Julian M. Davidson

The relationship between circulating testosterone levels and male sexual behavior in rats

Abstract The relationships between plasma testosterone (T) and various parameters of male sexual behavior were examined in intact and castrated T-treated male rats. Repeated blood sampling and behavioral testing revealed no correlation between any measure of sexual behavior and plasma T in normal untreated sexually active males. T-Filled Silastic capsules, implanted subcutaneously at the time of castration, were found to produce plasma T levels proportional to capsule size. Plasma T titers less than 10% of normal (0.2 ng/ml) maintained ejaculatory behavior near normal levels for the 58 days of the experiment. Measures of sexual behavior which showed androgen dependence were intromission latency, postejaculatory interval, and intromission frequency. The plasma T concentration required to maintain these parameters within the intact range was 0.7 ng/ml, which is less than one-third of the mean intact level (2.6 ng/ml). No significant improvement in the sex behavior measures was seen with plasma T levels between 0.7 and 3.1 ng/ml. It was concluded that the absence of relationships between circulating T and sexual behavior in the normal rat population is due to the androgen requirement for this behavior being less than the amount normally present. Findings on T levels and T treatment in noncopulator males are also presented.

The Psychobiology of Consciousness

1 Introduction: The Scientific Study of Human Consciousness in Psychobiological Perspective.- References.- 2 Consciousness and Information Processing: A Biocognitive Perspective.- 1. Introduction.- 2. A Brief Historical Overview.- 2.1. Biological Constraints on Learning Processes.- 2.2. Growth of the Developmental-Maturational Perspective.- 2.3. Constructive Nature of Perceptual Processes.- 2.4. Self-Regulation.- 3. Consciousness, Unconsciousness, and Biocognitive Structures.- 3.1. The Nature of the Unconscious.- 3.2. The Transition to Consciousness.- 3.3. Some Possible Functions of Consciousness.- 3.4. Hemispheric Specialization and the Representation of Consciousness.- 4. Influences on Biocognitive Structures and Styles of Information Processing.- 4.1. Species Characteristics.- 4.2. Genetic Influences and Individual Differences.- 4.3. Cultural and Social Influences.- 5. On Making the Unconscious Conscious.- References.- 3 Mind, Brain, and Consciousness: The Organization of Competence and Conduct.- 1. Consciousness and Information Processing.- 2. Consciousness and Self-Consciousness.- 3. Consciousness and Feelings.- 4. Consciousness and Information Measurement.- 5. Consciousness and Competency.- 6. Consciousness and Perception.- 7. Consciousness and Mind.- References.- 4 Stress-Induced Behavior: Chemotherapy without Drugs.- 1. Stress-Induced Behavior.- 1.1. Eating.- 1.2. Sexual Behavior.- 1.3. Aggression.- 1.4. Neuropharmacology of Stress-Induced Behavior.- 1.5. Parallels between Stress-Induced Behaviors in Animals and Humans.- 1.6. Possible Function of Stress-Induced Behavior.- 2. Stereotypy as a Consequence of Stress in Animals and Humans.- 2.1. Stereotypy.- 3. Why Dopamine?.- 4. Summary.- References.- 5 Redundancy in the Nervous System as Substrate for Consciousness: Relation to the Anatomy and Chemistry of Remembering.- 1. Introduction.- 2. Localization of Memory Consolidation Function.- 3. Redundancy of the Central Nervous System.- 4. Redundancy as a Neurobiological Substrate of Consciousness.- 5. Biochemistry of Memory.- 6. Conclusion.- References.- 6 Multipotentiality: A Statistical Theory of Brain Function-Evidence and Implications.- References.- 7 Genetic Factors in EEG, Sleep, and Evoked Potentials.- 1. Introduction.- 2. The Electroencephalogram-Resting and Response Measures.- 2.1. Visual Observations of Twin EEG.- 2.2. Alpha Waves.- 2.3. Alpha Blocking.- 2.4. Beta Waves.- 2.5. Complete Power Spectra.- 3. Sleep.- 3.1. Normal Sleep.- 3.2. Narcolepsy.- 4. Evoked Potentials.- 4.1. Waveform Similarity.- 4.2. EP Latency.- 4.3. EP Amplitude.- 4.4. Response to Stimulus Parameters.- 4.5. EP Asymmetry in Twins.- 5. Anatomic Features and Electrophysiology.- 6. Electrophysiology, Genetics, and Consciousness.- References.- 8 The Waking Stream of Consciousness.- 1. William James: Characteristics of Consciousness.- 2. The Variety of Conscious Experience.- 3. A Basic Model.- 3.1. The Mind as Activity.- 3.2. Sensory Input.- 3.3. A Continuum of Consciousness.- 3.4. Attention: The Ability to Screen and Select.