Biomedical subjects

P W Sorensen

Publications and source records attributed to P W Sorensen.

At least 19 recordsLinked to original sources

PubMed2004

Sexually mature male goldfish release large quantities of androstenedione into the water where it functions as a pheromone.

Previous studies have demonstrated that ovulatory female goldfish release a variety of sex steroids into the water where they function as a pheromonal blend dominated by C21 steroids that stimulates male hormone release, sperm production and behavior. This study investigated whether male goldfish might also release sex steroids with pheromonal activity. It found that spermiated male goldfish release substantial quantities of androstenedione (AD; about 50 ng/h) together with smaller (10-20 ng/h) quantities of several other related C19 steroids but only very small quantities (<5 ng/h) of C21 steroids. Further, when sexually aroused by females and/or their pheromones, males released even greater quantities of AD (up to 1 microg/h) while C21 steroid release rate changed little. This created a ratio of C19 to C21 steroids of about 50:1 that was dramatically different from that emitted by females (1:7). The male olfactory system was also found to be extremely sensitive to AD, detecting it to near picomolar concentrations. Together with previous studies that have shown water-borne AD to increase male aggressive behavior while suppressing responsiveness to female pheromones, this study establishes AD as a male pheromone in the goldfish. Because ovulating females also release AD but in the presence of C21 steroids, recognition of the male-derived steroid pheromone is presumably mixture dependent.

Androstenedione↗

PubMed2004

Evidence that 4-pregnen-17,20beta,21-triol-3-one functions as a maturation-inducing hormone and pheromonal precursor in the percid fish, Gymnocephalus cernuus.

Behavioral, biochemical, and electrophysiological studies suggest that the trihydroxylated progestin steroid, 4-pregnen-17,20beta,21-triol-3-one (20beta-S) stimulates oocyte maturation and pheromone release in the Eurasian ruffe, a freshwater percid fish. Behavioral observations found that female ruffe undergoing oocyte maturation (OM) release a pheromonal cue that stimulates swimming activity and social interactions among conspecific males. Neither vitellogenic nor ovulated females released the cue. Pheromone production was directly associated with elevated plasma levels of 20beta-S in maturing female ruffe which in vitro incubation suggested to be a possible maturation-inducing hormone (MIH) in this species along with 4-pregnen-17,20beta-diol-3-one (17,20betaP). However, neither of these steroids appear to be the pheromone because electrophysiological and behavioral studies found them to lack olfactory (EOG) and behavioral activity. Instead, studies of the odor of steroid-injected fish suggest the pheromone is a metabolite of 20beta-S. In particular, inter-peritoneal injection of 20beta-S (but not 17,20betaP) consistently induced release of a urinary cue with strong behavioral activity. The pheromone may be a highly polar and novel metabolite because it could not be extracted using octadecylsilane resin (C18) which has proven effective for other teleost hormonal pheromones.

Animals↗

PubMed2003

Polyamines as olfactory stimuli in the goldfish Carassius auratus.

Electrophysiological responses of goldfish olfactory receptor neurons (ORNs) and goldfish behavioral responses to polyamines were investigated in vivo. Electro-olfactogram (EOG) recordings indicated that polyamines (putrescine, cadaverine and spermine) are potent olfactory stimuli for goldfish with estimated electrophysiological thresholds of 10(-8)-10(-7) mol l(-1), similar to that for L-arginine, the most stimulatory amino acid. Although thresholds were similar, the magnitude of the EOG responses to intermediate (10(-5)-10(-4) mol l(-1)) and high (10(-3) mol l(-1)) concentrations of polyamines dwarfed the responses to amino acids and related single amine containing compounds (amylamine and butylamine). The EOG responses to 0.1 mmol l(-1) putrescine, cadaverine and spermine were, respectively, 4.2x, 4.3x and 10.3x the response of the standard, 0.1 mmol l(-1) L-arginine. Electrophysiological cross-adaptation experiments indicated that polyamine receptor sites are independent from those to L-amino acids (alanine, arginine, glutamate, lysine, methionine and ornithine), bile salts (sodium taurocholate and taurolithocholate), the single amine containing compounds (amylamine and butylamine) and ATP. Further, the cross-adaptation experiments revealed the existence of independent receptor sites for the different polyamines tested. Pharmacological experiments suggested that polyamine odorant transduction does not primarily involve the cyclic AMP and IP(3) second messenger pathways. Behavioral assays indicated that polyamines are attractants that elicit feeding behavior similar to that elicited by L-amino acids.

