Telencephalic connections of the sexually dimorphic area of the gerbil hypothalamus that influence male sexual behavior.

The sexually dimorphic area (SDA) of the gerbil hypothalamus is essential for mating in male gerbils. To determine if it affects mating through its connections with the ventral part of the lateral septal nucleus (LSv), the caudal part of the medial bed nucleus of the stria terminalis (caudal BSTm), or the medial amygdala-amygdalohippocampal area (MA-AHi), these connections were severed. Unilateral cell-body lesions were made in the SDA and in the contralateral LSv, caudal BSTm, or MA-AHi. Controls received the same lesions ipsilaterally. Other gerbils received lesions in the caudal BSTm and contra- or ipsilateral MA-AHi. Only contralateral lesions of the SDA and caudal BSTm severely impaired mating. Because contralateral lesions of the SDA and MA-AHi, or BSTm and MA-AHi, did not mimic this effect, the BSTm neurons that are needed for male sexual behavior through their connections with the SDA do not simply relay information to or from the MA-AHi. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Projection of the sexually dimorphic area of the gerbil hypothalamus to the retrorubral field is essential for male sexual behavior: Role of A8 and other cells.

To determine if the sexually dimorphic area (SDA) of the gerbil hypothalamus affects male sexual behavior through its projections to the retrorubral field (RRF) or ventrolateral periaqueductal gray (PAGvl), these pathways were lesioned asymmetrically. Unilateral radio frequency lesions of the lateral SDA (LSDA), the major source of the pathways, impaired mating when combined with contralateral RRF, but not PAGvl, lesions. N-methyl-{d}-aspartate (NMDA) lesions of the medial SDA, LSDA, and the area between them (the total pathway source) eliminated mating when combined with contralateral, but not ipsilateral, NMDA lesions of the RRF. To determine if A8 cells contributed to these effects, males received NMDA in the SDA and NMDA or 6-hydroxydopamine in the contralateral RRF. When combined with large SDA lesions, A8 lesions impaired but did not eliminate mating. Thus the SDA–RRF pathway, but not an SDA-A8 pathway, is essential for sexual behavior in male gerbils. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The role of sexually dimorphic medical preoptic area of the hypothalamus in the sexual behaviour of male and female rats

The human placental alkaline phosphatase (PLAP) gene was analysed for its utility as a histochemically detectable reporter gene in transgenic mice. A reporter gene was made by linking the PLAP structural gene to an enhancer-promoter element from the human beta-actin gene. This gene was inserted into the mouse genome by transfection of embryonic stem cells, and by microinjection of fertilized eggs. Histochemical staining showed that the transgene was uniformly expressed in four of four stable ES cell lines, and in all ten tissues examined from adult animals from five lines of transgenic mice. Non-transgenic cells did not stain. These results suggest that the human PLAP gene will be of utility in studies requiring phenotypic marking of cells in tissues of mice.     

Laterally asymmetrical cell number in a sexually dimorphic nucleus in the gerbil hypothalamus is correlated with vocal emission rates

A lateralized relationship between the total volume of a discrete area in a hypothalamic, sexually differentiated nucleus (SDApc) and stereotyped vocalization exists in male Mongolian gerbils. In this present study, using unbiased stereological methods, two cytoarchitectural estimates of the SDApc's structure, neuron number, and nuclear volume were found to be sexually differentiated and also laterally asymmetrical in adult males. In ovariectomized females receiving exogenous testosterone, no cytoarchitectural component was asymmetrical. Significantly, the estimate of neuron number, but not nuclear volume, in the left SDApc of males was correlated with vocal emission rate. The authors conclude that a specific, sex-related cytoarchitectural SDApc parameter shows left-right asymmetry, suggesting the SDApc has an intimate role in mediating hemispheric specialization rather than just being an end point index of individual structural variability.     

