Personality traits and personality disorders in gender dysphoria

Investigations in the field of gender dysphoria (GD) have been mostly related to psychiatric comorbidity and severe psychiatric disorders, but have focused less on personality traits and personality disorders (PDs).

We aimed to assess personality and the presence of PDs in a sample of 25 persons with GD attending the Psychiatric Clinic or the Department of Endocrinology of the University of Cagliari requesting sex reassignment therapy. They were assessed through the Minnesota Multiphasic Personality Inventory-2 (MMPI-2) and the Structured Clinical Interview for DSM-IV Axis II (SCID-II).

The sample consisted of 14 MtF and 11 FtM, with a mean age of 29.6 ± 9.5. Overall, 39.1% of the sample met the criteria for at least one PD, more frequently cluster-B PD (21.7%). MtF met a higher number of SCID-II criteria than FtM, especially regarding histrionic personality traits (P = 0.001). A total of 20 persons (9 MtF and 11 FtM) completed the MMPI-2. Mean T scores did not differ from the general population, except for the Psychopathic Deviate (Pd) scale (mean T = 66.2 ± 11.2). The Masculinity-Femininity (Mf) scale was slightly increased, and its score reduced after correction for perceived sex (P = 0.037). MtF scored significantly higher at the Family Problems (FAM) scale (P = 0.052) and lower at the Social Discomfort (SOD) scale (P = 0.005) compared to FtM.

The high prevalence of PDs confirms that this kind of assessment in GD is of great importance, as a key part of personalized treatment plan tailoring. The high scores on the Pd scale suggest misidentification with societal standards.

Disclosure of interest

The authors have not supplied their declaration of competing interest.

Socio-demographic features of gender dysphoria in a Sardinian adult population

Gender dysphoria (GD) is a rare entity in psychiatry; there are a lot of studies about its clinical aspects, but only few investigations considering the socio-demographic characteristics of these patients, especially concerning Italian population.

The aim of this study is to evaluate socio-demographic characteristics of GD individuals seeking assistance for gender transition and to assess possible differences between MtFs and FtMs.

A consecutive series of 25 patients (56% MtF and 44% FtM), from 17 to 49 years old (mean age: 29.6 ± 9.52), were evaluated for gender dysphoria from June 2011 to May 2015. All subjects met the criteria for gender identity disorder (GID), based on DSM-IV-TR.

The results have shown that FtMs refer for psychiatric help in younger age than MtFs (21–25 years vs. 36–50 years, P = .038); most of the patients are unemployed (48%; P = .014) and live with their parents (68%; P = .001), without statistically significant gender differences. Regarding sexual orientation, 84% of the sample report to feel attracted by individuals of the same-genotypic sex (P < .001); 81.8% of FtMs have a stable relationship instead of 21.4% of MtFs (P = .007). Moreover, a significant statistical difference was found between the two groups in the “real-life experience”; all FtMs live as males, while only 50% of MtFs show themselves as females in the daily life and activities (P = .008).

This is a preliminary study comparing the socio-demographic features of a MtF and FtM GD population in Sardinia. Although the limitation of a small sample, our results do not differ from the literature data; in particular, FtMs display significantly better global functioning and less problems in social integration.

Disclosure of interest

The authors have not supplied their declaration of competing interest.

Clinical characteristics of gender identity disorder

Traditionally, gender identity disorder (GID) is associated with high level of psychiatric comorbidity, particularly psychotic and affective disorders. The aim of this study is to evaluate clinical aspect of GID in a sample of patients in charge of the Operative Unit for Diagnosis and Therapy of GID, Psychiatric Clinic and the Department of Endocrinology, University of Cagliari.

Assessment was made by SCID-I, for Axis I comorbidity, GAF, for global functioning, BUT for body discomfort (BUT-A measures different aspects of body image, BUT-B looks at worries about particular body parts).

The sample comprised 14 MtF (56%) and 11 FtM (44%), of age between 17–49 years; a diagnosed psychiatric disorder was reported in 32%: 16% mood disorders, 12% anxiety disorders, 4% psychotic disorders. Among subject with GAF < 85, 58.3% were identify to have a Axis I disorder compare to 7,7% patients with GAF ≥ 85 (P = .011), especially for mood disorders (P = .039). Main score of Global Severity Index (GSI) for BUT-A was 2.45 ± 883; all subjects had a score GSI > 1.2 (clinically relevant discomfort index).

Regarding BUT-B, MtF have higher scores in PSDI global scale (3.37 ± .577; P = 0.019) and subscale VI (4.38 ± 1.496 vs. .81 ± 1.864; P = 0.006): there are not significant gender differences in the others subscales, although discomfort regards different aspects of both sexes.

According to literature, we observed a slightly higher prevalence of Axis I psychiatric disorders compare to general population, with functioning level statistically significant.

Generally, GID was not associated with higher level of psychopathology, appearing as specific diagnostic aspect, where the main origin of discomfort is dissatisfaction toward self-body imagine.

Disclosure of interest

The authors have not supplied their declaration of competing interest.

Orientational Coherent Effects of High-Energy Particles in a LiNbO3 Crystal

A bent lithium niobate strip was exposed to a 400-GeV/c proton beam at the external lines of CERN Super Proton Synchrotron to probe its capabilities versus coherent interactions of the particles with the crystal such as channeling and volume reflection. Lithium niobate (LiNbO3) exhibits an interplanar electric field comparable to that of Silicon (Si) and remarkable piezoelectric properties, which could be exploited for the realization of piezo-actuated devices for the control of high-energy particle beams. In contrast to Si and germanium (Ge), LiNbO3 shows an intriguing effect; in spite of a low channeling efficiency (3%), the volume reflection maintains a high deflection efficiency (83%). Such discrepancy was ascribed to the high concentration (10(4) per cm2) of dislocations in our sample, which was obtained from a commercial wafer. Indeed, it has been theoretically shown that a channeling efficiency comparable with that of Si or Ge would be attained with a crystal at low defect concentration (less than ten per cm2). To better understand the role of dislocations on volume reflection, we have worked out computer simulation via dynecharm++ Monte Carlo code to study the effect of dislocations on volume reflection. The results of the simulations agree with experimental records, demonstrating that volume reflection is more robust than channeling in the presence of dislocations.

Cannabinoid CB1 receptors in the paraventricular nucleus and central control of penile erection: Immunocytochemistry, autoradiography and behavioral studies

[N-(piperidin-1-yl)-5-(4-chlorophenyl)-4-methyl-1H-pyrazole-3-carboxyamide] (SR 141716A), a selective cannabinoid CB1 receptor antagonist, injected into the paraventricular nucleus of the hypothalamus (PVN) of male rats, induces penile erection. This effect is mediated by the release of glutamic acid, which in turn activates central oxytocinergic neurons mediating penile erection. Double immunofluorescence studies with selective antibodies against CB1 receptors, glutamic acid transporters (vesicular glutamate transporters 1 and 2 (VGlut1 and VGlut2), glutamic acid decarboxylase-67 (GAD67) and oxytocin itself, have shown that CB1 receptors in the PVN are located mainly in GABAergic terminals and fibers surrounding oxytocinergic cell bodies. As GABAergic synapses in the PVN impinge directly on oxytocinergic neurons or on excitatory glutamatergic synapses, which also impinge on oxytocinergic neurons, these results suggest that the blockade of CB1 receptors decreases GABA release in the PVN, increasing in turn glutamatergic neurotransmission to activate oxytocinergic neurons mediating penile erection. Autoradiography studies with [(3)H](-)-CP 55,940 show that chronic treatment with SR 141716A for 15 days twice daily (1 mg/kg i.p.) significantly increases the density of CB1 receptors in the PVN. This increase occurs concomitantly with an almost twofold increase in the pro-erectile effect of SR 141716A injected into the PVN as compared with control rats. The present findings confirm that PVN CB1 receptors, localized mainly in GABAergic synapses that control in an inhibitory fashion excitatory synapses, exert an inhibitory control on penile erection, demonstrating for the first time that chronic blockade of CB1 receptors by SR 141716A increases the density of these receptors in the PVN. This increase is related to an enhanced pro-erectile effect of SR 141716A, which is still present 3 days after the end of the chronic treatment.

