RESUMEN
1. Female MR ("anxious") and MNRA ("non-anxious") Maudsley rats were tested in the CSD behavioral conflict paradigm (anxiety-like measure) and also in the FST paradigm (depression-like measure). 2. As expected, MNRA rats accepted significantly more shocks in the CSD paradigm than did MR rats (i.e., MNRA rats were less "anxious"), MNRA rats also exhibited significantly less immobility in the FST procedure (i.e., MNRA rats were less easily made "depressed"). 3. When the data were pooled across the two strains, there was a significant correlation between CSD and FST behavioral scores; however, there was no significant correlation between these measures when the data from the two strains were evaluated separately. Multiple regression (independent variables of rat strain and CSD score, dependent variable of FST score) revealed a significant effect of rat strain, but not CSD score, on FST behavior. 4. The relationship of these findings to the apparent relationship between anxiety and depression in humans is discussed.
Asunto(s)
Ansiedad/fisiopatología , Conducta Animal/fisiología , Actividad Motora/fisiología , Animales , Femenino , Masculino , Ratas , Ratas Endogámicas , Factores de TiempoRESUMEN
Extracellular electrophysiological recording techniques were used to study serotonergic dorsal raphe (DRN) neurons in Maudsley Reactive (MR), Maudsley Non-Reactive (MNRA) and Sprague Dawley (SD; reference control strain) rats. No significant differences were observed in the average discharge rates of DRN neurons from SD, MR AND MNRA rats. The sensitivity of DRN neuron somatodendritic 5-HT1A autoreceptors to the inhibitory effects of i.v. 8-OH-DPAT or alpha 1-adrenoceptors to the excitatory effects of iontophoretic phenylephrine did not differ significantly among strains. These findings are discussed in light of the previously reported strain-dependent differences in anxiety-like behavior and noradrenergic locus coeruleus neurons.
Asunto(s)
Núcleos del Rafe/fisiología , Serotonina/fisiología , 8-Hidroxi-2-(di-n-propilamino)tetralin/farmacología , Análisis de Varianza , Animales , Electrofisiología , Femenino , Neuronas/efectos de los fármacos , Neuronas/fisiología , Núcleos del Rafe/efectos de los fármacos , Ratas , Ratas Sprague-DawleyRESUMEN
Extracellular single-unit recording techniques were used to evaluate the physiological and pharmacological characteristics of noradrenergic locus coeruleus (LC) neurons in urethane-anesthetized Maudsley reactive (MR) and non-reactive (MNRA) rat strains, a presumed genetic model for differences in 'anxiety'. LC neurons from MNRA rats were found to have a significantly higher basal discharge rate than LC neurons from either the MR or Sprague-Dawley (SD) rats. The discharge pattern of MNRA LC neurons also differed significantly from that of LC neurons from SD and MR rats, with LC neurons from MNRA rats exhibiting a burst-like pattern of discharge. Finally, MNRA LC neurons were significantly less sensitive to the inhibitory effects of i.v. clonidine on spontaneous activity.
Asunto(s)
Ansiedad/genética , Ansiedad/fisiopatología , Locus Coeruleus/fisiopatología , Neuronas/fisiología , Potenciales de Acción/efectos de los fármacos , Potenciales de Acción/fisiología , Animales , Clonidina/farmacología , Relación Dosis-Respuesta a Droga , Electrofisiología , Locus Coeruleus/citología , Locus Coeruleus/efectos de los fármacos , Conducción Nerviosa/efectos de los fármacos , Neuronas/efectos de los fármacos , Nicotina/farmacología , Ratas , Ratas Endogámicas , Ratas Sprague-Dawley , Especificidad de la EspecieRESUMEN
The present studies were designed to examine the effects of treatment with the noradrenergic neurotoxin N-(2-chloroethyl)-n-ethyl-2-bromobenzylamine HCl (DSP4; 65 mg/kg, IP) on conflict behavior in the Maudsley reactive (MR) and nonreactive (MNRA) rat strains. In daily 10-min sessions, water-restricted rats were trained to drink water from a tube that was occasionally electrified; electrification was signaled by the presence of a tone (7-s duration; ISI = 30 s). Consistent with previous reports, the number of shocks accepted by rats of the MR and MNRA strains did not differ initially, but MNRA rats exhibited a dramatic increase in punished responding relative to their MR counterparts over the course of several weeks of conflict testing. This MR vs. MNRA strain difference in punished responding did not exhibit extinction following discontinuation of CSD conflict behavior testing for a period of 6 weeks. Whether it was administered after conflict training or before, DSP4 treatment did not reduce the MR vs. MNRA strain difference in conflict behavior; rather, DSP4 treatment tended to increase the magnitude of the MR vs. MNRA difference in conflict behavior. The effects of DSP4 on norepinephrine (NE) and 5-hydroxytrypamine (5-HT) concentrations in the pons medulla region were determined in one group of conflict-experienced MR and MNRA rats (35 weeks after administration) and in a second group of naive MR and MNRA rats (3 weeks after administration). There were no MR vs. MNRA strain differences in NE or 5-HT concentrations in vehicle-treated rats. DSP4 treatment significantly reduced NE, but not 5-HT, concentrations when compared to control values; rats that were sacrificed 3 weeks following DSP4 administration exhibited a greater NE depletion than did rats sacrificed 35 weeks after DSP4 administration. Finally, there were no significant correlations between pons medulla region NE concentrations and conflict behavior in either strain alone or when the data from the two strains were combined. The present results are not consistent with the hypothesis that the MR vs. MNRA strain difference in conflict behavior is the result of strain differences in brain NE function.
Asunto(s)
Conducta Animal/fisiología , Conflicto Psicológico , Norepinefrina/metabolismo , Animales , Ansiedad/inducido químicamente , Ansiedad/fisiopatología , Bencilaminas/toxicidad , Encéfalo/efectos de los fármacos , Encéfalo/fisiología , Emociones/efectos de los fármacos , Emociones/fisiología , Femenino , Degeneración Nerviosa/efectos de los fármacos , Neuronas/metabolismo , Neurotoxinas/toxicidad , Ratas , Especificidad de la Especie , Factores de TiempoRESUMEN
The present studies were designed to characterize the behavior of Maudsley reactive (MR/Har) and nonreactive (MNRA/Har) rats in a modification of the Geller-Seifter operant conflict paradigm. Food-restricted (85% of free-feeding weights) female MR/Har and MNRA/Har rats were trained to lever press for food reinforcement in a multiple-schedule operant conflict paradigm. In the absence of a tone, a fixed ratio-30 (FR-30) schedule for reinforcement only was in effect (i.e., every 30th lever press resulted in the delivery of a 45-mg food pellet). During the presence of a tone, a fixed ratio-1 (FR-1) schedule of both reinforcement (food) and punishment (0.20 mA footshock applied for 500 ms) was in effect (i.e., each lever press resulted in both food and shock delivery). The tone periods were 27 s in duration and were presented on a variable interval (VI)-120-s schedule (approximately 20 tones/40-min session). Behavioral testing was conducted 5 days/week for 35 weeks. Initially, punished responding between the MR/Har and MNRA/Har rat strains did not differ dramatically. However, over the course of many weeks of conflict testing, rats of the MNRA/Har strain came to accept significantly more shocks than did subjects of the MR/Har strain. A direct examination of footshock sensitivity in these rats revealed that this difference in conflict behavior over time was not due to strain differences in shock sensitivity. The mechanism for this time-dependent difference in conflict behavior between the MR/Har and MNRA/Har rats remains undetermined.