Neonatal treatment with tamoxifen causes immediate alterations of the sexually dimorphic nucleus of the preoptic area and medial preoptic area in male rats

We have characterized two different types of Cl- currents in calf pulmonary artery endothelial (CPAE) cells by using a combined patch-clamp and Fura-2 microfluorescence technique to measure simultaneously ionic currents and the intracellular Ca2+ concentration, [Ca2+]i. Exposure of CPAE cells to 28% hypotonic solution induces cell swelling without a change in membrane capacitance and [Ca2+]i, and concomitantly activates a current. This current, I(Cl, vol), is closely correlated with the changes in cell volume and shows a modest outward rectification. It slowly inactivates at potentials more positive than +60 mV but is time- and voltage-independent at other potentials. Increase in [Ca2+]i by different maneuvers, such as application of vasoactive agonists (ATP), ionomycin, or loading of the cells directly with Ca2+ also activates a Cl- current, I(Cl, Ca). This current slowly activates at positive potentials, inactivates quickly at negative potentials and shows strong outward rectification. A time-independent component of the current activated by elevation of [Ca2+]i alone can be inhibited by cell shrinking by exposing the cells to hypertonic solution, indicating that an increase in [Ca2+]i also co-activates I(Cl, vol). Forskolin or cAMP never activated a current in CPAE cells, which indicates the lack of cAMP-activated channels in these cells. There is also no evidence for the existence of voltage-gated Cl- channels in resting, nonstimulated cells. Challenging a cell with elevated [Ca2+]i and hypotonic solutions activated I(Cl, vol) on top of I(Cl, Ca), suggesting that I(Cl, Ca) and I(Cl, vol) are different channels. We conclude that CPAE cells do not express voltage-gated (ClC-type) or cAMP-gated (CFTR-type) Cl- channels, but activate large Cl- currents after volume (mechanical?) or chemical (Ca2+) stimulation.     

Feeding and drinking pathways between medial and lateral hypothalamus in the rat.

Carried out 3 experiments, using 101 female rats of the CFE strain. Bilateral parasagittal transections were made at different lateral and dorsal-ventral positions in and between the ventromedial hypothalamus (VMH) and lateral hypothalamus (LH). Cuts through or just lateral to the VMH produced hyperphagia and obesity, while cuts through or medial to the LH produced, depending upon their exact position and the diet, either temporary aphagia-hypophagia, mild hyperphagia, or no effect. The cuts medial to the LH, but not the others, abolished insulin-induced eating. All cuts produced deficits in drinking regulation that varied according to their exact position. These deficits included hypodipsia, mild hyperdipsia, and reduced water/food ratios, as well as reduced drinking responses to food deprivation, water deprivation, hypertonic sodium chloride injections, and polyethylene glycol injections. The knife cuts also produced changes in gustatory reactivity. The hypothalamic pathways responsible for these effects are discussed. (54 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

c-Fos immunoreactivity in the sexually dimorphic area of the hypothalamus and related brain regions of male gerbils after exposure to sex-related stimuli or performance of specific sexual behaviors

