Binding studies of substance P anterior pituitary binding sites: changes in substance P binding sites during the rat estrous cycle

Tachykinins, new players in the control of reproduction and food intake: A comparative review in mammals and teleosts

In vertebrates, the tachykinin system includes tachykinin genes, which encode one or two peptides each, and tachykinin receptors. The complexity of this system is reinforced by the massive conservation of gene duplicates after the whole-genome duplication events that occurred in vertebrates and furthermore in teleosts. Added to this, the expression of the tachykinin system is more widespread than first thought, being found beyond the brain and gut. The discovery of the co-expression of neurokinin B, encoded by the tachykinin 3 gene, and kisspeptin/dynorphin in neurons involved in the generation of GnRH pulse, in mammals, put a spotlight on the tachykinin system in vertebrate reproductive physiology. As food intake and reproduction are linked processes, and considering that hypothalamic hormones classically involved in the control of reproduction are reported to regulate also appetite and energy homeostasis, it is of interest to look at the potential involvement of tachykinins in these two major physiological functions. The purpose of this review is thus to provide first a general overview of the tachykinin system in mammals and teleosts, before giving a state of the art on the different levels of action of tachykinins in the control of reproduction and food intake. This work has been conducted with a comparative point of view, highlighting the major similarities and differences of tachykinin systems and actions between mammals and teleosts.

Tachykinins and the control of prolactin secretion

Tachykinins are present in the pituitary gland and in brain areas involved in the control of the secretion of pituitary hormones. Tachykinins have been demonstrated to stimulate prolactin release acting directly on the anterior pituitary gland. These peptides have also been revealed to be able to act at the hypothalamic level, interacting with neurotransmitters and neuropeptides that have the potential to affect prolactin secretion. Tachykinins seem to act by stimulating or inhibiting the release of the factors that affect prolactin secretion. Among them, tachykinins have been demonstrated to stimulate oxytocin and vasopressin release, which in turn results in prolactin release. Tachykinins also potentiated the response to vasoactive intestinal peptide (VIP) and reinforced the action of glutamate, which in turn result in prolactin release. They have also been shown to interact with serotonin, a neurotransmitter involved in the control of prolactin secretion. In addition, tachykinins have been shown to inhibit GABA release, a neurotransmitter with prolactin-release inhibiting effect. This inhibition may result in an increased prolactin secretion by removal of the GABA inhibition. On the other hand, tachykinins have also been shown to stimulate dopamine release by the hypothalamus, an action that results in an inhibition of prolactin release. Dopamine is a well known inhibitor of prolactin secretion. In conclusion, although tachykinins have been shown to have a predominantly stimulatory effect on prolactin secretion, especially at the pituitary level, under some circumstances they may also exert an inhibitory influence on prolactin release, by stimulating dopamine release at the hypothalamic level.

Three-dimensional representation of the neurotransmitter systems of the human hypothalamus: inputs of the gonadotrophin hormone-releasing hormone neuronal system

The gonadotrophin-releasing hormone (GnRH) represents the final common pathway of a neuronal network that integrates multiple external and internal factors to control fertility. Among the many inputs GnRH neurones receive, oestrogens play the most important role. In females, oestrogen, in addition to the negative feedback, also exhibits a positive feedback influence upon the activity and output of GnRH neurones to generate the preovulatory luteinising hormone surge and ovulation. Until recently, the belief has been that the GnRH neurones do not contain oestrogen receptors and that the action of oestrogen upon GnRH neurones is indirect, involving several, oestrogen-sensitive neurotransmitter and neuromodulator systems that trans-synaptically regulate the activity of the GnRH neurones. Although this concept still holds for humans, recent studies indicate that oestrogen receptor-beta is expressed in GnRH neurones of the rat. This review provides three dimensional stereoscopic images of GnRH-immunoreactive (IR) and some peptidergic (neuropeptide Y-, substance P-, beta-endorphin-, leu-enkaphalin-, corticotrophin hormone-releasing- and galanin-IR) and catecholaminergic neurones and the communication of these potential oestrogen-sensitive neuronal systems with GnRH neurones in the human hypothalamus. Because the post-mortem human tissue does not allow the electron microscopic identification of synapses on GnRH neurones, the data presented here are based on light microscopic immunocytochemical experiments using high magnification with oil immersion, semithin sections or confocal microscopy.

Characterization of tachykinin NK2 receptor in the anterior pituitary gland

Tachykinins are a family of bioactive peptides that interact with three subtypes of receptors: NK1, NK2 and NK3. Substance P has greater affinity for NK1, and neurokinin A (NKA) for NK2 receptor subtype. Although only NK1 receptor has been characterized in the anterior pituitary gland, some evidence suggests the existence of NK2 receptors in this gland. Therefore, we investigated the presence of NK2 receptors in the anterior pituitary gland of male rats by radioligand binding studies using labeled SR48968, a non peptidic specific antagonist. [3H]SR48968 specific binding to cultured anterior pituitary cells was time-dependent and saturable, but with a lower affinity than previously reported values for cells expressing NK2 receptors. Unlabeled NKA inhibited only partially [(3)H]SR48968 specific binding to whole anterior pituitary cells. Since SR48968 is a non polar molecule, we performed experiments to discriminate surface from intracellular binding sites. SR48968 exhibited both surface and intracellular specific binding. Analysis of the surface-bound ligand indicated that [3H]SR48968 binds to one class of receptor with high affinity. Neurokinin A completely displaced [3H]SR48968 surface specific binding fitting to a two-site/two-state model with high and low affinity. Additionally, immunocytochemical studies showed that the NK2 receptor is expressed at least in a subset of lactotropes. These results demonstrate the presence of NK2 receptors in the anterior pituitary gland and suggest that NKA actions in this gland are mediated, at least in part, by the NK2 receptor subtype.

Differential effects of unopposed versus opposed hormone therapy, tibolone, and raloxifene on substance p levels

OBJECTIVE

To evaluate the effects of unopposed therapy (conjugated equine estrogens [CEE]) vs. opposed therapy (CEE and medroxyprogesterone acetate), tibolone, and raloxifene on serum substance p levels.

DESIGN

Clinical study.

SETTING

University hospital.

PATIENT(S)

One hundred eight postmenopausal women were assigned to four treatment groups: unopposed hormone therapy (HT) (n = 30), opposed HT (n = 48), tibolone (n = 18), and raloxifene (n = 12).

INTERVENTION(S)

Conjugated equine estrogens, CEE and medroxyprogesterone acetate, tibolone, and raloxifene were administered orally; blood samples were collected before therapy and 3 months after.

MAIN OUTCOME MEASURE(S)

Serum substance p levels were measured before and at the end of the third month of the treatment.The serum substance p levels were increased in the unopposed HT group after treatment. On the contrary, substance p levels were decreased in the opposed HT group, in the tibolone group, and in the raloxifene group.