Vasopressin excitatory action on smooth muscle from human renal calyx and pelvis

The motor response to vasopressin, a neuropeptide promoting the reabsorption of water, was isometrically investigated in vitro in human renal calyces and pelvis in relation to possible modulation of urinary flow by these tubular structures. Kidneys were obtained from nine male patients who underwent nephrectomy for either renal or ureteral cancer. Minor calyces and pelvis were carefully removed. Strips (10 mm x 3 mm) were cut from infundibular region of minor calyces and from renal pelvis and placed in 10 ml organ bath for isometric tension recordings. Calyceal and pelvic smooth muscle strips exhibited spontaneous phasic contractions which occurred with regular frequency and amplitude. Vasopressin induced a dose-dependent [10(-10) to 10(-6) M] enhancement of basal tone (P <0.01) and a decrease of spontaneous contractions on isolated strips from minor calyces and pelvis. The effect of vasopressin was inhibited by prior administration of D(CH2)5Tyr(Me)2-Arg8-Vasopressin antagonist [10(-7) M]. The excitatory response to vasopressin was Tetrodotoxin [TTX]-resistant and was not affected by pre-treatment with phentolamine [10(-5) M], atropine [10(-5) M], and hexamethonium [10(-5) M]. After incubation of the specimens in Ca2+-free medium containing EGTA [0.5 mM] or after treatment with nifedipine [10(-5) M], both spontaneous and vasopressin-induced contractions [10(-10) to 10(-6) M] were completely inhibited in all specimens. Our results can be interpreted to imply that the tonic contractions induced by vasopressin facilitate the reabsorption of water by increasing the hydraulic resistance of the tubular structures below collecting ducts.

The neurophysiology of the sexual cycle

The cycle of sexual activity in men and women occurs in 4 phases--excitation, plateau, orgasm, resolution--which are guided by sexual desire. Male sexual activity is characterized by erection, seminal emission and ejaculation (orgasm), whereas female sexual activity is characterized by vaginal lubrication, erection of the clitoris and orgasm. These responses are under the control of numerous central and peripheral neural systems. The central supraspinal systems are mainly localized in the limbic system (olfactory nuclei, medial preoptic area, nucleus accumbens, amygdala, hippocampus etc.), in the hypothalamus and its nuclei (paraventricular and ventromedial nuclei). Neural information travels through the brain stem, the medulla oblongata, the spinal cord and the autonomous nervous system to the genital apparatus. While we have very detailed knowledge of the neural mechanism, which controls the function of the male and female genital organs, in particular those mediating erection, very little is known of the central mechanism involved. Nevertheless, several neurotransmitters and neuropeptides, such as dopamine, glutamic acid, nitric oxide, oxytocin, ACTH-MSH peptides, are known to facilitate sexual function, while serotonin, gamma-aminobutyric acid (GABA) and opioid peptides reduce it. At the level of the paraventricular nucleus a group of oxytocinergic neurons projecting to extra-hypothalamic brain areas, including the spinal cord, have been identified, which facilitate erectile function and copulation when activated and reduce both when inhibited. Although the majority of results, which have clarified the mechanisms involved, have been performed in males, it is believed that similar mechanisms are also operative in females.

Central oxytocinergic neurotransmission: a drug target for the therapy of psychogenic erectile dysfunction

A group of oxytocinergic neurons originating in the paraventricular nucleus of the hypothalamus and projecting to extrahypothalamic brain areas (e.g. hippocampus, medulla oblongata and spinal cord) control penile erection. Activation of these neurons by dopamine and dopamine agonists, excitatory amino acids (N-methyl-D-aspartic acid) or oxytocin itself, or by electrical stimulation leads to penile erection, while their inhibition by GABA and GABA agonists or by opioid peptides and opiate-like drugs inhibits this sexual response. The activation of oxytocinergic neurons in the paraventricular nucleus by dopamine, oxytocin and excitatory amino acids is apparently secondary to the activation of nitric oxide (NO) synthase. NO in turn activates, by a mechanism that is as yet unidentified, the release of oxytocin from oxytocinergic neurons in extrahypothalamic brain areas. Several peptide analogues of hexarelin, a growth hormone releasing peptide, also induce penile erection when injected into the paraventricular nucleus and, to a lesser extent, systemically, apparently by acting on a specific receptor to activate oxytocinergic neurons as shown for the above drugs and oxytocin. Paraventricular oxytocinergic neurons and mechanisms similar to those reported above are also involved in the expression of penile erection in physiological contexts, namely when penile erection is induced in the male by the presence of an inaccessible receptive female, which is considered a model for psychogenic impotence in man, as well as during copulation. These findings show that paraventricular oxytocinergic neurons projecting to extra-hypothalamic brain areas and to the spinal cord are a likely target for the treatment of erectile dysfunction of central origin.

The activation of gamma aminobutyric acid(A) receptors in the paraventricular nucleus of the hypothalamus reduces non-contact penile erections in male rats

Male rats show 4-6 penile erection episodes when put in the presence of an inaccessible receptive female. These non-contact penile erections were reduced dose-dependently by muscimol, a gamma aminobutyric acid (GABA)(A) receptor agonist, when given into the paraventricular nucleus of the hypothalamus (0.1, 0.5, 1 and 2 microg). In contrast, baclofen, a GABA(B) receptor agonist (2 microg) was ineffective. Muscimol reduction of non-contact penile erections was not seen when male rats were pretreated with bicuculline methiodide (2 microg) given 5 min before muscimol into the paraventricular nucleus. Since muscimol injected into the paraventricular nucleus also prevents penile erection induced by drugs (e.g. apomorphine, oxytocin or N-methyl-D-aspartic acid), the present results show that an increased GABAergic activity in the paraventricular nucleus can impair the expression of penile erection induced not only by drugs but also by sexual physiological stimuli.

EP 91073 prevents EP 80661-induced penile erection: new evidence for the existence of specific EP peptide receptors mediating penile erection

The effect of EP 91073, EP 51389, EP 70555 and EP 51216, peptide analogues of the growth hormone releasing peptide hexarelin, on penile erection induced by EP 80661 or EP 60761 injected into the paraventricular nucleus of the hypothalamus, was studied in male rats. Of the above peptides only EP 91073 (0.2-1 microg) was found capable of reducing penile erection induced by EP 80661 or EP 60761, when given into the paraventricular nucleus. Despite its ability to prevent EP peptide-induced penile erection, EP 91073 (1 microg) was unable to prevent penile erection induced by the dopamine receptor agonist apomorphine (50 ng), oxytocin (30 ng) and N-methyl-D-aspartic acid (50 ng), when given into the paraventricular nucleus 10 min prior to the above substances. The EP 91073-induced prevention of penile erection occurred with a reduction in the increase in nitric oxide production that occurs in the paraventricular nucleus concomitant to penile erection induced by EP 80661 and EP 60761, as measured by intracerebral vertical microdialysis. The present results are in line with the hypothesis that EP 80661 and EP 60761 induce penile erection by activating specific receptors in the paraventricular nucleus, located possibly in oxytocinergic neurons mediating penile erection, and show that EP 91073 acts as an antagonist of these EP peptide receptors mediating penile erection.

A cluster of three single nucleotide polymorphisms in the 3'-untranslated region of human glycoprotein PC-1 gene stabilizes PC-1 mRNA and is associated with increased PC-1 protein content and insulin resistance-related abnormalities

Glycoprotein PC-1 inhibits insulin signaling and, when overexpressed, plays a role in human insulin resistance. Mechanisms of PC-1 overexpression are unknown. We have identified a haplotype in the 3'-untranslated region of the PC-1 gene that may modulate PC-1 expression and confer an increased risk for insulin resistance. Individuals from Sicily, Italy, carrying the "P" haplotype (i.e., a cluster of three single nucleotide polymorphisms: G2897A, G2906C, and C2948T) were at higher risk (P < 0.01) for insulin resistance and had higher (P < 0.05) levels of plasma glucose and insulin during an oral glucose tolerance test and higher levels of cholesterol, HDL cholesterol, and systolic blood pressure. They also had higher (P < 0.05-0.01) PC-1 protein content in both skeletal muscle and cultured skin fibroblasts. In CHO cells transfected with either P or wild-type cDNA, specific PC-1 mRNA half-life was increased for those transfected with P (t/2 = 3.73 +/- 1.0 vs. 1.57 +/- 0.2 h; P < 0.01). In a population of different ethnicity (Gargano, East Coast Italy), patients with type 2 diabetes (the most likely clinical outcome of insulin resistance) had a higher P haplotype frequency than healthy control subjects (7.8 vs. 1.5%, P < 0.01), thus replicating the association between the P allele and the insulin resistance-related abnormalities observed among Sicilians. In conclusion, we have identified a possible molecular mechanism for PC-1 overexpression that confers an increased risk for insulin resistance-related abnormalities.