- 3.5. A Bias Favoring Sensory Input.- 3.6. Predictable, Dull, or Barren Environments: An Opportunity for Private Processing.- 3.7. The Matching Function.- 3.8. The Affects.- 3.9. Current Concerns, Unfinished Business, and Unresolved Stress.- 3.10. Sets toward Internal or External Processing.- 3.11. Structural Characteristics of the Stimuli.- 4. The Activities of Mind and Body.- 5. The Stream of Consciousness and Brain Activity.- 6. Fantasy, Emotion, and Visual Imagination.- References.- 9 The Emergence of Emotions and the Development of Consciousness in Infancy.- 1. Biological Processes, Emotions, and Consciousness.- 1.1. Infant Consciousness as Affective Experiences.- 1.2. Affect-Perception-Cognition Relations and Levels of Consciousness.- 2. The Emergence of Emotions and Changes in Consciousness.- 2.1. Sensory-Affective Processes: Consciousness Level I.- 2.2. Affective-Perceptual Processes: Consciousness Level II.- 2.3. Affective-Cognitive Processes: Consciousness Level III.- 3. Summary.- References.- 10 A Systems Approach to Consciousness.- 1. Introduction.- 2. Some Generalities about the Systems Approach.- 3. A Particular System Model.- 3.1. Control Theory and Stabilized Consequences.- 3.2. Control Theory and Causation.- 3.3. Control Theory and Purpose.- 3.4. Control Theory and Volition.- 3.5. Ultimate Purposes.- 4. Consciousness.- 4.1. Causative Factors in the Brain.- 4.2. Ultimate Causes.- 4.3. The Nature of Consciousness: Point of View.- 5. Conclusions.- References.- 11 A Systems Approach to Altered States of Consciousness.- 1. Introduction.- 2. Constructed Nature of Ordinary Consciousness.- 3. States of Consciousness.- 4. Mapping Experience.- 5. Discrete States of Consciousness.- 6. Individual Differences.- 7. Major Subsystems of Consciousness.- 8. Stabilization of Discrete States.- 9. Induction of a Discrete Altered State.- 10. Methodological Consequences of the Systems Approach.- References.- 12 The Psychobiology of Sexual Experience.- 1. Introduction.- 1.1. The Evolutionary Background: Animal Sexual Behavior.- 1.2. From Animal Behavior to Human Sexuality.- 2. Physiology, Sensations, and Concepts of Sexuality.- 2.1. The Physiology of Sexual Arousal.- 2.2. Sexual Dualism.- 2.3. From Sexual Sensations to Sensational Sex.- 3. Orgasm as an Altered State of Consciousness (ASC).- 3.1. Psychological Phenomena.- 3.2. Physiological Phenomena.- 3.3. Psychophysiological Relationships.- 4. Sex Differences and the Role of Hormones.- 4.1. Physiological Differences.- 4.2. Psychological Differences and Psychophysiological Correlation.- 4.3. The Role of Sex Hormones.- 5. Summary.- References.- 13 The Psychophysiological Model of Meditation and Altered States of Consciousness: A Critical Review.- 1. The Meditative ASC.- 2. EEG Changes during Meditation.- 3. Oculomotor Processes and EEG.- 4. Meditation and Arousal.- 5. Specificity of the Meditative ASC.- 6. EEG, Arousal, and Sleep.- 7. Meditation and Attention.- 8. Meditation and Trance.- 9. Meditation and Brain-Wave Biofeedback.- 10. The Psychophysiological Principle.- 11. Meditation and the Psychophysiological Model.- References.- 14 Toward a Psychobiology of Transcendence: God in the Brain.- 1. An Argument for Implicit Knowledge in the Brain Sciences.- 2. The Pharmacological Bridge and the Modulation of Arousal and Fear.- 3. The Pharmacological Bridge and the Modulation of Rage.- 4. Neurobiological Transcendence: High-Dose Amphetamine, Cocaine, and the Hallucinogens.- 5. Neurobiological Antagonism of Amphetamine, Cocaine, the Hallucinogens, and Naturally Occurring Transient Hypomanic States by Lithiums Effect on Serotonin Biosynthesis.- 6. Kindling of Temporal Lobe Limbic Structures: Raphe and Hippocampal Pyramidal Cells as Double Gates to Transcendence.- 7. Bipolar Affect Disorder, the Temporal Lobes, and Transcendent Consciousness.- 8. Syndromes of Temporal Lobe Disinhibition.- 9. The Activated Sleep Syndrome, the Drive-Arrest-Release Sequence in Biogenic Amine Neurons, and the Psychopharmacology of the Bipolar Affect Disorders.- 10. Religious Ecstasy and Conversion.- References.- 15 Prospects for the Scientific Observer of Perceptual Consciousness.- 1. Introduction.- 2. The Scientific Observer and the Problem of Mind and Matter: A Phenomenological Argument.- 3. The Scientific Observer and the Problem of Mind and Brain: An Abstract Argument.- 3.1. Introduction.- 3.2. Intentionality and the Abstract Observer.- 3.3. The Mind-Brain Problem.- 4. Conclusion.- References.

