Efectos diferenciales del condicionamiento aversivo a sabores sobre la ingesta de sacarosa y estevia / Differential effects of conditioned taste aversion on sucrose and stevia intake

Resumen La asociación entre un estímulo alimentario y una sensación de malestar produce una aversión alimentaria, procedimiento denominado condicionamiento aversivo a sabores (CAS). Dado que no existen evidencias claras acerca de los efectos de este procedimiento sobre el consumo de endulzantes, el propósito de este estudio fue examinar la efectividad del CAS para disminuir el consumo de dos endulzantes naturales. Se trabajó con 30 ratas Wistar, distribuidas en tres grupos. En la fase 1 los grupos fueron expuestos a alimento y cada uno a una solución distinta: agua + sacarosa (G1), agua + estevia (G2) y agua sin endulzar (GC). En la fase 2 los grupos experimentales recibieron una inyección intraperitoneal de cloruro de litio. En la fase 3 los grupos retornaron a las condiciones de la primera fase. Después del CAS, G1 y G2 disminuyeron significativamente su consumo de bebida, sin embargo fue mayor al registrado en GC. Los resultados se discuten en función de la asociación entre el sabor y el contenido energético, lo que permite establecer nuevas directrices en el estudio del consumo de endulzantes. Se concluye que los procedimientos que producen aversión condicionada podrían resultar eficaces en el control de algunas conductas alimentarias alteradas.

Abstract The association between a food stimulus and a feeling of discomfort produces a food aversion; this procedure is called aversive taste conditioning (ATC). Since there is no clear evidence about the effects of this procedure on the consumption of sweeteners, the purpose of this study was to examine the effectiveness of ATC to decrease the consumption of two natural sweeteners. Thirty Wistar rats were divided into three groups. In phase 1 all groups were exposed to free food access and each group to a different solution: water + sucrose (G1), water + stevia (G2) and unsweetened water (CG). In phase 2 the experimental groups received an intraperitoneal injection of lithium chloride. In phase 3 the groups returned to the conditions of the first phase. After the ATC, the G1 and G2 significantly decreased their beverage consumption, although it was higher than the consumption of CG. The results are discussed in terms of the association between flavor and energy content, which allows establishing new guidelines in the study of the consumption of sweeteners. It is concluded that procedures such as ATC are effective in the control of some disordered eating behaviors.

Conditioning and aversion to toxic Solanum bonariense ("naranjillo") leaves in calves / Condicionado e aversão a folhas tóxicas de Solanum bonariense ("naranjillo") em bezerros

ABSTRACT: Solanum bonariense is a perennial poisonous shrub that induces cerebellar cortical degeneration when eaten by cattle. The aim of this research was to outline a protocol to induce a conditioned aversion to this plant. During the pre-conditioning period ten calves (126±12kg BW) were maintained at half of their normal energy intake with lucerne hay and water ad libitum, to stimulate consumption of S. bonariense. Every two days they were offered 100g ofS. bonariense leaves for 5 minutes. Calves began eating the target plant on day 10 and consumed all the plant material on day 12. The conditioning period began after each calf consumed the entire amount of S. bonariense for three consecutive sessions. Five animals were randomly selected for conditioning, and after ingestion ofS. bonariense they were dosed by oral gavage with lithium chloride (LiCl) at 200mg kg-1 BW (treated group), while the other five received a similar volume of water by oral gavage (control group). After 2 doses of LiCl the treated group ate no S. bonariense while the control group consumed the entire 100g. We confirmed that LiCl is a powerful tool to induce conditioned aversions against S. bonariense in calves, which persists for at least 3 months.

RESUMO: Solanum bonariense é uma planta tóxica, arbustiva e perene que induz a degeneração cortical cerebelar quando ingerida por bovinos. O presente trabalho objetiva criar um protocolo para induzir aversão condicionada para essa planta em bovinos. Durante o período de adaptação às condições experimentais, dez bezerros (126±12kg) foram mantidos com metade de seu fornecimento alimentar energético normal que incluiu feno de alfafa e água ad libitum, para estimular o consumo de S. bonariense. A cada dois dias, foram fornecidas oralmente 100g de folhas de S. bonariense por cinco minutos. Os bezerros começaram a ingerir a planta no 10o dia de experimento e consumiram toda a planta no 12o dia. O período condicionado começou após cada bezerro ter consumido a quantidade total de S. bonariense por três sessões consecutivas. Cinco animais foram aleatoriamente selecionados para aversão condicionada e, após ingestão da planta, receberam solução oral de 200mg kg-1 de peso vivo de cloreto de lítio (LiCl) (grupo tratado), enquanto que os outros cinco bovinos receberam dosagem oral com volume similar de solução fisiológica (grupo controle). Após duas doses of LiCl, o grupo tratado não comeu folhas de S. bonariense, enquanto que o grupo controle consumiu toda a quantidade fornecida. Os resultados do presente trabalho demonstram que LiCl é uma ferramenta útil para induzir aversão condicionada contra S. bonariense em bezerros, que persiste por pelo menos 3 meses.

