Ben Oberman

EXPRESSION PATTERN OF BOMBESIN FAMILY HOMOLOGS IN MOUSE BRAIN AND SPINAL CORD. Ben Oberman¹, Kaihua Zhang², Zhou-Feng Chen², Anesthesiology Department, Washington University Medical School, St. Louis, MO.

Bombesin is a peptide that was first isolated from the skin of Bombina bombina, a European frog, in 1971 (Anastasi et al.). Bombesin-like peptides have been found in mammalian neural and endocrine cells. These include gastrin-releasing peptide (GRP) and neuromedin B (NMB). There are three known receptors activated by bombesin-like peptides: the GRP receptor (GRPR), the NMB receptor (NMBR), and bombesin-receptor subtype 3 (BRS-3) whose natural ligand is unknown.

NMB exhibits many similarities with GRP, but generally acts as a less potent peptide. In NMBR deficient mice, the thermal regulation to a change in ambient temperature, the contraction of smooth muscle elicited by NMB, and feeding suppression were not significantly affected (Ohki-Hamazaki et al., 1999). The systems that NMB regulates strongly are not well known, but it is hypothesized that NMB/NMBR modulate the serotonergic (5-HT) system and stress response (Yamano et al., 2002).

Research on BRS-3 suggests that it regulates endocrine processes and metabolic processes responsible for energy balance. BRS-3 deficient mice have been shown to develop mild obesity, hypertension, impairment of glucose metabolism, insulin resistance, reduced metabolic rate, increased feeding efficiency, and hyperphagia (Ohki-Hamazaki et al.).

The goal of the current research was to identify the distribution patterns of NMB, NMBR, and BRS-3 peptides in the mouse brain and spinal cord. The cDNA for each peptide was isolated by using PCR and gel electrophoresis. NMB and BRS-3 peptides used sp6 labeled probes for in situ hybridization whereas NMBR used a T7 labeled probe for in situ hybridization. Adult mouse brain and spinal cord sections were successfully used for the in situ hybridization. The expression of NMBR and BRS-3 in the adult mouse brain are consistent with previous studies. NMBR was expressed moderately in the paracentral, centrolateral, and mediodorsal thalamic nuclei as well as strongly in the posterior hypothalamic area. BRS-3 was expressed weakly in the cerebellum and moderately in the pontine reticular nucleus of the brain stem. Both NMBR and BRS-3 were expressed strongly in most neurons in the dorsal root ganglion. Studies of the expression in the dorsal root ganglion will continue to determine the prominence of large versus small neuron expression of BRS-3 and NMBR. Determining large versus small neuron expression will possibly allow for associating these peptides with behavioral response systems.

The expression of NMBR in the dorsal horn of the spinal cord was inconclusive. Additionally, its expression in the ventral horn of the spinal cord was weak. The expression of BRS-3 in the dorsal and ventral horns of the spinal cord was also weak. Previous studies have shown NMBR to be sparsely expressed in the ventral horn and BRS-3 to be extensively expressed in the dorsal and ventral horns of the spinal cord. An investigation is continuing for the expression of NMB in the adult mouse brain and spinal cord. It is expected to be weakly expressed in areas where NMBR is present, and not expressed in the spinal cord.