Effect of chlordiazepoxide on schedule-controlled responding and schedule-induced drinking

Lever pressing of four rats was maintained under a multiple fixed ratio 80, fixed interval 2-min schedule of food presentation. Water was concurrently available from a drinking tube. Overall rates of lever pressing were highest under the fixed ratio schedule and, for three rats, most drinking occurred during the pause preceding responding under the fixed interval schedule. Chlordiazepoxide increased the lower rates of lever pressing maintained under the fixed interval schedule but generally decreased the higher response rates under the fixed ratio schedule. The effects of chlordiazepoxide on schedule-induced licking also depended on the extent to which this response occurred in each schedule component. Typically chlordiazepoxide produced relatively greater increases in the lower levels of licking and either increased less or decreased licking in that component where, under control conditions, this response was more extensive. Chlordiazepoxide also produced overall increases in the total amount of water consumed during the session. When the number of food pellets obtained during the experimental session was given all at one time in the home cage, the amount of water ingested over a period of time equivalent to the session duration was substantially less than that consumed during the experimental session. Chlordiazepoxide did not increase home cage water consumption under this condition.