Behavioral and electrophysiological effects of androstadienone, a human pheromone.

Androstadienone is the most prominent androstene present on male human axillary hair and on the male axillary skin surface. We have previously shown that this volatile steroid is able to stimulate [corrected] the human female vomeronasal organ in picogram (pg) quantities, resulting in changes in autonomic activity. These effects are gender-specific. The purpose of the present study was to ascertain whether androstadienone could be considered a human pheromone by altering behavior as well as autonomic function. Forty normal female subjects were randomized in a double-blind manner to receive either control or 100 pg of androstadienone directly to the vomeronasal organ. We report that administration of this steroid under these conditions results in a significant reduction of nervousness, tension and other negative feeling states. Concordant changes were observed in autonomic physiology.

Modulation of serum testosterone and autonomic function through stimulation of the male human vomeronasal organ (VNO) with pregna-4,20-diene-3,6-dione.

In mammals, external chemosensory signals from conspecifics of the opposite sex acting on vomeronasal organ receptors can modulate the release of gonadotropins. There is developmental, anatomical and functional evidence showing that the human vomeronasal organ (VNO) has the characteristics of a chemosensory organ. We have been using naturally occurring human pheromones to serve as models for designing novel synthetic compounds that we call vomeropherins. In previous publications we reported that vomeropherin pregna-4,20-diene-3,6-dione (PDD) delivered to the VNO of normal female and male human volunteers significantly affected male subjects only, decreasing respiration and cardiac frequency, augmenting alpha brain waves, and significantly decreasing serum luteinizing hormone (LH) and follicle stimulating hormone (FSH). Results of the present work confirm that PDD produces a local dose-dependent effect in the male human VNO. This is followed by a mild parasympathomimetic effect characterized by 10% increase of vagal tone, together with decreased frequency of electrodermal activity events. Furthermore, PDD locally delivered to the male human VNO significantly decreases serum LH and testosterone (p < 0.01). The present results contribute additional evidence supporting the functionality of the human VNO and its repercussions in autonomic and psychophysiological functions, as well as in neuroendocrine secretions.

The human vomeronasal system. A review.

Recent publications show that the human vomeronasal organ (VNO) develops and grows during gestation, and is present in all adult humans. The human VNO has a unique ultrastructure, with elongated bipolar microvillar cells that stain with several immunomarkers. These cells show physiological properties similar to chemosensory receptor cells of other mammalian species. The adult human VNO displays species-specific, gender-dimorphic and highly stereospecific responses to ligands. The organ's local response, or electrovomerogram, is followed by gender-specific behavioral changes, modulation of autonomic nervous system function, or the release of gonadotropins from the pituitary gland. Functional brain imaging studies revealed consistent activation of the hypothalamus, amygdala and cingulate gyrus-related structures during adult human VNO stimulation. These findings present new information supportive of a functional vomeronasal system in adult humans.

The functionality of the human vomeronasal organ (VNO): evidence for steroid receptors.

The human vomeronasal organ (VNO) is an anatomical entity which is generally considered to be vestigial or non-functional. Nevertheless, a steroidal vomeropherin applied to the human VNO, results in changes of autonomic function, pulsatile release of luteinizing and follicle-stimulating hormones, autonomic and electroencepholographic activity. The vomeropherin pregna-4,20-diene-3,6-dione (PDD) was delivered as pulses in an air stream directed into the lumen of the VNO or to the surface of the olfactory epithelium and respiratory epithelium of the nasal septum. Single stimuli at a concentration of 10(-10) to 10(-8) M produced dose-dependent changes of the electrovomerogram. No significant effects were observed when the same applicator delivered identical stimuli to the nasal respiratory epithelium or to the olfactory epithelium. Administration of the vomeropherin to male subjects changed gonadotropin pulsatility. In males, PDD (5 x 10(9) M) decreased luteinizing hormone (LH) pulsatility which resulted in a statistically significant reduction of plasma LH levels (P < 0.009) and follicle-stimulating hormone (FSH) pulsatility (P < 0.021), but it produced no significant effects in female subjects. Prolactin (PRL) was not significantly affected by this vomeropherin in either male or female subjects. These data demonstrate, for the first time, the existence of a functional vomeronasal-pituitary pathway in adult humans. In addition to the effect on gonadotropin pulsatility, the vomeropherin also produces concurrent reflex autonomic effects after VNO stimulation. These included decreased respiratory frequency, increased cardiac frequency, and event-related changes of electrodermal activity and EEG pattern. Therefore, this investigation also provides evidence for functional connections between the VNO and a variety of hypothalamic areas in adult humans.

The human vomeronasal system.

