The effects of early handling on latent inhibition in male and female rats

Abstract

Latent inhibition (LI) is a behavioral paradigm in which repeated exposure to stimuli not followed by meaningful consequences renders these stimuli ineffective for subsequent learning. The development of LI is considered to reflect learning not to attend to, ignore, or tune out irrelevant stimuli. The present study investigated the differences in the development of LI between handled and nonhandled males and females. Infantile handled (Days 1-22) and nonhandled, male and female Wistar rats were tested in maturity in the LI paradigm. The LI procedure consisted of two stages: pre-exposure, where animals received 60 presentations of the to-be-conditioned stimulus (tone) and test, where the animals acquired a two-way active avoidance response with the tone serving as the warning signal. Handled animals reached higher percentage of avoidance responses as compared with nonhandled animals. Latent inhibition was obtained in both the handled and the nonhandled females, but only the handled males showed the LI effect. Nonhandled males failed to develop LI. The results indicate that the effects of handling are evident in learning tasks that do not involve motivational-emotional variables, i.e., learning to ignore irrelevant stimuli; handling differentially affects males and females, with a much greater impact on males and the nonhandling procedure has significant deleterious consequences on adult behavior.

Environmental animal models for sensorimotor gating deficiencies in schizophrenia: a review

“…In contrast, relative to normal-husbandry controls, EH does not affect spontaneous or d-amphetamine induced locomotor hyperactivity in a circular corridor (Campbell and Spear 1999). EH rats have been reported to exhibit better performance in learning tasks (Weiner et al 1985(Weiner et al , 1987, reduced food-related neophobia and better discrimination, which could be attributed to their lower emotional reactivity (Weinberg et al 1978). Finally, latent inhibition (i.e.…”

“…Finally, latent inhibition (i.e. retarded conditioning to a stimulus that has previously been repeatedly presented without meaningful consequences) is not affected by EH, but is disrupted in NH male rats (Weiner et al 1985;Feldon et al 1990), the disruption being reversed by haloperidol (Feldon and Weiner 1988).…”

Neonatal Nonhandling andIn UteroPrenatal Stress Reduce the Density of NADPH-Diaphorase-Reactive Neurons in the Fascia Dentata and Ammon’s Horn of Rats

“…We have demonstrated previously that neonatal nonhandling can lead to an attenuation of latent inhibition (Weiner et al, 1985(Weiner et al, , 1987Weiner, 1988, 1992;Feldon et al, 1990). Recently, there is also evidence to suggest that prenatal stress can similarly disrupt the normal development of latent inhibition (J.…”

Immune Activation During Pregnancy in Rats Leads to a PostPubertal Emergence of Disrupted Latent Inhibition, Dopaminergic Hyperfunction, and Altered Limbic Morphology in the Offspring: A Novel Neurodevelopmental Model of Schizophrenia

“…Several previous studies have shown that LI is disrupted following various manipulations during the period of perinatal development, including postnatal restriction of environmental stimulation, maternal separation or hippocampal lesion, and prenatal stress or corticosterone administration (Ellenbroek and Cools, 1995;Grecksch et al, 1999;Shalev et al, 1998;Shalev and Weiner, 2001;Weiner et al, 1985Weiner et al, , 1987. However, LI was assessed in these studies only in adult rats.…”