Previous studies have revealed the existence of a gene family that encodes a group of neuronal nicotinic acetylcholine receptor (nAChR) subunits. Four members of this family have been characterized thus far; three of these subunits (alpha 2, alpha 3, and alpha 4) are structurally related to the ligand binding subunit expressed in muscle and form functional nAChRs when combined with the beta 2 gene product in Xenopus oocytes. In addition, the alpha 4 gene appears to encode two different products (alpha 4-1 and alpha 4-2) that have been proposed to arise by alternative mRNA splicing. Nine different [35S]-complementary ribonucleic acid (cRNA) probes were used in the present study to map the distribution of these nAChR subunit mRNAs throughout the central nervous system (CNS) of the rat. It was found that the beta 2 gene is expressed in most regions of the CNS, as are the alpha subunit genes as a group. However, each alpha gene is expressed in a unique, although partly overlapping, set of neuronal structures. Alpha 4 is the most widely expressed alpha gene, and the evidence suggests that mRNAs for the alpha 4-1 and alpha 4-2 products are virtually always found in the same regions, in approximately the same ratios (alpha 4-2 greater than alpha 4-1). In addition, there are several examples of cell groups that express beta 2 but none of the alpha subunit mRNAs examined here (particularly in the hypothalamus), as well as all groups that express the converse, thus suggesting that additional neuronal nAChR subunits remain to be characterized. Finally, the extensive expression of multiple alpha subunits in certain regions, particularly for alpha 3 and alpha 4 in the thalamus, suggests that there is microheterogeneity in a small population of cells or that some neurons may express more than one alpha subunit. This problem needs to be examined directly with double labeling methods but raises the possibility that some neuronal nAChRs may be composed of more than one kind of alpha subunit. The wide expression of these receptor genes suggests that nAChRs constitute major excitatory systems in the CNS.

Activation of microglia commonly occurs in response to a wide variety of pathological stimuli including trauma, axotomy, ischemia, and degeneration in the CNS. In the retina, prolonged or high-intensity exposure to visible light leads to photoreceptor cell apoptosis. In such a light-reared retina, we found that activated microglia invade the degenerating photoreceptor layer and alter expression of neurotrophic factors such as nerve growth factor (NGF), ciliary neurotrophic factor (CNTF), and glial cell line-derived neurotrophic factor (GDNF). Because these neurotrophic factors modulate secondary trophic factor expression in Müller glial cells, microglia-Müller glia cell interaction may contribute to protection of photoreceptors or increase photoreceptor apoptosis. In the present study, we demonstrate the possibility that such functional glia-glia interactions constitute the key mechanism by which microglia-derived NGF, brain-derived neurotrophic factor (BDNF), and CNTF indirectly influence photoreceptor survival, although the receptors for these neurotrophic factors are absent from photoreceptors, by modulating basic fibroblast growth factor (bFGF) and GDNF production and release from Müller glia. These observations suggest that microglia regulate the microglia-Müller glia-photoreceptor network that serves as a trophic factor-controlling system during retinal degeneration.

Mammalian bombesin-like peptides are widely distributed in the central nervous system as well as in the gastrointestinal tract, where they modulate smooth-muscle contraction, exocrine and endocrine processes, metabolism and behaviour. They bind to G-protein-coupled receptors on the cell surface to elicit their effects. Bombesin-like peptide receptors cloned so far include, gastrin-releasing peptide receptor (GRP-R), neuromedin B receptor (NMB-R), and bombesin receptor subtype-3 (BRS-3). However, despite the molecular characterization of BRS-3, determination of its function has been difficult as a result of its low affinity for bombesin and its lack of an identified natural ligand. We have generated BRS-3-deficient mice in an attempt to determine the in vivo function of the receptor. Mice lacking functional BRS-3 developed a mild obesity, associated with hypertension and impairment of glucose metabolism. They also exhibited reduced metabolic rate, increased feeding efficiency and subsequent hyperphagia. Our data suggest that BRS-3 is required for the regulation of endocrine processes and metabolism responsible for energy balance and adiposity. BRS-3-deficient mice provide a useful new model for the investigation of human obesity and associated diseases.

