Hughes, C. E., Pitts, R. C., & Branch, M. N. (1996).
Cocaine and food deprivation: Effects on food-reinforced fixed-ratio performance in pigeons.
Journal of the Experimental Analysis of Behavior,
65, 145-158.
Key pecking by 6 pigeons was maintained by a fixed-ratio 30
schedule of food presentation while body weights were 80% of
free-feeding weights. Acute administration of cocaine (0.3 to
13.0 mg/kg, i.m.) dose-dependently decreased response rates. Dose
- effect curves were shifted to the right when 3 of the 6 pigeons
were maintained at 70% of free-feeding weights and were shifted
to the left when the other 3 pigeons were maintained at 90% of
free-feeding weights. Then a dose of cocaine that initially
decreased response rates by more than 95% of control rates was
administered before each daily session. Comparable degrees of
tolerance to these rate-decreasing effects developed in the two
groups. The rate at which responding recovered was relatively
rapid for pigeons in the 70% free-feeding-weight group and was
slower for 2 of the 3 pigeons in the 90% free-feeding-weight
group. When body weights were then increased from 70% to 80% or
were decreased from 90% to 80% of free-feeding weight,
performance was disrupted initially only for pigeons whose weight
went from 70% to 80% of free feeding. In the present experiment
the degree of deprivation may have indirectly influenced the
degree of tolerance that developed to cocaine's response
rate-decreasing effects because it directly influenced the dose
chosen to be administered chronically. The degree of deprivation
appeared to have a more direct influence on the rate at which
tolerance developed.
Key words: deprivation level, behavioral tolerance, cocaine,
fixed-ratio schedule, key peck, pigeons