Organic molecules in the Sheepbed Mudstone, Gale Crater, Mars.

The Sample Analysis at Mars (SAM) instrument on board the Mars Science Laboratory Curiosity rover is designed to conduct inorganic and organic chemical analyses of the atmosphere and the surface regolith and rocks to help evaluate the past and present habitability potential of Mars at Gale Crater. Central to this task is the development of an inventory of any organic molecules present to elucidate processes associated with their origin, diagenesis, concentration, and long-term preservation. This will guide the future search for biosignatures. Here we report the definitive identification of chlorobenzene (150-300 parts per billion by weight (ppbw)) and C2 to C4 dichloroalkanes (up to 70 ppbw) with the SAM gas chromatograph mass spectrometer (GCMS) and detection of chlorobenzene in the direct evolved gas analysis (EGA) mode, in multiple portions of the fines from the Cumberland drill hole in the Sheepbed mudstone at Yellowknife Bay. When combined with GCMS and EGA data from multiple scooped and drilled samples, blank runs, and supporting laboratory analog studies, the elevated levels of chlorobenzene and the dichloroalkanes cannot be solely explained by instrument background sources known to be present in SAM. We conclude that these chlorinated hydrocarbons are the reaction products of Martian chlorine and organic carbon derived from Martian sources (e.g., igneous, hydrothermal, atmospheric, or biological) or exogenous sources such as meteorites, comets, or interplanetary dust particles. KEY POINTS: First in situ evidence of nonterrestrial organics in Martian surface sediments Chlorinated hydrocarbons identified in the Sheepbed mudstone by SAM Organics preserved in sample exposed to ionizing radiation and oxidative condition.

Mars atmosphere. The imprint of atmospheric evolution in the D/H of Hesperian clay minerals on Mars.

The deuterium-to-hydrogen (D/H) ratio in strongly bound water or hydroxyl groups in ancient martian clays retains the imprint of the water of formation of these minerals. Curiosity's Sample Analysis at Mars (SAM) experiment measured thermally evolved water and hydrogen gas released between 550° and 950°C from samples of Hesperian-era Gale crater smectite to determine this isotope ratio. The D/H value is 3.0 (±0.2) times the ratio in standard mean ocean water. The D/H ratio in this ~3-billion-year-old mudstone, which is half that of the present martian atmosphere but substantially higher than that expected in very early Mars, indicates an extended history of hydrogen escape and desiccation of the planet.

Elemental geochemistry of sedimentary rocks at Yellowknife Bay, Gale crater, Mars.

Sedimentary rocks examined by the Curiosity rover at Yellowknife Bay, Mars, were derived from sources that evolved from an approximately average martian crustal composition to one influenced by alkaline basalts. No evidence of chemical weathering is preserved, indicating arid, possibly cold, paleoclimates and rapid erosion and deposition. The absence of predicted geochemical variations indicates that magnetite and phyllosilicates formed by diagenesis under low-temperature, circumneutral pH, rock-dominated aqueous conditions. Analyses of diagenetic features (including concretions, raised ridges, and fractures) at high spatial resolution indicate that they are composed of iron- and halogen-rich components, magnesium-iron-chlorine-rich components, and hydrated calcium sulfates, respectively. Composition of a cross-cutting dike-like feature is consistent with sedimentary intrusion. The geochemistry of these sedimentary rocks provides further evidence for diverse depositional and diagenetic sedimentary environments during the early history of Mars.

Volatile and organic compositions of sedimentary rocks in Yellowknife Bay, Gale crater, Mars.