Amines↗

PubMed2001

The three steroidal components of the goldfish preovulatory pheromone signal evoke different behaviors in males.

The goldfish sex pheromone system is the best understood among the teleost fishes. Pheromones in this species are unspecialized hormonal products, which are released in ratios that vary with reproductive status. This study examined behavioral responses of male goldfish to three steroidal components of the female preovulatory pheromone: 17,20beta-dihydroxy-4-pregnen-3-one (1720betaP); 17,20beta-dihydroxy-4-pregnen-3-one-20-sulfate (1720betaP-S); and androstenedione (AD). Males were observed during exposure to nanomolar concentrations of each steroid over a 2-h period. We observed chasing, nudging (courtship behaviors) and pushing (an aggressive behavior). Each steroid elicited a different set of behaviors. 1720betaP, which is released by ovulatory females, elicited a low level of chasing and nudging that persisted throughout the experiment. Exposure to 1720betaP-S, which is released primarily by ovulatory females, triggered a large increase in nudging and chasing that lasted for only 5 min. In contrast, AD, which is released by females early in the ovulatory cycle and by mature males, elicited increases in aggressive behavior. 1720betaP and 1720betaP-S both caused increases in GtH-II release while AD did not. These results demonstrate that goldfish can discriminate components found in the female pheromone blend, suggesting that goldfish, and likely other fish species, may employ blends of hormonal products as pheromones.

Aggression↗

PubMed1999

Functional identification of a goldfish odorant receptor.

The vertebrate olfactory system utilizes odorant receptors to receive and discriminate thousands of different chemical stimuli. An understanding of how these receptors encode information about an odorant's molecular structure requires a characterization of their ligand specificities. We employed an expression cloning strategy to identify a goldfish odorant receptor that is activated by amino acids-potent odorants for fish. Structure-activity analysis indicates that the receptor is preferentially tuned to recognize basic amino acids. The receptor is a member of a multigene family of G protein-coupled receptors, sharing sequence similarities with the calcium sensing, metabotropic glutamate, and V2R class of vomeronasal receptors. The ligand tuning properties of the goldfish amino acid odorant receptor provide information for unraveling the molecular mechanisms underlying olfactory coding.

Animals↗

PubMed1998

Sex pheromones and amino acids evoke distinctly different spatial patterns of electrical activity in the goldfish olfactory bulb.

Until now, electrophysiological studies of the vertebrate olfactory bulb have tested only 'generalist' cues. These studies suggest that odorants are discriminated by a broadly distributed spatial map. In this study, we tested for the first time in a vertebrate the hypothesis that 'specialist' cues (pheromones) are discriminated by a more restricted component of the olfactory bulb. Our model is the male goldfish, Carassius auratus, for which five sex pheromones with both behavioral and physiological activity have now been identified. Electrical activity (electroencephalography: EEG) was recorded over a 12-point grid from the surface of the olfactory bulb, while fish were exposed to one of ten stimuli including: five sex pheromones, two amino acids, two bile steroids and a control. Evoked activity was evaluated by time series analysis. Power ratios were calculated by dividing the power of the dominant frequency in the power spectrum before stimulation by the power of the dominant frequency during stimulation. Next, the average magnitudes of odorant responses were compared using analysis of variance (ANOVA). The spatial patterning of these responses was also described using cluster analysis, which grouped odorants based on the similarity of their spatial patterns of activity. Although all odorants elicited EEG responses with similar dominant frequencies, odorant-specific differences were evident in the size and distribution of these responses. Sex pheromones and bile steroids elicited relatively small responses that were spatially restricted in distinctive manners, although some overlap was evident. In contrast, amino acids consistently produced large responses at all positions. These results are consistent with the hypothesis that vertebrate pheromones are discriminated by a distinctive subcomponent of the vertebrate olfactory system comprised of a relatively small number of olfactory neurons.

