RESUMEN
Previous research indicated that the suppression of consummatory behavior that follows incentive downshift in male rats is attenuated by testosterone (T) administration during training. The present experiments were designed to assess the role of pretraining T administration on two incentive contrast situations in consummatory behavior: successive negative contrast (cSNC) and anticipatory negative contrast (cANC). In cSNC (Experiment 1), a downshift from 32% to 4% sucrose leads to behavioral suppression relative to an unshifted, 4% sucrose condition (the cSNC effect). Pretraining T administration enhanced consummatory behavior directed at 4% sucrose, without affecting behavior directed at 32% sucrose. This effect obscured a reduction in the cSNC effect by the T treatment that was only detected when a proportional measure of behavior was used. In cANC (Experiment 2), groups received access to two bottles per day separated by a short midtrial interval. Consumption of 4% sucrose is suppressed when the second bottle offers 32% sucrose, relative to 4% sucrose (the cANC effect). Pretraining T did not affect the cANC effect, known to be insensitive to treatment with anxiolytics. These results suggest an anxiolytic-like effect of testosterone in adjustment to incentive downshifts.
Asunto(s)
Inhibición Psicológica , Motivación/efectos de los fármacos , Refuerzo en Psicología , Testosterona/farmacología , Animales , Conducta Consumatoria/efectos de los fármacos , Relación Dosis-Respuesta a Droga , Esquema de Medicación , Emociones/efectos de los fármacos , Masculino , Ratas , Sacarosa/administración & dosificación , Sacarosa/farmacología , Testosterona/administración & dosificaciónRESUMEN
Posttrial administration of corticosterone was previously shown to enhance consummatory successive negative contrast (cSNC) in rats. The present series of experiments provides additional information that helps determine the boundaries of this effect. Posttrial corticosterone administration (1) enhances cSNC when rats experience a large downshift (32% to 4% sucrose), but not after a small downshift (8% to 4% sucrose; Experiment 1); (2) has no effect in an anticipatory negative contrast situation in which 4% sucrose precedes 32% sucrose in daily trials (Experiment 2); (3) does not support the development of a conditioned taste aversion to 4% sucrose, in the absence of an incentive downshift (Experiment 3); and (4) facilitates the extinction of consummatory behavior (Experiment 4). These results suggest that corticosterone facilitates the encoding of an egocentric aversive memory of the incentive downshift experience.
Asunto(s)
Conducta Consumatoria/efectos de los fármacos , Corticosterona/administración & dosificación , Extinción Psicológica/efectos de los fármacos , Motivación , Análisis de Varianza , Animales , Aprendizaje por Asociación/efectos de los fármacos , Condicionamiento Operante/efectos de los fármacos , Relación Dosis-Respuesta a Droga , Preferencias Alimentarias/efectos de los fármacos , Objetivos , Masculino , Distribución Aleatoria , Ratas , Ratas Wistar , Sacarosa/administración & dosificación , Edulcorantes/administración & dosificaciónRESUMEN
Rats given access to a 32% sucrose solution and then downshifted to a 4% solution exhibit less contact with the sipper tube than unshifted controls always given access to 4% solution. This phenomenon, called consummatory successive negative contrast, was facilitated in Experiment 1 by a post-trial injection of corticosterone (3 mg/kg) administered immediately after the first downshift trial. Experiment 2 demonstrated that this facilitatory effect of post-trial corticosterone does not occur when administered 3 hr after the first downshift trial. These results support the hypothesis that corticosterone strengthens an aversive emotional component elicited by the surprising downshift in reward magnitude during the initial downshift trial.
Asunto(s)
Conducta Consumatoria/efectos de los fármacos , Corticosterona/administración & dosificación , Inhibición Psicológica , Análisis de Varianza , Animales , Conducta Animal/efectos de los fármacos , Condicionamiento Operante/efectos de los fármacos , Condicionamiento Operante/fisiología , Conducta Consumatoria/fisiología , Masculino , Ratas , Ratas Wistar , Sacarosa/farmacología , Factores de TiempoRESUMEN
Three experiments explored the role of the opioid system in consummatory successive negative contrast. In Experiment 1, rats treated with the nonspecific opioid-receptor antagonist naloxone (2mg/kg) exhibited increased suppression after a shift from 32% to 6% sucrose solution (32-->6), relative to 6-->6 unshifted controls. A similar but shorter effect was observed with the delta-opioid receptor antagonist naltrindole (1mg/kg). In Experiment 2, naloxone increased suppression after a more conventional 32-->4 sucrose shift. In Experiment 3, rats classified as expressing slow recovery from contrast (after a 32-->4 sucrose downshift) were more sensitive to naloxone in an activity test than fast-recovery rats. Whereas it was previously known that contrast was reduced by the extrinsic administration of opioid agonists, the effects reported here with antagonists provide the first evidence that the opioid system is intrinsically engaged by situations involving surprising reward loss.
Asunto(s)
Condicionamiento Operante/fisiología , Conducta Consumatoria/fisiología , Inhibición Psicológica , Receptores Opioides/fisiología , Refuerzo en Psicología , Animales , Condicionamiento Operante/efectos de los fármacos , Conducta Consumatoria/efectos de los fármacos , Masculino , Naloxona/farmacología , Naltrexona/análogos & derivados , Naltrexona/farmacología , Antagonistas de Narcóticos/farmacología , Distribución Aleatoria , Ratas , Ratas Long-Evans , Receptores Opioides/efectos de los fármacosRESUMEN
RATIONALE: Glutamate antagonists microinjected into the dorsolateral PAG (DLPAG) show an anxiolytic-like profile in the elevated plus maze. Other columns of the PAG are also involved in defensive reactions. Few studies, however, have investigated the effects of pharmacological manipulation of the ventrolateral PAG (VLPAG) on procedures that predict anxiolytic activity. OBJECTIVES: To investigate the effects of the NMDA receptor (NMDAr) antagonist 2-amino-7-phosphonoheptanoic acid (AP7) microinjected into the DL or VLPAG in two procedures that predict anxiolytic activity using distinct aversive contingencies, the elevated plus maze and the Vogel punished licking test. METHODS: Male Wistar rats (7-14/group) with cannulas aimed at the DLPAG or VLPAG received AP7 (2 nmol/0.5 microl) or saline and 10 min later were submitted to the behavioural tests. In the punished licking experiment, water deprived (48 h) animals were allowed to drink for 3 min, receiving a 0.5 mA shock every 20 licks. The elevated plus maze test was performed as described elsewhere. Using this test, a dose response-curve for AP7 (0.2-20 nmol) injected in a smaller volume (0.25 microl) into the VLPAG was also performed. RESULTS: AP7 increased exploration of open arms of the EPM when microinjected into either the DLPAG or VLPAG ( P<0.05, ANOVA). The drug also increased the number of punished licks when administered into those columns (ANOVA, P<0.05). CONCLUSIONS: The results suggest that antagonism of endogenous excitatory amino acid neurotransmission in the DLPAG or VLPAG is able to reverse behavioral suppression induced by distinct aversive contingencies.