H2O, CO2, SO2, O2, H2, H2S, HCl, chlorinated hydrocarbons, NO, and other trace gases were evolved during pyrolysis of two mudstone samples acquired by the Curiosity rover at Yellowknife Bay within Gale crater, Mars. H2O/OH-bearing phases included 2:1 phyllosilicate(s), bassanite, akaganeite, and amorphous materials. Thermal decomposition of carbonates and combustion of organic materials are candidate sources for the CO2. Concurrent evolution of O2 and chlorinated hydrocarbons suggests the presence of oxychlorine phase(s). Sulfides are likely sources for sulfur-bearing species. Higher abundances of chlorinated hydrocarbons in the mudstone compared with Rocknest windblown materials previously analyzed by Curiosity suggest that indigenous martian or meteoritic organic carbon sources may be preserved in the mudstone; however, the carbon source for the chlorinated hydrocarbons is not definitively of martian origin.

Soil diversity and hydration as observed by ChemCam at Gale crater, Mars.

The ChemCam instrument, which provides insight into martian soil chemistry at the submillimeter scale, identified two principal soil types along the Curiosity rover traverse: a fine-grained mafic type and a locally derived, coarse-grained felsic type. The mafic soil component is representative of widespread martian soils and is similar in composition to the martian dust. It possesses a ubiquitous hydrogen signature in ChemCam spectra, corresponding to the hydration of the amorphous phases found in the soil by the CheMin instrument. This hydration likely accounts for an important fraction of the global hydration of the surface seen by previous orbital measurements. ChemCam analyses did not reveal any significant exchange of water vapor between the regolith and the atmosphere. These observations provide constraints on the nature of the amorphous phases and their hydration.

Volatile, isotope, and organic analysis of martian fines with the Mars Curiosity rover.

Samples from the Rocknest aeolian deposit were heated to ~835°C under helium flow and evolved gases analyzed by Curiosity's Sample Analysis at Mars instrument suite. H2O, SO2, CO2, and O2 were the major gases released. Water abundance (1.5 to 3 weight percent) and release temperature suggest that H2O is bound within an amorphous component of the sample. Decomposition of fine-grained Fe or Mg carbonate is the likely source of much of the evolved CO2. Evolved O2 is coincident with the release of Cl, suggesting that oxygen is produced from thermal decomposition of an oxychloride compound. Elevated δD values are consistent with recent atmospheric exchange. Carbon isotopes indicate multiple carbon sources in the fines. Several simple organic compounds were detected, but they are not definitively martian in origin.

The petrochemistry of Jake_M: a martian mugearite.

"Jake_M," the first rock analyzed by the Alpha Particle X-ray Spectrometer instrument on the Curiosity rover, differs substantially in chemical composition from other known martian igneous rocks: It is alkaline (>15% normative nepheline) and relatively fractionated. Jake_M is compositionally similar to terrestrial mugearites, a rock type typically found at ocean islands and continental rifts. By analogy with these comparable terrestrial rocks, Jake_M could have been produced by extensive fractional crystallization of a primary alkaline or transitional magma at elevated pressure, with or without elevated water contents. The discovery of Jake_M suggests that alkaline magmas may be more abundant on Mars than on Earth and that Curiosity could encounter even more fractionated alkaline rocks (for example, phonolites and trachytes).

Curiosity at Gale crater, Mars: characterization and analysis of the Rocknest sand shadow.

The Rocknest aeolian deposit is similar to aeolian features analyzed by the Mars Exploration Rovers (MERs) Spirit and Opportunity. The fraction of sand <150 micrometers in size contains ~55% crystalline material consistent with a basaltic heritage and ~45% x-ray amorphous material. The amorphous component of Rocknest is iron-rich and silicon-poor and is the host of the volatiles (water, oxygen, sulfur dioxide, carbon dioxide, and chlorine) detected by the Sample Analysis at Mars instrument and of the fine-grained nanophase oxide component first described from basaltic soils analyzed by MERs. The similarity between soils and aeolian materials analyzed at Gusev Crater, Meridiani Planum, and Gale Crater implies locally sourced, globally similar basaltic materials or globally and regionally sourced basaltic components deposited locally at all three locations.

Wound healing and angiogenic properties of supernatants from Lactobacillus cultures.

