Distribution of Corticotrophin-Releasing Factor Type 1 Receptor-Like Immunoreactivity in the Rat Pituitary.

Corticotrophin-releasing factor (CRF) regulates the hypothalamic-pituitary-adrenal axis response to stress through its type 1 receptor (CRF1 ) in the corticotrophs of the anterior pituitary. Although CRF1 mRNA expression has been confirmed in the rat pituitary, the distribution pattern of CRF1 protein in the pituitary has not been reported. Therefore, we generated an antiserum against the amino acid fragment corresponding to the 177-188 sequence of the first extracellular loop of the rat CRF1 . Using the antiserum, CRF1 -like immunoreactivity (CRF1 -LI) was detected in the anterior lobe cells of the rat pituitary where some of them expressed intense signals. CRF1 -LI also appeared in the intermediate lobe cells and on the fibre-like elements of the posterior lobe of the pituitary. Dual immunofluorescence labelling showed that corticotrophs exhibited the highest percentage of CRF1 (male: 27.1 ± 3.0%, female: 18.0 ± 3.0%), followed by lactotrophs (male: 6.7 ± 3.0%, female: 12.1 ± 1.3%), gonadotrophs (male: 2.6 ± 1.0%, female: 7.5 ± 0.5%), thyrotrophs (male: 2.9 ± 0.1%, female: 5.3 ± 1.2%) and somatotrophs (male: 1.1 ± 0.3%, female: 1.2 ± 0.5%). The percentage of CRF1 -LI-positive cells that were corticotrophs was significantly higher in male rats than in female rats, whereas CRF1 -LI-positive lactotrophs and gonadotrophs were significantly higher in female rats than in male rats. Almost all of the melanotrophs were positive for CRF1 in the intermediate lobe (98.9 ± 0.2%). CRF1 -LI and the percentage of CRF1 -LI in corticotrophs were decreased in the anterior pituitary, and the distribution patterns were altered from a diffuse to punctate one by adrenalectomy; the changes were restored by treatment with dexamethasone (100 µg/kg bw). These results suggest that CRF1 is involved in the modulation of the functions of the pituitary; moreover, protein expression and the distribution patterns of CRF1 are regulated by glucocorticoids in the rat anterior pituitary.

Distribution of urocortin 2 in various tissues of the rat.

Urocortin (Ucn) 2 is a new member of the corticotrophin-releasing hormone (CRH) neuropeptide family that is expressed in the central nervous system and peripheral tissues. However, the expression levels of Ucn 2 in various tissues of the rat remains unclear. Thus, the aim of the present study was to characterise the expression of Ucn 2 in the various tissues of the rat. Reverse transcriptase-polymerase chain reaction analysis demonstrated that Ucn 2 mRNA is expressed in the hypothalamus, pituitary, adrenal, stomach, skin, ovary, uterus and skeletal muscle. Histologically, Ucn 2 mRNA and Ucn 2-like immunoreactivity (LI) were demonstrated in both the anterior and intermediate lobes of the pituitary, but not detected in the posterior lobe. Furthermore, all Ucn 2-positive cells in the anterior and intermediate lobes were also positive for beta-endorphin. Ucn 2 mRNA was detected in the adrenal cortex and medulla although Ucn 2-LI was only found in the adrenal medulla. High-performance liquid chromatography analysis of hypothalamic, pituitary, and adrenal extracts showed that the main Ucn 2-LI peak occurred at the same molecular size as that of synthetic Ucn 2. These results suggest that Ucn 2 is synthesised in various tissues, including the anterior and intermediate lobes of the pituitary and the adrenal.

Selective corticotropin-releasing factor type 1 receptor antagonist blocks conditioned fear-induced release of noradrenaline in the hypothalamic paraventricular nucleus of rats.