CONCLUSION(S)

Addition of progesterone (P) to estrogen (E) treatment significantly decreases serum substance p levels. Tibolone and raloxifene exert the same effect.

The autocrine/paracrine regulation of thyrotropin secretion

Peptides originally described in other tissues have been located in the anterior pituitary gland. Detection of their encoding mRNAs and specific receptors, together with demonstration of peptide local action led to the postulation of the existence of a paracrine/autocrine regulation of pituitary function. Direct evidence for the role of endogenous peptides has come from studies aiming to block their action through immunoneutralization or pharmacologic blockade. Here we review evidence of pituitary produced peptides as potential candidates as local regulators of thyrotropin secretion. Few studies have approached the subject and most data are not conclusive. Until now, the most consistent data relate to neuromedin B, a bombesin-like peptide. The combined observation of high peptide concentration in rat thyrotrophs, the ability of the exogenous peptide to inhibit thyrotropin (TSH) release in physiologic doses plus the effect of the specific neuromedin B antiserum to increase basal TSH release from isolated pituitaries suggest that neuromedin B acts as a constitutive autocrine TSH-release inhibitor. Neuromedin B is upregulated by thyroid hormones and downregulated by thyrotropin-releasing hormone (TRH) that is consistent with proposed role of local factors, namely to partially mediate or modulate the effects of hormones on pituitary function. However, future studies will certainly confirm other candidates as local regulators of TSH secretion, as well as their relevance at physiologic and pathologic conditions.

A comparison of modality-specific somatosensory changes during menstruation in dysmenorrheic and nondysmenorrheic women

OBJECTIVE

The objective was to evaluate somatosensory thresholds to a multimodality stimulation regimen applied both within and outside areas of referred menstrual pain in dysmenorrheic women, over four phases of confirmed ovulatory cycles, and to compare them with thresholds in nondysmenorrheic women during menstruation.

DESIGN

Twenty dysmenorrheic women with menstrual pain scoring 5.45 +/- 0.39 cm (mean +/- standard error of mean) on a visual analog scale (10 cm) participated. Fifteen nondysmenorrheic women with a menstrual pain score of 0.4 +/- 0.2 cm participated as controls. Ovulation was confirmed by an enzyme-multiplied immunoassay technique. Menstrual pain was described with the McGill Pain Questionnaire. Areas within menstrual pain referral were two abdominal sites and the midline of the low back, and the arm and thigh were the control areas. The pressure pain threshold (PPT) and pinch pain threshold were determined by a hand-held electronic pressure algometer, the heat pain threshold (HPT) by a contact thermode, and the tactile threshold with von Frey hairs.

RESULTS

In dysmenorrheic women the McGill Pain Questionnaire showed a larger sensory and affective component of pain than the evaluative and miscellaneous groups. The HPT and PPT were lower in the menstrual phase than in the ovulatory, luteal, and premenstrual phases, both within and outside areas of referred menstrual pain (p <0.01), with a more pronounced decrease at the referral pain areas. The pinch pain threshold was lower in the menstrual phase than in the ovulatory phase (p <0.02), and the tactile threshold did not differ significantly across the menstrual phases or within any site. Dysmenorrheic women had a lower HPT at the control sites and a lower PPT at the abdomen, back, and control sites, than in those of nondysmenorrheic women in the menstrual phase.

CONCLUSIONS

The results show reduced somatosensory pain thresholds during menstruation to heat and pressure stimulation, both within and outside areas of referred menstrual pain in dysmenorrheic women. Dysmenorrheic women showed a lower HPT at the control sites and a lower PPT at all the sites than those for nondysmenorrheic women in the menstrual phase. The altered somatosensory thresholds may be dependent on a spinal mechanism of central hyperexcitability, induced by recurrent moderate to severe menstrual pain.

Long-term effects of the mammary carcinogen 7,12-dimethylbenz(a) anthracene on hypothalamic gonadotropin-releasing hormone and its pituitary receptor gene expression, during the promotion stage, in female Sprague-Dawley rats

A single intragastric administration of 7,12-dimethylbenz(a)anthracene (DMBA) has been shown to induce mammary tumors in young cycling female Sprague-Dawley rats. The appearance of these tumors is preceded by a series of neuroendocrine disturbances, including attenuation of the preovulatory luteinizing hormone (LH) surge and amplification of the preovulatory 17beta-estradiol surge, and gonadotropin-releasing hormone (GnRH) released in vitro. In this study, we examined the hypothesis that DMBA administration decreases levels of GnRH mRNA in the preoptic area-anterior hypothalamus (POA-AH) and GnRH receptor (GnRH Rc) mRNA and protein in the anterior pituitary gland. Sprague-Dawley rats, 55-60 days of age with regular estrous cycles, received a single dose of 15 mg DMBA in 1 ml sesame oil delivered by intragastric intubation. A first series of experiments was performed for the measurement of hypothalamic GnRH mRNA and pituitary GnRH Rc mRNA levels. A second series of experiments was performed for the measurement of pituitary GnRH receptor. In both experiments, animals were sacrificed by decapitation at 11.00, 16.00, 18.00 and 20.00 h on each day of the 7th or 8th estrous cycle (28-32 days) after treatment. GnRH and GnRH receptor mRNAs were quantified using solution hybridization-RNase protection assay. The GnRH Rc was quantified using the 125I-D-Ala6-N-Met-Leu6-des-Gly10-ethylamide GnRH. DMBA-treatment produced no significant effect on the overall mean values of GnRH mRNA. GnRH mRNA levels in control rats rose significantly between 16.00 and 20.00 h on proestrus and between 18.00 and 20.00 h on diestrus I. DMBA-treated rats had a surge in GnRH mRNA levels at 18.00 h on proestrus, and showed additional surges at 18.00h on diestrus II and estrus. GnRH receptor mRNA content in the anterior pituitary gland surged at 16.00h on certain days of the cycle in both groups of rats. In control rats, only the surge on diestrus II proved significant, whereas DMBA-treated rats exhibited significant surges on diestrus I, diestrus II and proestrus. GnRH receptor mRNA values were significantly lower on both days of diestrus in DMBA-treated rats compared with controls. GnRH Rc peptide content, like GnRH receptor in RNA surged at 16.00h in both groups with the exception of a marked fall on proestrus day for DMBA treated rats. A reduction in the amplitude of the surge was also seen on the day of estrous and to a lesser extend on the day of diestrus DII in DMBA treated animal. Overall, there was a disruption of the GnRH Rc pattern which culminate on the day of proestrus in DMBA-treated animals. Interestingly, the daily rise between 11.00 and 16.00h which is the more pronounced on the day of proestrus in control animals, was completely blunted in DMBA-treated rats. Overall, the results are consistent with the hypothesis that the carcinogen attenuates, directly or indirectly, preovulatory biosynthesis of the GnRH receptor and LH release. Obviously, the changes in GnRH might occur simultaneously, independently from mammary tumorigenesis, but may play a role, in association with others DMBA-induced neuroendocrine disorders, in the promotion stage of mammary tumors in the Sprague-Dawley female rat.

