Evaluation of prenatal androgen and ovarian secretions on receptivity in female and male rats

Offspring of rats infected daily from Day 16 through Day 20 of gestation with either 2 mg of testosterone propionate (TP) in .1 ml of sesame oil or oil alone were tested for sexual receptivity following injections of 3.3 microgram of estradiol benzoate (EB) and .5 mg of progesterone (P) beginning at 40, 80, or 120 days of age. At each age, neonatally gonadectomized males and females from TP-injected litters exhibited less receptivity than corresponding oil-injected controls. Prenatally androgenized females were similar to neonatally castrated oil-injected males at all ages. Ovarian implants from birth to 35 days of age significantly increased receptivity in neonatally castrated males and androgenized females. Increasing the age at which testing was initiated systematically reduced receptivity in all groups.     

Positive and negative behavioral contrast in the rat

Three groups of rats received either 8, 23, or 53 sessions of multiple variable-interval variable-interval baseline training before being shifted to a multiple extinction variable-interval schedule. The rate of responding during the unaltered component was higher for the groups shifted to multiple extinction variable-interval than for control groups remaining on multiple variable-interval variable-interval (positive contrast). Furthermore, when the multiple variable-interval variable-interval schedule was re-instated, stable negative contrast was found in the groups that had received 23 or 53 baseline sessions, but not for the group that had received only eight sessions. Positive and negative contrast were also demonstrated in the eight and 23-session groups when the multiple extinction variable-interval and multiple variable-interval variable-interval schedules were re-administered in further phases of the experiment. These results suggest that both positive and negative behavioral contrast can be obtained reliably in a species other than the pigeon.     

Effect of behavioral inhibition on interactions in mixed-sex dyads

The present studies assessed the effect of behavioral inhibition on interactions of college students in mixed-sex groups. In Study 1, 20 participants were arranged into two dyadic groups based on self-rated measures of approach/withdrawal behavior. These dyads (inhibited men/uninhibited women; inhibited women/uninhibited men) were videotaped during an unstructured 5-min. interaction in a laboratory. Time series analysis indicated greater behavioral covariation in the inhibited men/uninhibited women dyads and less behavioral covariation in the inhibited women/uninhibited men dyads. Additional analyses indicated a relationship between inhibition and comfort experienced during the interaction. Inhibited participants, particularly women, reported feeling uncomfortable while interacting with an uninhibited male partner. A second study corroborated the findings reported in Study 1 and also noted elevated heart rate in the inhibited women. This increased discomfort in women appeared to be related to heightened self-consciousness during the interaction.     

Effects of selective forebrain noradrenaline loss on behavioral inhibition in the rat.

Virtually total depletion of cortical and hippocampal noradrenaline by stereotaxic injection of 6-hydroxydopamine into the fibers of the dorsal noradrenergic bundle produced no impairment in acquisition learning of a runway response for food reward. Extinction of this response, once learned, was markedly slower in the treated group than in controls, the treated animals perseverating in rapid running to the goal box even with no food present there. Similarly, no impairment was found on acquisition of a continuously reinforced lever-pressing response for food. Extinction of this response, however, was again slower in the treated group. Subsequent acquisition of a successive light-dark discrimination task was also slower in the treated group, with these animals perseverating in responding to the negative stimulus. Although selective forebrain noradrenaline loss does not impair the acquisition of appetitive responses, the suppression of responses in the absence of reward is impeded. A parallel is drawn with those effects found classically after surgical lesion to the hippocampus.     

Future and potentiality in the psychoanalytic process

A perspective is delineated on the dimension of the future in the psychoanalytic situation. Clinical manifestations are presented of the tension between actuality and potentiality that characterizes the treatment situation. This tension, an aspect of the intersubjective field that exists between patient and analyst, involves the analyst's hopes, expectations, anticipations, sense of purpose, and therapeutic intent, facets of the analyst's subjectivity that affect the clinical process. The question of the patient's individuality and autonomy is raised in the context of the notion of the "true self." To understand potentiality in the clinical situation, it is argued, the intersubjective emphasis on the inevitable mutual influence between analyst and patient must be complemented by a view of the self as emerging from within and gaining coherence through the unfolding of inherent dispositions and potentialities.     

Proactive behavioral effects of theta-blocking septal stimulation in the rat

The induction of hippocampal theta rhythm using low-frequency septal stimulation has been shown to proactively (1) facilitate the acquisition and (2) increase resistance to extinction of a food-rewarded fixed-ratio (FR) bar-press response (Holt & Gray, Quarterly Journal of Experimental Psychology, 35B, 97-118, 1983). Both (1) and (2) are also seen after septal lesions. This suggests that Holt and Gray's (1983) results may have been due either to stimulation-produced theta waves (the "theta" hypothesis), or a small septal lesion produced by the stimulating current (the "lesion" hypothesis). Both hypotheses were tested in the present experiment using high-frequency septal stimulation. In one of two treatment conditions male Sprague-Dawley rats, chronically implanted with a bilateral septal stimulating electrode and a unilateral bipolar hippocampal recording electrode, received (1) trains of continuous pulses at 77 Hz which blocked the hippocampal theta rhythm, or (2) trains of pulses at 100 Hz interrupted by a 30-msec interval at a frequency of 7.7 Hz. Control animals were implanted but not stimulated. Acquisition of a discrete-trial bar-press response on a fixed ratio 5 reinforcement schedule immediately followed the treatment phase. After 15 days' acquisition all animals were extinguished over the subsequent 12 days. Results indicated that both types of septal stimulation reduced resistance to extinction of barpressing; theta-blocking stimulation produced the greater effect. Theta-blocking stimulation retarded the acquisition of bar-pressing in the early stages of training. These overall results are exactly opposite to those produced by low-frequency (7.7 Hz) theta-driving septal stimulation (Holt & Gray, 1983) and contrary to the predictions of the lesion hypothesis. Furthermore, these findings support the idea that long-term changes in behavior may depend on stimulation-produced changes in the hippocampal theta rhythm.     

Age-dependent changes in olfactory-mediated behavioral investigations in the male rat.

In the present experiment male Sprague-Dawley rats at three different ages (young, middle-aged, and old) were tested in a series of olfactory-mediated behavioral tests. The amount of ano-genital investigation directed to receptive females by old rats was significantly reduced compared to that of young and middle-aged animals. In contrast, general body investigation of receptive females was similar among the three age groups. The amount of anogenital investigation directed to nonreceptive females or immature male rats indicated significant differences only between young and old rats, with values from middle-aged rats being intermediate and not significantly different from either of the two extreme groups. General body investigation of nonreceptive females and immature males did not differ among the three age groups. Old rats showed the best performance in a location of buried food test with latencies to locate food approximately one-half that obtained from young and middle-aged rats. Measures of general locomotor activity indicated significantly greater values from young compared to middle-aged and old rats, with the latter two showing very similar levels. These results demonstrate clear discriminatory differences in olfactory-mediated behavioral performance of the male rat as a function of the specific test and age of the animal. