The incremental nature of neuroendocrine aging suggests that subtle system dysregulation may precede overt axis failure. The present analyses unmask threefold disruption of pulsatile gonadotropin-releasing hormone (GnRH)-luteinizing hormone (LH) secretion in the aging male. First, by way of random effects-based deconvolution analysis, we document an elevated daily GnRH-LH pulse frequency in hea...

Neuropeptide Y (NPY) is a putative mediator of many physiological processes in the central nervous system including reproductive functions. In this study we examined the effect of NPY on the GnRH/LH secretory activity in early anoestrous ewes. Crossbreed ewes one week (group 1w, n=7) and six weeks (group 6w, n=7) after the last oestrous cycle were infused with Ringer solution (control) or 50 mi...

Reproductive aging is characterized by delayed and attenuated luteinizing hormone (LH) surges apparent in middle-aged rats. The suprachiasmatic nucleus (SCN) contains the circadian clock that is responsible for the timing of diverse neuroendocrine rhythms. Electrophysiological studies suggest vasoactive intestinal peptide (VIP) originating from the SCN excites gonadotropin-releasing hormone (Gn...

During spring sheep do not normally ovulate but exposure to a ram can induce ovulation. In some ewes an LH surge is induced immediately after exposure to a ram thus raising questions about the control of this precocious LH surge. Our first aim was to determine the plasma concentrations of oestradiol (E2) E2 in anoestrous ewes before and after the "ram effect" in ewes that had a "precocious" LH ...

The impact of suppressed concentrations of circulating luteinizing hormone (LH) during ovarian stimulation on the outcome of in-vitro fertilization or intracytoplasmic sperm injection treatment in 200 consecutive, normogonadotrophic women (couples) was analysed retrospectively. A standard stimulation protocol with mid-luteal gonadotrophin-releasing hormone (GnRH) agonist down-regulation and ova...

It is well known that majority of patients with collagen diseases are women and that collagen diseases take turn for the worse or the better when the secretion of sex hormones changes greatly at menarche, pregnancy, delivery or menopause. These facts suggest that sex hormones are involved in the pathophysiology of collagen diseases. In the present study, the responses of plasma luteinizing horm...

Slow local skin heating (LH) causes vasodilator responses, some of which are dependent on sympathetic nerve function. It is not known, however, how the rate of LH affects either the sympathetic or the nonadrenergic components of the responses to LH and whether the adrenergic effects of LH depend on tonic sympathetic activity or whether LH stimulates transmitter release. In part 1, cutaneous vas...

We tested two hypotheses about the disruption of luteinizing hormone (LH) pulsatility in exercising women by assaying LH in blood samples drawn at 10-min intervals over 24 h from nine young, habitually sedentary, regularly menstruating women on days 8, 9, or 10 of two menstrual cycles after 4 days of intense exercise [E = 30 kcal.kg lean body mass (LBM)-1.day-1 at 70% of aerobic capacity]. To t...

Pituitaries were collected from intact rams and rams that had been rendered bilaterally cryptorchid by surgery to examine the effects of cryptorchidism on gonadotropin heterogeneity, levels of uncombined luteinizing hormone (LH) subunits, and the apparent molecular sizes of LH and follicle-stimulating hormone (FSH). Cryptorchid rams had higher pituitary contents of LH and FSH as well as reduced...

The lateral hypothalamic (LH) projection to the ventral tegmental area (VTA) has been linked to reward processing, but the computations within the LH-VTA loop that give rise to specific aspects of behavior have been difficult to isolate. We show that LH-VTA neurons encode the learned action of seeking a reward, independent of reward availability. In contrast, LH neurons downstream of VTA encode...