Adam Z. Weitemier

Urocortin 1 distribution in mouse brain is strain-dependent

Urocortin 1 has been implicated in a number of specific behaviors, which include energy balance, stress reactivity and ethanol consumption. To elucidate genetically influenced differences in the mouse urocortin 1 system, we performed immunohistochemical characterization of urocortin 1 distribution in C57BL/6J and DBA/2J mouse brain. Urocortin 1 analysis reveals strain-dependent differences in distribution of urocortin 1 immunoreactive neurons and neuronal fibers. In both strains, the highest number of urocortin 1-positive neurons was observed in the Edinger-Westphal nucleus and lateral superior olive. Urocortin 1-positive neurons were detected in the dorsal nucleus of the lateral lemniscus of DBA/2J mice, but were absent in the C57BL/6J strain. Differences in urocortin 1 fibers were detected in many areas throughout the brain, and were most apparent in the septal areas, thalamic areas, several midbrain regions, and medulla. Strain-dependent distribution of urocortin 1-containing cells and fibers suggests that differences in this neuropeptide system may underlie differences in behavior and physiological responses between these strains. Further, we found that in both mouse strains, urocortin 1 in the Edinger-Westphal nucleus and choline acetyltransferase are not coexpressed. We show that the urocortin 1-positive neurons of this brain area form a separate population of cells that we propose to be called the non-preganglionic Edinger-Westphal nucleus.

Lesions of the Edinger-Westphal nucleus in C57BL⁄6J mice disrupt ethanol-induced hypothermia and ethanol consumption

The Edinger–Westphal nucleus (EW) is a brain region that has recently been implicated as an important novel neural target for ethanol. Thus, the EW is the only brain region consistently showing elevated c‐Fos expression following both voluntary and involuntary ethanol administration. Ethanol‐induced c‐Fos expression in the EW has been shown to occur in urocortin I‐positive neurons. Moreover, previous reports using several genetic models have demonstrated that differences in the EW urocortin I system are correlated with ethanol‐mediated behaviours such as ethanol‐induced hypothermia and ethanol consumption. The aim of this study was to confirm these relationships using a more direct strategy. Thus, ethanol responses were measured following electrolytic lesions of the EW in male C57BL/6J mice. Both EW‐lesioned and sham‐operated animals were tested for several ethanol sensitivity measures and ethanol consumption in a two‐bottle choice test. The results show that lesions of the EW significantly disrupted ethanol‐induced hypothermia, while having no effect on pupillary dilation, locomotor activity or ethanol‐induced sedation. In addition, EW‐lesioned animals showed significantly lower ethanol preference and total ethanol dose consumed in the two‐bottle choice test. EW‐lesioned animals also consumed less sucrose than sham‐operated animals, but did not have altered preferences for sucrose or quinine in a two‐bottle choice test. These data support previously observed genetic correlations between EW urocortin I expression and both ethanol‐induced hypothermia and ethanol consumption. Taken together, the findings suggest that the EW may function as a sensor for ethanol, which can influence ethanol consumption and preference.

Lesions of the Edinger-Westphal nucleus alter food and water consumption.

The Edinger-Westphal nucleus (EW) produces several neuropeptides, including urocortin 1 and cocaine-amphetamine-regulated transcript, which regulate feeding, energy balance, and anxiety. Additionally, the EW projects to feeding and anxiety-regulatory brain areas. The authors tested the effect of lesions of the EW on the consumption of food, water and flavored solutions, metabolic indices, and exploratory behavior on the elevated plus maze in male C57BL/6J mice. EW lesion significantly reduced basal and deprivation-induced food and fluid consumption compared with sham and placement controls, but it did not alter behavior on the elevated plus maze. EW lesion had no effect on indices of basal metabolic activity, including plasma glucose level and body temperature. These effects suggest that the peptidergic neurons of the EW regulate food consumption.

Subregion-specific differences in hippocampal activity between Delay and Trace fear conditioning: an immunohistochemical analysis.

Lesions of the hippocampus attenuate acquisition of the tone-shock contingency in Trace, but not in Delay fear conditioning. These findings suggest that hippocampal regions are differentially involved in these two forms of fear conditioning. The present study was aimed at testing the hypothesis that hippocampal neurons are differentially activated during acquisition and retrieval of Delay versus Trace fear conditioning. Male C57BL/6J mice were exposed to eight tone-shock pairings (in Trace conditioning the shock came 30 s after the tone), and tested for immobility upon reexposure to contextual stimuli or to one tone presentation. Ten brain regions were analyzed by immunohistochemistry for inducible transcription factors (ITF) c-Fos and Zif268 1.5 h after training, context test or tone test. Acquisition of both Delay and Trace fear conditioning produced significant induction of c-Fos in the majority of brain regions analyzed compared to naive control animals. Importantly, Delay fear conditioning caused a higher increase of c-Fos expression in the CA3 region of the hippocampus compared to Trace-trained animals. After cue reexposure, Zif268 levels in the dentate gyrus of the hippocampus were higher in Trace-conditioned than in Delay-conditioned animals. In addition, reexposure-related c-Fos expression in the anterior cingulate cortex was significantly higher in Delay-conditioned animals than in Trace-conditioned animals. The present study confirms differential activation of hippocampal subregions in Delay and Trace fear conditioning.

Urocortin 1 in the dorsal raphe regulates food and fluid consumption, but not ethanol preference in C57BL/6J mice

The midbrain-localized Edinger-Westphal nucleus is a major site of production of urocortin 1. Urocortin 1 is a neuropeptide related to corticotropin-releasing factor that has high affinity for corticotropin-releasing factor type-1 and corticotropin-releasing factor type-2 receptors. In several mouse models, the amount of urocortin 1 neurons within the Edinger-Westphal nucleus is positively associated with ethanol preference. Central administration of urocortin 1 exerts potent anorectic actions, and implicates endogenous urocortin 1 in the regulation of food intake. It is possible that brain areas such as the dorsal raphe, which receives urocortin 1 from the Edinger-Westphal nucleus and highly expresses corticotropin-releasing factor type-2 receptors, mediate the actions of urocortin 1 on feeding and ethanol preference. In this study the amount of food, water and ethanol consumed over the dark cycle by ethanol-preferring C57BL/6J mice was measured after injection of artificial cerebrospinal fluid vehicle, urocortin 1, corticotropin-releasing factor and the corticotropin-releasing factor type-2 receptor-selective antagonist antisauvagine-30 onto the dorsal raphe. Compared with vehicle, corticotropin-releasing factor and antisauvagine-30, urocortin 1 induced a significant reduction in the amount of food consumed overnight. Also, compared with antisauvagine-30 treatment, urocortin 1 significantly reduced the amount of weight gained during this time. Urocortin 1 also significantly reduced the total amount of fluid consumed, but did not alter ethanol preference, which was high during all treatments. These results suggest that the dorsal raphe is a neuroanatomical substrate of urocortin 1-induced reductions in feeding, possibly through modulation of serotonergic activity from this nucleus. In addition, it is suggested that endogenous urocortin 1 in this area, such as from the Edinger-Westphal nucleus, does not regulate ethanol preference in C57BL/6J mice.