Effects of progesterone and RU486 on the development and expression of adult male sexual behaviour and gene expression in the amygdala and preoptic area of the hypothalamus.

The number of progesterone receptors is greater in the male than female neonatal rat hypothalamus. The aims of the present study were to determine developmental effects of progesterone on the expression of adult male sexual behaviour and whether changes in behaviour were reflected by altered gene expression within the hypothalamic preoptic area (POA) or medial amygdala. Male rats were treated with progesterone (40 µg kg(-1), i.p.), the progesterone receptor antagonist RU486 (40 µg kg(-1), i.p.) or an equal volume of vehicle (10% ethanol, 90% corn oil) on postnatal Days 1-5. Treatment with either progesterone or RU486 inhibited (P ≤ 0.07) the initial expression of consummatory sexual behaviour at 10.5 weeks of age without influencing growth or serum concentrations of testosterone. Sexual interest, as measured by latency to exhibiting mounting behaviour or the number of mounts achieved, was not influenced by treatment with either progesterone or RU486. The effects of treatment with progesterone or RU486 on sexual behaviour were diminished by experience. Microarray analysis of the POA indicated 61 genes that were upregulated and 49 that were downregulated (P ≤ 0.01) following RU486 treatment of male rats. However, the altered expression of selected genes was not confirmed by real-time reverse transcription-polymerase chain reaction. The expression of targeted genes within the amygdala was not influenced by treatment with either progesterone or RU486. Neonatal treatment with RU486, but not progesterone, decreased testes weight (P=0.02) without affecting testes morphology. The results indicate that altering the progesterone environment during a critical developmental period affects the expression of behaviour, but that changes in behaviour are not mirrored by the altered expression of selected genes.

Evidence for alterations of synaptic inputs to sacral spinal reflex circuits after spinal cord transection in the cat.

Quantitative electron microscopy was used to study potential alterations in the synaptic inputs to HRP-labeled preganglionic neurons (PGNs) in the sacral parasympathetic nucleus (SPN) and to motoneurons (MNs) in Onuf's nucleus (ON) after short (4 days)- or longterm (10-11 weeks) spinal transection as compared to normal controls. Transection resulted in an apparent reorganization and replacement of synaptic input to ON MNs whereas chronic denervation of PGNs in the SPN was observed. These synaptic alterations may play a role in the changes in the eliminative reflexes (e.g., bladder-sphincter dyssynergia, induction of cutaneously elicited elimination) that are observed after spinal cord lesions.

Motoneurons innervating the external anal and urethral sphincters of the female cat have different patterns of dendritic arborization.

The locations and dendritic arbors of sacral motoneurons (MNs) innervating the striated external anal and urethral sphincters (EAS and EUS, respectively) of the cat were investigated using muscle injections of cholera toxin-conjugated HRP (CT-HRP). Serial reconstructions showed that all cells labelled after EAS injections were located in the dorsomedial (DM) subdivision of Onuf's nucleus, whereas all cells labelled from the EUS were located in the ventrolateral (VL) subdivision. The dendritic arbors of EAS and EUS MNs were very different, suggesting differences in afferent control. In addition, prominent bundles of dendrites extended preferentially into the regions occupied by functionally appropriate preganglionic neurons (PGNs) in the sacral parasympathetic nucleus (SPN) which innervate the colon and bladder.

Differences in synaptic inputs to preganglionic neurons in the dorsal and lateral band subdivisions of the cat sacral parasympathetic nucleus.

In the cat, preganglionic neurons (PGNs) found in the dorsal portion of the sacral parasympathetic nucleus (dorsal band or DB cells) participate in bowel control, while those found along the lateral edge (lateral band or LB cells) influence bladder function. In order to determine whether differences in the synaptic inputs exist between these two populations, HRP was applied to the sacral ventral rootlets of cats, and the S2 cord segment was prepared for sequential light and electron microscopy. When measured with light microscope, the LB somata had greater cross-sectional areas than did the DB cells. Ultrastructurally, the LB cells had a significantly greater percentage of their membrane apposed by synaptic active sites than did the DB cells. Also, the proximal dendrities of the labelled neurons received greater synaptic input than did the somata. No difference was found in the proportion of terminals containing dense cored vesicles (DCVs) when comparing LB and DB somata; however, the LB proximal dendrites had a higher proportion of their surface contacted by DCV-containing terminals than did the DB dendrites. These ultrastructural results offer evidence that these two populations of preganglionic neurons differ with respect to their synaptic input as well as their peripheral targets.