Penile erection induced by EP 80661 and other hexarelin peptide analogues: involvement of paraventricular nitric oxide

The effect of GAB-D-Trp(2-Me)-D-Trp(2-Me)-LysNH(2) (EP 80661), GAB-D-Trp(2-Me)-D-Trp(2-Me)-D-Trp(2-Me)-LysNH(2) (EP 60761), GAB-D-Trp(2-Me)-LysNH(2) (EP 91071) and GAB-D-Trp(2-Me)-D-beta Nal-Phe-LysNH(2) (EP 50885), four hexarelin peptide analogues that induce penile erection when injected into the paraventricular nucleus of the hypothalamus of male rats, on the concentration of NO(2)(-) and NO(3)(-) in the paraventricular dialysate was studied in male rats. EP peptides (1 microg) induced penile erection and increased the concentration of NO(2)(-) and NO(3)(-) in the paraventricular dialysate. In contrast, hexarelin (1 microg) was ineffective on either penile erection or paraventricular NO(2)(-) and NO(3)(-). EP peptide-induced penile erection was prevented by the nitric oxide synthase inhibitor N(G)-nitro-l-arginine methylester given into the paraventricular nucleus (20 microg), which also reduced the concomitant increase of NO(2)(-) and NO(3)(-) concentration in the paraventricular dialysate. In contrast, the oxytocin receptor antagonist [d(CH(2))(5)Tyr(Me)(2)-Orn(8)]vasotocin (1 microg) given into the paraventricular nucleus, was ineffective on penile erection and on the NO(2)(-) and NO(3)(-) increase induced by EP peptides, despite its ability to prevent the sexual response induced by the above peptides when given into the lateral ventricles. The present results show that EP peptides induce penile erection by activating nitric oxide synthase in the paraventricular nucleus of the hypothalamus, possibly in the cell bodies of oxytocinergic neurons that control penile erection.

Differential orexigenic effects of hexarelin and its analogs in the rat hypothalamus: indication for multiple growth hormone secretagogue receptor subtypes

We have previously reported that hexarelin and some of its analogs, including EP 50885, stimulated GH secretion and feeding after systemic administration in the rat, whereas EP 40904 selectively stimulated food intake and EP 40737 only GH release. The precise mechanism of growth hormone-releasing peptides (GHRPs) actions is still unclear, but the integrity of the arcuate nucleus of the hypothalamus (ARC) appears crucial for their endocrine effects. To better characterize the site(s) and mechanisms(s) of the orexigenic action of GHRPs, we have investigated their effects after infusion into the arcuate, paraventricular, ventromedial and medial preoptic areas of the hypothalamus. Food intake was measured for 60 min following injection of the test compound (2 microg/rat). Hexarelin, EP 40904 and EP 50885 had significant orexigenic effects after injection into the ARC. A specific NPY antagonist significantly inhibited the effect of hexarelin, whereas a GHRH antagonist was ineffective. In the paraventricular nucleus, only EP 50885 stimulated feeding, whereas all peptides were ineffective in the ventromedial nucleus and medial preoptic area. Taken altogether, these results demonstrate that GHRPs are endowed with site-specific orexigenic actions and that endogenous NPY, but not GHRH, mediates these effects. The additional orexigenic action of EP 50885 in the paraventricular nucleus suggests the existence of a GHRP receptor subtype different from the already cloned one.

EP 60761- and EP 50885-induced penile erection: structure-activity studies and comparison with apomorphine, oxytocin and N-methyl-D-aspartic acid

The effect of 10 peptides structurally related to the growth hormone (GH) releasing peptide hexarelin, injected into the paraventricular nucleus of the hypothalamus (PVN), on penile erection was studied in male rats. Six out of the 10 peptides tested induced penile erection in a dose-dependent manner. Among them, the most potent were EP 80661, EP 60761 and EP 91072, which were active at doses of 20-200 ng. The potency of these peptides in inducing penile erection is comparable to that of apomorphine, oxytocin and N-methyl-D-aspartic acid similarly injected into the PVN. Other peptides found active were EP 50885, EP 90101 and EP 91071, which induced penile erection at doses of 200-2000 ng. In contrast, EP 51322, EP 70555, EP 51216 and EP 91073 were inactive, as were hexarelin, EP 40904 and EP 40737 in a previous study. The majority of EP peptides found active when injected into the PVN induced penile erection, although to a lesser extent, also when given systemically (endovenously). The proerectile effect of EP peptides was prevented by the oxytocin receptor antagonist [d(CH2)5 Tyr(Me)2-Orn8]-vasotocin given into the lateral ventricles but not into the PVN, by the nitric oxide (NO) synthase inhibitor N(G)-nitro-1-arginine methyl ester given either into the lateral ventricles or into the PVN, by the N-type Ca2+ channel blocker omega-conotoxin GVIA and by morphine, but not by the dopamine receptor antagonist cis-flupenthixol or by the N-methyl-D-aspartic acid receptor antagonist dizolcipine, given into the PVN. As the structure-activity relationship of EP peptides for proerectile activity is different from those of other biological actions of these compounds, ie for GH release and eating behaviour, the present results suggest that EP peptides induce penile erection by acting on specific hypothalamic receptor sites that activate paraventricular oxytocinergic neurons projecting to extrahypothalamic brain areas that mediate this sexual function by a mechanism similar to that of dopamine receptor agonists, oxytocin and N-methyl-D-aspartic acid.

EP 60761 and EP 50885, two hexarelin analogues, induce penile erection in rats

The effect of hexarelin and four related peptide analogues, EP 40904, EP 40737, EP 50885 and EP 60761, injected into the paraventricular nucleus of the hypothalamus of male rats in doses between 2 and 2000 ng on spontaneous penile erection was studied. Of these peptides, EP 60761 and EP 50885, but not hexarelin, EP 40904 or EP 40737, increased dose-dependently the number of spontaneous penile erections. EP 60761 was active already at the dose of 20 ng, which induced the sexual response in 70% of the treated rats. The maximal response was induced by 200 ng of the peptide. EP 50885 was less potent than EP 60761, with 1000 ng being the minimal effective dose and 2000 ng as the dose required to induce the maximal response. At the doses used, both peptides also increased slightly the number of spontaneous yawning episodes. EP 60761- and EP 50885-induced penile erection was prevented by the oxytocin receptor antagonist [d(CH(2))(5)Tyr(Me)(2)-Orn(8)]vasotocin (0.1-1 microg) given intracerebroventricularly (i.c.v.), but not into the paraventricular nucleus (0.1-1 microg), by the competitive nitric oxide (NO) inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME) given either into the paraventricular nucleus (10-20 microg) or i.c.v. (75-150 microg), by the N-type Ca(2+) channel blocker omega-conotoxin-GVIA (2-5 ng) or by the opiate morphine (1-10 microg), but not by the dopamine receptor antagonist (Z)-4-[3-[2-(trifluoromethyl)-9H-thioxanthen-9-ylidene]propyl]-1-p ipe razine-ethanol (cis-flupenthixol) (10 microg) or by the N-methyl-D-aspartic acid (NMDA) receptor antagonist (5R, 10S)-(+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5, 10-imine ((+)-MK-801) (1 microg), all given into the paraventricular nucleus before either peptide. The present results show that EP 60761 and EP 50885 induced penile erection by increasing central oxytocin transmission, possibly by activating NO synthase in the cell bodies of oxytocinergic neurons located in the paraventricular nucleus that control penile erection.

Effect of excitatory amino acid, dopamine, and oxytocin receptor antagonists on noncontact penile erections and paraventricular nitric oxide production in male rats

In male rats, noncontact erections occur concomitantly with an increase in NO2- and NO3- in the paraventricular nucleus of the hypothalamus (PVN). In the present study, both responses were reduced by the blockade of PVN excitatory amino acid receptors by dizocilpine, (+)-MK-801(1 and 5 microg), but not by 6-cyano-7-nitro-quinoxaline-2,3-dione (5 microg) or (+)-2-amino-4-phosphono-butanoic acid (5 microg). Also ineffective when injected into the PVN were the dopamine antagonists SCH 23390 (5 microg), S(+)-raclopride (10 microg), and cis-flupenthixol (10 microg), and the oxytocin antagonist d(CH2)5Tyr(Me)2-Om8-vasotocin (1 microg). However, when the last was given into the lateral ventricles, it reduced noncontact erections without modifying NO2- and NO3- increases. These results suggest that excitatory amino acid transmission increases in the PVN during noncontact erections. This may contribute to increased NO production in the PVN, and it may activate oxytocin neurons mediating this sexual response.

ACTH- and alpha-MSH-induced grooming, stretching, yawning and penile erection in male rats: site of action in the brain and role of melanocortin receptors

The effect of adrenocorticotropin (ACTH)(1-24) and alpha-melanocyte stimulating hormone (alpha-MSH) on grooming, stretching, yawning and penile erection was studied after injection into different brain areas. Both peptides induce the above responses when injected into the hypothalamic periventricular region of the third ventricle. This region includes the paraventricular nucleus, the dorsomedial nucleus, the ventromedial nucleus and the anterior hypothalamic area. The minimal effective dose of both peptides was 0.5 microg and the maximal effect was seen with 2 microg, the highest dose tested. Irrespective of the injection site, grooming started 5-7 min after injection of either peptide, while stretching, yawning and penile erection started only after 15-35 min and lasted for 90-120 min. In contrast both peptides were ineffective when injected into the preoptic area, the caudate nucleus or the CA1 field of the hippocampus. Grooming, stretching and yawning, but not penile erection, were prevented by cyclic[AcCys(11), D-Nal(14), Cys(18), AspNH(2)(22)]-beta-MSH (11-22) (HS014), a selective melanocortin 4 receptor antagonist, injected into the same periventricular area 10 min before of ACTH(1-24) or alpha-MSH. The results show that ACTH(1-24) and alpha-MSH act in the hypothalamic periventricular region to induce the above responses and that grooming, stretching and yawning, but not penile erection, are mediated by melanocortin 4 receptors.