Extracts or supernatants from cultures of Lactobacilli are used for their medicinal effects, including wound healing and immune system stimulating activity. We have studied the in vivo and in vitro effects of supernatants from bacterial cultures of two strains of Lactobacillus (LS) on tissue repair and angiogenesis. Subcutaneous injection of LS into rodent ears led to proliferation of blood vessels that also exhibited strong immunostaining for Flk-1 receptor. Some inflammatory cells were scattered among the blood vessels. The continuous influx of polymorphonuclear leukocytes (PMNs) and macrophages into transcutaneous wounds in mice treated with LS resulted in prolonged inflammatory phase of wound healing and delayed wound closure, including reepithelialization. Subcutaneous injection of Matrigel impregnated with LS into the abdominal wall led to rapid and transient influx of PMNs in the vicinity of the gel. LS stimulated the proliferation of murine macrophage J774.A1 cell line and porcine lymphocytes but not that of murine fibroblast AKR-2B cells. LS also induced production of TNF-alpha by J774.A1 cells and by porcine kidney epithelial LLC-PK1 cells. LS did not appear to have an effect on collagen production. In conclusion, our study demonstrates the potential of LS to function as a stimulator of the inflammatory stage of tissue repair, TNF-alpha production, and of angiogenesis.

Physiological regulation of maternal behavior in heifers: roles of genital stimulation, intracerebral oxytocin release, and ovarian steroids.

We tested the hypotheses that 1) epidural anesthesia at parturition would block both peripheral and central release of oxytocin and eliminate the development of maternal behavior in primiparous heifers and 2) estradiol priming, genital stimulation, and appropriate neonatal stimuli would induce maternal behavior in nulliparous heifers. In experiment 1, primiparous crossbred heifers (n = 13) with cannulas in the third cerebroventricle (IIIV) were assigned randomly to receive epidural treatments of saline (SAL; n = 6) or lidocaine HCl (EPI; n = 7) at the onset of labor induced between Days 270 and 280 of gestation. Epidural anesthesia blocked (P < 0.001) both central and peripheral release of oxytocin and markedly reduced (P < 0.05) or eliminated licking behaviors during a 3-h period following parturition as compared with SAL. Following approximately 1 wk of controlled daily suckling, during which calves were permitted access only to the inguinal region of their dams (three times daily for 10 min each time), a second maternal behavior test was performed. Although licking behavior remained markedly reduced (P < 0.001) in the EPI compared with the SAL groups, all heifers accepted their calf at the udder. In experiments 2-4, neither estradiol priming in ovariectomized heifers nor estradiol plus progesterone in intact heifers resulted in an induction of maternal behaviors following genital stimulation and presentation of a neonate wetted with amniotic fluid. Pelvic sensory deficits apparently block oxytocin release and disturb both short-latency and long-term maternal behaviors but do not result ultimately in rejection of the calf. Combinations of hormonal, sensory, olfactory, and visual cues observed previously to induce maternal behavior in nulliparous ewes do not appear adequate for induction of maternal behavior in nulliparous heifers.

Gonadotropin-releasing hormone secretion into third-ventricle cerebrospinal fluid of cattle: correspondence with the tonic and surge release of luteinizing hormone and its tonic inhibition by suckling and neuropeptide Y.