A longitudinal study of the effects of menopause on sexuality

From an initial group of 39, 16 cycling peri-menopausal women completed a longitudinal study in which they recorded menstrual and sexual behavior daily and were interviewed at roughly 4-mth intervals until 1 yr or more without cycling. At each interview women gave 20-ml blood samples, completed sexuality questionnaires, and rated themselves for menopausal symptoms. As predicted, the difference in weekly rate of sexual intercourse before and after the cycle showed a significant decline (P less than 0.05). For each subject, mean weekly rates of sexual intercourse for 13-wk periods over the entire transition period were plotted and the slope of the line was calculated. Overall, the mean slope was negative, as predicted, and was significantly different from zero (P less than 0.05). The questionnaire data showed that compared with their pre-menopause data, the women had fewer sexual thoughts or fantasies (P less than 0.01), suffered more from lack of vaginal lubrication during sex (P less than 0.01), and were less satisfied with their partners as lovers (P less than 0.05) after menopause. While estradiol (E) and testosterone (T) levels showed significant declines (P less than 0.02), testosterone showed the most consistent association with coital frequency. The findings generally supported our initial hypothesis of a decline in sexual interest and coital frequency after menopause.

Relationships among cardiovascular, muscular, and oxytocin responses during human sexual activity

To determine the psychophysiological correlates of hormonal response during sexual activity, systolic blood pressure (SBP), anal electromyography (EMG), and anal photoplethysmography (APG) were monitored continuously throughout testing in 13 women and 10 men. Each subject completed two or more tests of self-stimulation to 5 min beyond orgasm. Blood samples were obtained continuously for measurement of oxytocin (OT) levels. In both men and women, very high positive correlations were observed between the percentage change in levels from baseline through orgasm of: OT and SBP; OT and EMG intensity prior to and during orgasm; APG and EMG. The number of anal contractions and duration of orgasm were also highly correlated. Two patterns of orgasm were defined by the presence or absence of a quiescent period between orgasmic contractions. EMG and APG amplitudes correlated with the pattern of orgasm. Subjective orgasm intensity correlated significantly with increased levels of OT in multiorgasmic women only. The positive correlations between measures are consistent with a possible functional role for OT in human sexual response.

Characteristics of sex behaviour in male rats following castration

Summary The decline of sex behaviour following castration, and the qualitative changes in behaviour resulting therefrom, were studied in adult male Long-Evans rats. Percentages of animals showing the ejaculatory pattern decreased rapidly but the rate of decline was quite variable. In two different experimental series the percentages of rats showing the complete pattern of mating behaviour in the fourth postoperative week were 42·0 and 8 per cent (n=46 and 63, respectively). Some animals were tested for 7 months and in one animal an ejaculatory pattern was noted 147 days after castration. Ejaculation latency (period from first intromission to ejaculation) and the number of intromissions to ejaculation were both decreased in the first 2 or 3 weeks postoperatively. Ejaculation latency increased thereafter over preoperative levels, but intromission frequency remained below them until the ninth week. The latency to first intromission, the frequency of mounting and the post-ejaculatory refractory period were generally increaed on all postoprative tests. It is concluded that (1) male rats may retain all components of sex behavour for relatively long periods after castration although the extent of retention is vairable, and (2) in the early postoperative period the ejaculatory mechanism is facilitated, although sexual ‘arousal’ is inhibited.