Testosterone-induced plasticity of synaptic inputs to adult mammalian motoneurons.

The effects of testosterone administration on penile reflexes, and on the motoneurons of the spinal nucleus of the bulbocavernosus which innervate perineal muscles involved in these reflexes, were investigated in castrated male rats. Penile reflexes were restored following 48 h of testosterone administration initiated 6 weeks after castration. The amount of synaptic input to the identified motoneurons was increased following short term testosterone treatment, compared to that seen in animals receiving no testosterone, albeit to a lesser extent than that seen in animals receiving long term testosterone treatment. This increase in synaptic inputs in the short term testosterone group occurred despite the lack of an increase in somatic area. Thus, plasticity of the synaptic input to these neurons, as well as recovery of penile reflexes, occurred as a result of alterations in the hormonal state of the animal, and such changes occurred relatively rapidly.

Stimulus and hormonal determinants of flehmen behavior in cats.

Felids are the main group of animals, other than ungulates, that display flehmen behavior during sociosexual interactions. In ungulates the behavior is evoked most readily by olfactory investigation of urine and vaginal secretions, and is believed to be involved in the transport of fluid-borne chemical stimuli, such as sex pheromones, from the oral cavity to the vomeronasal organ. In this study of cats flehmen was virtually always preceded by nasooral contact with the stimulus material, supporting the notion that flehmen in this species is also involved in the transport of fluid-borne stimuli. As in ungulates, flehmen in cats during heterosexual encounters was found to be displayed by males only. However, the sexual dimorphism was situation specific. In exploring a urine-marked room without another cat present, females also performed flehmen, albeit less frequently than males, and when urine was applied to the nasooral surface, flehmen was evoked equally reliably in females and males. Administration of testosterone propionate to spayed female cats paired with estrogen-treated females markedly increased their tendency to genitally inspect the female partner and subsequently perform flehmen. Thus the sexually dimorphic attributes of flehmen behavior are not only stimulus dependent, but also influenced by concurrent hormone stimulation.

Medial preoptic-anterior hypothalamic lesions in prepubertal male cats: effects on juvenile and adult sociosexual behaviors.

Bilateral lesions of the medial preoptic-anterior hypothalamic (MP-AH) area were made in prepubertal male cats at 6-8 weeks of age. All subjects were subsequently reared in groups containing male and female peers, until the last phase of the juvenile period when an adult estrous female was inserted in these social groups. In spite of such optimal conditions for the practice of sociosexual behaviors during development, no sparing of adult male copulatory behavior was observed in these MP-AH animals during testing in adulthood. This finding, while consistent with earlier work on dogs, contrasts with the results obtained in prepubertally lesioned rats. Urine spraying, another sexually dimorphic behavior which is eliminated by MP-AH lesions in adult cats, was spared by prepubertal lesion placement. Heterotypical sexual behavior was not enhanced by prepubertal MP-AH lesion placement, as it is with postpubertal placement. In the present study, therefore, different behavioral systems influenced by the MP-AH area showed varying degrees of plasticity. As found in dogs, prepubertal MP-AH lesions enhanced and accelerated testosterone secretion in cats.

Female and male sexual responses in female cats with ventromedial hypothalamic lesions.

The effects of lesions in the ventromedial hypothalamus (VMH) on male and female sexual behavior in female cats were examined. Following preoperative testing for receptivity, proceptivity, and male mating behavior, 27 female cats received either lesions in the anterior or posterior portion of the VMH or sham lesions. Neither of the VMH lesion placements reduced proceptivity and receptivity scores. However, the female mating pattern was significantly altered in that although females in both lesion groups initially allowed a stud male to mount, they usually did not allow the male to intromit. As in rodents, the VMH in the cat appears to be an important neural area for the display of normal female sexual behavior. Low levels of male sexual behavior were seen in the three groups preoperatively, and no changes were observed in the levels of male behavior following lesion placement. Thus, because lesions that disrupted female behavior did not affect male sexual behavior, it appears that the neural areas controlling homotypical and heterotypical sexual behaviors are not necessarily neurally linked.

Analysis of the catnip reaction: mediation by olfactory system, not vomeronasal organ.

