Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
Mean responses on the active (filled symbols) and inactive (open symbols) levers as a function of session for rats self-administering α-PVP (top panel), 4MMC (bottom panel), or saline (both panels) during autoshaping. * indicates a significant difference from saline. n=16/group.