The sexually dimorphic area of the gerbil hypothalamus is essential for male sex behavior. To determine which aspects of mating activate its cells, or cells near or connected to it, we visualized c-Fos in the brains of male gerbils that had been exposed to various types of sex-related stimuli or that had displayed various aspects of sex behavior. Five groups of males were placed in familiar arenas containing sex-related odors. All subjects had previously mated in these arenas. For four groups, a female was introduced and remained with the male until he ejaculated, intromitted, mounted or sniffed her. Males in the fifth group remained in the arena alone. Males in a sixth group were placed in a clean arena in another room. These males were also familiar with this arena but had never encountered a female there. The seventh group remained in their home cages. The posterodorsal preoptic nucleus, the lateral part of the posterodorsal medial amygdala, the medial part of the sexually dimorphic area and the parvicellular part of the subparafascicular nucleus of the thalamus expressed c-Fos after ejaculation. Whether these cells triggered ejaculation or responded to it is not clear. The latter two areas also expressed c-Fos whenever males were exposed to the sex arena, but the sexually dimorphic area pars compacta did not express c-Fos under any condition. The medial core of the nucleus accumbens, the ventrolateral septum, the caudomedial bed nucleus of the stria terminalis, the medial/central part of the posterodorsal medial amygdala and the lateral part of the sexually dimorphic area also expressed c-Fos when males entered the sex arena. The ventrolateral part of the ventromedial nucleus of the hypothalamus expressed c-Fos whenever males were with females. None of the 31 areas studied responded to mounting or intromission, but the zona incerta, the amygdalohippocampal area, the lateral part of the sexually dimorphic area and the area lateral to the medial part of the sexually dimorphic area showed progressive increases in c-Fos expression as mating progressed. The area dorsal to the medial part of the sexually dimorphic area, the paraventricular nucleus of the hypothalamus, the ventral premammillary nucleus and the retrorubral field showed the same level of c-Fos expression when males were exposed to the non-sexual context as when they were exposed to the sexual one. While a projection to the retrorubral field from the sexually dimorphic area is critical for male sex behavior, the retrorubral field did not show a sex-related c-Fos response. The data suggest that brain regions involved in male sex behavior are involved in different aspects of it and that this can also apply to different subsets of cells in each area. The data also indicate that cells involved in mating do not necessarily show mating-related patterns of c-Fos expression. Thus, while c-Fos is useful for identifying areas involved in mating, or other behaviors, its characteristics could cause relevant areas to be overlooked.     

Effects of morphiceptin in the medial preoptic area on male sexual behavior

Morphiceptin, a selective mu opioid agonist, injected into the medial preoptic area (MPOA), delayed the onset of copulation in male rats, but did not affect genital reflexes, sexual motivation or general motor activity. In a dose-dependent manner, morphiceptin (100 ng and 1000 ng) injected into the MPOA increased mount and intromission latencies. Similar injections of morphiceptin into the ventromedial hypothalamus had no effect on any parameter of copulation. The increase in copulatory latencies following the injection of the highest dose of morphiceptin was blocked by pretreatment with the opioid antagonist naloxone. In the X-maze task, morphiceptin had no effect on sexual motivation, as measured by the percentage of trials on which the male chose the female's chamber, but it increased the number of trials in which the subject did not select a chamber within 60 s and the latency to the female the first time he chose her chamber. Similar to the copulation task, the mount and intromission latencies were also increased in the X-maze, after the male reached the female. Morphiceptin in the MPOA had no effect on ex copula genital reflexes, tested in restrained supine males, or on motor activity, tested in a grid box. These results suggest that morphiceptin disrupts either the specific copulatory somatomotor pattern or a more general motivational component.     

Hypothalamic knife cuts that disrupt mating in male gerbils sever efferents and forebrain afferents of the sexually dimorphic area.

The sexually dimorphic area (SDA) of the gerbil hypothalamus is essential for male sexual behavior. To determine (1) if the SDA can affect mating via laterally projecting axons and (2) which SDA afferents might affect mating, male gerbils were given bilateral, parasagittal knife cuts lateral to the medial or lateral SDA. Others were given cuts with a knife coated with horseradish peroxidase to label cells of which axons were cut. Medial cuts eliminated mating and consistently labeled cells in the medial SDA. Lateral cuts did neither. Medial cuts also labeled more cells in the ventral part of the lateral septal nucleus, the encapsulated part of the bed nucleus of the stria terminalis, the medial nucleus of the amygdala, the amygdalohippocampal area, and the ventral premammillary nucleus than lateral cuts did. Thus, medial cuts may disrupt mating by severing SDA efferents or by severing SDA afferents from 1 or more of these 5 sites. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Opioids and sexual behavior of male rats: Involvement of the medial preoptic area.

