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Biomedical subjects

S E Hendricks

Publications and source records attributed to S E Hendricks.

At least 37 records · Page 2Linked to original sources
PubMed1993

Defensiveness, anxiety and the amplitude/intensity function of auditory-evoked potentials.

This study measured relationships between defensiveness, anxiety, and auditory-evoked potentials to tones of varied intensity. Subjects were designated as defensive if they scored > or = 7 on the L-scale of the Eysenck Personality Questionnaire, and high-anxious if they scored > or = 11 on the N-scale. Four groups resulted: 'high anxious', 'defensive high anxious', 'repressors' (i.e., defensive low anxious) and 'low anxious'. Evoked potentials were recorded from FZ, CZ, PZ, C3, C4, T3 and T4, referenced to linked ears in response to 74, 84, 94 and 104 dB SPL tones. High-defensive subjects showed lower P2 amplitudes to the 94 and 104 dB tones and lower amplitude/intensity slopes at FZ, CZ, C3 and C4. High-anxious subjects showed lower P2 amplitudes to all four stimulus intensities at FZ, CZ and PZ. The results are consistent with the hypothesis that defensiveness is associated with desensitization to intense or painful stimulation.

Adult↗
PubMed1993

Increases in heart rate variability with successful treatment in patients with major depressive disorder.

We obtained Hamilton Rating Scale for Depression (HAM-D) scores and recorded 5 minutes of rhythm strip both before and after a therapeutic trial of antidepressant medications in 17 patients diagnosed with major depressive disorder (MDD). We calculated the standard deviation (SD) of interbeat intervals and the mean squared successive difference (MSSD) as measures of heart-rate variability (HRV). We then calculated Spearman rank-ordered correlation coefficients between the HRV measures and the HAM-D scores. Changes in SD and MSSD correlated with post-treatment HAM-D scores and with changes in HAM-D scores. These relationships were strongest in patients who responded positively to nontricyclic antidepressant medications. HRV before treatment was not predictive of treatment response, nor did HRV reliably reflect the severity of depressive symptoms. These findings indicate that pharmacologic treatment leading to improvement in MDD is associated with increased HRV. Hence, brief measures of HRV could be developed as a useful adjunctive, physiologic measure of treatment response to pharmacotherapy in clinical trials and other settings. Further, increased HRV associated with successful treatment of MDD may reflect improved autonomic function, decreasing the risk of cardiovascular mortality found in patients with MDD.

Adult↗
PubMed1992

Lesions of the nucleus paragigantocellularis: effects on mating behavior in male rats.

We evaluated the effects of bilateral radio-frequency lesions of the paragigantocellular (PGi) reticular nucleus in the ventral medulla on male rat copulatory behavior. In Experiment 1, sexually naive male rats with such lesions were more likely than sham-operated controls to copulate to ejaculation during their first exposure to an estrous female. Additionally, among the rats that copulated to ejaculation, those with lesions demonstrated a reduction in mount frequency (MF), intromission frequency (IF), and ejaculation latency (EL), and an increase in copulatory efficiency (CE). In Expt. 2, sexually experienced male rats were allowed to mate to sexual exhaustion. Males with PGi lesions showed an increased latency to sexual exhaustion and an increased number of ejaculations prior to exhaustion. Additionally, rats with PGi lesions displayed reductions in IF, EL, and post-ejaculatory interval (PEI) as they approached sexual exhaustion. Our results provide further evidence that the PGi is a supraspinal locus of descending inhibitory influence on spinal nuclei mediating ejaculatory reflexes in the male rat.

Analysis of Variance↗
PubMed1989

Neuroendocrine responses to exogenous estrogen: no differences between heterosexual and homosexual men.