Activation of gamma-aminobutyric acid(A) receptors in the paraventricular nucleus of the hypothalamus reduces apomorphine-, N-methyl-D-aspartic acid- and oxytocin-induced penile erection and yawning in male rats

The effect of muscimol and baclofen injected into the paraventricular nucleus of the hypothalamus on penile erection and yawning induced by apomorphine, oxytocin and N-methyl-D-aspartic acid (NMDA) was studied in male rats. Muscimol (20-200 ng), but not baclofen (200 ng), injected into the paraventricular nucleus of the hypothalamus 10 min before apomorphine (50 ng), oxytocin (10 ng) or NMDA (50 ng) reduced penile erection and yawning induced by the above compounds given into the paraventricular nucleus. Bicuculline (250 ng) injected into the paraventricular nucleus 5 min before muscimol (100 ng) prevented the inhibitory effect of muscimol on penile erection and yawning induced by apomorphine, oxytocin and NMDA. The present results show that gamma-aminobutyric acid (GABA) inhibits penile erection and yawning by acting on GABA(A) receptors in the paraventricular nucleus of the hypothalamus.

A PC-1 amino acid variant (K121Q) is associated with faster progression of renal disease in patients with type 1 diabetes and albuminuria

Insulin resistance characterizes type 1 diabetes in patients with albuminuria. A PC-1 glycoprotein amino acid variant, K121Q, is associated with insulin resistance. We examined the impact of the PC-1 K121Q variant on the rate of decline of the glomerular filtration rate (GFR) by creatinine clearance derived from the Cockroft-Gault formula in 77 type 1 diabetic patients with albuminuria who were followed for an average of 6.5 years (range 2.5-15). Patients carrying the Q allele (n = 22; 20 with KQ and 2 with QQ genotypes) had a faster GFR decline than those patients with the KK genotype (n = 55) (median 7.2 vs. 3.7 ml x min(-1) x year(-1); range 0.16 to 16.6 vs. -3.8 to 16.0 ml x min(-1) x year(-1); P < 0.001). Significantly more patients carrying the Q allele belonged to the highest tertile of GFR decline (odds ratio = 5.7, 95% CI 4.1-7.2, P = 0.02). Levels of blood pressure, HbA1c, and albuminuria were comparable in the two genotype groups. Albuminuria (P = 0.001), mean blood pressure (P = 0.046), and PC-1 genotype (P = 0.036) independently correlated with GFR decline. Because all patients were receiving antihypertensive treatment, the faster GFR decline in the patients carrying the Q allele could be the result of reduced sensitivity to the renoprotective effect of antihypertensive therapy. PC-1 genotyping identifies type 1 diabetic patients with a faster progression of diabetic nephropathy.

Neuropeptides and sexual behaviour

Many neuropeptides are involved in the control of sexual behaviour at the central level. Among these, the most studied are adrenocorticotropin, alpha-melanocyte stimulating hormone, oxytocin and opioid peptides. This attempt to review old and new neuropharmacological, biochemical and psychobiological studies in this field, shows that all these neuropeptides apparently facilitate sexual behaviour, except for opioid peptides, which inhibit sexual performance, in most of the species studied so far (rats, mice, monkeys and humans). However, gonadotropin-releasing hormone, corticotropin releasing factor, neuropeptide Y, galanin, cholecystokinin, substance P and vasoactive intestinal peptide may be also involved in the control of sexual behaviour. Apparently, corticotropin releasing factor, neuropeptide Y and cholecystokinin inhibit, while substance P and vasoactive intestinal peptide facilitate, sexual behaviour. In contrast, gonadotropin-releasing hormone has been reported to exert a facilitative, inhibitory or no effect at all on sexual behaviour. Galanin was also shown either to facilitate or inhibit sexual behaviour. The above-mentioned putative role of the neuropeptides in sexual behaviour derives mainly from studies done in rats. In these studies, neuropeptides, their antisera or drugs that act as agonists or antagonists of neuropeptide receptors, were tested for their effect on sexual behaviour after systemic, intracerebroventricular, or intracerebral administration. The latter were infused into brain areas relevant for sexual behaviour, such as the medial preoptic area, and the ventromedial and paraventricular nuclei of the hypothalamus. The above studies show that little information is available on the mechanisms by which neuropeptides influence sexual behaviour. Also unclear is whether the above neuropeptides influence the anticipatory phase (sexual arousal and/or motivation) or the consummatory phase (performance) of sexual behaviour, except for opioid peptides. New information about the role of neuropeptides may come from the application of molecular biology and genetic manipulation techniques to the study of sexual behaviour. Of these, FOS protein determination, antisense oligonucleotides aimed at the neutralisation of neuropeptide and/or neuropeptide receptor mRNAs in specific brain areas, and gene ablation seem the most promising. Although still in the early stages, it is likely that these methodologies will provide new insights into the role of neuropeptides in the control of sexual behaviour.

A polymorphism (K121Q) of the human glycoprotein PC-1 gene coding region is strongly associated with insulin resistance

The genes responsible for insulin resistance are poorly defined. Plasma cell differentiation antigen (PC-1) glycoprotein inhibits insulin receptor signaling and is associated with insulin resistance. We describe here a novel polymorphism in exon 4 of the PC-1 gene (K121Q) and demonstrate that it is strongly associated with insulin resistance in 121 healthy nonobese (BMI <30 kg/m2) nondiabetic (by oral glucose tolerance test [OGTT]) Caucasians from Sicily. Compared with 80 KK subjects, Q allele carriers (n = 41, 39 KQ and 2 QQ) showed higher glucose and insulin levels during OGTT (P < 0.001 by two-way analysis of variance) and insulin resistance by euglycemic clamp (M value = 5.25 +/- 1.38 [n = 24] vs. 6.30 +/- 1.39 mg x kg(-1) x min(-1) [n = 49], P = 0.005). Q carriers had higher risk of being hyperinsulinemic and insulin resistant (odds ratio [CI]: 2.99 [1.28-7.0], P < 0.001). Insulin receptor autophosphorylation was reduced (P < 0.01) in cultured skin fibroblasts from KQ versus KK subjects. Skeletal muscle PC-1 content was not different in 11 KQ versus 32 KK subjects (33 +/- 16.1 vs. 17.5 +/- 15 ng/mg protein, P = 0.3). These results suggest a cause-effect relationship between the Q carrying genotype and the insulin resistance phenotype, and raise the possibility that PC-1 genotyping could identify individuals who are at risk of developing insulin resistance, a condition that predisposes to type 2 diabetes and coronary artery disease.

Yawning: role of hypothalamic paraventricular nitric oxide

Yawning is a phylogenetically old, stereotyped event that occurs alone or associated with stretching and/or penile erection in humans, in animals from reptiles to birds and mammals, under different conditions. Several neurotransmitters and neuropeptides are involved in its control at the central level. One of these at the level of the paraventricular hypothalamic nucleus (PVHN) is nitric oxide (NO). First, NO synthase inhibitors injected into this hypothalamic nucleus prevent yawning induced by dopamine agonists, oxytocin or N-methyl-D-aspartic acid (NMDA), which induce yawning by activating PVHN oxytocinergic neurons projecting to extra-hypothalamic brain areas. The inhibitory effect of NO synthase inhibitors was not observed when these compounds were given concomitantly with L-arginine, the precursor of NO. Second, dopamine agonists, NMDA and oxytocin given at doses that induce yawning, increase NO production in the PVHN, as determined by in vivo microdialysis. Conversely, the opiate morphine, which prevents yawning induced by dopamine agonists, oxytocin and NMDA, also prevents the increase in the paraventricular NO production induced by these compounds. Third, NO donors, such as nitroglycerin, sodium nitroprusside and hydroxylamine, induce yawning when injected into the PVHN apparently by activating oxytocinergic transmission. Since guanylate cyclase inhibitors and NO scavengers (hemoglobin) injected into the PVHN do not prevent drug-induced yawning, nor 8-Br-cGMP injected into the PVHN induces this behavioral response, it is likely that NO acts as an intracellular rather than an intercellular modulator inside the PVHN oxytocinergic neurons in which NO is formed to facilitate the expression of this phylogenetically old event by guanylate cyclase-independent mechanisms.