Animal Communication↗

PubMed1998

Discrimination of pheromonal cues in fish: emerging parallels with insects.

Many fish species employ hormonal products as sex pheromones, and these cues are often mixtures that are released with a temporal pattern. This behavior is strikingly similar to that of insects, as moths use precise blends of odorants as sex pheromones and are skillful at tracking them in spite of changes in odor intensity associated with aerial dispersal. New studies in both groups of animals suggest many parallels in the functional anatomy of olfactory pathways and the organization of information-coding circuits.

Animals↗

PubMed1996

Effect of dominance status on sex hormone levels in laboratory and wild-spawning male trout.

We investigated the relationship between male social status and hormone levels in salmonids spawning under laboratory and field conditions. In small groups of rainbow trout (Onchorhynchus mykiss) spawning in the laboratory, dominant males had higher plasma levels of testosterone (T) and 17 alpha, 20 beta-dihydroxy-4-pregnen-3-one (17,20 beta-P) compared with subordinates. Steroid levels increased in subordinate males that became dominant after dominant males were experimentally removed; higher steroid levels in dominant males appears to be a result rather than a cause of their social status. In free-ranging brown trout (Salmo trutta) sampled in the field, we found higher levels of 11-ketotestosterone (11KT) but not T in dominant males. No significant differences in levels of either androgen were found between dominant and subordinate male brook trout (Salvelinus fontinalis) sampled at the same field location. Furthermore, in marked contrast with the laboratory fish, there were no significant differences in plasma 17,20 beta-P between dominant and subordinate males in either species of fish in the wild. The different findings in the laboratory and field may indicate species differences in behavioral endocrinology among brook, brown, and rainbow trout. Alternatively, the greater differential in hormonal profile of dominant and subordinate males in the laboratory may reflect the relative uniformity of the laboratory environment; this simple environment may allow competitively superior males to more completely dominate less competitive tank-mates and to exclude them from female sexual cues. In any case, these results suggest that the relationship between steroid hormones and spawning behavior in male salmonids is likely more complex than suggested by experiments conducted solely on laboratory-held rainbow trout.

Animals↗

PubMed1996

Pheromones as tools for olfactory research.Introduction.

We have long been fascinated by the unique ability of odors to stir our emotions and to evoke long-forgotten memories, but certain odors play a much more fundamental role in that they vastly improve an organism's chances for reproductive success and survival. These odorants are called pheromones, a term commonly applied to semiochemicals that are released by one member of a species and evoke a specific reaction or reactions from members of the same species. Pheromones are known for both the specificity and the potency of their actions, which can be behavioral and/or neuroendocrinological. Pheromones can stimulate individuals to aggregate, to disperse, or to react defensively in the presence of a predator, but they are probably best known for bringing the sexes together. Some pheromones have also been found to trigger a dramatic release of pituitary hormones in several vertebrate species. Although first identified in insects, more recent studies show that sex pheromones influence the lives of a wide range of organisms, from microbes to man. The hormonally-derived sex pheromones in teleost fish, and the airborne pheromones of moths are two systems that illustrate how scientists have used these specialized chemical signals as important tools to investigate the morphology, physiology and biochemistry of olfactory-receptor systems, the mechanisms of odor-information processing in the brain, and the diverse range of behaviors and endocrinological changes associated with pheromonal communication. While our focus is on these two animal models, other examples, including mammalian pheromone systems, are also discussed.

Animals↗

PubMed1996

Biological responsiveness to pheromones provides fundamental and unique insight into olfactory function.