Context-switch Effect Produced by the Ambiguity of the Meaning of a Cue / Efecto de cambio de contexto producido por la ambigüedad del significado de la clave

One experiment analyzed whether context dependency of a flavor-illness association depends on the extinction of a different flavor-illness association in rats. There were two sessions per day, one in context A and the other session in context B. A half of the rats were allowed to drink distilled water within context B, while the other half of the group spent the same amount of time in context B without access to water. In context A, half of the subjects received conditioning and extinction of flavor X, while the other half did not received extinction. Then conditioning of flavor Y was conducted for all rats in context A. Finally, testing of Y was conducted in context A for half of the rats, while the other half received the test in context B. Results shown that extinction of flavor X affected the recovery of subsequently acquired information about flavor Y regardless the treatment received in context B. This data is consistent with Atttentional Theory of Context Processing.

Un experimento analizó si la dependencia contextual de una asociación sabor - enfermedad depende de la extinción de una asociación sabor - enfermedad distinta en ratas. Se realizaron dos sesiones diariamente, una en el contexto A y la otra en el contexto B. Una mitad del grupo ratas bebieron agua destilada en el contexto B, mientras que la otra mitad del grupo se colocó por el mismo tiempo en el contexto A sin beber nada. La mitad de las ratas recibieron condicionamiento y extinción de un sabor X en el contexto A, mientras que la otra mitad no recibió extinción. Luego todas las ratas fueron condicionadas con el sabor Y en el contexto A. Por ultimo, se hizo la prueba de Y en el contexto A para la mitad del grupo, y en el contexto B para la otra mitad. Los resultados mostraron que la extinción del sabor X afectó la recuperación del favor Y sin importer si el tratamiento se hizo en el contexto B. Estos datos son consistentes con la Teoría Atencional de Procesamiento del Contexto.

Modulación contextual en la extinción: recuperación de una aversión condicionada al sabor en un tercer contexto / Modulação contextual na extinção: recuperação de uma aversão condicionada ao sabor em um terceiro contexto / Contextual modulation of extinction: recovery of taste-aversion conditioning in a third context

Este experimento se diseñó para evaluar la renovación ABC con un procedimiento de condicionamiento de aversión al sabor (CAS) en tres fases: adquisición, extinción y prueba. Durante la adquisición, 15 ratas Wistar, asignadas a los grupos ABC y ABB, tuvieron acceso a una solución con sacarosa y posteriormente recibieron una inyección de cloruro de litio (liCl) en el Contexto A. En la extinción, ambos grupos bebieron la solución con sacarosa sin la administración del liCl en el Contexto B. En la prueba, los grupos tuvieron acceso a la solución con sacarosa sin administrarles liCl en el contexto de extinción para el grupo ABB, y en un tercer contexto para el grupo ABC. Los resultados mostraron la recuperación de la aversión condicionada al sabor únicamente en el grupo ABC.

This experiment was designed to evaluate ABC renewal in a conditioned taste aversion (CTA) procedure consisting of three phases: acquisition, extinction and test. During the acquisition phase, 15 Wistar rats assigned to groups ABC and ABB had access to a sucrose solution, after which they were injected with lithium chloride (liCl) in Context A. In the extinction phase, both groups of rats had access to the sucrose solution in Context B, but no liCl was administered. Finally, during the test, group ABB received sucrose solution without liCl in the extinction context, while group ABC was tested in a third context. Results showed renewal of conditioned taste aversion only in the ABC group.

Este experimento foi elaborado para avaliar a renovação ABC com um procedimento de condicionamento de aversão ao sabor (CAS) em três fases: aquisição, extinção e prova. Durante a aquisição, 15 ratos Wistar, designados aos grupos ABC e ABB, tiveram acesso a uma solução com sacarose e posteriormente receberam uma injeção de cloreto de lítio (liCl) em Contexto a. Na extinção, ambos grupos beberam a solução com sacarose sem a administração do liCl em Contexto B. Na prova, os grupos tiveram acesso à solução com sacarose sem administrar-lhes liCl num contexto de extinção para o grupo ABB, e num terceiro contexto para o grupo ABC. Os resultados mostraram a recuperação da aversão condicionada ao sabor unicamente no grupo ABC.

