Expression of mammalian RF-amide peptides neuropeptide FF (NPFF), prolactin-releasing peptide (PrRP) and the PrRP receptor in the peripheral tissues of the rat.

The mRNA expression of neuropeptide FF (NPFF), prolactin-releasing peptide (PrRP) and the UHR-1/GPR10 receptor were examined using in situ hybridization in rat peripheral tissues. In the hypophysis, modest expression of PrRP and receptor mRNA were seen in the anterior lobe. The trigeminal ganglion was devoid of expression signals. PrRP and UHR-1/GPR10 receptor mRNA:s were found in the adrenal medulla and PrRP mRNA was found in the pancreas. NPFF mRNA was detected in the spleen. In the testis and epididymis, PrRP and UHR-1/GPR10 receptor mRNA:s were detected. The results suggest a limited expression of mammalian RF-amide peptides in the peripheral organs.

Gene for pain modulatory neuropeptide NPFF: induction in spinal cord by noxious stimuli.

Neuropeptides FF (NPFF), AF (NPAF), and SF (NPSF) are homologous amidated peptides that were originally identified on the basis of similarity to the molluscan neuropeptide FMRF-amide. They have been hypothesized to have wide-ranging functions in the mammalian central nervous system, including pain modulation, opiate function, cardiovascular regulation, and neuroendocrine function. We have cloned the NPFF gene from human, bovine, rat, and mouse, and show that the precursor mRNA encodes for all three of the biochemically identified peptides (NPFF, NPAF, and NPSF). We demonstrate that NPFF precursor mRNA expression by Northern analysis and map sites of expression by in situ hybridization. We confirm the validity of the in situ hybridization by showing that its distribution in the brain and spinal cord matches the distribution of NPFF and NPSF immunoreactivity. We go on to show that the mRNA levels (as measured by in situ hybridization) in the spinal cord can be up-regulated by a model for inflammatory pain (carrageenan injection), but not by a model for neuropathic pain (lumbar nerve ligation). Our results confirm the evolutionary conservation of NPFF, NPAF, and NPSF neuropeptide expression in mammalian brain. They also provide a context for the interpretation of the pain-sensitizing effects of injections of these peptides that have been previously reported. Our results support a model for the role of these peptides in pain regulation at the level of the spinal cord.

Platelet taurine concentration and uptake in the Brattleboro diabetes insipidus rat.

Since platelets accumulate taurine, they provide a model for studying the taurine transport in anisosmotic disorders. Thus, in this work we studied the taurine concentration and uptake in the platelets of Brattleboro rats, homozygous (DI) and heterozygous (HZ) for hereditary hypothalamic diabetes insipidus, and Long Evans (LE) normal rats after free water intake and after dehydration induced by water deprivation for 24 h. The decreased ability of the DI rats to concentrate urine led to plasma hypernatremia and hyperosmolality despite excessive drinking. Water deprivation in the DI rats induced drastic dehydration with exacerbated hypernatremia and hyperosmolality. Plasma hypernatremia and hyperosmolality resulted in a significant elevation of the taurine concentration and uptake by platelets of the DI rats. Kinetic assays showed that plasma hypernatremia and hyperosmolality did not alter the affinity of taurine to platelet membrane carrier, as expressed by Km, but caused a profound increase in the maximal transport capacity, Vmax. After free water intake the Vmax of the DI rats was about two times higher than that in the HZ and LE rats and after water deprivation it was about three times higher. Water deprivation doubled the Vmax of the DI rats without changing the Km.

Taurine in the osmoregulation of the Brattleboro rat.

The function of taurine in mammalian osmoregulation was studied in the Brattleboro rat with hereditary hypothalamic diabetes insipidus (DI). DI rats are chronically dehydrated because of their inability to synthesize vasopressin. One day of water deprivation did not affect the water balance in rats with normal vasopressin synthesis, whereas DI rats were markedly dehydrated and lost considerably body weight. Taurine content and 3H-taurine accumulation by platelets were significantly higher in DI rats, with a further increase after one day of water deprivation. In DI rats, water deprivation also evoked a clear taurine increase in skeletal muscle and in the brain. These findings indicate that taurine has an osmoregulatory function in mammals.