When exposed to the odor of conspecifics, most organisms exhibit an adaptive behavioral response, particularly if the individuals are sexually mature. Evidence increasingly suggests that behavioral responsiveness to these odors, which are termed 'pheromones', reflects neuroethological mechanisms associated with olfactory function. Reproductive pheromones, which are the best understood, are commonly used by both invertebrates and vertebrates. In both instances they are generally comprised of mixtures of compounds and behavioral responsiveness to them is largely instinctual, sexually-dimorphic, and attributable to a specialized component(s) of the olfactory system. While pheromonal responsiveness in some systems (e.g. moths) appears highly stereotypic and symptomatic of a relatively simple 'labeled line', behavioral responsiveness of other animals (e.g. rodents) can be modified by experience, suggesting a more complex underlying central mechanism. In any case, our understanding of these fascinating systems is progressing only because of an active dialogue between behavioral and neurological investigations. This review briefly examines how behavioral studies have provided fundamental insight into the neuroethology of olfactory function by drawing comparisons between some of the better understood sex pheromone systems which have been described in heliothine moths, the goldfish, and the pig. Many similarities between invertebrate and vertebrate pheromone systems are noted.

Animals↗

PubMed1995

Sulfated 17,20 beta-dihydroxy-4-pregnen-3-one functions as a potent and specific olfactory stimulant with pheromonal actions in the goldfish.

This study demonstrates that in addition to using the maturational steroid hormone 17,20 beta-dihydroxy-4-pregnen-3-one (17,20 beta-P) as a potent sex pheromone, the goldfish uses its sulfated metabolite 17,20 beta-dihydroxy-4-pregnen-3-one 20-sulfate (17,20 beta-P-20S). As measured by electro-olfactogram recording (EOG), the goldfish olfactory epithelium is extremely sensitive to both free and sulfated 17,20 beta-P (detection thresholds of approximately 10(-12) and 10(-11) M) but not to glucuronidated or phosphated 17,20 beta-P. Furthermore, both structure-activity and cross-adaptation studies using EOG indicated that 17,20 beta-P-20S and 17,20 beta-P are detected by different olfactory receptor sites, suggesting that these cues function as a distinguishable mixture. Finally, although the pheromonal activity of 17,20 beta-P-20S appears to be slightly less than that of 17,20 beta-P, it too stimulates gonadotropin release and sperm production in male goldfish. The precise function of 17,20 beta-P-20S remains somewhat enigmatic, however, because it does not appear to enhance the actions of 17,20 beta-P and is released by a different mechanism. In any case, our findings clearly establish that a fish olfactory system can detect particular conjugated steroidal compounds in a highly specific manner and that naturally released conjugated steroids can function as components of a pheromonal mixture.

Animals↗

PubMed1995

The olfactory system of migratory adult sea lamprey (Petromyzon marinus) is specifically and acutely sensitive to unique bile acids released by conspecific larvae.

Larval sea lamprey inhabit freshwater streams and migrate to oceans or lakes to feed after a radical metamorphosis; subsequently, mature adults return to streams to spawn. Previous observations suggested that lamprey utilize the odor of conspecific larvae to select streams for spawning. Here we report biochemical and electrophysiological evidence that this odor is comprised of two unique bile acids released by larvae. High performance liquid chromatography and mass spectrometry demonstrated that larval sea lamprey produce and release two unique bile acids, allocholic acid (ACA) and petromyzonol sulfate (PS). Electro-olfactogram (EOG) recording also demonstrated that the olfactory system of migratory adult sea lamprey is acutely and specifically sensitive to ACA and PS; detection thresholds for these compounds were approximately 10(-12) M. ACA and PS were the most potent of 38 bile acids tested and cross-adaptation experiments suggested that adult sea lamprey have specific olfactory receptor sites associated with independent signal transduction pathways for these bile acids. These receptor sites specifically recognize the key substituents of ACA and PS such as a 5 alpha-hydrogen, three axial hydroxyls, and a C-24 sulfate ester or carboxyl. In conclusion, the unique lamprey bile acids, ACA and PS, are potent and specific stimulants of the adult olfactory system, strongly supporting the hypothesis that these unique bile acids function as migratory pheromones in lamprey.

