Rostral midbrain lesions and copulatory behavior in male rats

Discrete electrolytic lesions were placed in the mesencephalic dorsal noradrenergic (DNE) bundle of 22 male Sprague-Dawley rats, and sham operations were performed on 14 control animals. Eight components of copulatory behavior were compared in 2 preoperative and 2 postoperative heterosexual mating tests. A significant postlesion decrease in the postejaculatory interval (PEI), number of intromissions, number of incomplete mounts and the ejaculation latency from the first intromission (ELI) occurred. Norepinephrine levels were significantly reduced in the hippocampus, amygdala and hypothalamus, but not in the preoptic area. The only statistically significant correlations between NE concentrations and behavior in the lesioned animals were negative (hippocampal NE with PEI and ELI). The results support the hypothesis that rostral midbrain lesions disinhibit some components of male rodent copulatory behavior, but suggest that a system or systems other than the DNE bundle may be responsible for this disinhibition.     

Effects of castration and sex steroid treatment on the motor copulatory pattern of the rat

The effect of castration and sex steroid (testosterone propionate, TP or estradiol benzoate, EB) treatment on the motor copulatory pattern was studied by an accelerometric technique in 14 male Wistar rats. This technique allows precise measurements of the following parameters: (a) duration of mounts (M), intromissions (I) and ejaculations (E); (b) thrusting frequency, and (c) amplitude of pelvic movements. Analysis of the signals generated during M, I or E, allows clear differentiation among the three behavioral patterns. Castration abolished sexual activity in most of our rats. The motor copulatory pattern was analyzed in four castrated rats, which continued to display sexual behavior for some time after castration. Castration did not alter thrusting frequency nor vigor of mounting. Duration of M, but not that of I or E, was prolonged by castration. TP (5 mg/day) restored sexual behavior to precastration levels in all 6 TP-treated rats. The motor copulatory pattern of the TP-treated rats was similar to that of intact rats. EB treatment (5 μg or 50 μg/day) induced mounting in 6 out of 7 subjects, but only two rats ejaculated once. EB failed to restore M duration to precastration levels and increased the frequency of pelvic thrusting above control values. Present results suggest that estrogen in large dosages exerts subtle effects on the motor copulatory pattern of the rat.     

Cuticular hydrocarbon analysis of an awake behaving fly using direct analysis in real-time time-of-flight mass spectrometry

In mammals and insects, pheromones strongly influence social behaviors such as aggression and mate recognition. In Drosophila melanogaster, pheromones in the form of cuticular hydrocarbons play prominent roles in courtship. GC/MS is the primary analytical tool currently used to study Drosophila cuticular hydrocarbons. Although GC/MS is highly reproducible and sensitive, it requires that the fly be placed in a lethal solution of organic solvent, thereby impeding further behavioral studies. We present a technique for the analysis of hydrocarbons and other surface molecules from live animals by using direct analysis in real-time (DART) MS. Cuticular hydrocarbons were sampled from the surface of a restrained, awake behaving fly by using several brief, carefully controlled depressions of the abdomen with a small steel probe. DART mass spectral analysis of the probe detected ions with mass-to-charge ratio (m/z) of the protonated molecule corresponding to many of the previously identified unsaturated hydrocarbons. Six additional cuticular hydrocarbons also were identified. Consistent with previous GC/MS studies, male and female differences in chemical composition were evident. Spatial differences in the expression profile also were observed on males. Sampling from an individual female first as a virgin and then 45 and 90 min after successful copulation showed that mass signals likely to correspond to cis-vaccenyl acetate, tricosene, and pentacosene increased in relative intensity after courtship. This method provides near-instantaneous analysis of an individual animal's chemical profile in parallel with behavioral studies and could be extended to other models of pheromone-mediated behavior.     