Morphine injected into the paraventricular nucleus of the hypothalamus prevents noncontact penile erections and impairs copulation: involvement of nitric oxide

Male rats show four to six penile erection episodes when put in the presence of an inaccessible receptive female for 80 min. These noncontact erections occur concomitantly with an increase in nitric oxide production in the paraventricular nucleus of the hypothalamus. This is shown by the increases in the NO2- and NO3- concentrations in the paraventricular dialysate obtained from these males by in vivo microdialysis. The NO2- concentration increased from 0.75 +/- 0. 10 microm to 2.89 +/- 0.39 microm and that of NO3- from 4.13 +/- 0. 58 microm to 9.5 +/- 1.2 microm. Morphine (0.5, 1 and 5 microg), given unilaterally into the paraventricular nucleus 15 min before the introduction of the receptive female, prevented the NO2- and NO3- increases, and noncontact erections, dose-dependently. In contrast, the kappa opioid receptor agonist U-69 593 (5 microg) was ineffective. The effects of morphine on NO2- and NO3-, and on noncontact erections, were prevented by the opiate receptor antagonist naloxone (10 microg) injected into the paraventricular nucleus 15 min before morphine. The NO2- and NO3- concentrations were also increased in the paraventricular dialysate of male rats during copulation, i.e. when in copula penile erections occurred. As found with noncontact erections, morphine, but not U-69 593, injected into the paraventricular nucleus prevented the NO2- and NO3- increases and impaired copulatory behaviour, and naloxone prevented these responses when given before morphine. Although some diffusion of the opiate to surrounding brain areas cannot be completely ruled out, the present results suggest that morphine acts through mu receptors in the paraventricular nucleus to impair noncontact erections and copulation. These effects of morphine are apparently mediated by a prevention of the increased nitric oxide production that occurs in the paraventricular nucleus of the hypothalamus of male rats during sexual activity.

The oxytocin antagonist d(CH2)5Tyr(Me)2-Orn8-vasotocin reduces non-contact penile erections in male rats

Male rats show four to six penile erection episodes when put for 80 min in the presence of an inaccessible receptive female. These non-contact penile erections were reduced dose-dependently by d(CH2)5Tyr(Me)2-Orn8-vasotocin, a potent and selective oxytocin receptor antagonist, when given into the lateral ventricles (0.1, 0.5 and 1 microg), but not when given into the paraventricular nucleus of the hypothalamus (0.1 and 1 microg). In contrast, non-contact erections were reduced by N(G)-nitro-L-arginine methyl ester, a competitive inhibitor of nitric oxide synthase, given into the lateral ventricles (50, 100 and 200 microg), or into the paraventricular nucleus (10 and 20 microg). The present results show that central oxytocin is involved in the expression of penile erection induced not only by drugs but also by sexual physiological stimuli.

Different effects of omega-conotoxin on penile erection, yawning and paraventricular nitric oxide in male rats

A dose of apomorphine or oxytocin that induces penile erection and yawning increases nitric oxide production in the paraventricular nucleus of the hypothalamus, as determined by the increase in NO2- and NO3- concentration induced by these substances in the paraventricular dialysate obtained from male rats. All the above responses were prevented by a dose of omega-conotoxin-GVIA as low as 5 ng. This potent inhibitor of N-type Ca2+ channels was injected into the paraventricular nucleus 15 min before apomorphine (50 ng) or oxytocin (10 ng). In contrast, omega-conotoxin was ineffective when the above responses were induced by N-methyl-D-aspartic acid (50 ng). The peptide toxin (5 ng) was also ineffective on the penile erection and yawning induced by the nitric oxide donors sodium nitroprusside (50 microg) or hydroxylamine (50 microg), injected into the paraventricular nucleus. The present results suggest that omega-conotoxin-sensitive Ca2+ channels are involved in the activation of nitric oxide synthase, penile erection and yawning induced by apomorphine and oxytocin, but not by N-methyl-D-aspartic acid, at the paraventricular level.

Nitric oxide production is increased in the paraventricular nucleus of the hypothalamus of male rats during non-contact penile erections and copulation

Male rats put in the presence of a receptive female rat that they can see, hear and smell, but cannot touch, show penile erection episodes. These non-contact erections occur concomitantly with an increase in nitric oxide production in the paraventricular nucleus of the hypothalamus, as detected by the increase in the NO2- and NO3- concentration in the paraventricular dialysate obtained from these males by in vivo microdialysis. NO2- concentration increased from 0.81+/-0.12 to 2.51+/-0.43 microM and that of NO3- from 4.50+/-0.73 to 8.31+/-2.3 microM. The NO2- increase was prevented by the nitric oxide synthase inhibitor NG-nitro-L-arginine methylester (20 microg) given unilaterally in the paraventricular nucleus, which also prevented non-contact erections. In contrast, the nitric oxide scavenger haemoglobin (20 microg) prevented the NO2- increase, but not non-contact erections; while the guanylate cyclase inhibitor methylene blue (20 microg) was ineffective on either response. NO2-and NO3- concentration was also increased in the paraventricular dialysate of male rats during in copula penile erections, that is, when sexual activity was allowed with the receptive females. As found with non-contact erections, NG-nitro-L-arginine methylester prevented NO2- increase and impaired copulatory behaviour; haemoglobin prevented NO2- increase only; and methylene blue was ineffective on either response. The present results confirm that nitric oxide is a physiological mediator of penile erection at the level of the paraventricular nucleus of the hypothalamus.

The neuropharmacology of yawning

Yawning is a phylogenetically old, stereotyped event that occurs alone or associated with stretching and/or penile erection in humans and in animals from reptiles to birds and mammals under different conditions. Although its physiological function is still unknown, yawning is under the control of several neurotransmitters and neuropeptides at the central level as this short overview of the literature on the neurochemistry of yawning shows. Among these substances, the best known are dopamine, excitatory amino acids, acetylcholine, serotonin, nitric oxide, adrenocorticotropic hormone-related peptides and oxytocin, that facilitate yawning and opioid peptides that inhibit this behavioral response. Some of the above compounds interact in the paraventricular nucleus of the hypothalamus to control yawning. This hypothalamic nucleus contains the cell bodies of oxytocinergic neurons projecting to extra-hypothalamic brain areas that play a key role in the expression of this behavioral event. When activated by dopamine, excitatory amino acids and oxytocin itself, these neurons facilitate yawning by releasing oxytocin at sites distant form the paraventricular nucleus, i.e. the hippocampus, the pons and/or the medulla oblongata. Conversely, activation of these neurons by dopamine, oxytocin or excitatory amino acids, is antagonized by opioid peptides, that, in turn, prevent the yawning response. The activation and inhibition, respectively of these oxytocinergic neurons is related to a concomitant increase and decrease, respectively, of paraventricular nitric oxide synthase activity. However, other neuronal systems in addition to the central paraventricular oxytocinergic neurons are involved in the control of yawning, since they do not seem to be involved in the expression of yawning induced by the stimulation of acetylcholine or serotoninergic receptors, nor by adrenocorticotropic hormone (ACTH) and related peptides. Nitric oxide is also involved in the induction of yawning by the latter compounds and neuronal links, for instance between dopamine and acetylcholine and dopamine and serotonin, seem to be involved in the yawning response. Finally, other neurotransmitters, i.e. gamma-aminobutyric acid (GABA) and noradrenaline, and neuropeptides, i.e. neurotensin and luteinizing hormone-releasing hormone (LH-RH), influence this behavioral response. In conclusion, in spite of some recent progress, little is known of, and more has to be done to identify, the neurochemical mechanisms underlying yawning at the central level.

Prevention by morphine of N-methyl-D-aspartic acid-induced penile erection and yawning: involvement of nitric oxide

The effect of morphine on the increase of NO2- and NO3- concentration in the dialysate obtained with a microdialysis probe implanted in the paraventricular nucleus of the hypothalamus, and penile erection and yawning induced by N-methyl-D-aspartic acid (NMDA) was studied in male rats. NMDA (50 ng) injected in the paraventricular nucleus of the hypothalamus, induced penile erection and yawning and increased NO2- from 1.10 +/- 0.28 microM to 7.30 +/- 1.10 microM and NO3- from 5.05 +/- 0.71 microM to 11.03 +/- 1.61 microM. Morphine (1-10 microg), but not U-69,593 (10 microg), a selective agonist of the kappa opiate receptor subtype, prevented in a dose-dependent manner NMDA-induced increase in NO2- and NO3- concentration when injected in the paraventricular nucleus 15 min before NMDA. Morphine prevention of NMDA-induced NO2- and NO3- increase was related to a concomitant decrease in the number of penile erection and yawning episodes induced by the excitatory amino acid. Morphine effect was not observed in male rats treated with the opiate receptor antagonist naloxone (10 microg) microinjected in the paraventricular nucleus 15 min before morphine. The present results suggest that morphine prevents an NMDA-induced increase in paraventricular NO production, penile erection, and yawning by inhibiting NO synthase activity in the paraventricular nucleus of the hypothalamus through the stimulation of opioid receptors of the micro subtype.