Objectives of the current studies were to characterize the pattern of GnRH secretion in the cerebrospinal fluid of the bovine third ventricle, determine its correspondence with the tonic and surge release of LH in ovariectomized cows, and examine the dynamics of GnRH pulse generator activity in response to known modulators of LH release (suckling; neuropeptide Y [NPY]). In ovariectomized cows, both tonic release patterns and estradiol-induced surges of GnRH and LH were highly correlated (0.95; p < 0.01). Collectively, LH pulses at the baseline began coincident with (84%) or within one sampling point after (100%) the onset of a GnRH pulse, and all estradiol-induced LH surges were accompanied by corresponding surges of GnRH. A 500- microg dose of NPY caused immediate cessation of LH pulses and lowered (p < 0.001) plasma concentrations of LH for at least 4 h. This corresponded with declines (p < 0.05) in both GnRH pulse amplitude and frequency, but GnRH pulses were completely inhibited for only 1.5-3 h. In intact, anestrous cows, GnRH pulse frequency did not differ before and 48-54 h after weaning on Day 18 postpartum, but concentrations of GnRH (p < 0.05) and amplitudes of GnRH pulses (4 of 7 cows) increased in association with weaning and heightened secretion of LH. We conclude that the study of GnRH secretory dynamics in third-ventricle CSF provides a reasonable approach for examining the activity and regulation of the hypothalamic pulse generator in adult cattle. However, data generated using this approach must be interpreted in their broadest context. Although strong neurally mediated inhibitors of LH pulsatility (suckling; NPY) had robust effects on one or more GnRH secretory characteristics in CSF, only high doses of NPY briefly abolished GnRH pulses. This implies that the GnRH signal received at the hypophyseal portal vessels under these conditions may differ quantitatively or qualitatively from those in CSF, and theoretically would be undetectable or below a biologically effective threshold when LH pulses are absent.

Oxygen isotopic abundances in calcium- aluminum-rich inclusions from ordinary chondrites: implications for nebular heterogeneity.

The oxygen isotopic compositions of two calcium-aluminum-rich inclusions (CAIs) from the unequilibrated ordinary chondrite meteorites Quinyambie and Semarkona are enriched in 16O by an amount similar to that in CAIs from carbonaceous chondrites. This may indicate that most CAIs formed in a restricted region of the solar nebula and were then unevenly distributed throughout the various chondrite accretion regions. The Semarkona CAI is isotopically homogeneous and contains highly 16O-enriched melilite, supporting the hypothesis that all CAI minerals were originally 16O-rich, but that in most carbonaceous chondrite inclusions some minerals exchanged oxygen isotopes with an external reservoir following crystallization.

Immunostimulatory effects of pig seminal proteins on pig lymphocytes.

Pig seminal proteins PSP-I and PSP-II are major protein components of boars' ejaculate and are present as heterodimers (PSP-dimer) in seminal plasma. These proteins were examined for their ability to modulate pig lymphocyte activity in vitro in mitogen-induced lymphocyte proliferation assays and in one-way mixed lymphocyte reactions. Pig lymphocytes were cultured with phytohaemagglutinin, concanavalin A, or pokeweed mitogen (PWM) in the presence or absence of pig seminal proteins and the amount of cellular [3H]thymidine was used as an indication of proliferation. In the absence of mitogens, none of the three pig seminal proteins affected lymphocyte proliferation suggesting that these proteins are not antigenic or mitogenic. PSP-dimer enhanced lymphocyte proliferation induced by PWM (156-227%, P < 0.05) in a concentration-dependent manner, but had no effect on phytohaemagglutinin- or concanavalin A-induced proliferation. PSP-I enhanced (127-185%, P < 0.05) phytohaemagglutinin-induced proliferation. PSP-II augmented (130-240%, P < 0.05) lymphocyte proliferation induced by concanavalin A and PWM. Lymphocytes from gilts were significantly more responsive to concanavalin A- and PWM-induced lymphocyte proliferation in the presence of PSP-I compared with boars (concanavalin A: gilts 131%, boars 91%; PWM: gilts 188%, boars 134%; P < 0.05). In the mixed lymphocyte reaction, pretreating stimulating cells with increasing concentrations of PSP-I or PSP-II elicited a 400% concentration-dependent increase (P < 0.01) in lymphocyte proliferation. The abundance of pig seminal proteins in boar seminal plasma, their ability to enhance lymphocyte proliferation, and their previously reported ability to bind to lymphocytes suggest that these proteins are immunostimulatory and supports the hypothesis that they modulate uterine immune activity to ensure reproductive success.

Origin of magnetite in oxidized CV chondrites: in situ measurement of oxygen isotope compositions of Allende magnetite and olivine.