Physiological,anatomical, and behavioral changes after acoustic trauma in Drosophila melanogaster

Noise-induced hearing loss (NIHL) is a growing health issue, with costly treatment and lost quality of life. Here we establish Drosophila melanogaster as an inexpensive, flexible, and powerful genetic model system for NIHL. We exposed flies to acoustic trauma and quantified physiological and anatomical effects. Trauma significantly reduced sound-evoked potential (SEP) amplitudes and increased SEP latencies in control genotypes. SEP amplitude but not latency effects recovered after 7 d. Although trauma produced no gross morphological changes in the auditory organ (Johnston’s organ), mitochondrial cross-sectional area was reduced 7 d after exposure. In nervana 3 heterozygous flies, which slightly compromise ion homeostasis, trauma had exaggerated effects on SEP amplitude and mitochondrial morphology, suggesting a key role for ion homeostasis in resistance to acoustic trauma. Thus, Drosophila exhibit acoustic trauma effects resembling those found in vertebrates, including inducing metabolic stress in sensory cells. This report of noise trauma in Drosophila is a foundation for studying molecular and genetic sequelae of NIHL.Noise-induced hearing loss (NIHL) is a pervasive and growing health issue arising from occupational and recreational hazards, with significant costs in health care and personal quality of life. Despite this, the molecular and physiological mechanisms involved in the etiology or recovery from injury are not yet fully understood. Importantly, intense acoustic trauma can induce permanent damage—unlike other vertebrates, mammals cannot regenerate auditory hair cells (1, 2). NIHL associated with permanent changes in auditory sensitivity causes multiple consistent effects: stereocilia bundle disruption, inner (IHC) and outer hair cell (OHC) death or damage, supporting cell tissue disruption, and eventual spiral ganglion cell damage or loss (3–7). Most studies to date used mammalian model organisms such as mice (8, 9), rats (10), and guinea pigs (11–14). These animals have difficult access to the inner ear inside the temporal bone and high maintenance costs coupled with relatively long generation times.Drosophila is a compelling alternative model system with strong genetic tools, inexpensive production of large numbers of animals, and an accessible auditory system that is becoming better understood genetically and physiologically. During courtship, Drosophila males vibrate their wings to produce a courtship song composed of pulse and sinusoidal components (15, 16). This song facilitates species identification and mate selection (16, 17). Drosophila males and females detect airborne vibrations via Johnston’s organ (JO) in the second antennal segment (18). The JO is an array of chordotonal mechanoreceptors (or scolopidia; Fig. 1 A–C). Via the aristae, acoustic energy is transformed to rotational movement of the third antennal segment, activating mechanosensitive channels on JO neuron dendrites. Like vertebrate hair cells, JO neurons are ciliated and respond to mechanical stimulation. Although JO has morphologically diverged from hair cells in the human inner ear, the genetic program for its development shares a strong homology (19, 20). For example, the Atoh1 gene required for vertebrate auditory hair cell specification was found by direct homology to the fly atonal gene required for JO specification and atonal/Atoh1 genes can be functionally exchanged between mice and flies (21, 22). The advantages of studying hearing in Drosophila are that the genome is fully sequenced, genetic tools for extensively manipulating the genome are at hand, genetic background effects can be effectively eliminated, and large numbers of individuals can be tested.Open in a separate windowFig. 1.Organization of Drosophila JO and physiological response to sound. (A) Deconvolution micrograph of labeled scolopidia in JO. The actin scolopale rods are labeled with phalloidin (magenta), mitochondria in some JO neurons are labeled with mito-GFP (green), and nuclei are labeled with TOPRO-3 (blue). (B) Schematic diagram of an individual scolopidium, oriented and colored similarly to scolopidia in A. (C) Approximate longitudinal section of JO in an untraumatized control 40AG13 fly. bb, basal bodies; cap, dendritic cap; cd, ciliary dilation; m, membranous structure; mt, mitochondria; N, nuclei of JO neurons; ScN, nuclei of scolopale cells; t, trachiole. (Scale bar: 1 μm.) (D) Example of SEPs recorded in response to acoustic stimulation (stim). The top trace is the synthetic courtship song pulse stimulus; immediately below is the resulting SEP, with the analyzed amplitude and latency parameters indicated. The bottom trace shows multiple SEPs from a wild-type fly in response to a pulse train.In this study, we establish Drosophila as an inexpensive and flexible model system for genetic and physiological study of NIHL. We exposed two control strains [Canton-S (CS) and 40AG13] to acute acoustic trauma and examined physiological, behavioral, and anatomical effects. Our findings show immediate effects on auditory function, with reduced and delayed evoked activity. Although evoked potential amplitudes were restored after 7 d, the latency of these potentials did not fully recover and we found significant changes in JO neural mitochondrial morphology. We also tested mutant flies with a reduced copy number of nervana 3 (nrv3) encoding a Na⁺/K⁺ ATPase β subunit expressed in JO neurons (23). We hypothesized that compromised JO ionic homeostasis would confer susceptibility to noise trauma. Indeed, nrv3 heterozygotes showed increased sensitivity to trauma and a significantly reduced auditory functional recovery.     

