Pharmacology Biochemistry& Behavior, Vol. 31, pp. 523-531.©PergamonPress plc, 1989. Printedin the U.S.A. Specific Effects of Punishment on Amino Acids Turnover in Discrete Rat Brain Regions TATSUO MIYAUCHI, 1 STEVEN I. DWORKIN, CONCHITO CO AND JAMES E. SMITH Psychiatry Research Unit, Departments of Psychiatry and Pharmacology Louisiana State University Medical Center, Shreveport, LA 71130 Received 3 April 1987 MIYAUCHI, T., S. I. DWORKIN, C. CO AND J. E. SMITH. Specific effects of punishment on amino acids turnover in discrete rat brain regions. PHARMACOL BIOCHEM BEHAV 31(3) 523-53 !, 1988.--Specific effects of punishmenton the turnover rates of aspartate (Asp), glutamate (Glu) and gamma-aminobutyric acid (GABA) in 14 brain regions were investi- gated in rats exposed to punishment. Two yoked controls were also used in an attempt to separate the nonspecific effects of response rate, reinforcement density and direct effects of punisher (foot shock). Punished and unpunished littermate rats had similar response rates, and the reinforcement density was almost identical for both groups. A third group (yoked- shock rats) received food and shock independent of responding whenever these were given to the punished rats. When compared to the unpunished rats, the punishment increased the turnover rates of the three amino acids in all brain regions examined except GABA turnover in the caudate-putamen and preoptic-diagonal band. The majority of these changes by the punishment were similarto the effects of the yoked-shock (yoked-shock versus unpunished), although the magnitude of increase by the punishment was mostly larger than that by the yoked-shock. Six changes by the punishment (increase in the turnover rates of Asp in the thalamus, Glu in the hypothalamus and GABA in the cingulate cortex, entorhinal-subicular cortex, dentate gyrus and hypothalamus) appeared to be the specific effects of punishment since the yoked-shock did not affect these parameters. These results suggest that the punishment caused a hyperexcitation of the amino acidergic neurons in the limbic systems, particularly those in Papez's circuit. Punishment Conflict Amino acid neurotransmitters Neurotransmitter turnover rates Gamma-aminobutyric acid Anxiety GELLAR-SEIFTER type of conflict-punishment proce- dures (17) are useful animal behavioral techniques to investi- gate the effects and mechanisms of action of anxiolytic drugs. In this procedure, operant responding which is main- tained by positively reinforcing stimuli (food, water, etc.) is suppressed (punished) by response-dependent presentation of noxious stimuli (electric foot shock, etc.), and anxiolytic drugs increase the rate of punished responding. A large body of pharmacological evidence exists implicating central gamma-aminobutyric acid (GABA) [reviewed by Sepinwall (38), Enna (14) and Sanger (36)] or serotonin [reviewed by Sepinwall (38) and Iversen (21)] in the antipunishment effect of anxiolytics in rats. In contrast to the numerous phar- macological studies using punishment procedures, however, there has been no report, to our knowledge, assessing the neurochemical consequence of punishment. This study was designated to detect punishment-specific changes in turn- over rates of amino acid neurotransmitters as indexes of amino acidergic neuronal activities in discrete brain regions in rats. Most punishment experiments utilize multiple schedule procedures in which punished (2-5 min duration) and unpun- ished (5-15 min duration) periods appear alternately during a session. However, these schedules are not suitable for the neurochemical procedure we are using to determine turnover rates (8, 24, 25, 39, 40). In this procedure, animals are killed 60 and 90 min after intravenous pulse injection of radiolabel- led precursors of neurotransmitters, which requires animals being under a single component (punished or unpunished) during the pulse interval. Also, response rate and reinforce- ment density during the punished period are usually less than those during the unpunished period. The difference in motor activity (response rate) and food intake (reinforcement den- sity) between the two components may obscure punish- ment-specific neurochemical effects. In the present experiments, therefore, a behavioral pro- cedure which was suitable for the neurochemical examination of punishment was developed. To separate the neurochemical effects of nonspecific factors described above, we used a be- havioral procedure [yoked-box procedure (16)] which resulted in similar rates of responding and reinforcement density for punished and unpunished littermate rats. The yoking proce- 1Present address: Fujigotemba Research Laboratories, Chugai Pharmaceutical Co. Ltd. 705-1 Komakado, Gotemba 412, Japan. 523