WITHDRAWAL FROM ORAL COCAINE IN RATS - ULTRASONIC VOCALIZATIONS AND TACTILE STARTLE

While anxiety appears to characterize humans who administer high doses of cocaine or experience withdrawal from cocaine, it is difficult to capture this aspect of cocaine effects in animals. The present study i nvestigated if acute or protracted withdrawal from prolonged low-dose cocaine that is self-administered via the oral route could be detected in tactile startle and vocal ''distress'' responses of rats. Adult ma le Long-Evans rats had access to cocaine solution (0.1 mg/ml) either f or 24 or 4 h/day using the two-bottle choice technique. The amount of solution consumed from each bottle was measured daily for 30 or 60 day s. On days 1, 3, 7, 14, 21, 28 of withdrawal, startle and ultrasonic v ocal responses (USV, 15-35 <Hz) were measured in response to 18 air-pu ff stimuli (20 psi). Rats drank an average of 5-20 mg/kg per day of th e cocaine solution. On average, about half of the daily liquid was con sumed from the cocaine solution-containing bottle. USVs were emitted a t significantly increased rates on day 3 of withdrawal from 30 or 60 d ays of cocaine drinking. Startle reactions were slightly, but non-sign ificantly increased on day 1 of withdrawal. Comparable to withdrawal f rom ethanol, morphine, and diazepam treatments, withdrawal from oral s elf-administration of low to moderate doses of cocaine increases the r ate of ultrasonic vocalizations while increasing minimally the amplitu de of startle responses to low-intensity tactile stimuli. Nevertheless , no correlation between the total amount of cocaine self-administered or the duration of treatment with the intensity of the withdrawal man ifestations could be detected.