The association of hormone replacement therapy with experimental pain responses in postmenopausal women

Considerable experimental research suggests that ovarian hormones can influence pain perception, and recent epidemiologic and clinical research suggests that exogenous hormone use may influence the prevalence and severity of clinical pain among women. However, to date no studies have examined the influence of hormone replacement therapy (HRT) on experimental pain responses and recent pain complaints among postmenopausal women. In this study, self-reported recent pain and general health were obtained, and thermal pain responses were assessed in three groups of healthy older adults: (1) women on HRT, (2) women not on HRT (No-HRT), and (3) men. Results indicated no group differences in recent pain complaints or self-reported health, but differences emerged for measures of thermal pain perception. Specifically, HRT women showed lower pain thresholds and tolerances than No-HRT women and men, and the latter two groups did not differ from each other. The potential explanations and limitations of the observed findings are discussed.

Prolactin: structure, function, and regulation of secretion

Prolactin is a protein hormone of the anterior pituitary gland that was originally named for its ability to promote lactation in response to the suckling stimulus of hungry young mammals. We now know that prolactin is not as simple as originally described. Indeed, chemically, prolactin appears in a multiplicity of posttranslational forms ranging from size variants to chemical modifications such as phosphorylation or glycosylation. It is not only synthesized in the pituitary gland, as originally described, but also within the central nervous system, the immune system, the uterus and its associated tissues of conception, and even the mammary gland itself. Moreover, its biological actions are not limited solely to reproduction because it has been shown to control a variety of behaviors and even play a role in homeostasis. Prolactin-releasing stimuli not only include the nursing stimulus, but light, audition, olfaction, and stress can serve a stimulatory role. Finally, although it is well known that dopamine of hypothalamic origin provides inhibitory control over the secretion of prolactin, other factors within the brain, pituitary gland, and peripheral organs have been shown to inhibit or stimulate prolactin secretion as well. It is the purpose of this review to provide a comprehensive survey of our current understanding of prolactin's function and its regulation and to expose some of the controversies still existing.

Sex-related hormonal influences on pain and analgesic responses

Considerable evidence indicates sex-related differences in pain responses and in the effectiveness of various analgesic agents. Specifically, females are at greater risk for experiencing many forms of clinical pain and are more sensitive to experimentally induced pain relative to males. Regarding analgesic responses, nonhuman animal studies indicate greater opioid analgesia for males, while a limited human literature suggests the opposite. Though the mechanisms underlying these effects remain unclear, the influence of gonadal hormones on nociceptive processing represents one plausible pathway whereby such sex differences could emerge. The present article reviews the complex literature concerning sex steroid effects on pain responses and analgesia. First, nonhuman animal research related to hormonal effects on nociceptive sensitivity and analgesic responses is presented. Next, human studies regarding gonadal hormonal influences on experimental pain responses are reviewed. Several potential mechanisms underlying hormonal effects on nociceptive processing are discussed, including hormonal effects to both peripheral and central nervous system pathways involved in pain transmission. Finally, based on these findings we draw several conclusions and make specific recommendations that will guide future research as it attempts to elucidate the magnitude and importance of sex-related hormonal effects on the experience of pain.

Variations in plasma levels of substance P and effects of a specific substance P antagonist of the NK(1) receptor on preovulatory LH and FSH surges and progesterone secretion in the cycling cynomolgus monkey

These studies investigated the role of substance P (SP) in the regulation of the hypothalamic-pituitary-ovarian axis in cynomolgus monkeys with normal menstrual cycles. Plasma concentrations of SP were determined in blood samples taken every morning in normally menstruating cynomolgus monkeys throughout the menstrual cycle. There was a significant decreasing linear trend of SP during the follicular phase (cycle day -13 to day 0) and a significant inverse relationship between SP plasma values and plasma 17beta-estradiol (E(2)) values from day -13 to day 0 of the adjusted cycle. Correspondingly, SP area under the curve was significantly greater during the follicular phase than the luteal phase. In a second experiment, plasma concentrations of E(2), luteinizing hormone (LH), follicle-stimulating hormone (FSH) and progesterone and length of cycles were measured after five daily intragastric administrations (10 mg/kg) of an NK(1) receptor (SP receptor) antagonist (RPR 100893; 10 mg/kg) initiated after serum E(2) concentrations had exceeded 125 pg/ml. There was a statistically significant reduction in the amplitude (41% of control) and the area under the curve (37% of control) of the preovulatory LH surge. In addition, there was a reduction of the duration of the LH surge (3 +/- 0.1 days in controls vs. 2.1 +/- 0.2 days in treated animals). The present results show for the first time that there are significant variations in plasma levels of SP, with a strong negative correlation with serum levels of E(2) during the follicular phase of the cynomolgus monkey, and that endogenous SP has a potentiating role in the interactive hypothalamo-anterior-pituitary mechanisms which lead to the preovulatory LH and FSH surges during the menstrual cycle in the monkey.

Interaction between substance P and gastrin-releasing peptide on thyrotropin secretion by rat pituitary in vitro

The effect of substance P (SP) on thyrotropin (TSH) secretion is controversial. In this study we evaluated the effect of SP on TSH secretion by hemipituitaries of 3-month-old Wistar rats in vitro and its interaction with gastrin-releasing peptide (GRP) at equimolar concentrations (1 microM and 10 microM). TSH release was measured under basal conditions and 30 min after incubation in the absence or presence of SP, GRP or both peptides. Pituitary TSH content was also measured in the pituitary homogenate after incubation. SP at both concentrations caused a significant (P<0.05) increase in TSH secretion compared with all other groups, which was approximately 60% (1 microM) and 85% (10 microM) higher than that of the control group (23.3 +/- 3.0 ng/ml). GRP at the lower concentration did not produce a statistically significant change in TSH secretion, whereas at the concentration of 10 microM it produced a 50% reduction in TSH. GRP co-incubated with substance P completely blocked the stimulatory effect of SP at both concentrations. Pituitary TSH content decreased in the SP-treated group compared to controls (0.75 +/- 0.03 microg/hemipituitary) at the same proportion as the increase in TSH secretion, and this effect was also blocked when GRP and SP were co-incubated. In conclusion, in an in vitro system, SP increased TSH secretion acting directly at the pituitary level and this effect was blocked by GRP, suggesting that GRP is more potent than SP on TSH secretion, and that this inhibitory effect could be the predominant effect in vivo.

