George J. Bloch

Estrogen-concentrating cells within cell groups of the medial preoptic area: sex differences and co-localization with galanin-immunoreactive cells

Male and female rats have approximately equal numbers of estrogen(E)-concentrating cells within the medial preoptic area (MPOA). Several cell groups within this brain region are sexually dimorphic, however, and these groups may have sexually different numbers of E-containing cells; this, in turn, may reflect sex differences in neural-regulated functions. In order to study this possibility, the distribution of E-concentrating cells was determined using estrogen autoradiography. Except for the lateral portion of the medial preoptic nucleus (MPNl), the density of E-concentrating cells was 3-5-times higher within the most medially situated cell groups of the female than the male, i.e., within the anteroventral periventricular nucleus (AVPv), periventricular preoptic area (PVPO), medial portion of the medial preoptic nucleus (MPNm), and its central portion (MPNc). In addition, we determined whether E-concentrating cells also express the neuropeptide, galanin. An average of 13% of the E-concentrating cells were galanin positive, which represented 15% of the galanin-immunoreactive population. These results demonstrate a frank and dramatic sex difference in the distribution of E-concentrating cells within sexually dimorphic regions of the MPOA, and also suggest that an interaction between galanin and gonadal steroids may be an important means by which cells within the MPOA regulate reproductive function.

Microinjection of galanin into the medial preoptic nucleus facilitates copulatory behavior in the male rat

The medial preoptic area (MPOA) is an important region for masculine sexual behavior. Because galanin (GAL) immunoreactive cells within the MPOA are affected by the gonadal steroid environment and GAL binding is apparent, GAL was microinjected site specifically in 0, 10, 50, 100, and 500 ng doses in order to determine effects on copulatory behavior. Unilateral microinjection of GAL within the medial preoptic nucleus facilitated copulatory behavior in a dose-responsive fashion, evidenced by an increase in the percentage of males that displayed sexual behaviors and a decrease in mount and intromission latencies. These effects required the presence of gonadal steroids, and were not due to general arousal as measured in open field testing. The techniques of survival analysis were used to display data and for statistical analysis of intromission and mount latencies; these approaches revealed significant effects that were not evident with more commonly used procedures. The results support the suggestion that sexually dimorphic galaninergic cell groups within the MPOA are involved in gonadal steroid-induced masculine sexual behavior.

Distribution of galanin-immunoreactive cells within sexually dimorphic components of the medial preoptic area of the male and female rat

A high percentage of galanin-immunoreactive (GAL-I) cells within sexually dimorphic components of the medial preoptic area (MPOA) of the rat also concentrate estrogen and GAL microinjected within the medial preoptic nucleus (MPN) facilitates masculine sexual behavior after testosterone priming. Thus, we determined the distribution of GAL-I cells within the MPOA and their response to gonadal steroids. We report significantly greater numbers of GAL-I cells within the central division of the medial preoptic nucleus (MPNc) and fewer within the anteroventral periventricular nucleus (AVPv), of the gonadectomized male than the gonadectomized female; that GAL-I cell numbers and densities within the AVPv are increased significantly in the intact, testosterone- or estrogen-treated male compared to the gonadectomized male and that GAL-I cell numbers and densities within the MPNc and GAL-I cell densities within the medial division of the MPN (MPNm), are increased significantly by gonadal steroids in rats of both sexes. The results suggest an involvement of galaninergic cells within the MPOA in the regulation of sexually dimorphic, gonadal steroid-sensitive functions.

Galanin microinjected into the medial preoptic nucleus facilitates female- and male-typical sexual behaviors in the female rat

Galanin (GAL) microinjected within the sexually dimorphic medial preoptic nucleus (MPN) facilitates male-typical sexual behaviors in the male rat, a response that requires the presence of testosterone. As in the male, GAL-immunoreactive cells located within the MPN of the female also concentrate gonadal steroids and become less immunoreactive after gonadectomy. Thus, to investigate sexual behaviors in the female and to determine whether effects are comparable to those obtained in the male, GAL was microinjected unilaterally within the MPN of female rats. We report that GAL stimulated female-typical lordosis behavior after estrogen priming, and that the effect was not due to general arousal as measured by nonspecific locomotor activities. In a separate experiment, GAL microinjected within the MPN dose-responsively increased mount frequencies and decreased mount latencies in testosterone-primed females. A higher dose of testosterone was required in females for this stimulation of male-typical sexual behavior than required in a previous experiment in males.

Gonadal Steroid-Dependent GAL-IR Cells within the Medial Preoptic Nucleus (MPN) and the Stimulatory Effects of GAL within the MPN on Sexual Behaviors a

Abstract: More GAL‐I cells exist within sexually dimorphic cell groups of the medial preoptic nucleus (MPN) in male rats than females, a large percentage of estrogen‐concentrating cells within MPN cell groups are also GAL‐immunoreactive (GAL‐IR), and significantly more GAL‐IR cells are visible with estrogen or its precursor, testosterone. Gonadal steroids also increase the size (diameter) of MPN GAL‐IR cells and the number of GAL‐IR cell processes within a portion of the MPN called the “GAL‐IR MPOA plexus,” which exists in males only. GAL microinjected into the MPN stimulated male‐typical sexual behaviors, with more testosterone required in females than males. Immunoneutralization with anti‐GAL serum inhibited male‐typical sexual behavior, indicating a role for endogenous GAL within the MPN. Microinjection of GAL into the MPN also stimulated female‐typical sexual behaviors in estrogen‐treated females and males, and GAL within the MPN dramatically overrode an inhibition of lordosis by dihydrotestosterone in rats of both sexes.