Role of central nitric oxide in the control of penile erection and yawning

1. Recent experimental evidence has shown that nitric oxide (NO) plays an important role in the expression of penile erection and yawning and that this molecule has to be added to the list of the best known neurotransmitters and neuropeptides involved in this symptomatology. 2. This was first suggested by the ability of NO synthase inhibitors injected in the lateral ventricles (i.c.v.) or in the paraventricular nucleus of the hypothalamus (PVN) to prevent these behavioral responses induced by dopamine agonists, oxytocin and NMDA. The inhibitory effect of NO synthase inhibitors was not observed when these compounds were injected concomitantly with L-arginine, the precursor of NO. Most important, this hypothalamic nucleus is one of the richest brain areas of NO synthase and also the brain site where dopamine, NMDA and oxytocin act to induce penile erection and yawning by activating central NO synthase containing oxytocinergic neurons. 3. NO synthase inhibitors given i.c.v. but not in the PVN prevent also penile erection and yawning induced by ACTH and serotonin1c agonists, which induce these responses by acting with mechanisms unrelated to oxytocinergic transmission. 4. Dopamine agonists, NMDA and oxytocin increase NO production in the PVN at doses that induce penile erection and yawning, as determined by measuring the concentration of NO2- and NO3- in the dialyzate obtained with a vertical probe implanted in the PVN by in vivo microdialysis. 5. NO donors, such as nitroglycerin, sodium nitroprusside and hydroxylamine, induce penile erection and yawning indistinguishable from those induced by oxytocin, dopamine agonists or NMDA when injected in the PVN. The NO donor response was prevented by the i.c.v. injection of the oxytocin receptor antagonist d(CH2)5-Tyr(Me)-Orn8-vasotocin, indicating that these compounds also induce penile erection and yawning by activating oxytocinergic transmission. 6. Finally, guanylate cyclase inhibitors (i.e. methylene blue and LY 83583) and hemoglobin injected in the PVN do not prevent drug-induced penile erection and yawning, nor 8-Br-cGMP injected in the PVN induces these behavioral responses suggesting that the mechanism by means of which endogenous or NO donor-derived NO facilitates oxytocinergic transmission to induce penile erection and yawning is not related to the activation of guanylate cyclase. Furthermore, since hemoglobin, in spite of its ability to prevent drug-induced NO production in the PVN, does not prevent penile erection and yawning, it is likely that NO acts as an intracellular rather than an intercellular modulator in the PVN neurons in which is formed to facilitate the expression of these behavioral responses.

N-methyl-D-aspartic acid-induced penile erection and yawning: role of hypothalamic paraventricular nitric oxide

A dose of N-methyl-D-aspartic acid (NMDA, 50 ng) that induces penile erection and yawning when injected into the paraventricular nucleus of the hypothalamus, increased the concentration of NO2- from 1.10 +/- 0.28 microM to 7.32 +/- 1.12 microM and of NO3 from 4.96 +/- 0.69 microM to 10.5 +/- 1.61 microM in the paraventricular dialysate obtained from male rats by in vivo microdialysis. NO2- concentration was not increased by (+/-)-alpha-(amino)-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA, 100 ng) or by trans-(+/-)-1-amino-1,3-cyclopentanedicarboxylic acid (ACPD) (100 ng), which were unable to induce these behavioral responses. N-Methyl-D-aspartic acid effect on NO2- concentration, penile erection and yawning was prevented by dizolcipine (MK-801) (10-100 ng) or by the nitric oxide synthase inhibitor N(G)-nitro-L-arginine methyl ester (20 microg), but not by the oxytocin receptor antagonist [d(CH2)5,Tyr(Me)2,Orn8]vasotocin (100 ng), or by the guanylate cyclase inhibitor methylene blue (20 microg) given in the paraventricular nucleus 15 min before N-methyl-D-aspartic acid or by the dopamine receptor antagonist haloperidol (0.5 mg/kg) given intraperitoneally 30 min before N-methyl-D-aspartic acid. In contrast, the nitric oxide scavenger hemoglobin (20 microg) given in the paraventricular nucleus prevented N-methyl-D-aspartic acid-induced NO2- concentration increase, but was unable to prevent penile erection and yawning. The results suggest that N-methyl-D-aspartic acid induces penile erection and yawning by increasing nitric oxide synthase activity in the paraventricular nucleus of the hypothalamus, possibly in the cell bodies of oxytocinergic neurons projecting to extra-hypothalamic brain areas and mediating these behavioral responses.

Prevention by morphine of apomorphine- and oxytocin-induced penile erection and yawning: involvement of nitric oxide

The possible involvement of nitric oxide in the prevention by morphine of apomorphine- and oxytocin-induced penile erection and yawning was investigated by measuring the concentration of NO2- and NO3- in the dialysate obtained with a vertical microdialysis probe implanted in the paraventricular nucleus of the hypothalamus of male rats. Either apomorphine (80 micrograms/kg s.c.) or oxytocin (30 ng i.c.v.) increased significantly basal NO2- and NO3- concentration in the paraventricular dialysate, penile erection and yawning. Morphine (1.5 and 10 mg/kg i.p.) prevented dose-dependently either apomorphine or oxytocin responses when given 15 min before apomorphine or oxytocin. Prevention by morphine of apomorphine and oxytocin responses was abolished by naloxone (3 mg/kg i.p.) given 15 min before morphine. Morphine prevented apomorphine and oxytocin responses also when given in the lateral ventricles or directly in the paraventricular nucleus. In contrast, the selective agonist of the kappa opioid receptor subtype U-69,593 was found to be ineffective. The present results confirm previous findings showing that morphine acts through mu receptors in the paraventricular nucleus to prevent apomorphine and oxytocin-induced penile erection and yawning and suggest that this morphine effect is mediated by a decreased activity of nitric oxide in the paraventricular nucleus of the hypothalamus.

Oxytocin increases nitric oxide production in the paraventricular nucleus of the hypothalamus of male rats: correlation with penile erection and yawning

A dose of oxytocin (50 ng i.c.v.) that induces penile erection and yawning, increased the concentration of NO2- from 0.98 +/- 0.29 to 4.2 +/- 0.79 microM and of NO3- from 5.6 +/- 0.33 to 12.03 +/- 0.99 microM in the dialysate from the paraventricular nucleus of the hypothalamus of male rats, as measured by in vivo microdialysis. NO2- concentration was also increased by [Thr4, Gly7]-oxytocin (100 ng i.c.v. and oxytocin(8) (1 microgram i.c.v.) which also induced penile erection and yawning, but not by oxytocin(1-6) (1 microgram i.c.v.) or oxytocin (7-9) 1 microgram i.c.v.), which were unable to induce these behavioral responses. The oxytocin effect on NO2 concentration, penile erection and yawning was prevented by the oxytocin receptor antagonist. d(CH2)5,Tyr(Me)-Orn8-vasotocin (1 microgram i.e.v.) or by the nitric oxide synthase inhibitor, NG-nitro-1-arginine methyl ester (200 micrograms i.c.v.), but not by the dopamine receptor antagonist, haloperidol (0.5 mg/kg i.p.). The nitric oxide scavenger, hemoglobin (200 micrograms i.c.v.), prevented oxytocin-induced NO2- concentration increase, but was unable to prevent penile erection and yawning. Methylene blue (300 micrograms i.c.v.) an inhibitor of guanylate cyclase, was ineffective on oxytocin-induced NO2- concentration increase, but prevented the behavioral responses. The results suggest that oxytocin induces penile erection and yawning by increasing nitric oxide synthase activity in the cell bodies of oxytocinergic neurons projecting to extra-hypothalamic brain areas and mediating the behavioral responses.

Two novel PAH gene mutations detected in Italian phenylketonuric patients

We report the identification by denaturing gradient gel electrophoresis and sequence analysis of two new phenylalanine hydroxylase (PAH) gene mutations (IVS4nt-2 and N207S) in single chromosomes of two unrelated Italian phenylketonuric (PKU) patients. Interestingly, mutation Y204C, found on the second mutant allele of family F1, has been previously detected in Chinese patients. Haplotype analysis showed that the latter mutation is linked to the same haplotype (H4) in both Chinese and Italian patients, suggesting a common origin. In vivo assessment of mutation severity indicates that N207S is associated with classic PKU. The identification of these two new mutations further extends the remarkable heterogeneity of the PAH locus in the Italian population.

