La administración de nicotina aguda retarda la extinción en automoldeamiento pavloviano: un estudio preliminar / Acute nicotine administration retards extinction from pavlovian autoshaping: A preliminary study

Resumen Introducción y objetivo: Los procesos de aprendizaje y motivación han sido centrales para la comprensión de los mecanismos que subyacen al tabaquismo. En particular, existe evidencia creciente sobre la importancia de valores motivacionales de incentivo para entender el inicio y mantenimiento del tabaquismo. El objetivo general de este experimento fue evaluar el papel de la nicotina aguda sobre el valor de incentivo de una recompensa natural, (comida) asociada con un estímulo ambiental, (palanca experimental). Método: Se utilizaron ratas Wistar. Se administró nicotina (0.4 mg/kg) de manera aguda en momentos específicos del entrenamiento, utilizando un procedimiento de diez sesiones de adquisición y cuatro sesiones extinción en una tarea pavloviana de automoldeamiento. El diseño experimental incluyó tres grupos, el grupo control de solución salina y grupos de nicotina durante la adquisición y la extinción. Resultados: Se encontró que la administración aguda de nicotina, de manera específica y en comparación con los otros dos grupos experimentales, resultó en un efecto de retardo durante la fase de extinción, y que una administración similar de nicotina no resultó en efectos observables durante el desempeño comportamental en adquisición. Conclusiones: Estos resultados apoyan el papel de la nicotina como fortalecedora del valor de incentivo de las claves ambientales durante la extinción para una tarea de automoldeamiento.

Abstract Introduction and goal: Learning and motivational processes have been central for a modern understanding of tobacco addiction. There is evidence that supports the importance of incentive motivational processes for the maintenance of tobacco addiction. The main goal of the present experiment was to evaluate the effects of acute nicotine on the incentive value of a natural reward, (food) paired with an environmental cue (pressing lever). Method: Wistar rats were used. Accute nicotine (0.4 mg/kg) was administered on key sessions, using a pavlovian autoshaping procedure involving ten acquisition and four extinction sessions. The experimental design included three groups, a saline administration control group and groups with specific nicotine administration during either acquisition or extinction. Results: We found that acute administration of nicotine, in contrast with saline only or previous nicotine administration during acquisition, had an enhancing effect on responding for the environmental cue during autoshaping extinction, but we did not find evidence that acute nicotine affected acquisition performance. Conclusion: Our results are consistent with a role of nicotine enhancing the incentive value of stimuli during extinction from a pavlovian autoshaping task.

The effect of conditioned inhibitors and preexposed cues on the outcome-specific Pavlovian-to-instrumental transfer effect in humans.

Using a human Pavlovian-to-instrumental transfer (PIT) task, Alarcón and Bonardi showed that the selective elevation of instrumental responding produced by excitatory transfer cues was reduced when these cues were presented with a conditioned inhibitor (CI), relative to a control cue that was simply preexposed. However, previous research has shown that preexposed cues might also acquire inhibitor-like properties. This study aimed to contrast the inhibitory properties of CIs and preexposed cues, using novel stimuli as controls, in summation and PIT tests. Participants were trained to perform two actions, each reinforced with a distinct outcome (O1 or O2). Two images were trained as CIs, each signalling the absence of one of the outcomes, by presenting them with a cue that was otherwise followed by that outcome (e.g., A→O1, AI→no O1). In contrast, the preexposed cues were simply presented in the absence of the outcomes. In the summation test, participants rated the likelihood of the outcomes in the presence of two independently trained excitatory cues, each presented with a CI, a preexposed cue, or a novel stimulus. Similarly, in the PIT test, participants performed both actions in the presence and absence of these compounds. In the summation test, the CIs and the preexposed cues reduced participants' expectations of the outcomes more than the novel stimuli. However, in the PIT test, only the CIs reduced the selective elevation of responding produced by the transfer cues. These results might reflect distinct properties of stimuli trained as CIs and those simply preexposed.

Sexual behaviour is impaired by the abused inhalant toluene in adolescent male rats.

Inhalant misuse is a worldwide problem, especially among adolescents. Toluene is the most widely misused inhalant. One hallmark of adolescence is the emergence of sexual behaviour, which can be affected by drug use. The aim of this study was to analyse the effects of toluene inhalation on different aspects of male rats' sexual behaviour using a binge pattern of exposure in adolescent rats. Male Wistar rats were individually exposed to air or 6,000 ppm toluene for 30 min (acute exposure; n = 8 each) or twice a day for 12 days (repeated exposure; n = 9 each) in static exposure chambers. Independent groups of sexually experienced, adolescent rats (postnatal day 63, PN63) were tested after acute toluene exposure for copulation, sexual incentive motivation or noncontact erections. Sexually naïve, adolescent rats (PN45-59) were repeatedly exposed to toluene and tested for sexual behaviour after completing the 1st, 3rd, 5th, 7th, 9th, 11th and 13th exposure sessions. Acute toluene exposure impaired copulatory performance, diminished sexual incentive motivation and delayed noncontact erection occurrence in sexually experienced rats. Repeated toluene exposure during adolescence completely inhibited the onset of copulatory behaviours in sexually naïve rats, at the time at which they should have appeared. However, once the inhalant exposure ended, copulatory responses appeared gradually, and animals attained a typical, stable copulatory pattern. In conclusion, acute toluene exposure impairs sexual behaviour in young, sexually experienced animals, while repeated toluene exposure during adolescence prevents the onset of copulatory behaviour, although this effect is transitory.