Modulation of gonadotropin levels by peptides acting at the anterior pituitary gland

There are several lines of evidence that point to peptides participating in the regulation of LH and/or FSH levels by action at the pituitary. This evidence includes altered secretion of gonadotropins from the anterior pituitary cells or tissue in vitro when exposed to the peptide. Additionally, modification of GnRH-stimulated LH/FSH secretion has been observed. Furthermore, there is potential for a separately modulated interaction with the primed response. Another potential of action is by interaction among non-GnRH peptides on gonadotropin-regulating processes, although there are no good data available on this aspect. Other observations, consistent with a pituitary role for the peptides in modulation of LH, include detection of the peptides in portal blood, detection of high-affinity receptors or receptor mRNA in the pituitary, and detection of intrapituitary peptide or peptide mRNA in the pituitary. The modulation by steroids of both concentrations and type of activities provides a further level of physiological refinement. There is, however, some confusion regarding the involvement of these peptides in gonadotropin control. The reasons can be seen by considering aspects of investigations. There are experimental variations such as 1) species studied, e.g., NPY has been reported to have an effect on LH secretion from rat cells (168) but not on sheep anterior pituitary tissue (64), and substance P inhibits GnRH-stimulated release from rat cells (182) but potentiates the response in prepubertal porcine cells (92); 2) the steroidal conditions under which the study is performed, e.g., NPY has opposite effects in certain endocrine environments, augmenting GnRH-stimulated LH release in proestrus-like conditions (168), and inhibiting in metestrus-like environment (66); 3) the type of cell preparation, e.g., responsiveness to substance P might depend on whether cells in overnight culture were in separated or clustered state (91); 4) the time course considered, e.g., oxytocin that might induce marked LH release from pituitary cells after a longer length of incubation than GnRH requires (68); 5) length of exposure to peptide, e.g., endothelin that augmented or inhibited GnRH-stimulated LH release (50); 6) In addition, it is possible that the traditional endpoint selected in such studies, namely, observation of gonadotropin secretion, is not necessarily the most important for these peptides (56, 81, 117). Unfortunately, at this stage a definitive answer to the question "What do the peptides actually do?" cannot be provided and we remain tantalized by the glimpses of potential roles. Perhaps in a few years an updated review will be able to include a more complete answer. It is necessary for the full understanding of LH control that not only the properties of the peptides in isolation be characterized but also their interactions.

Plasma substance-P and substance-K and gonadal steroids in relation to the gonadotropin surge in normal human reproductive cycles

PURPOSE

This study was designed to examine changes in peripheral plasma substance-P and -K levels, their association with follicle-stimulating hormone and luteinizing hormone release in normal reproductive cycles in humans, and their correlation with plasma estradiol and progesterone.

METHODS

Fourteen healthy, normally menstruating women underwent daily blood sampling (cycle day 4, 4-14 days) for measurement of estradiol, progesterone, luteinizing hormone, and follicle-stimulating hormone, substances-P and -K, and daily transvaginal ultrasounds assessing follicular growth and documentation of ovulation.

RESULTS

Estradiol peaked on day 13, luteinizing hormone and follicle-stimulating hormone peaked on day 14, and progesterone began an exponential increase on about day 13.

CONCLUSIONS

In contrast to other experimental designs using in vitro or in vivo rat or monkey tissue, peripheral levels of substances-P (P = 0.8391) and -K (P = 0.3205) reflected no modulation related to midcycle gonadotropin release in cycling woman.

The in vitro effect of substance P on the GnRH-induced LH release depends on the steroidal environment and is reverted by a NK1 receptor antagonist (RP 67580) in the cycling female rat

A previously study reported that administration of substance P on the morning of the proestrous day induces an inhibition of afternoon gonadotropin preovulatory surges in the female rat. It has also been shown, with a non-peptide specific antagonist of the neurokinin 1 (NK1) receptor (RP 67580), that this effect is mediated by NK1 receptors. The present study used perifused anterior pituitaries from proestrous morning female rats and showed that the SP modulation of the GnRH-induced LH release is markedly dependent on the steroidal environment. In the absence of steroids or in the presence of 17beta estradiol, or a combination of 17beta estradiol and progesterone, SP inhibited the GnRH-induced LH release. In contrast, SP stimulated the GnRH-induced LH secretion in the presence of progesterone alone. However, the inhibitory or stimulatory effect of SP was antagonized by the specific NK1 receptor antagonist RP 67580.

Role of tachykinins in the regulation of the hypothalamo-pituitary-adrenal axis

Tachykinins are a family of neuropeptides, which act by binding to three main subtypes of G protein-coupled receptors, named NK1, NK2 and NK3. Tachykinins are contained in both nerve fibers and secretory cells of the hypothalamo-pituitary-adrenal (HPA) axis, and evidence indicates that they take part in the functional control of it. Tachykinins involved in this function include substance P (SP), neuropeptide K and its derivative neurokinin A (NKA), and neurokinin B, which preferentially bind to NK1, NK2 and NK3 receptors, respectively. NK1 agonists exert an inhibitory effect on the hypothalamo pituitary CRH/ACTH system, while NK2 and perhaps NK3 agonists stimulate it, thereby controlling the secretion and growth of the adrenal cortex via circulating ACTH. Intra-adrenal tachykinins may also affect the cortex function. Their direct action on adrenocortical cells is doubtful and probably pharmacologic in nature, but several investigations suggest that tachykinins indirectly stimulate the cortex by acting on medullary chromaffin cells, which in turn exert a paracrine control on adrenocortical cells. SP enhances aldosterone production of zona glomerulosa by eliciting catecholamine secretion; neuropeptide K and NKA raise glucocorticoid production of zonae fasciculata and reticularis through the activation of the intramedullary CRH/ACTH system. The relevance of these effects of tachykinins under basal conditions is questionable, although there are indications that SP is involved in the maintenance of a normal growth and steroidogenic capacity of rat zona glomerulosa, and that SP and NKA play an important role in the stimulation of the adrenal growth during the fetal life. In contrast, evidence has been provided that the role of tachykinins, and especially of SP, could become very relevant under paraphysiological (e.g., physical or inflammatory stresses) or pathological conditions (e.g., ACTH-secreting pituitary tumors), when an excess of steroid-hormone production has to be counteracted.

17beta-estradiol stimulates substance P receptor gene expression

The actions of substance P (SP), a widely distributed tachykinin neuropeptide, are mediated by the NK1 receptor, a seven trans-membrane spanning domain cell surface receptor coupled to heterotrimeric G-proteins. SP regulates cellular processes in the CNS, placenta and vasculature including permeability, inflammation, mitogenesis and transformation. Examples of sexual dimorphism in tissue distribution and expression of SP and the SP receptor (SPR) in various organ systems (breast, uterus, brain) suggest the SPR may be under hormonal control. Using Northern blot analysis of SPR mRNA levels, we studied the effects of 17beta-estradiol (E2) on SPR gene expression in AR42J (rat pancreatic acinar) cells which constitutively express high levels of SPR. E2 (100 nM) led to a 2.5-fold increase in SPR mRNA levels (4.7 kb band) which was time- and concentration-dependent. The increase was inhibited by the RNA polymerase inhibitor actinomycin D (5 microg/ml) but not by the translational inhibitor cycloheximide (10 microg/ml). In addition, the antiestrogen tamoxifen (1 microM) blocked the stimulatory effect of E2 on SPR mRNA. Increased SPR mRNA levels in response to E2 were linearly related to increased [3H]SP binding to the SPR. This study has implications for understanding molecular mechanisms of hormonal control of receptor gene expression.