Dopamine agonists increase nitric oxide production in the paraventricular nucleus of the hypothalamus: correlation with penile erection and yawning

A low dose of apomorphine (80 micrograms/kg s.c.), a mixed D1/D2 agonist that induces penile erection and yawning, increased the concentration of NO2-from 1.12 +/- 0.45 microM to 3.8 +/- 0.75 microM and NO3-from 5.53 +/- 0.82 to 11.25 +/- 2.30 microM in the dialysate collected from the paraventricular nucleus of the hypothalamus of male rats by in vivo microdialysis. The NO2-concentration was also increased by LY 171555 (50 micrograms/kg s.c.), a D2 agonist that induces penile erection and yawning, but not by SKF 38393 (5 mg/kg s.c.), a D1 agonist with no effect on these responses. Conversely, apomorphine's effect on NO2-was prevented by haloperidol (0.5 mg/kg i.p.), a mixed D1/D2 antagonist and L-sulpiride (25 mg/kg i.p.), a D2 antagonist, but not by the D1 agonist SCH 23390 (50 micrograms/kg s.c.), although all three compounds prevented penile erection and yawning. The apomorphine effect on NO2-, penile erection and yawning was also prevented by the nitric oxide synthase inhibitor NG-nitro-L-arginine methyl ester (200 micrograms i.c.v.). The nitric oxide scavenger haemoglobin (200 micrograms i.c.v.) also prevented the NO2-increase, but was ineffective against penile erection and yawning. In contrast, the oxytocin antagonist d(CH2)5Tyr(Me)-Orn8-vasotocin (1 microgram i.c.v.) and the guanylate cyclase inhibitor methylene blue (300 micrograms i.c.v.) had no effect on the NO2-increase, but did prevent the behavioural responses. We infer from this that dopamine agonists induce penile erection and yawning by acting on D2 receptors that increase nitric oxide synthase activity in the cell bodies of paraventricular oxytocinergic neurons projecting to extra-hypothalamic brain areas.

Nitric oxide donors induce penile erection and yawning when injected in the central nervous system of male rats

In order to provide further support for a role of central nitric oxide as a mediator of penile erection and yawning, the nitric oxide donors sodium nitroprusside, hydroxylamine, isoamyl nitrite and S-nitroso-N-acetyl-penicillamine were injected into the lateral ventricles (i.c.v.) or into the paraventricular nucleus of the hypothalamus of male rats. Of the above compounds injected i.c.v., only isoamyl nitrite (10-100 micrograms) induced penile erection and yawning, while the others induced dramatic behavioral changes, such as motor hyperactivity and convulsions, that masked the above responses. Nevertheless, nitric oxide donors in doses ranging from 10 to 50 micrograms, for except S-nitroso-N-acetyl-penicillamine that was injected only at the dose of 10 micrograms and isoamyl nitrite that was not injected at all because of poor solubility, induced penile erection and yawning when injected in the paraventricular nucleus. Nitric oxide donor-induced responses were prevented by methylene blue and LY 83583, inhibitors of guanylate cyclase, the best known target of nitric oxide, given i.c.v. but not in the paraventricular nucleus. However, 8-bromo-guanosine 3':5'-cyclic monophosphate (8-Br-cGMP), a stable cGMP analog, and hemoglobin, a nitric oxide scavenger, were ineffective in inducing and preventing, respectively, penile erection and yawning when injected either i.c.v. or in the paraventricular nucleus. Nitric oxide donor-induced responses were also prevented by the nonapeptide oxytocin receptor antagonist d(CH2)5-Tyr(Me)-Orn8-vasotocin given i.c.v. but not in the paraventricular nucleus. The present results suggest that nitric oxide donors induce penile erection and yawning by activating central oxytocinergic transmission in the paraventricular nucleus of the hypothalamus via a cGMP-independent mechanism.

Opposite changes in the content of oxytocin- and vasopressin-like immunoreactive peptides in the rat thymus during aging

The content of oxytocin- and vasopressin-like immunoreactive (IR) peptides was measured in the thymic extract of 2, 5, 10, 15 and 20 month-old rats by radioimmunoassay before or after fractionation by high-pressure liquid chromatography. In both cases the content of the oxytocin-like IR peptide, which behaved like authentic oxytocin in the chromatography column, increased during aging. Compared to 2 month-old rats a significant 30% increase was observed in 5 month-old rats, whereas the maximal increase (200%) was found in 20 month-old rats. In contrast, the content of the vasopressin-like IR peptide, which behaved like authentic arg8-vasopressin in the chromatography column, decreased during aging. The decrease (30%) was evident in 5 month-old rats, and was maximal (80%) in 15 month-old rats. The present results suggest that the mechanisms regulating the content of oxytocin- and vasopressin-like IR peptides in the rat thymus undergo differential changes during aging. These processes might be linked to thymic involution.

Neuromodulation of penile erection: an overview of the role of neurotransmitters and neuropeptides

erection is regulated by several neurotransmitters and neuropeptides at penile tissue and central nervous system levels. At penile level, the key event is the relaxation of corpora cavernosa smooth muscles. Here, three kinds of neural autonomic control have been characterized in detail. one adrenergic stimulatory, that under normal conditions maintains the corpora cavernosa contracted (that is a flaccid penis), a second cholinergic inhibitory that is believed to cooperate with a third, nonadrenergic-noncholinergic control also inhibitory, possibly mediated by nitric oxide (NO), to reduce the adrenergic tone favouring the relaxation of corpora cavernosa, as during a sexual stimulus. However, the complex interactions between these neurotransmitters that determine the final condition of the corpora cavernosa, e.g. the presence or the absence of penile erection, are still a matter of controversy. This is further complicated by the presence of several neuropeptides in nervous penile vascular and smooth muscle tissues such as vasoactive intestinal polypeptide, peptide histidine- isoleucine, peptide histidine-methionine, neuropeptide Y and endothelins,that often exert very potent (relaxant or contractant) effects in penile tissues. Also at the central level, several neurotransmitters and neuropeptides that influence penile erection have been identified. Among neurotransmitters, the most studied are dopamine (DA), serotonin (SHT), acetylcholine (ACh), glutamic acid and NO. DA, ACh. glutamic acid and NO seem to have a facilitatory role, while 5HT may be either facilitatory or inhibitory, depending on the receptor subtype involved. Among neuropeptides, the best known are oxytocin, adrenocorticotropin (ACTH)-cc-melanocyte stimulating hormone (r-MSH)-related peptides and opioid peptides. Interestingly DA, glutamic acid and NO seem to facilitate while opioid peptides inhibit penile erection by increasing and decreasing, respectively, central oxytocinergic transmission by acting in the paraventricular nucleus of the hypothalamus. ACTH-MSH peptides also facilitate penile erection, although with a mechanism(s) different from those recalled above. Despite some recent progress, more has still to be done to clarify the role played by neurotransmitters and neuropeptides at peripheral and central levels in the control of this primary sexual function.

Melanocortins and opioids modulate early postnatal growth in rats

This study was undertaken to investigate the effects of melanocortins and opioids on rat early postnatal body and organ growth. Among melanocortins tested desacetyl-alpha-melanocyte-stimulating hormone (alpha-MSH) at dosages of 0.3 and 3 micrograms/g/day was effective in stimulating neonatal growth with a weight gain of 7 and 5.6%, respectively, after 2 weeks of treatment. Likewise, a weight rise of 4.2 and 3% was obtained with 3 micrograms/g/day of both alpha-MSH and Nle4-D-Phe7 alpha-MSH. As far as opioids were concerned, while N-acetyl-beta-endorphin (beta-End) was ineffective, the activity of beta-End was dependent on dosage. Indeed, newborns treated with 0.03 microgram/g/day showed a slight, but significant, increase in weight, whereas a marked decrease in growth followed treatment with 0.3 and, mainly, 3 micrograms/g/day, with a final weight loss of 3.4 and 5.5%, respectively. All melanocortins exerted a positive action on muscular and brain trophism and, in addition, desacetyl-alpha-MSH also induced a rise of fat deposits. On the contrary, while the 0.03 microgram/g/day beta-End dose caused an increase in muscular and brain weight, the higher dosages of the opioid were detrimental, not only for muscle and brain, but also for both liver and spleen weight. A slight, although significant (P < 0.05), enhancement of serum dehydroepiandrosterone sulfate (DHEAS) level was found after the injection of 0.3 microgram/g desacetyl-alpha-MSH, whereas both the 0.3 and 3 micrograms/g doses of desacetyl-alpha-MSH and the 3 micrograms/g dose of alpha-MSH determined the rise of plasma androstenedione (P < 0.05). All tested melanocortins and opioids failed to modify the concentrations of corticosterone. Our results suggest that melanocortins and opioids can modulate early postnatal growth in rats either by direct or indirect mechanisms.

Role of nitric oxide in penile erection and yawning induced by 5-HT1c receptor agonists in male rats

The effect of the intracerebroventricular (i.c.v.) administration of NG-nitro-L-arginine methyl ester and NG-monomethyl-L-arginine, two inhibitors of nitric oxide (NO) synthase, on penile erection and yawning induced by 1-(3-chlorophenyl)-piperazine (m-CPP)- and N-(3-trifluoromethylphenyl)-piperazine (TFMPP), two selective 5HT1c receptor agonists, was studied in male rats. Both NO synthase inhibitors (50-500 micrograms i.c.v.) prevented dose-dependently the behavioural responses induced by m-CPP (0.5 mg/kg s.c.) or by TFMPP (1 mg/kg s.c.), but NG-nitro-L-arginine methyl ester was about 4-5 times more potent than NG-monomethyl-L-arginine. The D-isomer of NG-monomethyl-L-arginine, which does not inhibit nitric oxide synthase, was ineffective. The inhibitory effect of NG-nitro-L-arginine methyl ester on m-CPP- and TFMPP-induced responses was prevented by the administration of L-arginine (1 mg i.c.v.). In contrast, NG-nitro-L-arginine methyl ester (20 micrograms) was ineffective when injected in the paraventricular nucleus of the hypothalamus, a brain area that plays a key role in the expression of these behavioural responses. m-CPP- and TFMPP-induced penile erection and yawning was prevented also by the i.c.v. administration of LY 83583 (50-200 micrograms) or methylene blue (50-400 micrograms), two inhibitors of guanylate cyclase but not by reduced hemoglobin (50-400 micrograms), a NO scavenger. The results suggest that central nitric oxide is involved in the expression of penile erection and yawning induced by 5-HT1c receptor agonists.