Persistencia Temporal de la Conducta de Atracón en un Modelo con Ratas / Temporal Persistency of Binge Eating Behavior in Rats

Resumen La conducta de ingesta tipo atracón, se define como un consumo considerable de alimento sabroso en un periodo reducido y discreto. Los modelos experimentales con roedores que se han enfocado en este patrón de conducta asumen implícita o explícitamente que se genera un cambio permanente en el consumo de alimento sabroso, no obstante, aún no se describe la persistencia del patrón de ingesta tipo atracón, lo cual resulta de interés ya que para evaluar cualquier tratamiento es necesario conocer por cuánto tiempo los sujetos continúan presentando atracones, por lo tanto los objetivos del presente trabajo fueron: a) determinar si la conducta de ingesta tipo atracón permanece estable después de su inducción con el acceso durante 2 horas una solución de sacarosa concurrente con el acceso al alimento estándar durante 24 horas y, b) evaluar si la presencia o ausencia de alimento estándar afecta el mantenimiento de la conducta de atracón. Con este fin se dio acceso diario durante 2 horas a la solución sacarosa al 10%, mientras el acceso al alimento estándar y agua fue libre. Se observó que en 25 días los sujetos desarrollaron el patrón de ingesta tipo atracón. La conducta de atracón se mantuvo estable a lo largo de ocho semanas; ni el acceso ni la privación de alimento estándar afectaron el mantenimiento de la conducta de ingesta de atracón y el patrón de ingesta del alimento estándar se mantuvo similar al del inicio de la inducción. La estabilidad de la conducta de atracón reproduce observaciones con humanos y posibilita el estudio a largo plazo de los cambios neuronales generados durante la inducción de la conducta de atracón.

Abstract Binge eating behavior has been defined as an increased intake of palatable food during a short time period. The experimental models with rodents that had studied this eating behavior had implicitly or explicitly assumed that the induction protocol produced a permanent change in palatable eating, although there is no description of the persistence of the behavioral pattern despite this pice of information may be needed to evaluate any therapeutic strategy. Therefore, present objectives were: a) determine whether binge eating behavior persist after its induction with a 2h access to sucrose solution concurrent to free access to rat chow food for 24 h and, b) determine whether the deprivation level of chow food modulates maintenance of binge eating behavior. To this aim, rats had a 2h daily access to 10% sucrose with concurrent access to ad lib food and water. It was observed that after 25 days subjects develop binge eating behavior. It was also observed that along 8 weeks at least, binge eating behavior was stable and neither ad lib access or food deprivation modulated binge eating behavior, that remained similar to the last induction day. Stability of binge eating behavior reproduced observations with human patients and may aloud the study of long term neural changes induced after binge induction.

Deficits in odor-guided behaviors in the transgenic 3xTg-AD female mouse model of Alzheimer׳s disease.

Alzheimer׳s disease (AD) is characterized by a number of alterations including those in cognition and olfaction. An early symptom of AD is decreased olfactory ability, which may affect odor-guided behaviors. To test this possibility we evaluated alterations in sexual incentive motivation, sexual olfactory preference, sexual olfactory discrimination, nursing-relevant olfactory preference and olfactory discrimination in female mice. We tested 3xTg-AD (a triple transgenic model, which is a "knock in" of PS1M146V, APPSwe, and tauP300L) and wild type (WT) female mice when receptive (estrous) and non-receptive (anestrous). Subjects were divided into three groups of different ages: (1) 4-5 months, (2) 10-11 months, and (3) 16-18 months. In the sexual incentive motivation task, the receptive 3xTg-AD females showed no preference for a sexually active male at any age studied, in contrast to the WT females. In the sexual olfactory preference test, the receptive WT females were able to identify sexually active male secretions at all ages, but the oldest (16-18 months old) 3xTg-AD females could not. In addition, the oldest 3xTg-AD females showed no preference for nursing-relevant odors in dam secretions and were unable to discriminate between cinnamon and strawberry odors, indicating olfactory alterations. Thus, the present study suggests that the olfactory deficits in this mouse model are associated with changes in sexual incentive motivation and discrimination of food-related odors.