Innervation of the mammalian anterior pituitary: a mini review

The mammalian anterior pituitary was not known to be innervated other than by a few autonomic nerve fibers. Recent studies, however, have demonstrated otherwise. A hypothesis of neural-humoral dual regulation of the mammalian anterior pituitary has been postulated based on the following findings: (1) the presence of substantial amounts of nerve fibers in the anterior pituitary of a number of mammalian species; (2) close contact of the nerve fibers with the gland cells, even forming synapses; (3) the nerve fibers originate, as least partly, from the hypothalamus; (4) the nerve fibers respond actively to changes in hormonal levels of the organism; and (5) stimulation of the nerve fibers changes the secretory activities of the gland cells.

Stimulatory effect of a specific substance P antagonist (RPR 100893) of the human NK1 receptor on the estradiol-induced LH and FSH surges in the ovariectomized cynomolgus monkey

Utilizing a human NK1 receptor antagonist (RPR 100893), the present in vivo study was designed to test the hypothesis that endogenous substance P (SP) modulates the action of 17beta-estradiol in inducing luteinizing hormone (LH) and follicle stimulating hormone (FSH) surges in ovariectomized cynomolgus monkey. Plasma concentrations of LH and FSH as well as NK1 receptor antagonist and SP were measured during the development of the negative and positive feedback phases which follow a single administration of estradiol benzoate (50 microg/kg) to long-term ovariectomized monkeys. Daily administration by gastric intubation of 1 mg/kg or 10 mg/kg of the NK1 receptor antagonist (RPR 100893) leads to detectable levels of the antagonist in the blood of treated animals for at least 6 hr after its administration. These levels are in agreement with the experimentally determined IC50 value of the antagonist. The most striking finding of this study is that LH and FSH releases are enhanced during the descending arm of the estradiol benzoate-induced LH and FSH surges, which suggests that endogenous SP normally has an inhibitory role during this time. The enhancement of LH release is approximately 50%, regardless of the amount of the NK1 antagonist used. However, the enhanced FSH release is more important. Furthermore, blockade of the NK1 receptor with the smaller dose of the antagonist leads to a small, but significant, increase in plasma levels of SP, indicating that blockade of SP receptors leads to an increased release of SP. Collectively, these results further substantiate the link which exists between the ovarian steroid 17beta-estradiol and SP systems. Also, for the first time, these results demonstrate an inhibitory involvement of the human NK1 receptor in the 17beta-estradiol-induced pseudo-ovulatory gonadotropin surges in the ovariectomized monkey.

Reduction of the amplitude of preovulatory LH and FSH surges and of the amplitude of the in vitro GnRH-induced LH release by substance P. Reversal of the effect by RP 67580

The effects of Substance P (SP) and of a specific nonpeptide antagonist of the NK1 receptor (RP 67580) on preovulatory gonadotropin surges and on the in vitro GnRH induced LH surge were investigated in cycling female rats. A subcutaneous injection of SP (0.5 mg/kg body weight) at 12.00 h on the proestrous day significantly decreased the LH preovulatory surge. RP 67580 (1.5 mg/kg) significantly increased this LH surge. However, when SP and its antagonist were administered together, LH preovulatory surge was normal. The FSH preovulatory surge at 18.00 h and also at 19.00 h was significantly inhibited by SP administration. RP 67580 alone had no effect on the FSH preovulatory surge. When SP and RP 67580 were both administered, there was no diminution of FSH plasma levels at 18.00 h and 19.00 h. In vitro perifusions of anterior pituitaries showed that SP inhibits GnRH-induced LH release via a NK1 receptor. Thus, SP inhibits the LH preovulatory surge via NK1 receptors and SP modulation of gonadotropin surges is at least partly exerted at the pituitary.

Development of a specific radioimmunoassay for neuropeptide K: its application to Siberian hamster tissues

In this report we describe the development of a radioimmunoassay for neuropeptide K (NPK) that is not influenced by the presence of free neurokinin A (NKA) or neuropeptide gamma (NPG). The antisera for the radioimmunoassay were obtained by immunizing rabbits with beta-preprotachykinin A fragment 69-91. This fragment contains the sequence 1-20 of NPK and has only the sequence 18-20 (Gly-His-Gly) in common with NPG. Two antisera were obtained, neither cross-reacting with NKA or NPG. The specificity of these antisera was confirmed by the finding of a major immunoreactive peak in the eluates obtained from HPLC separation, corresponding to NPK. This radioimmunoassay was applied to the determination of NPK in hypothalamic and anterior pituitary extracts from Siberian hamsters. Hypothalami from male and female hamsters contained similar concentrations of NPK, although slightly higher in males. NPK levels in the hypothalamus of female Siberian hamsters showed few fluctuations during the estrous cycle, with the levels measured at estrus being significantly lower than at proestrus, diestrus I, and diestrus II. In anterior pituitaries from Siberian hamsters the concentrations of NPK were significantly lower in females than in males. This radioimmunoassay has demonstrated the presence of NPK in the anterior pituitary gland of the Siberian hamster, and it should be very useful for future studies on mechanisms of regulation of NPK secretion in different tissues.

Expression and characterization of the substance P (NK1) receptor in the rat pituitary and AtT20 mouse pituitary tumor cells

Although substance P is known to take part in the regulation of the anterior pituitary, no conclusive evidence for the expression of the tachykinin NK1 receptor has been found yet in the pituitary or pituitary derived cells. With the reverse transcription-polymerase chain reaction (RT-PCR) method we could detect the low abundant transcripts of the NK1 receptor in the rat pituitary and in the AtT20 cell line (clone D16v). Furthermore, the functional expression of the NK1 receptor in AtT20 cells was confirmed by activation of the phosphatidylinositol-calcium second messenger system when the cells were treated with substance P. In addition, binding studies also indicated the functional expression of this receptor in AtT20 cells. Thus we provide the first evidence that the NK1 receptor is expressed in AtT20 cells and the rat pituitary.