Plasma LH concentrations were determined in 55 men before and for four days following injection of 10 mg, 20 mg, or 30 mg Premarin or a placebo injection of vehicle. Testosterone (T) and dihydrotestosterone (DHT) concentrations were also determined in plasma samples taken just prior to Premarin or placebo injection and in samples taken three days later. All subjects provided self-descriptions of their sexual orientation and, based upon these descriptions, were classified as heterosexual (N = 39) or homosexual (N = 16). Premarin injection resulted in a reliable reduction in plasma LH 24 hr later. In subsequent samples, LH values rose and in many cases exceeded baseline levels, most reliably in those subjects receiving the 10 mg dose. Contrary to some previous reports, we observed no significant differences between heterosexual and homosexual subjects in the likelihood of their exhibiting elevated LH concentrations following exogenous estrogens. T, but not DHT, concentrations were suppressed after Premarin injection in both groups of subjects. Other than Premarin dosage, we could not identify any variable which predicted the likelihood of elevated LH values.

Adult↗
PubMed1988

Brain structure and function in sexual molesters of children and adolescents.

Sixteen men incarcerated in a state psychiatric facility pursuant to sexual molestation of children and/or adolescents were evaluated by computed tomography (CT) head scans and regional cerebral blood flow (rCBF) estimation. Compared with controls, child molesters were found to have thinner and less dense skulls and lower rCBF values. Variations from control values in rCBF and characteristics of CT head scans for the sex offenders suggest a role for cerebral dysfunction in the etiology of their aberrant behavior.

Adult↗
PubMed1986

Anxiolytic effects of progesterone are sexually dimorphic.

We evaluated the effects of progesterone administration to estrogen-primed rats on licking behavior during a lick suppression test. This test assesses the behavior of water-deprived rats to lick a drinking tube for water reinforcement that is paired to electric shock. Chlordiazepoxide (a commonly used tranquilizer) is very effective in increasing licking during this test. Normal females and neonatally castrated males displayed an increase in shock-punished responses in tests conducted after hormone injections. Normal males and neonatally androgenized females were unaffected. Our results suggest that ovarian steroids, and particularly progesterone, can modulate anxiety in females and feminized males. In addition, the anxiolytic effect of progesterone appears to be mediated by a mechanism different from that of Chlordiazepoxide.

Animals↗
PubMed1986

Effects of two-stage lesions of the medial preoptic area on sexual behavior of male rats.

The effects of lesions of the medial preoptic area (MPOA) on sexual behavior of adult male rats were examined. Bilateral lesions were performed in either one or two stages. Bilateral, but not unilateral, destruction of the MPOA virtually eliminated mounts, intromissions, and ejaculation. No sparing of the male rats' sexual behavior was observed after two-stage MPOA lesions.

Animals↗
PubMed1984

Effect of ovarian hormones on conflict behavior.

We injected ovariectomized female rats with estrogen and progesterone. Some of the injection regimens used are known to induce estrus, while other do not. The effects of these treatments on operant behavior were evaluated. Operant behavior was maintained under a reinforcement schedule, one segment of which involved experimentally induced conflict. Such behaviors previously have been shown to be modified by anti-anxiety drugs. Those hormone treatments effective in inducing estrus had behavioral effects similar to the effects observed for established anti-anxiety agents. Hormone-injection regimens not capable of inducing estrus were without effect on operant behavior. Our findings suggest that the reproductive cycles of female rats are associated with behavioral changes which may be indicative of changing anxiety levels mediated in part by changing titers of ovarian hormones. We suggest that the evaluation of hormonal influences on operant behaviors sensitive to tranquilizers should be a useful model system for studying possible mechanisms underlying emotional changes associated with reproductive cycles.

Animals↗
PubMed1983

Dissociation between increased growth hormone and prolactin secretion during the morning hours of early pregnancy in the rat.

We investigated whether serum growth hormone (GH) concentration changes in association with the rise in serum prolactin (PRL) concentration known to occur during the early morning hours in the pregnant rat. Animals were kept in a room with the lights on from 0500 to 1900 hours (hr) daily and decapitated for the collection of trunk blood at 2200 or 2400 hr on Day 6 of pregnancy or at 0200, 0400, 0800 or 1000 hr on Day 7 of pregnancy. Serum GH concentration rose more than 4-fold from low levels at 2200 and 2400 hr to higher levels at 0400 and 0800 hr and then declined by 1000 hr. Serum prolactin (PRL) concentration followed a similar pattern except that it returned to low levels earlier, by 0800 hr. Serum luteinizing hormone, follicle-stimulating hormone and thyroid-stimulating hormone concentrations showed no significant changes. Serum GH levels at 0800 hr in pregnant rats were higher than those observed in cyclic rats (13 time periods sampled). The results demonstrate that serum GH concentration is elevated during a circumscribed period in the 6- to 7-day pregnant rat. The time of onset of the rise is similar to that for serum PRL but the elevation in GH levels persists longer than that for PRL.