Magnetite in the oxidized CV chondrite Allende mainly occurs as spherical nodules in porphyritic-olivine (PO) chondrules, where it is associated with Ni-rich metal and/or sulfides. To help constrain the origin of the magnetite, we measured oxygen isotopic compositions of magnetite and coexisting olivine grains in PO chondrules of Allende by an in situ ion microprobe technique. Five magnetite nodules form a relatively tight cluster in oxygen isotopic composition with delta 18O values from -4.8 to -7.1% and delta 17O values from -2.9 to -6.3%. Seven coexisting olivine grains have oxygen isotopic compositions from -0.9 to -6.3% in delta 18O and from -4.6 to -7.9% in delta 17O. The delta 17O values of the magnetite and coexisting olivine do not overlap; they range from -0.4 to -2.6%, and from -4.0 to -5.7%, respectively. Thus, the magnetite is not in isotopic equilibrium with the olivine in PO chondrules, implying that it formed after the chondrule formation. The delta 17O of the magnetite is somewhat more negative than estimates for the ambient solar nebula gas. We infer that the magnetite formed on the parent asteroid by oxidation of metal by H2O which had previously experienced minor O isotope exchange with fine-grained silicates.

Immunocytochemical distribution of catecholamine-synthesizing neurons in the hypothalamus and pituitary gland of pigs: tyrosine hydroxylase and dopamine-beta-hydroxylase.

This study describes the distribution of catecholaminergic neurons in the hypothalamus and the pituitary gland of the domestic pig, Sus scrofa, an animal that is widely used as an experimental model of human physiology in addition to its worldwide agricultural importance. Hypothalamic catecholamine neurons were identified by immunocytochemical staining for the presence of the catecholamine synthesizing enzymes, tyrosine hydroxylase and dopamine-beta-hydroxylase. Tyrosine hydroxylase-immunoreactive perikarya were observed in the periventricular region throughout the extent of the third ventricle, the anterior and retrochiasmatic divisions of the supraoptic nucleus, the suprachiasmatic nucleus, the ventral and dorsolateral regions of the paraventricular nucleus and adjacent dorsal hypothalamus, the ventrolateral arcuate nucleus, and the posterior hypothalamus. Perikarya ranged from parvicellular (10-15 microns) to magnocellular (25-50 microns) and were of multiple shapes (rounded, fusiform, triangular, or multipolar) and generally had two to five processes with branched arborization. No dopamine-beta-hydroxylase immunoreactive perikarya were observed within the hypothalamus or in the adjacent basal forebrain structures. Both tyrosine hydroxylase- and dopamine-beta-hydroxylase-immunoreactive fibers and punctate varicosities were observed throughout areas containing tyrosine hydroxylase perikarya, but dopamine-beta-hydroxylase immunoreactivity was very sparse within the median eminence. Within the pituitary gland, only tyrosine hydroxylase fibers, and not dopamine-beta-hydroxylase immunoreactive fibers, were located throughout the neurohypophyseal tract and within the posterior pituitary in both pars intermedia and pars nervosa regions. Generally, the location and patterns of both catecholamine-synthesizing enzymes were similar to those reported for other mammalian species except for the absence of the A15 dorsal group and the very sparse dopamine-beta-hydroxylase immunoreactive fibers and varicosities in the median eminence in the pig. These findings provide an initial framework for elucidating behavioral and neuroendocrine species differences with regard to catecholamine neurotransmitters.

Immunocytochemical localization of the catecholamine-synthesizing enzymes, tyrosine hydroxylase and dopamine-beta-hydroxylase, in the hypothalamus of cattle.