Electron microscopic observation of substance P-like immunoreactive nerve fibres and innervation in the anterior pituitary of macaques

The anterior pituitary has recently been confirmed to be innervated by substance P-immunoreactive nerve fibres in the monkey and human. The present study investigated the morphology of the nerve fibres and their relationship with anterior pituitary gland cells in the macaque by means of immunoelectron microscopy. Many substance P-immunoreactive and unlabelled nerve fibres were distributed among the gland cells or formed nerve fibre bundles. These nerve fibres were unmyelinated and varicose, and contained a great many clear and/or large dense-cored vesicles. Substance P-immunoreactive cells were seen in the pars distalis of the anterior pituitary. Direct contacts between these nerve fibres and every cell type of the gland could be ascertained, including substance P-immunoreactive cells. Synaptoid contacts were seen among the substance P-immunoreactive varicosities and somatotropes, opiocortico-melanotropes and folliculostellate cells. Typical synapses were identified in somatotropes and opiocortico-melanotropes.

Effect of substance P on uterine mast cell cytokine release during the reproductive cycle

There is increasing evidence that neuropeptides, steroid hormones and inflammatory cytokines influence the immune response during the reproductive cycle. In the present study, we focus on the effects of neuropeptide Substance P (SP) during the pre-implantation stage of embryo development (day 4 of pregnancy), at pro-estrus and di-estrus (two phases with different hormonal states). We found heterogeneous responses to SP and anti-IgE by the rat uterine mast cells (MCs), as detected by ELISA. In fact, MCs purified from uteri on day 4 of pregnancy released histamine, granulocyte macrophage-colony stimulating factor (GM-CSF) and tumor necrosis factor-alpha (TNF-alpha) in response to anti-IgE, but not to SP. When pre-incubated with SP, the release to anti-IgE was significantly enhanced compared to anti-IgE alone. Exposure of SP to antibodies to SP, prior to pre-incubation with MCs, negated the SP effect on IgE-mediated release. At the pro-estrus phase SP showed similar behavior as on day 4 of pregnancy, whereas at the di-estrus phase SP alone was capable of inducing release of histamine and cytokines from purified uterine MCs. Moreover, non-quantitative RT-PCR analysis of the TNF-alpha mRNA level suggested an SP stimulation at the di-estrus phase, but neither on day 4 of pregnancy nor at the pro-estrus phase. Taken together, these data strongly suggest that SP can modulate IgE-mediated uterine MC release of histamine and inflammatory cytokines in different ways, depending on the phase of the reproductive cycle.

Translocation of protein kinase C isozymes in rat pituitary lactotroph-enriched cell cultures by substance P: effects of sex and age

It is generally accepted that the phospholipid and calcium-dependent enzyme protein kinase C (PKC) plays a significant role in secretion of hormones from anterior pituitary cells. The present study was undertaken to study age and sex-related changes in 1. levels of immunoreactivity of PKC isozymes and 2. distribution of immunoreactivity of PKC isozymes after stimulation with substance P (SP) in rat lactotroph-enriched cell cultures. The alpha, beta, delta and zeta isozymes were present in both sexes and at all ages. There was a sex-specific differential regulation of the different PKC isozymes as a function of sexual maturation. In male rats there was an up-regulation of the alpha isozyme throughout the sexual development, while the beta subtype showed a small, but significant decrease in immunoreactivity with increasing age. In female rats, on the other hand, the beta species was up-regulated with increasing age while the other subtypes remained constant. The concentration of the delta and zeta isozymes was unaffected of sex and age. Stimulation of lactotroph-enriched cell cultures with substance P (SP) resulted in translocation of the alpha and beta isozymes from the soluble to the particulate fraction while the delta and zeta species were left unchanged independently of age and sex. However, a decrease in responsiveness was observed in adult male rats, although a significant degree of translocation of alpha and beta species was still detected. On the basis of these results it is suggested that in lactotroph-enriched cell cultures basal levels of PKC subtype immunoreactivity and distribution of immunoreactivity of PKC isozymes after SP challenge might be regulated as a function of sex and age.

Sample preparation, high-performance liquid chromatographic separation and determination of substance P-related peptides

This review deals with the determination of low levels of substance P and peptide fragments derived from the undecapeptide, i.e. covers the whole amount of so-called substance P-like immunoreactivity (SPLI) in biological samples. First an overview of the most currently used sample pretreatment procedures is given, followed by a description of the most effective high-performance liquid chromatographic (HPLC) separation methods. Special attention is paid to the choice of the appropriate column and the possible pitfalls encountered in separation of fmol amounts of peptide material. Subsequently the most important techniques of detection are discussed. This section primarily focuses on the coupling of HPLC with radioimmunoassay (RIA), which is indispensable for detection of components in the fmol range at present. Finally, some aspects of preparation and chromatographic separation of radiolabelled antigens for use in RIA are discussed.

Tachykinergic synaptic inputs to neurons of the medial preoptic region which project to the rat arcuate nucleus

Anatomical relationships between tachykinin-containing terminals and neurons of the medial preoptic area that innervate the arcuate nucleus were studied using silver staining of the retrograde tracer wheat germ agglutinin-apoperoxidase-gold (WGA-ApoHRP-gold) complex injected in the arcuate nucleus and pre-embedding immunocytochemistry for neurokinin A (NKA). At the histological level, retrogradely labeled cells not stained for NKA were seen to be surrounded by numerous NKA-immunopositive punctate profiles, in particular in the dorsal part of the medial preoptic area. At the ultrastructural level, retrogradely labeled cell bodies and dendritic profiles displayed highly electron-dense silver particle accumulations over the cytoplasm. The were seen in synaptic contact with one or several NKA-immunoreactive axon terminals containing small clear vesicles and dense-cored vesicles. Such synapses were either symmetrical or asymmetrical. The occurrence of synaptic contacts between tachykinin terminals and cells innervating the arcuate nucleus in the medial preoptic region provides a morphological support for a tachykinergic regulation of preoptic afferences to the arcuate nucleus. These results suggest that tachykinins are implicated in the indirect control of neuronal activity in the arcuate nucleus notably via the preoptic area. Consequently, tachykinins are potentially able to regulate indirectly numerous neuroendocrine events involving the tuberoinfundibular system.

Synaptic inputs of tachykinin-containing nerve terminals to target tyrosine-hydroxylase-, beta-endorphin- and neuropeptide Y-producing neurons of the arcuate nucleus. Double pre-embedding immunocytochemical study in the rat

Anatomical connections between tachykinin-containing terminals and three neuronal populations of the arcuate nucleus, chemically defined respectively by beta-endorphin (beta-END), tyrosine-hydroxylase or neuropeptide Y (NPY) and well represented in the arcuate nucleus, were studied using electron microscope double pre-embedding immunocytochemistry involving a combination of two sensitive chromogens: diaminobenzidine and tetramethylbenzidine. Following tachykinin immunodetection by diaminobenzidine, and tyrosine-hydroxylase, beta-END or NPY immunolabelling by tetramethylbenzidine, tachykinin-immunoreactive terminals were seen presynaptic to tyrosine-hydroxylase immunopositive cells and dendrites principally in the dorsomedial portion of the arcuate nucleus. Tachykinin-immunoreactive processes were also seen in synaptic contact with ventrolaterally located beta-END immunopositive perikarya. Tachykinin-immunopositive terminals also contacted NPY-immunoreactive cells and dendritic processes ventromedially. These results demonstrate the existence of a direct tachykinergic input onto three neuronal populations expected to play a role in the control of reproductive events. Consequently, they suggest, at least, an indirect action for tachykinins in the regulation of reproduction. Especially, tachykinins may indirectly control the luteinizing hormone-releasing hormone neurons via dopamine, beta-END and NPY cells and thereby influence luteinizing hormone secretion.