Evidence for the modulation of sexual behavior by α-adrenoceptors in male rats

Clonidine, a commonly used antihypertensive agent believed to act by stimulation of central α- adrenoceptors, produced a dose-related suppression of ejaculatory behavior in sexually vigorous male rats

The effects of estrogen and progesterone on female rat proceptive behavior

Abstract The relative importance of estrogen (EB) and progesterone (P) in stimulating proceptivity in ovariectomized female rats was studied. Proceptive behavior was measured quantitatively, providing a clear measure of response to experimental manipulation. When rats were tested biweekly after daily treatment with 0.4 μg/100 g body wt EB for 4 days, they showed maximal lordosis but low levels of proceptive behavior by the second test. Additional EB (3.0 μg/100 g body wt daily) failed to stimulate additional proceptivity. A graded increase in proceptive behavior resulted from administration of increasing doses of P (50, 100, 500 μg and 1.0 mg) to animals receiving EB priming as described above. The level of “soliciting” was significantly higher than EB-only-treated rats when 500 μg or 1.0 mg P was given. Ovariectomized, adrenalectomized rats, primed with 2.5 μg/100 g body wt EB daily for 7 days and tested on Day 8, were significantly less proceptive than ovariectomized, sham-adrenalectomized rats with the same hormone treatment. Four hours after injection of 1.0 mg P, there was no difference in proceptive or receptive behavior between sham- and adrenalectomized rats. It was concluded that if an EB dose is sufficient to induce maximal receptivity, additional estrogen does not stimulate proceptivity; unlike previous studies, the present data are not consistent with a global effect of ovarian steroids on both components of female behavior. Progesterone is more effective than estrogen in stimulating proceptive behavior, although proceptivity is not absolutely dependent on progesterone for expression. Proceptivity in EB-only-treated rats appears to be facilitated by adrenal P.

Intracerebral androgens and sexual behavior in the male rat

Abstract Intracerebral implants of crystalline testosterone propionate (TP) and dihydrotestosterone propionate (DHTP) were used to determine whether (1) the uncertainty regarding the location of the androgen-sensitive, sexual behavior-activating area of the hypothalamus could be resolved and (2) the failure of DHTP to stimulate sexual behavior in castrates could be overcome by placing the steroid directly at the putative receptor area in the brain. TP implants in the anterior hypothalamic-preoptic area were significantly more effective in restoring copulatory behavior in castrates than were those in the posterior hypothalamus. These results could not be explained by release of testosterone into the systemic circulation. Systemic injections of DHTP were ineffective in maintaining sexual behavior when administered from the day of castration, and DHTP implants in the anterior region were markedly less effective than TP in restoring sexual behavior. Implantation of DHTP in the medial basal hypothalamus, but not the pituitary of immature rats suppressed gonadotropin secretion, as indicated by reduction in growth of testes and sexual accessory glands. It was concluded that (1) androgen-sensitive structures regulating male sexual behavior in the rat are more concentrated in the anterior than the posterior hypothalamic region and (2) testosterone probably does not activate male sexual behavior via conversion to dihydrotestosterone.

Effects of Lesions in Various Structures of the Suprachiasmatic-Preoptic Region on LH Regulation and Sexual Behavior in Female Rats

Lesions of the suprachiasmatic nuclei (SCN) completely eliminated phasic LH release in ovariectomized rats as measured by the positive feedback response to estradiol benzoate (EB)/progesterone or the response to mating. Basal LH levels and the negative feedback response to EB were not affected. Lesions of the medial preoptic area (MPOA) or bed nucleus-dorsal MPOA also inhibited phasic LH release in ovariectomized rats as measured by positive feedback. However, the inhibition was not complete if there was no damage to the SCN, and the degree of inhibition was correlated with the size ofthe lesion. Basal LH levels and negative feedback were not significant affected. It is suggested that both the SCN and MPOA are involved in phasic LH release, the former in its role as a neural regulator of circadian rhythms and the latter as part of a diffuse system possibly including estrogen-sensitive and/or LH-RH neurons. Sexual behavior (lordosis) in hormone-primed, ovariectomized rats was not significantly affected by lesions of any structure in the suprachiasmatic-preoptic region.

Relative thresholds of behavioral and somatic responses to estrogen

Abstract The effects of 17 β-estradiol benzoate on sexual receptivity, vaginal and pituitary cytology, and uterine growth were studied in spayed rats in order to compare the relative sensitivities of the behavioral and somatic responses to this steroid. The most sensitive measure was the vaginal smear; full cornification followed administration of 0.2 μg of the estrogen per day. The threshold for attainment of normal levels of sexual receptivity was between 0.8 and 1.6 μg/day. Similar dosage was required to reverse completely the changes in adenohypophyses and uteri resulting from ovariectomy. These results demonstrate that apparently normal sexual behavior may be restored in spayed rats by daily administration of “physiological” doses of estrogen in the absence of progesterone treatment.