Animals↗

PubMed1994

Time course of release of pheromonally active gonadal steroids and their conjugates by ovulatory goldfish.

Previous studies have demonstrated that ovulatory goldfish synthesize and release a variety of steroids into the water, where some of them function as sex pheromones. Among the steroids which have been measured are free androstenedione, testosterone, 17 alpha,20 beta-dihydroxy-4-pregnen-3-one (17,20 beta-P), 17 alpha,20 beta,21-trihydroxy-4-pregnen-3-one (17,20 beta,21-P), 17 alpha-hydroxy-4-pregnene-3,20-dione (17-P), 11-deoxycortisol (17,21-P), and 17 alpha,20 alpha-dihydroxy-4-pregnen-3-one (17,20 alpha-P), glucuronidated testosterone, 17,20 beta-P, and 17,20 beta,21-P, and sulfated 17,21-P, 17,20 beta-P, and 17,20 beta,21-P. This study reports the changes in the amounts of these steroids released into the water, at 3-hr intervals, by 12 female goldfish injected with human chorionic gonadotrophin (HCG). Eight fish ovulated. The amounts of steroids released into the water were significantly higher in the fish which ovulated than in those which did not. The peak rate of release (ng per hour) of free androstenedione (91), glucuronidated testosterone (143), and sulfated 17,21-P (33) occurred at ca. 4 hr postinjection; free 17-P (163) and free 17,21-P (217) at ca. 6 hr.; free 17,20 beta-P (58) and free 17,20 beta,21-P (58) at ca. 7.5 hr; and glucuronidated 17,20 beta-P (96), glucuronidated 17,20 beta,21-P (264), sulfated 17,20 beta-P (64) and sulfated 17,20 beta,21-P (153) at ca. 9 hr. Amounts of all of the steroids were at their lowest between 12 and 15 hr and, in the ovulated fish, had risen significantly again between 18 and 21 hr. The amounts of glucuronidated testosterone, 17,20 beta-P and 17,20 beta,21-P, and of sulfated 17,20 beta-P and 17,20 beta,21-P, in water exceeded those of free steroid. Elevated levels of free and glucuronidated steroids were also found in the blood plasma of HCG-injected fish. Considerably more androstenedione than testosterone was released into the water. Assessment of the "pheromonal effectiveness" of each steroid indicated that the free and sulfated forms of 17,20 beta-P and 17,20 beta,21-P, and androstenedione were the most important pheromonal steroids released by female goldfish.

Androgens↗

PubMed1991

Sex pheromones selectively stimulate the medial olfactory tracts of male goldfish.

The olfactory tracts of teleost fish are comprised of medial and lateral sub-tracts which previous studies suggest convey responses to pheromones and food odors respectively. This study tested this possibility by recording electrical responses from the medial and lateral tracts of male goldfish exposed to sex pheromones and food odors. Only the medial olfactory tract responded to pheromones and both tracts responded to an L-amino acid and crude food odor. These findings verify earlier studies of peripheral olfactory sensitivity to pheromones and confirm that pheromonal information is carried within the medial tracts. They also suggest that the neural processes responsible for food recognition are more complex than previously supposed.

Animals↗

PubMed1991

The olfactory system, not the terminal nerve, functions as the primary chemosensory pathway mediating responses to sex pheromones in male goldfish.

Studies of the neural mechanisms underlying responsiveness to sex pheromones in male goldfish suggest that, contrary to a currently popular hypothesis, the olfactory system (cranial nerve 1), and not the terminal nerve (cranial nerve 0), mediates chemosensory responses to pheromones. When the olfactory epithelium of male goldfish was exposed to two identified sex pheromones, 17 alpha, 20 beta-dihydroxy-4-pregnen-3-one and a mixture of prostaglandin F2 alpha and its metabolite 15-keto-prostaglandin F2 alpha, the spontaneous activity of olfactory neurons located in the medical portion of the olfactory bulb changed, while activity of terminal nerve cell bodies did not. A variety of other synthetic and natural odors also failed to alter the activity of terminal nerve cell bodies as did visual, magnetic, thermal, and auditory cues. Terminal nerve activity was, however, inhibited by tactile stimulation, suggesting that this system may have a modulatory role associated with the physical interactions that characterize goldfish spawning behavior.

