding for access or proximity to three resources differing in biological significance: food, vixens in oestrus and males.
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It also led to a maximum rate of responding that occurred 2 3 s later than in the control condition, where the maximum occurred at the usual time of reinforcement.
Maximum time for responding was 1500 ms. The inter-trial interval was 1500 ms. In Experiments 1 and 2 participants performed ten experimental blocks of 120 trials per block (Experiment 1: 30 zero-target, 30 one-target, 30 two-target and 30 three-target trials; Experiment 2: 60 zero-target, 20 one-target, 20 two-target and 20 three-target trials).
Compared with the limited cytokine production by PMN, PBMC secreted significant amounts of all substances investigated and were found to require a 100× lower concentration of LPS than granulocytes to obtain the maximum number of responding cells.
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Males also produced longer vocalizations and reached the maximum frequency faster when responding to playbacks (Table 2).