Immunocytochemical staining for the presence of catecholamine synthesizing enzymes, tyrosine hydroxylase and dopamine beta-hydroxylase, was used to characterize the regional distribution of catecholaminergic neurons in the hypothalamus and adjacent areas of domestic cattle, Bos taurus. In steers, heifers and cows, tyrosine hydroxylase-immunoreactive perikarya was located throughout periventricular regions of the third cerebral ventricle, in both anterior and retrochiasmatic divisions of the supraoptic nucleus, suprachiasmatic nucleus, and ventral and dorsolateral regions of the paraventricular nucleus, dorsal hypothalamus, ventrolateral aspects of the arcuate nucleus, along the ventral hypothalamic surface between the median eminence and optic tract, and in the posterior hypothalamus. Immunostained perikarya ranged from small (10-20 microns, parvicellular) to large (30-50 microns, magnocellular) and were of multiple shapes: round, triangular, fusiform or multipolar, often with 2-5 processes of branched arborization. There were no dopamine-beta-hydroxylase immunoreactive perikarya observed within the hypothalamus and adjacent structures. However, both tyrosine hydroxylase and dopamine-beta-hydroxylase immunoreactive fibers and punctate varicosities were observed throughout regions of tyrosine hydroxylase immunoreactivity perikarya. Generally, the location and pattern of hypothalamic tyrosine hydroxylase immunoreactivity and dopamine-beta-hydroxylase immunoreactive were similar to those reported for most other large brain mammalian species, however, there were several differences with commonly used small laboratory animals. These included intense tyrosine hydroxylase immunoreactivity of perikarya within the retrochiasmatic division of the supraoptic nucleus (ventral A15 region), the absence of tyrosine hydroxylase immunoreactive perikarya below the anterior commissure or within the bed nucleus of stria terminalis (absence of the dorsal A15 region), an abundance of tyrosine hydroxylase immunoreactive perikarya within the ependymal layer of the median eminence, heavy innervation of the arcuate nucleus with dopamine-beta-hydroxylase immunoreactive fibers and varicosities, and the paucity of dopamine-beta-hydroxylase immunoreactive throughout the median eminence.

Catecholaminergic region A15 in the bovine and porcine hypothalamus.

Magnocellular perikarya within the retrochiasmatic division of the supraoptic nucleus of bovine and porcine hypothalami were immunoreactive (ir) with antiserum against tyrosine hydroxylase (TH), but not dopamine-beta-hydroxylase (DBH). Few cells in this region were also immunoreactive for vasopressin (VP) or oxytocin (OT). In contrast, the main division of the supraoptic nucleus contained numerous perikarya immunoreactive for VP and OT, but not TH nor DBH. Both the retrochiasmatic and principal divisions of the supraoptic nuclei contained TH- and DBH-ir fibers and varicosities. This region in bovine and porcine hypothalami corresponds to the ventral A15 catecholaminergic (dopamine-producing) cell group.

Opioid modulation of gonadotropin releasing hormone release from the hypothalamic preoptic area in the pig.

Two experiments (Exp) were conducted to examine in vitro the release of gonadotropin releasing hormone (GnRH) from the hypothalamus after treatment with naloxone (NAL) or morphine (MOR). In Exp 1, hypothalamic-preoptic area (HYP-POA) collected from 3 market weight gilts at sacrifice and sagittally halved were perifused for 90 min prior to a 10 min pulse of morphine (MOR; 4.5 x 10(-6) M) followed by NAL (3.1 x 10(-5) M) during the last 5 min of MOR (MOR + NAL; n = 3). The other half of the explants (n = 3) were exposed to NAL for 5 min. Fragments were exposed to KCl (60 mM) at 175 min to assess residual GnRH releasability. In Exp 2, nine gilts were ovariectomized and received either oil vehicle im (V; n = 3); 10 micrograms estradiol-17 beta/kg BW in 42 hr before sacrifice (E; n = 3); .85 mg progesterone/kg BW in twice daily for 6 d prior to sacrifice (P4; n = 3). Blood was collected to assess pituitary sensitivity to GnRH (.2 microgram/kg BW) on the day prior to sacrifice. On the day of sacrifice HYP-POA explants were collected and treated as described in Exp 1 except tissue received only NAL. In Exp 1, NAL increased (P < .05) GnRH release. This response to NAL was attenuated (P < .05) by coadministration of MOR. Cumulative GnRH release after NAL was greater (P < .05) than after MOR + NAL. All tissues responded similarly to KCl with an increase (P < .05) in GnRH release.(ABSTRACT TRUNCATED AT 250 WORDS)

Growth hormone-releasing hormone and somatostatin neurons within the porcine and bovine hypothalamus.

