We provide the first evidence that prolactin is a neuromodulator of behavioral and neuroendocrine stress coping in the rat. In virgin female and male rats, intracerebral infusion of ovine prolactin (oPRL) into the lateral cerebral ventricle (intracerebroventricular) exerted an anxiolytic effect on the elevated plusmaze in a dose-dependent manner (0.1 and 1.0 g/5 l; p Ͻ 0.01). In contrast, downregulation of the expression of the long form of brain prolactin receptors by chronic intracerebroventricular infusion of an antisense oligodeoxynucleotide (ODN) (osmotic minipump, 0.5 g ⅐ 0.5 l Ϫ1 ⅐ hr Ϫ1 ; 5 d) increased anxiety-related behavior on the plus-maze compared with mixed bases-treated and vehicle-treated rats ( p Ͻ 0.01), again demonstrating an anxiolytic effect of PRL acting at brain level. Furthermore, in jugular vein-catheterized female rats, the stress-induced increase of corticotropin secretion was decreased after chronic intracerebroventricular infusion of oPRL (osmotic minipump, 1.0 g ⅐ 0.5 l Ϫ1 ⅐ hr Ϫ1 ; p Ͻ 0.05) and, in contrast, was further elevated by antisense targeting of the brain prolactin receptors ( p Ͻ 0.01). This provides evidence for a receptor-mediated attenuation of the responsiveness of the hypothalamo-pituitary-adrenal (HPA) axis by prolactin. The antisense ODN sequence was selected on the basis of secondary structure molecular modeling of the target mRNA to improve antisense ODN-mRNA hybridization. Receptor autoradiography confirmed the expected improvement in the efficacy of downregulation of prolactin receptor expression [empirically designed antisense, 30%; p Ͼ 0.05, not significant; adjustment of target position after mRNA modeling, 72%; p Ͻ 0.05). Taken together, prolactin acting at brain level has to be considered as a novel regulator of both emotionality and HPA axis reactivity.

We recently found that human small cell lung carcinomas (SCLCs) express, in addition to other neuroendocrine markers, vesicular monoamine transporters. Our present results indicate that SCLCs are histaminergic. We detected the biosynthetic enzyme histidine decarboxylase by immunohistochemistry in paraffin sections of 12 biopsies of SCLC tumors. This finding was supported by immunoblotting and reverse transcription-polymerase chain reaction experiments using established SCLC cell lines, frozen and paraffin-embedded SCLC tumors. Moreover, we found histamine to be synthesized, stored, and released by cultured SCLC cells. Our novel observations may be useful for developing new diagnostic tools for this frequent and highly malignant tumor.

Gastric enterochromaffin-like (ECL) cells are histamine-producing cells in the gastric epithelium which are responsible for the peripheral regulation of acid secretion. The gastric mucosa is frequently infected with Helicobacter pylori, leading to increased levels of the pro-inflammatory cytokine tumor necrosis factor-α (TNF-α). The aim of our current study was to identify the effect of TNF-α on programmed cell death. ECL cells were isolated from the rat corpus mucosa to a purity >90%. TNF receptor and adapter protein presence were determined using RT-PCR, Western blot and immunocytochemistry. Apoptosis was measured by Tdt-mediated dUTP nick end labeling reaction and by DNA fragmentation based ELISA. Isolated ECL cells were found to express the TNF receptor p55 and IFN-γ receptor, but not the TNF receptor p75 or CD95. TNF-α (25 ng/ml) increased apoptosis in ECL cells approximately 4-fold, IFN-γ had no effect. Western blot analysis revealed that TNF-α caused degradation of IĸBα within 10 min. EMSA demonstrated that TNF-α led to increased DNA-binding activity of NFĸB and that proteasome inhibitors counteracted NFĸB activation. Proteasome inhibitors, specific antisense oligodeoxynucleotides against the p65 subunit of the NFĸB complex and the NO synthase inhibitor N^G-monomethyl-L-arginine completely prevented TNF-α-induced apoptosis. Our data suggest that TNF-α induces apoptosis of isolated gastric ECL cells via activation of NFĸB and the generation of NO.

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