Tachykinergic afferents to the rat arcuate nucleus. A combined immunohistochemical and retrograde tracing study

The location of the cells giving rise to the tachykinergic innervation of the rat arcuate nucleus was studied by combining immunohistochemistry and retrograde axonal transport of a protein-gold complex (WGA-ApoHRP-gold). Small volumes (20 nl) of this marker were injected into the arcuate nucleus of the rat. Twenty-four to 30 h later, rats were injected with colchicine. After 24-h survival time, the paraformaldehyde-fixed brains were investigated for silver intensification of the gold particles and for tachykinin immunohistochemistry. Doubly immuno-silver-labeled cells were observed mainly in brainstem structures such as raphe nuclei, central gray pontine, and laterodorsal tegmental nucleus. Intranuclear and intrahypothalamic (ventromedial, dorsomedial, premamillary, and supramamillary) cell bodies were also doubly labeled, principally ipsilateral to the injection site. Minor afferent projections arise from the medial preoptic area. This anatomohistochemical study demonstrates that the arcuate nucleus receives intra- and extrahypothalamic tachykinergic inputs and shows that infundibular neurons undergo convergent tachykinergic influences.

Two classes of binding sites for [3H]substance P in rat cerebral cortex

The binding characteristics of [3H]substance P ([3H]SP) were investigated in membranes prepared from rat cerebral cortex. Binding of [3H]SP reached equilibrium after 50 min at 25 degrees C and was saturable at 8 nM. Saturation data could be resolved into high affinity (equilibrium dissociation constant, Kd, 0.22 nM) and low affinity sites (Kd, 2.65 nM). The low affinity sites were more numerous than the high affinity sites, with a ratio of 4:1. The non-hydrolyzable GTP analogue GppNHp had no effect on binding, indicating that the high and low affinity sites are not guanine nucleotide-regulated states of the same (NK-1) receptor. The low affinity sites are unlikely to represent NK-3 receptors since coincubation with the selective NK-3 receptor agonist senktide did not alter the biphasic nature of [3H]SP binding. The rank order of potency for inhibition of [3H]SP (2 nM) binding was SP > or = [Sar9, Met(O2)11]-SP > or = physalaemin >> SP(3-11) > NP gamma = [Ala3]-SP > or = SP(4-11) > or = NPK > or = SP(5-11) > or = NKB approximately NKA >> SP(1-9), compatible with binding to an NK-1 site. N-terminal fragments and non-amidated analogues were ineffective competitors for [3H]SP binding. However, competition data for several peptides including substance P (SP) and the NK-1 selective agonist [Sar9, Met(O2)11]-SP could be resolved into two components.(ABSTRACT TRUNCATED AT 250 WORDS)

Luteinizing hormone response to an intravenous infusion of substance P in normal men

The effect of synthetic substance P (SP), infused intravenously in doses of 0.5, 1.0, or 1.5 pmol/kg-1/min-1 for 60 minutes, on gonadotropin secretion was evaluated in seven healthy men. SP tests and a control test with normal saline were randomly performed at weekly intervals. During the tests, SP infusion did not produce untoward side effects or changes in blood pressure. Plasma testosterone concentrations were normal in all subjects and remained unmodified during all tests, regardless of the infused dose of SP. Plasma luteinizing hormone (LH) levels were not modified when either normal saline or the lowest dose of SP were infused, whereas they were significantly increased in a dose-dependent fashion when larger amounts of SP were administered. In contrast, plasma follicle-stimulating hormone (FSH) concentrations did not change significantly during any test. These data demonstrate for the first time in normal men that the systemic infusion of SP stimulates LH release, without modifications of FSH secretion.

Substance P variations in the hypothalamus of golden hamsters at different stages of the estrous cycle

The changes in substance P concentrations in the hypothalamus of female golden hamsters were studied at the different stages of the estrous cycle. Substance P levels in the hypothalamus of hamsters were highest during estrus and lowest during diestrus I and proestrus. The concentrations of substance P during diestrus II were not significantly different from those observed during estrus. These results show that substance P levels in the hypothalamus of female hamsters undergo significant changes during the estrous cycle.

Distribution of substance P-immunoreactive elements in the preoptic area and the hypothalamus of the rat

The localization and morphology of neurons, processes, and neuronal groups in the rat preoptic area and hypothalamus containing substance P-like immunoreactivity were studied with a highly selective antiserum raised against synthetic substance P. The antiserum was thoroughly characterized by immunoblotting; only substance P was recognized by the antiserum. Absorption of the antiserum with synthetic substance P abolished immunostaining while addition of other hypothalamic neuropeptides had no effect on the immunostaining. The specificity of the observed immunohistochemical staining pattern was further confirmed with a monoclonal substance P antiserum. The distribution of substance P immunoreactive perikarya was investigated in colchicine-treated animals, whereas the distribution of immunoreactive nerve fibers and terminals was described in brains from untreated animals. In colchicine-treated rats, immunoreactive cells were reliably detected throughout the preoptic area and the hypothalamus. In the preoptic region, labeled cells were found in the anteroventral periventricular and the anteroventral preoptic nuclei and the medial and lateral preoptic areas. Within the hypothalamus, immunoreactive cells were found in the suprachiasmatic, paraventricular, supraoptic, ventromedial, dorsomedial, supramammillary, and premammillary nuclei, the retrochiasmatic, medial hypothalamic, and lateral hypothalamic areas, and the tuber cinereum. The immunoreactive cell groups were usually continuous with adjacent cell groups. Because of the highly variable effect of the colchicine treatment, it was not possible to determine the actual number of immunoreactive cells. Mean soma size varied considerably from one cell group to another. Cells in the magnocellular subnuclei of the paraventricular and supraoptic nuclei were among the largest, with a diameter of about 25 microns, while cells in the supramammillary and suprachiasmatic nuclei were among the smallest, with a diameter of about 12 microns. Immunoreactive nerve fibers were found in all areas of the preoptic area and the hypothalamus. The morphology, size, density, and number of terminals varied considerably from region to region. Thus, some areas contained single immunoreactive fibers, while others were innervated with such a density that individual nerve fibers were hardly discernible. During the last decade, knowledge about neural organization of rodent hypothalamic areas and mammalian tachykinin biochemistry has increased substantially. In the light of these new insights, the present study gives comprehensive morphological evidence that substance P may be centrally involved in a wide variety of hypothalamic functions. Among these could be sexual behavior, pituitary hormone release, and water homeostasis.