Hypothalamic growth hormone-releasing hormone (GHRH) and somatotropin release-inhibiting factor or somatostatin (SS) immunoreactive (ir) neurons were localized in pigs (n = 8) and cattle (n = 7) to identify neuroanatomical sites involved in the regulation of growth hormone secretion. Coronal and sagittal frozen sections (30-60 microns) of Zamboni's fixed hypothalamic tissue, without prior colchicine treatment were incubated with GHRH or SS primary antisera for 48 h, then visualized by peroxidase-diaminobenzidine immunocytochemistry. Fusiform, bipolar SS-ir perikarya were located about the third ventricle in the periventricular nucleus, extending from rostral aspects of preoptic periventricular nucleus to a level approximate with caudal regions of the paraventricular nucleus. Rounded or fusiform, bipolar GHRH-ir perikarya were mostly located in ventrolateral portions of the arcuate nucleus in pigs and cattle, and within ventral aspects of the ventromedial nucleus in pigs but rarely in cattle. In both pigs and cattle, SS-ir and GHRH-ir fibers projected ventrally into the median eminence with dense and overlapping innervation of the external layer, especially dense in lateral regions. In pigs, but not as distinguishable in cattle, SS-ir fibers also densely innervated the ventromedial and arcuate hypothalamic nuclei. Double immunostained sections revealed close apposition of SS-ir fibers and varicosities with GHRH-ir perikarya in arcuate and ventromedial nuclei, and apposition of SS-ir and GHRH-ir varicosities in the median eminence.

Involvement of the central noradrenergic system in opioid modulation of luteinizing hormone and prolactin secretion in the pig.

The role of norepinephrine (NE) in the progesterone (P)-dependent endogenous opioid peptide (EOP) suppression of LH and prolactin (PRL) secretion in the pig was studied. Fifteen ovariectomized gilts treated with P (0.85 mg/kg b.w. i.m.) twice daily for 10 days were assigned, 5 gilts each, to the following treatment groups: 1) control, 2) AIMAX (N-methyl-N1[1-methyl-2-propenyl]1,2 hydrazinedicarbothioamide), and 3) anti-GnRH serum. On day 4 of P treatment, AIMAX (125 mg per 1.8 kg feed/day), previously shown to be an NE synthesis inhibitor, was fed daily for 7 days to group 2. On the last day of P treatment, group 3 gilts received an i.v. injection of anti-GnRH serum at 0800 h while Group 1 animals received an i.v. injection of serum collected from hypophysectomized gilts. Jugular blood samples were collected every 15 min for 9 h starting at 1000 h. All gilts received two injections of naloxone (NAL; 1 mg/kg b.w., i.v.) at 1400 h and 1600 h and an injection of a GnRH analogue (D-[Ala6-desGly-NH10]-ethylamide; 5 micrograms/pig, i.v.) at 1800 h. Pretreatment serum LH concentrations were lower (p < 0.05) in AIMAX-treated gilts (0.19 +/- 0.09 ng/ml) than in controls (0.53 +/- 0.09 ng/ml), but were similar to those in GnRH antiserum-treated gilts (0.32 +/- 0.09 ng/ml). NAL increased (p < 0.001) serum LH concentrations in control animals and averaged 1.6 +/- 0.2 ng/ml the first h. AIMAX and anti-GnRH serum blocked the NAL-induced LH secretion. Serum PRL concentrations averaged 6.0 +/- 0.1 ng/ml for all groups.(ABSTRACT TRUNCATED AT 250 WORDS)