Interleukin-1 Receptor Type I mRNA Levels in Brain Regions From Male and Female Rats

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Abstract

Interleukin-1 (IL-1) induces a variety of neurological manifestations by direct action in the central nervous system (CNS). The IL-1 receptor type I (IL-1RI) mediates IL-1 signalling. In the present study, the steady-state content of IL-1RI mRNA was determined by a sensitive RNase protection assay in brain regions obtained from normal male and nonestrous female Wistar rats. The results show that brain regions differ in IL-1RI mRNA content. Highest levels of IL-1RI mRNA were detected in the male and female cerebral cortex. High levels of IL-1RI mRNA were also observed in the brain stem and its structures, and the cerebellum. Male and female rats exhibited similar differential profile of IL-1RI mRNA levels in the frontal cortex, hippocampus, hypothalamus, and cerebellum. The present data on brain distribution of IL-1RI mRNA levels suggest that distinct brain regions may depend differentially on the IL-1 system.

Introduction

Interleukin-1 (IL-1) induces a variety of neurological manifestations including anorexia, fever, sleep changes, and activation of the neuroendocrine system by direct action in the central nervous system (CNS) 18, 19. Evidence suggests that the IL-1 receptor type I (IL-1RI) is critical for IL-1 signalling [20]; IL-1RI modulates the in vivo acute phase response [15] and IL-1-induction of neurological manifestations [14].

In situ hybridization has localized the IL-1RI mRNA in various brain regions including the olfactory bulb, cerebral cortex, hippocampus, thalamus, hypothalamus, cerebellum, and/or brainstem structures 4, 7, 25, 26. Previous studies, however, have not reported on statistical differences concerning IL-1RI mRNA levels distribution in the brain. In addition, no studies have been reported on the brain distribution of IL-1RI mRNA when considering the circadian cycle, or directed to identify differences between male and female rats.

In the present study, a RNase protection assay using rat IL-1RI specific riboprobe was used to investigate the distribution of IL-1RI mRNA in brain regions from male and female rats. Tissue samples were obtained from rats during the initial interval of the light cycle, that is, during the rats' period of inactivity. In this manner, the steady-state levels of IL-1RI mRNA in the resting and unstimulated rodent were obtained. The data was quantified and analyzed statistically. The results show that brain regions differ significantly in IL-1RI mRNA content.

Section snippets

Dissection of Brain Regions

Normal adult male and female (in nonestrous period) Wistar rats (250 to 300 g) were used. They were maintained ad lib on pellet rat food (Prolab Animal Diet 3000, Agway Inc., Syracuse, NY) and tap water as previously described [19]. Artificial light illumination was from 0600 to 1800 h and room temperature was kept at 21 ± 2°C. Between 0700 and 1000 h (initial interval of the light cycle or period of resting), rats were decapitated and their brains with cervical cord were quickly removed (< 30

Results

The level of steady-state IL-1RI mRNA was determined in brain regions obtained from rats during the initial interval of the light cycle or period of inactivity. An example of the RNase-protection assay used in the brain regions examined is shown in Fig. 1. The summary of the IL-1RI mRNA profile is presented in Fig. 2. Controls for these studies were: 1) samples from male and female rats were processed, electrophoresed, and analyzed concomitantly; 2) consistency was verified by (a) analyzing all

Discussion

The present studies show that brain regions from male or female Wistar rats differ significantly in IL-1RI mRNA content. High levels of IL-1RI mRNA were detected in the cerebral cortex, brain stem and its structures, and the cerebellum of male rats. Female rats showed similar IL-1RI mRNA profile to that observed in male rats. There was no significant difference between the male and female IL-1RI mRNA profiles in the frontal cortex, hippocampus, hypothalamus, and cerebellum. The dissimilar

Acknowledgements

We thank Dr. Ronald P. Hart (Department of Biological Sciences, Rutgers University) for providing the rat IL-1RI cDNA. This research was supported by grants from the University of Delaware to CRPS.

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