Chronic haloperidol treatment decreases preproenkephalin mRNA in the anterior pituitary: a study by solution-hybridization-RNase protection assay

Reduction in somatostatin and substance P levels and choline acetyltransferase activity in the cortex and hippocampus of the rat after chronic intracerebroventricular infusion of beta-amyloid (1-40)

The present study investigated the neurochemical and behavioural sequelae following chronic intracerebroventricular infusion of beta-amyloid (1-40) in rats. beta-amyloid was either infused intermittently via implanted cannulae on the day of operation and subsequently on postsurgical days 4, 7, 10, and 13 (Experiment 1), or continuously using osmotic pumps for 14 days (Experiment 2). The same amount of beta-amyloid was delivered under both infusion regimes. In both experiments, beta-amyloid infusion led to severe deficits in the acquisition of a spatial reference memory task conducted on postoperative days 10 to 14. The animals were sacrificed on the postoperative day 15 for neurochemical analyses. These included radioenzymatic and radioimmunoassays, designed to determine choline acetyltransferase activity and the contents of neuropeptides (somatostatin, substance P, and neuropeptide Y), respectively. Experiment 2 also included solution-hybridisation-RNAase protection assay for preprosomatostatin mRNA quantification. There was a significant reduction in choline acetyltransferase activity and in the levels of substance P as well as somatostatin and preprosomatostatin mRNA in the cortical mantle of beta-amyloid-treated rats, compared to controls in both experiments. Appreciable reductions in choline acetyltransferase activity and somatostatin level were also apparent in the hippocampus. In contrast, beta-amyloid infusion did not significantly affect the brain level of neuropeptide Y. The present study demonstrated that chronic infusion of beta-amyloid can lead to a reduction in the levels of selected neuropeptides resembling the pattern seen in Alzheimer's disease patients.

The distribution and gene expression of adrenomedullin in the rat brain: peptide/mRNA and precursor/active peptide relationships

The highest immunoreactive adrenomedullin (AM) concentrations were found in the pituitary gland, hypothalamus and brainstem. Rat preproadrenomedullin mRNA levels were highest in the pituitary, followed by the hypothalamus. The peptide to mRNA ratios are higher in the neurointermediate lobe, brainstem and hypothalamus. Immunocytochemical study showed discrete localization of AM immunostaining in various brain regions including the cerebral cortex, hypothalamus and brainstem and in the pituitary gland. By gel filtration chromatography, the precursor peaks were low in the pituitary, hypothalamus and brainstem but high in other brain regions.

The effect of streptozotocin-diabetes on beta-endorphin level and proopiomelanocortin gene expression in the rat pituitary

Streptozotocin-induced diabetes for 4 weeks resulted in a decrease in proopiomelanocortin (POMC) mRNA in both the anterior lobe (AL) and the neuro-intermediate lobe (NIL) of the rat pituitary. The beta-endorphin levels decreased in the NIL but not in the AL. It is concluded that the synthesis of POMC in the pituitary is inhibited in diabetic rats and that there is a decrease in beta-endorphin release from the anterior pituitary.

The effect of aging on the response of striatal preproenkephalin and preprotachykinin mRNA contents to chronic haloperidol treatment in rats: measurement by solution-hybridization RNase protection assay

The preproenkephalin (PPeK) and preprotachykinin (PPT) mRNA contents in 3-, 10- and 23-month-old rats in the striatum were measured by solution hybridization-RNase protection assay after 3 weeks of haloperidol injection. Haloperidol increased striatal PPek mRNA. There was no age-related difference in the response of striatal PPeK mRNA to chronic haloperidol treatment. The PPT mRNA decreased by 21% after the haloperidol treatment in young rats only. Meanwhile, age decreased the PPT mRNA by 27 and 24% in 10- and 23-month-old rats, respectively. It is concluded that there is a difference in the effects of aging on the response of PPek and PPT mRNA contents to haloperidol and that the loss of PPT mRNA response in 10- and 23-month-old rats might be due to the change of dopamine system of the striatum in these rats.