Nigrostriatal dopaminergic neurons express many nicotinic acetylcholine receptor (nAChR) subunits capable of forming multiple nAChR subtypes. These subtypes are expressed differentially along the neuron and presumably mediate diverse responses. beta3 subunit mRNA has restricted expression but is abundant in the substantia nigra and ventral tegmental areas. To investigate the potential role(s) of nicotinic receptors containing the beta3 subunit in dopaminergic tracts, we generated mice with a null mutation in the beta3 gene. We were thereby able to identify a population of beta3-dependent alpha-conotoxin MII-binding nAChRs that modulate striatal dopamine release. Changes were also observed in locomotor activity and prepulse inhibition of acoustic startle, behaviors that are controlled, in part, by nigrostriatal and mesolimbic dopaminergic activity, respectively, suggesting that beta3-containing nAChRs modulate these behaviors.

In response to nerve growth factor (NGF), clonal pheochromocytoma cells flatten and extend neurites capable of making functional synapses. Although no significant changes in overall phospholipid composition occur in the presence of NGF, there is increased incorporation of 32PO4 into phosphatidylinositol and phosphatidic acid within 10 min after the addition of NGF. NGF stimulates the incorporation of 32PO4 into other lipids, such as phosphatidylcholine, to a lesser extent. The kinetics of the NGF-induced phosphatidylinositol responses are different when the cells are in suspension from when they are attached to culture dishes. These changes in phospholipid metabolism are discussed with respect to their role in NGF-induced nerve differentiation.

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When screening supernatant fluids from hybridoma clones, Dulbecco and co-workers found that a mouse monoclonal antibody generated against a mammary tumor cell line showed rather striking high binding to rat oocytes and granulosa cells. In this study we have specifically investigated the reactivity of the monoclonal antibody (designated anti-OA-1) with granulosa cells during the differentiation process. This was accomplished using the two-step indirect immunocytochemical technique. When a primordial follicle is recruited to initiate growth, intense immunoreactivity appears in the surface membrane of the granulosa cells. As a follicle proceeds through the preantral stages, the plasma membrane of the granulosa cells is strongly positive for anti-OA-1 reactivity, and the granulosa appear as a homogeneous population. However, once Graafian follicle development is initiated, a major shift in anti-OA-1 immunoreactivity occurs among the granulosa cells. As the antrum expands, 75% of the granulosa in the mural region (those nearest the basal lamina) elongate and become negative for anti-OA-1. This is in contrast to the periantral and cumulus granulosa, which remain rounded and show strong anti-OA-1 reactivity up to the preovulatory stage. The disappearance of anti-OA-1 reactivity in the subpopulation of mural cells is specifically initiated by FSH and occurs very rapidly after a 12-h lag phase. After the loss of anti-OA-1 reactivity, the elongated mural granulosa cells express their terminal differentiated state by acquiring LH/hCG receptor, 3 beta-hydroxysteroid dehydrogenase activity and cytoplasmic lipid inclusions. By contrast, the periantral and cumulus granulosa, which remain positive for anti-OA-1, do not express these differentiated functions; however, they do differentiate ultrastructurally, indicating that they respond to the FSH signal. These results strongly suggest that a monoclonal antibody recognizes a major surface differentiation antigen in the granulosa cell. This antigen is under hormonal control and is inversely linked to expression of the terminal differentiation program in the granulosa cells. We anticipate that the monoclonal antibody will be a valuable probe to aide in the analysis of structure/function relationships in subpopulations of granulosa cells.