Two experiments were performed to investigate the relationship between the expression of sodium appetite and the appearance of Fos-like immunoreactivity (Fos-IR) in the brain of rats. In the first experiment, rats were depleted of sodium by treatment with furosemide 24 h prior to sacrifice and without access to either food or sodium solution. Some rats had access to distilled water, and others had no fluids available during the 24 h. All of the furosemide-treated rats showed Fos-IR in both the subfornical organ (SFO) and around the organum vasculosum laminae terminalis (OVLT). Rats with access to distilled water during the depletion period showed no Fos-IR in the supraoptic (SON) or paraventricular hypothalamic nuclei (PVN) and, in parallel behavioral studies, comparably-treated rats consumed only 0.3 M NaCl solution at the end of the 24 h. In rats that had no fluids during the deprivation period, only about one half showed Fos-IR in SON and PVN and, in parallel behavioral studies, comparably treated rats consumed both water and 0.3 M NaCI solution at the end of 24 h. In a second experiment, cerebroventricular administration of renin stimulated short latency intake of 0.3 M NaCI and water. The relative intakes of water and NaCl were comparable at a low dose of renin, but intake of water exceeded that of NaCl after higher doses. Renin induced Fos-IR in SFO, MnPO, peri-OVLT region, SON and PVN. Both Fos-IR and fluid intake were antagonized by administration of losartan, an angiotensin 11 type 1 receptor antagonist. Thus, only the circumventricular organs of the lamina terminalis showed Fos-IR during each natriorexigenic regimen in these studies. These data support the view that Ang 11 of both central and peripheral origin activates the SFO and/or peri-OVLT region and contributes to sodium appetite. 相似文献
Summary A specific radioimmunoassay for the quantitative measurement of ACTH 4-10 and a procedure for its extraction from plasma have been developed.Its pharmacokinetics was studied in eight healthy male volunteers given ACTH 4-10 125 µg/kg body weight as a bolus i.v. injection, by infusion and intranasally. Following the i.v. bolus, plasma levels rapidly declined biexponentially, with half-lives of 0.39±0.05 min for the -phase and 3.84 ± 1.5 min for the -phase (mean±SD). The constant rate i.v. infusion yielded steady-state levels between 0.74 and 5.06 ng/ml plasma. Administered as intranasal spray, absorption of intact ACTH 4-10 was low and variable (maximal bioavailability 7.6%).The results are discussed in relation to the dose-dependent effects of ACTH 4-10 on the auditory evoked potential. 相似文献
A high-performance liquid chromatographic (HPLC) method is described for the assay of the active metabolite [1-(2-pyrimidinyl)piperazinel of buspirone, an anxiolytic agent, in rat plasma.
The method is based on the use of ion-pair HPLC coupled to a liquid—solid extraction scheme. Samples of rat plasma (2 ml) with internal standard (1-phenylpiperazine), adjusted to pH 10.5 with borate buffer, were loaded on to a preactivated C-18 cartridge. The metabolite and the internal standard were eluted with 5 ml of methanol and injected on to a reversed-phase 10-μm Spherisorb ODS-2 column. The column was eluted with a mobile phase of 0.005 M sodium lauryl sulphate in citrate buffer (pH 3.6)-acetonitrile (65:35, v/v) at 2 ml min−1. Detection was carried out at 248 nm. The recovery of the metabolite was 55%. The method was applied to the determination of the metabolite in rat plasma after oral dosing (25 mg kg−1) of the parent compound. 相似文献
Summary Low doses of the dopamine (DA) agonist apomorphine (APO) induces a behavioural syndrome characterized by reduced spontaneous activity, reduced food and water intake and induction of yawning and penile erections. Traditionally these effects of APO have been considered to be caused by a preferential stimulation of DA autoreceptors, causing a decreased amount of transmitter at the postsynaptic receptors. If this is so, it could be hypothesized that 1) the same behavioural effects should be obtained if DA transmission is decreased by some other means, for example by synthesis inhibition, and that 2) the response to APO should be altered if DA transmission is already lowered.It was found that high doses of -methyl-p-tyrosine (-MPT; 50–200 mg/ kg) did not reduce water intake in thirsty rats, which low doses of APO do. It was further found that pretreatment with -MPT did not alter the response to APO. These results are difficult to reconcile with the DA autoreceptor hypothesis claiming that behavioural effects of low doses of APO are caused by a decreased release of DA. An alternative interpretation is that low doses of APO stimulates a certain population of sensitive postsynaptic D-2 receptors. 相似文献
The time for reproduction in mammals largely depends on the availability of water and food in their habitat. Therefore, in regions where rains are limited to definite seasons of the year, mammals presumably will restrict their breeding correspondingly. But while mammals living in predictable ecosystems would benefit by timing their season to an ultimate predictable cue, such as photoperiod, in unpredictable ecosystems (e.g., deserts) they will need to use a more proximate signal. We suggest a mechanism by which water shortage (low water content in plants) could act as a proximate cue for ending the reproductive season. The golden spiny mouse (Acomys russatus), a diurnal rodent living in extreme deserts, may face an increased dietary salt content as the summer progresses and the vegetation becomes dry. Under laboratory conditions, increased diet salinity lead to reproductive hiatus in females, notable in imperforated vagina, and a significant decrease in the ovaries, uteri, and body masses. In females treated with vasopressin (VP), a hormone expressed during water stress, the uteri and body masses have decreased significantly, and the ovaries exhibited an increased number of atretic follicles. VP has also led to a significant decrease in relative medullary thickness (RMT) of the kidney. It is thus suggested that VP could act as a modulator linking the reproductive system with water economy in desert rodents, possibly through its act on the energetic pathways. 相似文献
Permeabilities to glycerol and small non-electrolytes of three Aquaporin 1 CHIP (AQP1) water channels were measured in AQP1 cRNA-injected Xenopus laevis oocytes and in human AQP1 channels reconstituted in proteoliposomes. By an osmotic swelling assay, significant increases of ethylene glycol, glycerol and 1,3-propanediol apparent permeability coefficients (Psolutes) were found in oocytes expressing human, rat and frog AQP1. p-Chloromercuribenzene sulphonate (PCMBS) and CuSO4 inhibited, by 95% and 58% respectively, apparent glycerol permeability (Pgly) in oocytes expressing human AQP1. pCMBS inhibition was reversed by -mercaptoethanol and CuSO4 inhibition was partly reversed by the Cu2+-binding peptide Gly-Gly-His. Tritiated glycerol uptakes confirmed the augmented Pgly value of AQP1 cRNA-injected oocytes. In contrast, no increases of urea, meso-erythritol, D- or L-threitol, xylitol and mannitol uptakes were detected. Stopped-flow light scattering experiments performed with human AQP1 proteoliposomes also revealed a much greater increase of Pgly than did those with protein-free liposomes; the initial rate of proteoliposomes also swelling was inhibited by 96.2% with HgCl2 and by 72.5% with CuSO4. In AQP1 cRNA-injected oocytes and in proteoliposomes, the value of the glycerol reflection coefficient was 0.74–0.80, indicating that water and glycerol share the same pathway. All these results provide strong evidence that water and certain small solutes permeate the AQP1 channels expressed at the surface of X. laevis oocytes or reconstituted in proteoliposomes. The urea exclusion suggests that the selectivity of the AQP1 channels not only depends on the size of the solutes but probably also on their flexibility and their ability to form H-bonds. 相似文献