The effects of conditioned fear on the release of noradrenaline in the hypothalamic paraventricular nucleus (PVN) and the involvement of corticotropin-releasing factor (CRF) receptor type 1 (CRFR1) in conditioned fear-induced changes in noradrenaline release were examined by intracerebral microdialysis in rats. Conditioned fear was produced by placing animals into a box where they had previously been exposed to a 5-min period of electric footshock, 135 min prior to the start of experiment. Conditioned fear for 20 min produced a significant increase in the release of noradrenaline in the PVN. Intraperitoneal preadministration of a selective nonpeptidic CRFR1 antagonist, CRA1000, completely blocked the conditioned fear-induced release of noradrenaline. These results suggest that CRFR1 is involved in the release of noradrenaline in the hypothalamic PVN induced by conditioned fear.

High voltage electrical stimulation of the proximal hypoglossal nerve in normal subjects.

OBJECTIVES: It is often difficult to stimulate the proximal hypoglossal nerve by magnetic occipital stimulation, even in normal subjects. Therefore, we tested an improved method of stimulating the proximal hypoglossal nerve, using high voltage electrical stimulation. METHODS: The proximal hypoglossal nerve was activated by high voltage electrical stimulation using surface electrodes over the occipital skull. The compound muscle action potential (CMAP) was recorded from the lingual muscles using surface electrodes in 10 normal subjects. CMAP and F waves produced by distal hypoglossal nerve stimulation and motor evoked potentials produced by transcranial magnetic stimulation were also recorded. RESULTS: When the anode electrode was placed at the mastoid process and the cathode below the inion, the unilateral proximal hypoglossal nerve was readily stimulated supramaximally in all the subjects. The CMAP latency was the same as that obtained with magnetic occipital stimulation. The central motor conduction time (CMCT) calculated from the proximal CMAP was 4.1+/-0.4 ms in the contralateral corticobulbar tract and 4.4+/-0.4 ms in the ipsilateral. The CMCT calculated from the minimal F wave latency was 3.3+/-0.2 ms. CONCLUSIONS: The high voltage electrical stimulation is a useful method for stimulating the proximal hypoglossal nerve to estimate the CMCT of the corticobulbar tract.

Nicotine infusion alters leptin and uncoupling protein 1 mRNA expression in adipose tissues of rats.

We attempted to clarify whether leptin and uncoupling protein 1 (UCP1) are involved in the action of nicotine on the energy balance. Male Wistar rats were infused subcutaneously with nicotine (12 mg x kg(-1) x day(-1)) for 4 or 14 days. At the end of the 4-day period, the plasma concentrations of leptin of the nicotine-treated and pair-fed rats were lower than those of the freely fed rats, although the levels of leptin mRNA expression in various white adipose tissues did not differ among the three groups. At the end of the 14-day nicotine infusion period, plasma concentrations of leptin were higher, and leptin mRNA expression in the omentum and epididymal and retroperitoneal adipose tissues was stronger in the nicotine-treated rats than in the pair-fed and freely fed rats. UCP1 mRNA expression in the brown adipose tissue of nicotine-treated was stronger than that of the pair-fed rats. These results suggest that continuous nicotine infusion differentially affects the synthesis and secretion of leptin according to the duration of infusion and stimulates UCP1 mRNA expression, probably in a manner independent of leptin.

Electrophysiological features of central motor conduction in spinocerebellar atrophy type 1, type 2, and Machado-Joseph disease.

OBJECTIVES: To characterise electrophysiologically the central motor conduction of spinocerebellar atrophy type 1 (SCA1), type 2 (SCA2), and Machado-Joseph disease (MJD). METHODS: Motor evoked potentials (MEPs) triggered by transcranial magnetic stimulation (TMS) was used to investigate the functions of corticospinal tracts of 10 patients with SCA1, 10 with MJD, and eight with SCA2 in addition to pathological study of the spinal cord in a patient with SCA1. RESULTS: Central motor conduction time (CMCT) was extremely prolonged and the MEP threshold increased in all patients with SCA1, whereas both were normal in patients with SCA2 or MJD. The MEP size in MJD was larger than normal, but was normal in SCA1 and SCA2. A pathological investigation of the corticospinal tract of the spinal cord of a patient with SCA1 showed selective loss of large diameter fibres. CONCLUSIONS: SCA1, SCA2, and MJD differ in their pathophysiological features of the central motor tract and can be differentiated from each other by MEP values for the lower limb muscles, even though their neurological symptoms are sometimes similar.