Dopamine and sexual behavior

Among central neurotransmitters involved in the control of sexual behavior, dopamine is certainly one of the most extensively studied. Our attempt to review old and recent neuropharmacological, biochemical, electrophysiological, and psychobiological studies performed so far only in rats, monkeys, and humans, provides evidence that dopamine through its different neuronal systems and receptor subtypes plays different roles in the control of several aspects of sexual behavior. In fact, while the nigrostriatal system is necessary for the control of the sensory-motor coordination required for copulation, the mesolimbic-mesocortical system plays a key role in the preparatory phase of the behavior, mainly in sexual arousal, motivation and possibly reward. Conversely, the incertohypothalamic system plays a major role in the consummation of the behavior, mainly in seminal emission and erectile performance, but evidence for its involvement in sexual motivation also exists. The dopaminergic receptors playing the major role in the control of male sexual behavior belong to the D2 receptor subtype. However a D1/D2 receptor interaction is well established and an opposite role for D1 and D2 receptors in the preoptic area suggested. Despite some differences, most studies show that treatments that increase or decrease, respectively, brain dopaminergic activity improve or worsen, respectively, several parameters of copulatory activity, supporting a facilitatory role of dopamine in male sexual behavior. In contrast, no conclusion can be deduced from the available studies on the role of central dopaminergic systems in the control of proceptivity and receptivity, the two main components of female sexual behavior.

Nitroglycerin-induced penile erection and yawning in male rats: mechanism of action in the brain

The effect of the central administration of nitroglycerin, a potent organic nitrate vasodilator, on penile erection and yawning was studied in male rats. When given intracerebroventricularly (ICV), nitroglycerin (33-99 micrograms) induced the above responses dose-dependently. The minimal effective dose was 33 micrograms, which was active in 60% of the rats. Nitroglycerin (1.65-6.6 micrograms) induced penile erection and yawning also when injected in the paraventricular nucleus of the hypothalamus. Nitroglycerin responses were prevented by methylene blue (200-400 micrograms ICV), by d(CH2)5Tyr(Me)2-Orn8-vasotocin (0.5-1 micrograms ICV) but not hemoglobin (100-200 micrograms ICV). In contrast methylene blue (10-20 micrograms), d(CH2)5Tyr(Me)2-Orn8-vasotocin (0.05-0.1 microgram) and hemoglobin (10-20 micrograms) were ineffective when injected in the paraventricular nucleus. Systemic haloperidol (0.5-1 mg/kg IP) was also ineffective. The results suggest that nitroglycerin induces penile erection and yawning by activating brain oxytocinergic transmission through the formation of nitric oxide in the paraventricular nucleus of the hypothalamus.

Oxytocin in human intrauterine tissues at parturition

The recent detection of oxytocin (OT) mRNA in human gestational tissues suggests that OT may be locally synthesized and released to act on the uterus as a local mediator in the mechanism of parturition. In order to investigate this possibility the OT immunoreactive (I.R.) content was examined directly in placental decidua and amniochorial membranes after term and preterm delivery and in their culture media at term gestation. I.R.OT concentrations were also measured in maternal, retroplacental and umbilical plasma as well as in amniotic fluid in the presence or the absence of labour. Low I.R.OT concentrations (below 15 fmol g-1 wet tissue) were found in both amniochorial membranes and placental decidua. Moreover, whereas in amniochorion they were higher (P < 0.05) after preterm than term spontaneous parturition, in decidua they were higher (P < 0.05) after term than preterm vaginal delivery. Detectable amounts (below 15 fmol g-1 wet tissue per h) of I.R.OT were also found in culture media from explants of the above tissues. Among all the examined maternal and fetal fluids a rise in I.R.OT content at parturition was detected only in the amniotic liquor (P < 0.05). These findings suggest that I.R.OT concentrations in intrauterine tissues are very low; however, considering that OT is the most potent endogenous uterotonic agent, OT as such concentrations might play a paracrine function in the biochemical events leading to human parturition. Therefore, a role for amniotic OT in parturition can not be excluded.

Nitric oxide is a central mediator of penile erection

In order to evaluate a possible role of brain nitric oxide (NO) on the control of penile erection, the effect of nitroglycerin, that is thought to act by producing NO, was studied on spontaneous penile erection in male rats. In addition the effect of drugs that prevent NO formation and/or activity such as NG-nitro-L-arginine methyl ester (NAME) and methylene blue, on N-methyl-D-aspartic acid (NMDA)-, apomorphine- and oxytocin-induced penile erection was also studied. Nitroglycerin induced penile erection in a dose-dependent manner when given intracerebroventricularly (i.c.v.) (33-99 micrograms) or in the paraventricular nucleus of the hypothalamus (0.8-3.3 micrograms). Nitroglycerin-induced penile erection was prevented by the guanylate cyclase inhibitor methylene blue injected i.c.v. (200-400 micrograms) but not in the paraventricular nucleus of the hypothalamus (10-20 micrograms). Conversely, NMDA-, apomorphine- and oxytocin-induced penile erection was prevented by NAME (150 micrograms) or methylene blue (400 micrograms) given i.c.v. NAME (20 micrograms), but not methylene blue (20 micrograms), was effective in preventing the behavioral response also when injected in the paraventricular nucleus. The present results suggest that NO is a common mediator of several neurotransmitters involved in the control of this primary male sexual function.

Nitric oxide synthase inhibitors prevent N-methyl-D-aspartic acid-induced penile erection and yawning in male rats

The effect of NG-nitro-L-arginine methylester (NAME) and N-mono-methyl-L-arginine (NMMA), inhibitors of nitric oxide (NO) synthase on penile erection and yawning induced by N-methyl-D-aspartic acid (NMDA) injected in the paraventricular nucleus of the hypothalamus (PVN) was studied in male rats. NAME (75-150 micrograms) and NMMA (250-500 micrograms), but not N-monomethyl-D-arginine (D-NMMA)(250-500 micrograms) prevented both responses in a dose-dependent manner when given intracerebroventricularly (i.c.v.) 15 min before NMDA (50 ng). NMDA-induced penile erection and yawning was also prevented by the guanylate cyclase inhibitor methylene blue (200-400 micrograms i.c.v.), but not by the NO scavenger methemoglobin (50-100 micrograms i.c.v.). NAME (10-20 micrograms), but not Methylene blue or methemoglobin (10-20 micrograms), prevented NMDA-induced responses also when injected in the PVN 15 min before NMDA. The present results suggest that NMDA-induced penile erection and yawning is mediated by an increased NO synthesis in the PVN.

Penile erection and yawning induced by 5-HT1C receptor agonists in male rats: relationship with dopaminergic and oxytocinergic transmission

1-(3-Chlorophenyl)piperazine (m-CPP) (0.1-4 mg/kg s.c.) and N-(3-trifluoromethylphenyl)-piperazine (TFMPP) (0.5-4 mg/kg s.c.), 5-HT1C receptor agonists, but not 8-hydroxy-dipropylamino-tetralin (8-OH-DPAT) (0.1 and 0.2 mg/kg s.c.), a 5-HT1A receptor agonist, induced penile erection and yawning with a U-inverted dose-response curve in male rats. The maximal effect was found with 0.5 mg/kg s.c. of m-CPP and with 1 mg/kg s.c. of TFMPP. The m-CPP (0.5 mg/kg s.c.) and TFMPP (1 mg/kg s.c.) responses were prevented by mianserin (0.2 mg/kg s.c.) and by ritanserin (1 mg/kg s.c.) given 15 min before m-CPP and TFMPP. In contrast, m-CPP- or TFMPP-induced penile erection and yawning were not antagonized by haloperidol (0.1 mg/kg s.c.) or by [d(CH2)5Tyr(Me)2,Orn8]vasotocin (5 micrograms i.c.v.). Apomorphine- and oxytocin-induced penile erection, but not yawning, was also antagonized by mianserin and less effectively by ritanserin. The results suggest that 5-HT1C receptor agonist-induced penile erection and yawning are not mediated by increased dopaminergic and/or oxytocinergic transmission, and raise the possibility that a neuronal dopamine-oxytocin-5-HT link is involved in the control of penile erection and not necessarily of yawning in male rats.