Animals↗

PubMed1989

Direct evidence that 17 alpha,20 beta-dihydroxy-4-pregnen-3-one functions as a goldfish primer pheromone: preovulatory release is closely associated with male endocrine responses.

This study directly tested the hypothesis that 17 alpha,20 beta-dihydroxy-4-pregnen-3-one (17,20 beta-P) is a goldfish preovulatory pheromone (pheromone released at peak levels during oocyte final maturation) which increases blood gonadotropin (GtH) and milt volume in males. During spontaneous ovulation, GtH and 17,20 beta-P in female blood and 17,20 beta-P released to the water increased dramatically 7-10 hr prior to ovulation, peaked 1-4 hr prior to ovulation, and then rapidly declined. Males held with these females, or exposed to their odors, had increased GtH levels and milt volumes at approximately the time when increased 17,20 beta-P release by ovulatory females commenced. Although these findings strongly support the hypothesis that 17,20 beta-P is a preovulatory female sex pheromone in goldfish which stimulates male GtH levels and milt production prior to spawning, the milt increases occurred earlier than predicted, suggesting either that preovulatory 17,20 beta-P release begins earlier than the data indicate or that other steroids known to have pheromonal activity are released before 17,20 beta-P.

Animals↗

PubMed1989

Periovulatory female goldfish release three potential pheromones: 17 alpha,20 beta-dihydroxyprogesterone, 17 alpha,20 beta-dihydroxyprogesterone glucuronide, and 17 alpha-hydroxyprogesterone.

Our previous studies have shown that 17 alpha,20 beta-dihydroxy-4-pregnen-3-one (17,20 beta-P) produced by preovulatory female goldfish functions both as a hormone promoting oocyte final maturation and as a primer sex pheromone stimulating rapid reproductive endocrine responses in the male. In the present study, the amounts of free and glucuronated 17,20 beta-P as well as free 17 alpha-hydroxyprogesterone (17P) released to the holding water by female goldfish throughout the periovulatory period were determined. Compared to nonovulating female goldfish, ovulating goldfish released very high levels of each of these steroids. This study confirmed that 17,20 beta-P is released to the water by ovulating fish in sufficient amounts to have pheromonal activity and indicated that 17P may also function as a pheromone. Although considerable quantities of 17,20 beta-P glucuronide were also released, its physiological actions are unknown.

Animals↗

PubMed1989

Differing behavioral and endocrinological effects of two female sex pheromones on male goldfish.

Ovulatory female goldfish sequentially release at least two sex pheromones: 17 alpha, 20 beta-dihydroxy-4-pregnen-3-one (17,20 beta P) and a mixture of F prostaglandins (PGFs). This study sought to determine whether these pheromones have different endocrinological and behavioral actions and whether the PGF pheromone, which is released by spawning females, is responsible for increasing the gonadotropin (GtH) and milt (sperm and seminal fluid) levels of spawning males. Grouped and isolated males were exposed to combinations of these pheromones, food odor, and spawning and nonspawning females. 17,20 beta P stimulated GtH increases in both grouped and isolated males but had only minor effects on behavior; because its principal function appears to be physiological it may be considered a "primer" pheromone. In contrast, exposue to the PGFs elicited large increases in sexual behavior but increased GtH only when fish were exposed as groups; this pheromone's principal action appears to be behavioral and it should be considered a "releaser" pheromone. Although males had increased GtH and milt levels after 1 hr of spawning, males allowed to interact with nonspawning females also had elevated GtH; thus, behavioral interactions appear capable of elevating GtH in the absence of either pheromone. The existence of an independent behavioral mechanism which stimulates GtH was supported by the fact that males exposed to 17,20 beta P while spawning had GtH levels much greater than males exposed to only one of these stimuli.

Animals↗