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The formation of rabbit oviduct fluid was monitored continuously by using an in situ vascular perfusion technique. Oviduct fluid was secreted linearly for at least 3 h at a mean rate of 20.8 +/- 1.5 microliter/h in estrous does. The rate more than doubled on Day 1 following mating, was similar to the value at estrus on Day 2, and dropped to 8.3 microliter on Day 3. Dibutyryl cyclic adenosine 3',5'-monophosphate (cAMP, 1 mM) added to the vascular medium abolished fluid secretion. The same response was obtained, after a lag period, following the addition of cholera toxin (1 mM), forskolin (1 mM), theophylline (1 mM), phorbol dibutyrate (40 microM), A23187 (2 micrograms/ml), 4-acetamido-4'-isothiocyonatostilbene-2,2'-disulphonic acid (SITS, 1 mM), and bumetanide (10 microM) to the vascular medium. N-ethylmaleimide (1 mM), which inhibits adenylate cyclase, stimulated oviduct fluid formation. The transmural potential difference (p.d.) across the oviduct was 5.46 +/- 1.01 mV. This was increased after cAMP addition to 8.7 +/- 1.22 mV. The p.d. in oviducts taken 3 days post-ovulation was 7.6 +/- 1.75 mV, and was increased by cAMP to 12.7 +/- 0.53 mV. Exposure to cholera toxin and forskolin almost doubled the cAMP content of the oviduct. The undirectional flux of chloride ions from the vascular compartment into the lumen was reduced by about 75% after the addition of cAMP, SITS, and bumetanide. A tentative model to account for the formation and regulation of rabbit oviduct fluid in terms of ion fluxes and cAMP and calcium ion concentrations is presented.

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The present literature characterising the pharmacology of the hypothalamic receptor(s) responsible for mediating the hyperphagic effect of NPY is fragmented and far from comprehensive. Different groups of workers have studied NPY, its fragments and substituted analogues in the rat by administering these substances into the lateral or third brain ventricle or via direct administration into discrete hypothalamic nuclei [ 1-51. Much of this work has been performed using single doses of agonists and has utilised the porcine rather than the native series of neuropeptides.In the present work, we have performed a systematic analysis of the dose-feeding response relationship for hNPY and a number of its fragments and derivatives in order to define their relative potency and intrinsic activity for this action. These agents or vehicle were administered icv, during the light phase, to free-fed conscious male Sprague Dawley rats with an implanted lateral ventricular cannula. Food intake was measured hourly for 4 hours. Results were analysed by ANOVA using the 4 hour data.