Comparative distribution of substance P (SP) and cholecystokinin (CCK) binding sites and immunoreactivity in the brain of the sea bass (Dicentrarchus labrax)

Specific binding sites for cholecystokinin (CCK) and substance P (SP) were detected in the brain of a marine teleost fish, the sea bass, after in vitro incubation of tissue sections with the tritiated peptides and light microscopic autoradiography. Specific binding sites for [3H]-CCK were detected in the dorsal and ventral telencephalon, in the preoptic, tuberal and posterior hypothalamus, in the optic tectum, in the valvulla cerebelli, in the vagal lobe and further in a dorsal location in the medulla oblongata. Areas rich in [3H]-SP binding were located in the ventral telencephalon, in the entire hypothalamic and thalamic region, in the midbrain tegmentum, in the optic tectum, in the valvulla cerebelli and in the medulla oblongata. The distribution of these binding sites seemed to match fairly well with the location of the corresponding immunoreactive elements, although some minor mismatches could be observed. These autoradiographic findings provide the first anatomical evidence for the presence of CCK-like and SP-like binding sites in the brain of a teleost fish.

Distribution of substance P, GnRH, Met-enkephalin in the central nervous system of the pig

The distribution of substance P (SP), gonadotropin releasing hormone (GnRH) and Met-enkephalin in the brain and spinal cord of the domestic pig is described for the first time. The levels of SP, GnRH and Met-enkephalin were measured by specific radioimmunoassays in various regions of the brain and spinal cord of the pig. Substance P and Met-enkephalin are widely distributed within the central nervous system of the pig. High levels of SP were found in the preoptic area (POA), suprachiasmatic area (SCA), medial basal hypothalamus (MBH) and brain stem while moderate amounts of SP were found in olfactory bulb (OB). High levels of Met-enkephalin were found in POA, SCA and MBH, and moderate levels of Met-enkephalin in OB and brain stem. Both SP and Met-enkephalin levels were higher in the dorsal spinal cord in comparison with the levels of these peptides in the ventral spinal cord. This finding is in agreement with the predominant role played by these neural systems in primary afferent mediation of nociceptive impulses. The POA and SCA contained only low levels of GnRH while the MBH contained high levels of GnRH. Finally, some differences in the quantitative distribution of these peptides in the pig and rat are discussed.

Marked improvement of a substance P radioimmunoassay by reduction of 125I-labelled [Tyr8]-substance P prepared by the chloramine-T method with mercaptoethanol and subsequent purification by reversed-phase liquid chromatography

[Tyr8]-substance P was radiolabelled with 125I by the application of the chloramine-T method. Due to the high oxidative potential of the 125I-chloramine-T system the purified reaction product was converted into a derivative, which presumably had been oxidized to the corresponding sulphoxide at Met11. This conversion was shown by reversed-phase high-performance liquid chromatography after consecutive reduction-oxidation experiments of the freshly prepared radiopeptide. The oxidized derivative exhibited only negligible binding to substance P receptors isolated from rat brain homogenates. However, in contrast, it showed marked cross-reaction to the antibody raised in rabbits against synthetic SP(1-11). The variance in the quantification of identical samples was marked, and the measurement of concentrations in the lower pg/ml range was not sensitive enough to determine levels of substance P-like immunoreactivity in human cerebrospinal fluid. Assay sensitivity could be substantially improved and variance significantly decreased by the use of a radiopeptide, which had been labelled by the chloramine-T method and which had been subsequently reduced with mercaptoethanol and purified by liquid chromatography.

Neurokinin A in the hypothalamus and anterior pituitary during the estrous cycle in the golden hamster

The fluctuations in the neurokinin A concentrations in the hypothalamus and anterior pituitary of female golden hamsters were studied in the different stages of the estrous cycle, and they were correlated with the changes in serum estradiol levels. Neurokinin A levels in the hypothalamus were lowest at day 4 of the cycle (proestrus), when serum estradiol levels were highest. Neurokinin A levels in the hypothalamus of hamsters in day 1 (estrus), day 2 (diestrus I), and day 3 (diestrus II) were not significantly different from each other. In the anterior pituitary, the highest neurokinin A concentrations were found during day 1 of the cycle (estrus), the levels in day 2 (diestrus I), day 3 (diestrus II), and day 4 (proestrus) were significantly lower than at estrus, again showing the lowest levels during proestrus, when estradiol levels were maximal. These results show that neurokinin A levels in the hypothalamus and anterior pituitary of the female hamster undergo significant changes during the estrous cycle.

Effect of early exposure to delta-9-tetrahydrocannabinol on the levels of opioid peptides, gonadotropin-releasing hormone and substance P in the adult male rat brain

The effects of neonatal exposure to delta-9-tetrahydrocannabinol (THC) on the adult animal brain neurochemistry and pain perception were evaluated. Newborn rat pups were culled to a litter size of 8 (males and females) and treated either with THC (2 mg/kg) or oil (control) daily, during days 1-4 after birth. After weaning, the THC-treated males were housed 4 per cage. During the juvenile period (day 50), the THC-treated animals exhibited significantly lower baseline tail-flick values (a measure of pain perception) than the control. However, as adults, the THC-treated animals exhibited significantly higher sensitivity to pain following 5 mg/kg morphine challenge. Furthermore, the THC-treated animals had significantly elevated beta-endorphin and methionine-enkephalin levels in almost all the brain areas sampled for the study. In addition, the neonatally THC-treated rats exhibited significantly higher levels of substance P (SP) and significantly lower levels of gonadotropin releasing hormone (GnRH) in the anterior hypothalamus-preoptic area. The SP and GnRH levels did not differ among the THC-treated and control animals in the medial basal hypothalamus. The results of this study indicate that even a very low dose of THC administered during the neonatal period has a long-lasting effect on the brain neurochemistry. In particular, neonatal administration of THC appears to alter functioning of the endogenous opioid system.

Substance P-like immunoreactive nerve fibers in the pars distalis of the anterior pituitary in the dog

The pars distalis of the anterior pituitary is known to be regulated by hypothalamic hormones. Recently, we have discovered the presence of substance P-like immunoreactive nerve fibers in the pars distalis of the monkeys. Substance P-like immunoreactivity in the pars distalis of the dog was investigated in this study. A substantial amount of substance P-like immunoreactive nerve fibers with a large amount of varicosities were found. They were widely distributed in the gland, more abundant along its periphery. Most of them were closely related to the glandular tissue, some were located on vascular walls. Substance P-like immunoreactive nerve fibers were also found in the meningeal sheath of the anterior pituitary. They could be followed into the parenchyma of the gland.