3. ACh-evoked responses were blocked by d-tubocurarine (d-TC), hexamethonium and mecamylamine, but were insensitive to a-bungarotoxin. These characteristics define a neuronal type of nicotinic receptors.4. The whole-cell current induced by ACh showed a strong inward rectification with no outward current being obtained. This phenomenon was observed when the intracellular ion is either sodium or caesium, and even when Ca2+ and Mg2+ were totally removed from the intracellular medium.5. ACh-gated channels in intermediate lobe cells were cation selective and were permeable to Na+ and Cs+. In Ca2+-free extracellular solution, single-channel conductances were much larger (46 pS) than in the presence of 2 mM-Ca2+ (26 pS).6. The possibility of an excitatory cholinergic control of intermediate lobe cells is discussed.

Three-dimensional collagen-chitosan scaffolds were fabricated with type I collagen and chitosan through freeze drying and glutaraldehyde cross-linking. Dermal fibroblasts were isolated from neonatal Sprague-Dawley rat skin by dispase II/collagenase I digestion. The fibroblasts were then seeded into the scaffolds to construct tissue-engineered dermis. The microstructure of the scaffolds as well as the fibroblasts' proliferation, cytokine secretion and cell cycle were investigated. Flow cytometry analysis indicated that cells in the scaffolds proliferated steadily. IL-6 concentration measurement by the ELISA test suggested that the scaffolds could promote secretion of the fibroblasts' cytokine. These results show that the fibroblasts and the scaffolds interact well with each other, and the fibroblasts have better proliferation ability and biological activity in the scaffolds than in monolayer culture. The scaffolds are a promising candidate for tissue repair and regeneration with enhanced biostability and good cytocompatibility.