Local infusion of β-endorphin (β-END) into the medial preoptic area (MPOA) dose-dependently impaired the gating of the copulatory response and the execution of the sexual performance of sexually experienced, intact male rats. Local naloxone treatment prevented the impairment of the sexual response by β-END, but failed to facilitate unimpaired copulation. Local infusion into the MPOA of equimolar doses of α-endorphin, dynorphin-A-(1-17) or met-enkephalin were less effective than β-END. It is suggested that endogenous opioid systems in the MPOA are normally quiescent, and increased activity may be related to disrupted or inhibited male sexual behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Paraventricular nucleus: changes in the medial and lateral cell groups during dehydration and rehydration in the rat

Cell area, percentage of cells with more than one nucleolus, and percentage of cells with the nucleolus apposed to the nuclear membrane (marginated) were compared in the medial and lateral magnocellular portions of the paraventricular nucleus (PVN) during water deprivation and voluntary rehydration. Lateral cells were larger and had a greater percentage of cells with multiple nucleoli in all conditions of deprivation and rehydration. In addition laterals were found to have more cells with marginated nucleoli in these cells with only one nucleoli. Medial and lateral cells showed similar responses to deprivation and rehydration.     

A revised critical period for the sexual differentiation of the sexually dimorphic nucleus of the preoptic area in the rat

A 540 kDa protein was isolated from crayfish claw muscle (closer). The secondary structure mainly consisted of beta-sheet (70%). The rotary shadowed images were long filaments, 300-360 nm long. It is localized in the sides of the Z-lines extending to the I band and elongatable upon stretch of muscle. Immunological crossreactivities strongly suggested that this protein corresponds to kettin (500-700 kDa) of insect striated muscle. In view of molecular shape and secondary structure, and immunological crossreactivities, it is suggested that this kettin-like protein belongs to connectin/titin family of striated muscle.     

Physiological identification and analysis of dentate granule cell responses to stimulation of the medial and lateral perforant pathways in the rat

Stimulation of the dorsomedial or ventrolateral perforant pathways resulted in quantitatively different extracellularly recorded EPSPs in the fascia dentata of the rat. The two potentials differed in latency to peak and in width at half amplitude in a manner consistent with the different locus of termination of the two pathways on the granule cell dendrites. Both potentials were able to follow brief stimulus trains of 100 Hz, which suggests that they are monosynaptic. Medially elicited responses had their peak negativity approximately 100 to 180 micrometer deeper in the molecular layer than laterally elicited responses. Stimulation at short intervals along a dorsomedial to ventrolateral track in the angular bundle yielded a step function rather than a continuum of EPSP peak latency and half-width, in agreement with Hjorth-Simonsen's ('72) evidence for the separateness of the two pathways. Both pathways were able to induce granule cell discharge. Laterally elicited spikes, however, were delayed. Stimulation at intermediate locations frequently elicited double spikes from the granule cell population. Population spikes elicited by either pathway were inhibited for as long as 100 msec after a single discharge. Both pathways showed facilitation with double stimuli at short intervals, and both showed post-tetanic potentiation lasting at least 30 minutes. Under conditions where it could be shown that the two pathways at least partially converged onto the same granule cells, the response of one pathway did not increase when long lasting potentiation was induced on the other.     

Differential response for female and male law students on the Strong-Campbell Interest Inventory: The question of separate sex norms.

Analyzed differential responses to Female and Male Lawyer scale items on the Strong-Campbell Interest Inventory (SCII) for 67 male and 35 female law students. While there was systematic difference in responses between the sexes, the pattern of differential response on items unique to one or the other of the scales indicates that this difference would not affect scores if the scales were combined. Furthermore, the nature of the relation between the occupational groups and between the occupational and in-general groups on these items suggests that combined scales are feasible. Because there is an implicit bias in maintaining separate sex scales, it is suggested that the SCII be considered an intermediate step to a combined instrument. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Castration decreases single cell levels of mRNA encoding glutamic acid decarboxylase in the diagonal band of broca and the sexually dimorphic nucleus of the preoptic area