Animals↗
PubMed1982

Responses to copulatory stimulation in neonatally androgenized female rats.

A series of experiments evaluated the extent to which copulatory stimulation could ameliorate the anestrus and sterility exhibited by neonatally androgenized female rats. The age at which animals began to exhibit persistent vaginal estrus and the degree of sexual receptivity exhibited under several testing paradigms were found to be inversely related to the dose of testosterone propionate (TP) injected neonatally. With increasing numbers of mounts received, both the number of androgenized animals exhibiting sexual receptivity and the quality of the estrous behavior exhibited tended to increase. The extent to which copulatory stimulation modified receptivity varied with the dose of TP injected neonatally and the condition of testing. Animals injected with high doses of TP (500 microgram) usually showed little or no receptive behavior even in the most extensive behavioral tests. However, under some testing conditions animals receiving 50 micrograms of TP neonatally, while showing little or no receptivity during initial mounts, showed increased receptivity as behavioral tests were extended. Following matings that included one to five ejaculations, only control animals were observed to become pregnant. However, when androgenized females cohabited with males for an extended period, animals that had neonatally received .5 microgram of TP, but not higher doses, did become pregnant. It is concluded that the capacity of systems mediating reproductive physiology and behavior to be facilitated by stimuli associated with males and that mating is a characteristic of the female rat which can be manipulated by injection of hormones during the neonatal period.

Animals↗
PubMed1982

Anterior pituitary gland secretion after forebrain ablation: periovulatory gonadotropin release.

We sought to determine whether the estrous phase of FSH release in cyclic female rats is dependent on the immediate presence of the diencephalon. A piece of forebrain, the diencephalon and part of the telencephalon, was surgically removed from female rats between 1130--1300 or 2000-2200 h on proestrus. Blood was withdrawn through indwelling venous cannulae during the afternoon and evening of proestrus and the early morning of estrus for RIA of plasma LH, FSH, and PRL concentrations. In rats sham operated at either time period, plasma LH, FSH, and PRL levels rose from 1345 to 1800 h on proestrus. Whereas the plasma LH and PRL concentrations fell from 1800 h on proestrus to 0300 h on estrus, the plasma FSH concentrations remained elevated during this period. The removal of the piece of forebrain around noon on proestrus blocked the rises in the plasma LH and FSH levels and caused high plasma PRL concentrations from 1345 h on proestrus to 0300 h on estrus. The removal of the piece of forebrain during the evening of proestrus did not interfere with the fall in plasma LH concentrations or the maintenance of elevated plasma FSH concentrations during either late proestrus or the early morning estrus, but did cause high plasma PRL levels during that time interval. Hypophysectomy combined with removal of the forebrain piece during the evening of proestrus resulted in a drop in plasma FSH and PRL concentrations. The results confirm that in the rat, 1) the prosencephalon plays an acute stimulatory role n causing the preovulatory LH surge and the proestrous phase of FSH release, 2) the prosencephalon exerts effects during the afternoon and/or early evening of proestrus that cause the estrous phase of FSH release, and 3) the estrous phase of FSH release occurs in the absence of acute diencephalic stimulation.

Animals↗
PubMed1977

The delayed anovulation syndrome: influence of hormones and correlation with behaviour.

Experiments were conducted to assess the influence of the ovary and various steroid treatments on the development of the delayed anovulatory syndrome (DAS) in female rats. The influence of neonatally administered androgen on the development of ovarian function and female sexual behaviour was studied. It was found that neither the presence of the ovary nor the administration of oestrogen or androgen affected the time-course of the DAS. Doses of androgen which produced the DAS had little effect on female sexual behaviour and there was no evidence of time-dependent changes in sexual behaviour comparable to the time-dependent changes of ovarian physiology observed during the DAS.

Animals↗