Hyperactivity in hyposexual male rats.

It is widely accepted that some male rats fail to copulate because of a decrease in arousability, measured as decreased general locomotor activity (hypoactivity). This relationship, however, failed to explain an observation made in our laboratory that rats that failed to copulate exhibited increased general locomotor behavior. To directly address this issue, we quantified open-field and male sexual behaviors in 360 rats from two different strains. Twenty-two out of 49 hyposexual males were also hyperactive; this was a significantly greater number than would be expected by chance (p < 0.002, binomial test). Interestingly, only 6 of the 49 hyposexual males were hypoactive; this number was actually significantly smaller than would be expected by chance (p < 0.02). There was no correlation between behavioral measures and plasma levels of testosterone or progesterone. A decrease in selective attention and a failure to be stimulated by amphetamine was apparent in all hyperactive rats--those normal-sexual as well as hyposexual. The hyperactive rats were not hypertensive. We conclude that a significant percentage of hyposexual rats are hyperactive, and that hypoactive rats generally exhibit normal levels of sexual behavior. Decreased selective attention and decreased responsiveness to amphetamine do not explain this result, which is also not related to blood pressure or androgen levels.

A rat model for attention deficit-hyperactivity disorder

A number of animal models for attention deficient-hyperactivity disorder (ADHD), a common childhood disorder, have been developed. However, none of these models are truly representative of naturally occurring developmental ADHD. In such models, hyperactivity is induced by electrical or chemical brain lesions, by pharmacological manipulation, or by genetic breeding that is coupled with hypertension. Based on the observation that some hyposexual rats also are hyperactive, we have studied these rats in order to determine whether they portray characteristics representative of ADHD. Results of open field testing, response to stimulant medication challenge, and measurement of the rats ability to block irrelevant information in a conditioned avoidance response demonstrate three properties characteristic of ADHD: a) a high level of spontaneous motor activity; b) an attenuation of motor activity in response to amphetamine; and c) a deficit in selective attention. These data indicate that these rats may be a model for the study of ADHD.

Inhibition of lordosis behavior in male and female rats by androgens and progesterone.

Several studies suggest that when manipulated experimentally in adulthood, the lordosis response to estrogen can be increased dramatically in male rats. Because adult-gonadectomized (Gx) animals were used in these studies, the lack of testicular hormones in adulthood may have been a factor. To examine this possibility, adult-Gx rats were implanted with blank (Bk)-, testosterone (T)-, 5alpha-dihydrotestosterone (DHT)-, or progesterone (P)-filled capsules, alone or in combination. We report a new finding, that a combined treatment of T plus P (T+P) at physiological doses for the male, but not T or P alone, reduced lordosis significantly in males, with and without estrogen priming. T+P did not inhibit lordosis in females, nor did this specific treatment affect open field, aggressive, and male copulatory behaviors. In confirming studies done with much higher doses, DHT reduced lordosis in both sexes. DHT and T+P also reduced lordosis in adrenalectomized/Gx males. Mechanisms responsible for the T+P inhibition of lordosis in males are not known, but they may include an upregulation of androgen receptors by P, and this possibility is discussed.

Validation of the Symptoms of Illness Checklist (SIC) as a Tool for Health Psychology Research

We developed the Symptoms of Illness Checklist (SIC) to study psychological influences on physical symptoms of illness. A total of 520 participants completed the SIC and, in some samples, the Salient Stressor Impact Questionnaire, Perceived Stress Scale, Daily Hassles and Uplifts Scale, Derogatis Stress Profile, Life Experiences Survey, and the Symptoms CheckList-90-R. The SICs test—retest, internal reliability, and validity verified by physician ratings, were very good. SIC correlations with diverse stress measures were less inflated than those of other instruments indicating the SIC is a reliable and valid tool to study psychological influences on physical illness.

The Salient Stressor Impact Questionnaire (SSIQ): a measurement of the intensity and chronicity of stress.

High stress is known to affect health, but stress impact, determined by events and responses to them, has not been studied systematically. For the Salient Stressor Impact Questionnaire (SSIQ), the impact of events was assumed to depend on their salience and chronicity and the impact of responses on their chronicity and intensity with greater unfavorable appraisal associated with greater response. The SSIQ assessed a person’s two most salient stressors. Chronicity items discriminated between clinically stressed and nonclinical participants and measured the chronicity of stressful feelings (distress) and the event. The remaining items measured the degree of distress and unfavorable appraisal. The SSIQ showed good test-retest and internal consistency reliability, concurrent validity, and stability across diverse populations. Exploratory analyses grouped items into distress, chronicity, and appraisal elements, and confirmatory analysis revealed a good fit to the hypothesized model. Preliminary data suggest that the SSIQ will be useful for studying relationships between stress and health.