Using quantitative in situ hybridization histochemistry (ISHH), we determined the effect of castration on single cell levels of glutamic acid decarboxylase (GAD) mRNA in discrete hypothalamic regions of the male rat brain associated with the control of gonadotropin secretion. A 48-base oligodeoxynucleotide probe was used to detect with equal affinity the two isoforms of GAD message, GAD65 and GAD67. GAD message also was quantitated in a number of selected areas of the brain to contrast GAD gene expression amongst several populations of GABAergic neurons. Comparison of 11 brain regions demonstrated a 9.3-fold range in the quantity of single cell GAD mRNA with levels being highest in the amygdala and the diagonal band of Broca, moderate in the piriform cortex, caudate nucleus, substantia innominata, globus pallidus, cingulate cortex and medial septal nucleus, and lowest in the lateral septal nucleus and the medial preoptic nucleus (MPN). Castration markedly reduced single cell GAD mRNA levels in the DBB and the MPN, two discrete hypothalamic structures known to contain dendritic fields, cell bodies, and axons of GnRH neurons projecting to the median eminence. A striking finding was a dense core of steroid-sensitive GABAergic neurons within the MPN comprising the sexually dimorphic nucleus of the preoptic area (SDN-POA). Similar to the MPN as a whole, the amount of GAD mRNA expressed by cells in the SDN-POA of sham operated control rats was greater than in castrated animals. GAD mRNA levels were inversely related to serum LH titers, suggesting a role for these neurons in the mechanism controlling gonadal steroid negative feedback on LH secretion. This report provides the basis for future work to determine if GAD65, GAD67 or whether both isoforms are affected by gonadal steroid input.     

The dopaminergic and serotoninergic components of the self-stimulation reaction of the lateral hypothalamus in rats with disruption of the medial prefrontal cortex

The hospital in the future will be faced with the major problem of managing and optimizing the use of images provided from numerous sources examining both anatomy (MRI, CT-scan...) and function (gamma-camera, PET-scan...). One of the first to benefit from such rationalization will be the surgeon. After studying the results of the physical examination, the laboratory reports and the medical imaging, the surgeon will decide on the best curative measured and the best surgical route before operating. He thus needs a computer to assist him in integrating the multi-modal information available for his patient, in particular the imaging with automatic integration and visualisation in synoptic mode (perception step), showing the trajectory of possible access routes to the target organ, memorization of the chosen route (decision step) and real operation either using laser or a manuel tool, or with robot assistance under human control (action step). This close cooperation between surgery and computers is called computer-assisted surgery. A few examples of current uses an future perspectives of this new field of surgery are presented.     

Differential effects of amphetamine and food deprivation on self-stimulation of the lateral hypothalamus and medial frontal cortex.

Intracranial self-stimulation of the lateral hypothalamus in 5 male Sprague-Dawley rats was markedly increased by subcutaneous dextroamphetamine administration and by food deprivation. In contrast, similar self-stimulation response rates obtained in the same Ss from the medial frontal cortex were unaffected by food deprivation and only slightly increased by dextroamphetamine administration. Furthermore, a large difference between dextro- vs levoamphetamine on response rate was obtained for lateral hypothalamic but not for medial frontal cortex self-stimulation. Results are consistent with a noradrenergic self-stimulation system for the lateral hypothalamus. Medial frontal cortex self-stimulation, however, appears to be mediated by a neuroanatomical and neurochemical system different from that of the lateral hypothalamus. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sensorimotor functions of the striatopallidal system and lateral hypothalamus and consummatory behavior in rats.

Conducted 5 experiments with male albino Holtzman rats (N = 98) to evaluate the roles of the globus pallidus, entopeduncular nucleus, and lateral hypothalamus in the control of limb movement and consummatory behavior. The entopeduncular nucleus, but not the lateral hypothalamus, was shown to be part of a lateralized system controlling forelimb use. In contrast, the 3 structures displayed shared functions in the control of consummatory behavior. Whether these shared functions pertained to either sensorimotor, dispositional, or reward mechanisms was not determined, although experiments were designed to limit the possibilities. Additional experimentation demonstrated marked gustatory disturbances after pallidal lesions that seemed to reflect destruction of thalamocortical fibers of passage through the pallidum. (43 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)