Neurons in the upper lumbar spinal cord project axons containing gastrin-releasing peptide (GRP) to innervate lower lumbar regions controlling erection and ejaculation. This system is vestigial in female rats and in males with genetic dysfunction of androgen receptors, but in male rats, pharmacological stimulation of spinal GRP receptors restores penile reflexes and ejaculation after castration. GRP offers new avenues for understanding potential therapeutic approaches to masculine reproductive dysfunction.GRP, a member of the bombesin-like peptide family 1 , is distributed widely in the central nervous system and gastrointestinal tract of mammals 2 , 3 . GRP and neuromedin B (NMB), the mammalian counterpart of bombesin, play a role in many physiological processes, including itch 4 , circadian rhythms 5 , food intake 6 and fear memory consolidation 7 , 8 . In mammals, bombesin-like peptides act through a family of at least three G protein-coupled receptors: GRP-preferring receptor (GRP-R), NMB-preferring receptor (NMB-R) and bombesin receptor subtype-3 (BRS-3) 9 .Using immunocytochemistry (ICC) directed at GRP, we found a group of neurons within a region previously dubbed the 'spinal ejaculation generator' because toxins that selectively lesion galanin-containing neurons there virtually eliminate ejaculation in rats 10 . These galaninergic neurons project to the thalamus 10 , but it had been unclear whether there are also direct connections between this center and the lower spinal cord regions that directly trigger ejaculation 11 . The separate, GRP-containing neurons that we found within the center projected axons to more caudal spinal regions and were much more prominent in wild-type (WT) males than in WT females ( Fig. 1a,b; Supplementary Fig. 1 online) (n = 5, F 2,12 = 299.9, P < 0.001). Semiquantitative reverse transcription (RT)-PCR confirmed more pre-pro NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author ManuscriptGrp transcripts in this region of males than of females ( Supplementary Fig. 2 online). To test whether androgen receptors direct sexual dimorphism of these neurons, we examined genetically male (XY) Long-Evans rats carrying the testicular feminization mutation (Tfm) of the androgen receptor gene Ar. These rats develop testes embryologically and secrete testosterone pre-and postnatally but, because their androgen receptor protein is dysfunctional, develop a wholly feminine exterior, including a clitoris rather than a penis. The spinal cord of Tfm rats was hyperfeminine, having even fewer GRP-positive neurons in this region than did WT females (P <0.001) (Fig. 1c,d). In normal males, GRP-expressing neurons also expressed androgen receptor (96.1 ± 1.7%; n = 4 WT males), but not estrogen receptor alpha (ERα) (Fig. 1e-h). Because androgens such as testosterone augment ejaculation in male rats and humans 12 , the presence of androgen receptor in the GRPpositive neurons of the ejaculation center offers a locus for androgenic modulation of ejaculation and other sexual reflexes.ICC r...

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Maternal obesity may affect the child's long-term development and health. However, there is little information about the involvement of maternal obesity in the brain development of offspring. Here, we investigated the effects of maternal obesity on the hippocampal formation of offspring. Adult female mice were fed either a normal diet (ND, 4% fat) or a high-fat diet (HFD, 32% fat) 6 wk before mating and throughout pregnancy and the majority of lactation. We found that infants from HFD-fed dams (HFD offspring) showed obesity and hyperlipidemia during suckling. In HFD offspring, lipid peroxidation was promoted in serum and the hippocampal dentate gyrus, where neurogenesis takes place throughout postnatal life. Using a BrdU-pulse labeling study, we showed that malondialdehyde, a product of peroxidized lipids, reduced the proliferation of hippocampal progenitor cells in vitro and that neurogenesis in HFD offspring during postnatal development was similarly lowered relative to the ND animals. These results indicated that maternal obesity impairs hippocampal progenitor cell division and neuronal production in young offspring possibly due to metabolic and oxidative changes.

ABSTRACTproposed to regulate the progression from G, to S phase. In this work, we have cloned and structurally characterized a third member ofthe cdc2 kinase family with 58% amino acid sequence identity to mouse cdkl and 61% identity to human cdk2. We call this kinase neuronal cdc2-like kinase (ndk) because, in contrast to either cdkl or cdk2, nclk is expressed at high levels in terminally differentiated neurons no longer in the cell cycle.