Pituitary-adrenal effects on sexual behavior in isolated and group-housed mice.

The duration and intensity of some components of the male copulatory pattern was studied in ten male (seven experienced, three inexperienced) and two female New Zealand white rabbits by using high speed cinematography, accelerometry and by recording the pressure of the seminal vesicles. Duration of mounts varied greatly within and among subjects. Effective mounts, i.e., those terminating in ejaculation, lasted less (2.61±1.50 sec, mean ± SD; n, 59) than ineffective mounts (3.08 ± 2.16 sec, mean ± SD; n, 199). Frequency of pelvic thrusting was significantly higher in effective (13.54 ± 1.11 sec, mean ± SD; n, 59) than in ineffective mounts (12.08 ± 0.98 sec, mean ± SD; n, 176). No pelvic thrusting occurred during intromission which usually lasted less than one second (722 ± 266 msec SD; n, 43). Shortly after intromission (230 ± 107 msec, mean ± SD; n, 32) the pressure of the seminal vesicles raised. This rise in pressure outlasted copulation (1040 ± 369 msec, mean ± SD; n, 32). The mounting pattern of inexperienced rabbits was similar to that of experienced rabbits. The mounting pattern of females differed from that of males both in rate of pelvic thrusting and duration of pelvic thrusts.     

The motor neurons innervating the direct flight muscles of Drosophila melanogaster are morphologically specialized

The anatomy of the motor neurons innervating six direct flight muscles in Drosophila melanogaster has been investigated by using a horseradish peroxidase backfilling technique. The somata of these motor neurons are arranged in two distinct clusters ipsilateral to the muscle they innervate. One cluster of cell bodies is located in the ventrolateral region between the prothoracic neuromere and the mesothoracic leg-related neuropil and the other is situated dorsally and posteriorly to the mesothoracic leg-related neuropil. Axons from somata in the ventrolateral cluster run in the anterior dorsal mesothoracic nerve, while axons from somata in the other cluster run in the mesothoracic accessory nerve. This distribution of somata and axons is discussed in the light of the morphological similarity and proximity of these functionally related muscles. On the basis of the branching patterns of their neurites, direct flight muscle motor neurons can be classified as stubbly, fibrous or tufted. The terminal arborizations of the motor neurons over the direct flight muscles are also morphologically specialized. Both the central and the peripheral morphological specializations of the direct flight muscle motor neurons correlate with the activity patterns exhibited by their associated muscles during flight and courtship song. © Wiley-Liss, Inc.     

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 μm and that of NO₃^– from 4.50 ± 0.73 to 8.31 ± 2.3 μm . The NO₂^– increase was prevented by the nitric oxide synthase inhibitor N^G–nitro-l -arginine methylester (20 μg) given unilaterally in the paraventricular nucleus, which also prevented non-contact erections. In contrast, the nitric oxide scavenger haemoglobin (20 μg) prevented the NO₂^– increase, but not non-contact erections; while the guanylate cyclase inhibitor methylene blue (20 μg) 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, N^G–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.