We studied the functional characteristics of the vomeronasal system in clinically normal adult subjects of both sexes (ages 20-45). Chemosensory substances were administered in punctate pulses in a continuous air stream from the tip of a multifunctional miniprobe, which contained a nonpolarizable electrode. Negative potentials with the characteristics of receptor potentials were recorded from the surface of the vomeronasal organ (VNO) and olfactory epithelium (OE) in response to certain substances defined here as vomeropherins (see definition in the introduction of the main text) and to olfactants. Stimulation of the VNO with femtomole amounts of vomeropherins produced a local depolarization with the characteristics of a receptor potential. The same substances produced only a small response from the OE, and no response from the nasal respiratory mucosa. Three vomeropherins PH15, PH78, and PH84 were particularly well recognized by the VNO of most male subjects (p < .01; n = 30). Substances PH30, PH56, and PH94B, produced similar effects in the VNO of most female subjects (p < .01; n = 30). Responses to virtually all vomeropherins exhibited a sexual dimorphism. Stimulation of the OE with the same quantity of odorants 1,8-cineole and l-carvone produced depolarization of 6.8 +/- 2.6 mV, but little or no response in the VNO. Therefore, the human VNO seems to have a unique specificity for certain chemosensory substances when compared to the OE. Administration of PH15 and PH78 to the VNO of male subjects (but not to female subjects) significantly increased electrodermal activity (p < .02) and skin temperature (p < .01). On the other hand, administration of PH84 to the VNO of male subjects decreased skin temperature but had little effect on electrodermal activity. Autonomic changes were accompanied by an increased percentage of alpha-cortical activity for all three vomeropherins. In female subjects (but not in male subjects) vomeropherins PH56 and PH94B significantly increased electrodermal activity (p < .01), skin temperature (p < .01), and alpha-cortical activity (p < .01). Local application of the olfactants 1,8-cineole and l-carvone to the VNO did not trigger autonomic responses or significant changes in the electroencephalographic pattern in male or in female subjects. Our studies indicate the adult human VNO is a functional chemosensory organ with a sexually dimorphic specificity and the ability to transduce signals which modulate certain autonomic parameters.

The human skin: fragrances and pheromones.

Non-human mammalian pheromones are commonly used as perfumery ingredients. The actual purpose for using these compounds is as a fixative or carrier for the odor effects of the other ingredients as well as a contributor, in part, to the over-all scent of the perfume. Although such materials are used for their fixative and odor qualities rather than their pheromonal effects, perfumes are generally marketed as having the ability to enhance sexual attractiveness. While providing a scent may elicit a positive pleasant response, this should not be confused with a pheromone response. The attractive effect of perfumes is principally related to the effect of the pleasant scent. A more logical approach would be to use human pheromones which, for humans, are both more natural and more effective as true sensual attractants. It seems likely that implementation of this approach will constitute an important paradigm in the perfume industry as perfumery moves from the realm of art to that of science.

Synthesis and biological activity of pentapeptide analogues of the potent angiotensin converting enzyme inhibitor 5(S)-benzamido-4-oxo-6-phenylhexanoyl-L-proline.

Two pentapeptide analogues of the ketomethylene-containing angiotensin converting enzyme (ACE) inhibitor 5(S)-benzamido-4-oxo-6-phenylhexanoyl-L-proline (1) were synthesized and evaluated as ACE inhibitors and antihypertensive agents. Compounds 14 and 15 were very potent ACE inhibitors with I50 values of 7.0 and 3.0 nM, respectively, compared to an I50 value of 70 nM for 1. Neither 14 nor 15 showed significant blood pressure lowering activity in renal hypertensive rats. Investigations conducted on a tritiated analogue of 14 showed that 70% of an oral dose of this compound is absorbed but is rapidly excreted from the blood with a half life of 24 min. Thin-layer chromatography of bile and urine contents in rats given tritiated 14 orally showed that it is excreted in greater than 90% unchanged form. This implies that a ketomethylene linkage can stabilize peptide amide linkages adjacent to it to peptidase degradation.

Synthesis and biological activity of carboxylic acid replacement analogues of the potent angiotensin converting enzyme inhibitor 5(S)-benzamido-4-oxo-6-phenylhexanoyl-L-proline.

The carboxylic acid group on the proline of 1 was replaced by a phosphoric acid, a hydroxamic acid, and a tetrazole to give compounds 2-4, respectively. Testing of 2-4 as angiotensin converting enzyme (ACE) inhibitors gave I50 values of 100, 1.6, and 22 microM, respectively, compared to 0.07 microM for 1. A hydroxamic acid derivative of the ketomethylene pentapeptide analogue 18 was then synthesized. This compound, 17, had an ACE I50 of 0.011 microM compared to 0.0076 microM for 18. Oral administration of 10 mg/kg of 17 to renal hypertensive rats had no effect on blood pressure or heart rate.

Derivatives of the potent angiotensin converting enzyme inhibitor 5(S)-benzamido-4-oxo-6-phenylhexanoyl-L-proline: effect of changes at positions 2 and 5 of the hexanoic acid portion.

Several derivatives of the potent angiotensin converting enzyme inhibitor 5(S)-benzamido-4-oxo-6-phenylhexanoyl-L-proline (1) were synthesized and tested for converting enzyme inhibition activity and blood pressure lowering effects in rats. One compound, 5(S)-benzamido-2(R)-methyl-4-oxo-6-phenylhexanoyl-L-proline (2a), had and I50 against angiotensin converting enzyme of 1.0 x 10(-9) M and is the most potent inhibitor prepared thus far in this class of compounds. Testing of 2a orally at 30 mg/kg for inhibition of the angiotensin I induced blood pressure increase in conscious normotensive rats gave 100% inhibition that required 143 min before the angiotensin I blood pressure response returned to 70% of the pretreatment control response. In the conscious renal hypertensive rat, 2a given orally at a dose of 3 mg/kg caused a lowering of blood pressure that reached its maximum of 40 mmHg 8 h following drug administration.