Pet owners and behavioral scientists alike are fascinated by unique behavioral reactions that cats show in the presence of catnip. These experiments explored the possibility that the catnip reaction might be triggered by chemosensory stimulation of the vomeronasal organ. In the chewing and mouthing of the catnip source, substances might be dissolved in saliva and transported to the vomeronasal organ. The rolling and rubbing during a catnip reaction might be a sexual response activated by the accessory olfactory system since the system projects to parts of the brain involved in mediation of sexual behavior. However, removal of the vomeronasal organ did not attenuate any of the behavioral reactions to catnip. Olfactory bulbectomy immediately eliminated catnip responding, revealing that the chemosensory stimulus evoking the catnip reaction is undoubtedly mediated through the main olfactory system. Catnip activates behavioral elements associated with several species-specific behaviors, including sniffing and chewing as associated with oral appetitive behavior, rolling and rubbing characteristic of female sexual behavior, batting the catnip source characteristic of play behavior, and a type of kicking associated with predatory behavior. These behavioral reactions occur randomly and intermittently.

Testosterone and cortisol levels in crewmen of U.S. Air Force fighter and cargo planes.

Serum levels of cortisol and testosterone were measured in 39 United States Air Force personnel on active duty flying status. The subjects selected belonged to one of the following categories: pilot of a fighter-type aircraft, nonpilot on a fighter plane, pilot of a cargo-type aircraft, or nonpilot on a cargo plane. Blood samples were taken prior to and after a routine flying mission. Cortisol levels prior to the flight did not differ across groups. However, postflight samples of cortisol were elevated in the nonpilots, in comparison to the pilots, regardless of aircraft type. Conversely, while testosterone levels were unaffected by crew position, the men flying on fighter-type planes had lower serum levels than did those on cargo planes. These results suggest that hormone levels may be differentially affected by the stressors of routine military flight.

Effects of small medial preoptic lesions on estrous cycles and receptivity in female rats.

The effects of small lesions in the preoptic area (POA) of female rats on estrous cycles, LH responsiveness, and receptivity were studied. Regularly cycling rats received lesions confined to either the periventricular portion or the ventral portion of the rostral preoptic area, or a combination of these two sites. Nine animals showed persistent vaginal cornification (PVC) following lesion placement. All of these had lesions in the periventricular preoptic area. In contrast, five of six animals which showed repeated periods of pseudopregnancy (RPP) had lesions in the most ventral portion of the preoptic area. Lesions which damaged both the periventricular POA and the ventral POA gave mixed results. Following ovariectomy and estrogen and progesterone stimulation, the RPP animals had higher levels of LH 6 hr after the P injection than did the control animals or PVC animals. In three different tests for female sexual behavior--with estrogen alone, estrogen plus progesterone, and low estrogen priming and repetitive sexual stimulation--the PVC animals had consistently lower receptivity than the controls. The RPP animals were more receptive than the controls in all but the estrogen plus progesterone tests. The decreased levels of receptivity of the PVC animals could be related to a disruption of the LHRH system, while the RPP group responses could reflect a hypersensitivity of remaining neurons to estrogen.

Female sexual responses in male cats facilitated by olfactory bulbectomy and medial preoptic/anterior hypothalamic lesions.

Bilateral lesions of the medial preoptic/anterior hypothalamic area and olfactory bulbectomies were performed sequentially in sexually active male cats, with the order of operations balanced. Male sexual behavior was virtually eliminated by the combined operations in all cats. Increased levels of female proceptive behavior were seen following either type of lesion alone, and combined operations resulted in increased levels of receptivity. The results support the concept that there exists, within the brains of male animals, the neural basis for the display of female as well as male sexual responses and that certain brain operations may potentiate the display of female responses. However, it does not appear that the reduction of male behavior is necessarily coupled with an increase in female behavior since no correlation was seen between the degree of enhancement of female behavior and the decrement in male behavior.

Measurement of scoliosis by orthopedic surgeons and radiologists.

Minimum medical standards for USAF flying personnel have been compiled in Air Force Regulation 160-43. This regulation specifies the maximum allowable amount of scoliosis, but does not specify who should read the X-ray film to determine, using the Cobb method, the degree of curvature in scoliotic individuals. In the present study, an X-ray of an individual with mild scoliosis was sent to departments of radiology and orthopedics at major U.S. Armed Forces Medical Centers. Although the mean estimated degree of curvature was the same for both the orthopedists and the radiologists, the variance in the radiologists' replies was considerably higher than normally expected. It is, therefore, recommended that scoliosis films of individuals being screened for flying duties should be reviewed by a qualified orthopedic surgeon.