Development of conditioned taste aversion to Mascagnia rigida in goats / Desenvolvimento de condicionamento aversivo ao sabor de Mascagnia rigida em caprinos

The aim of this study was to determine whether goats could be averted from consuming Mascagnia rigida, a toxic plant found in the semiarid region of northeastern Brazil. Fourteen male goats not previously familiarized to M. rigida were randomly allocated to two treatment groups: control (treated with 5.5mL water orally by a drenching gun) and lithium group (treated with 100mg LiCl/kg body weight orally by a drenching gun). For conditioning, goats were allowed to feed on M. rigida leaves for 15 min, followed by LiCl or water administration. The time spent on eating M. rigida leaves was measured. The conditioning was repeated daily until the LiCl-treated goats stopped eating M. rigida. On the 10th, 17th, and 24th day after conditioning, extinction trials of the M. rigida aversion were performed in goats by using single-choice tests. There was no difference between the two treatment groups with respect to the consumption of M. rigida on the first day of aversion conditioning, however, controls ingested increasing amounts of the plant on consecutive conditioning days. On the second day, five out of the seven goats in the lithium group did not eat the leaves, but on the third day, all the goats in the lithium group did not ingest M. rigida. This aversion persisted throughout all evaluated days. This indicates that goats can be easily conditioned by using lithium chloride to avoid eating M. rigida temporarily.(AU)

O objetivo do presente estudo foi determinar se os caprinos podem desenvolver aversão ao consumo de Mascagnia rigida, uma planta tóxica encontrada na região semi-árida do nordeste brasileiro. Catorze caprinos machos não familiarizados com M. rigida foram separados ao acaso em dois grupos de tratamento: controle (tratados com 5,5mL de água por via oral por meio de uma seringa dosadora) e grupo tratado lítio (tratados com 100mg de LiCl/kg de peso corpóreo por via oral por meio de uma seringa dosadora). Para o condicionamento, os caprinos puderam ingerir folhas de M. rigida por 15 minutos, seguido pela administração de LiCl ou de água. O tempo de ingestão das folhas de M. rigida foi anotado. O condicionamento foi repetido diariamente até que os caprinos tratados com LiCl parassem de ingerir M. rigida. Nos 10º, 17º e 24º dias após o condicionamento, testes de extinção da aversão a M. rigida foram realizados nos caprinos usando provas de única escolha. Não houve diferença entre os dois grupos de tratamento no consumo de M. rigida no primeiro dia do condicionamento aversivo, mas os animais do grupo controle ingeriram quantidades crescentes da planta nos dias seguintes ao condicionamento. No segundo dia, cinco dos sete caprinos do grupo tratado com lítio não ingeriram as folhas, mas no terceiro dia, todos os caprinos tratados com lítio não ingeriram M. rigida. Esta aversão persistiu durante todos os dias avaliados. Isto indica que os caprinos podem ser facilmente condicionados utilizando o cloreto de lítio para produzir aversão à ingestão de M. rigida temporariamente.(AU)

Stimulus specificity in the acquisition and extinction of conditioned taste aversion

An experiment evaluated whether the acquisition and extinction of conditioned taste aversion in the rat is stimulus-specific by testing the degree of response transfer between sweet and salty tastes. Animals in the paired-same and paired-different groups received a presentation of a gustatory CS and a cyclophosphamide injection US. Nonconditioned control groups received unpaired CS /US presentations or the CS followed by a vehicle injection. Taste avoidance was evaluated in three nonreinforced test sessions. In the paired-same, unpaired and vehicle groups, all test sessions were conducted with the same flavor as originally used in training, whereas the paired-different group was tested with a novel flavor on the first and second sessions and with the originally trained flavor in last session. Stimulus specific acquisition was apparent in the first test session, when the animals in the group paired-same exhibited lower fluid intake than the other three groups. Evidence of specificity of extinction was apparent in the last test session, when animals in the group paired-different exhibited lower fluid intake than the other three groups. These results provide further evidence of stimulus specificity in acquisition and extinction of conditioned taste aversion, supporting the associative interpretation of these phenomena.

Central N omega-nitro-L-arginine Methyl Ester Does not Influence Lithium-induced c-Fos and Conditioned Taste Aversion

LiCl at doses sufficient to induce conditioned taste aversion (CTA) causes c-Fos expression in the brain regions implicated in CTA formation. It has been reported that nitric oxide (NO) may play a role in CTA learning and LiCl increases both the synthesis and activity of NO synthase (NOS) in the brain. In this study, we examined the effect of central N omega-nitro-L- arginine methyl ester (L-NAME) on the brain c-Fos expression and CTA learning induced by lithium in rats. In the results, intracerebroventricular L-NAME given prior to lithium did not change either the lithium-induced CTA or c-Fos in the relevant brain regions. This suggests that the brain NO system may not be involved in the neuronal activation during lithium-induced CTA formation.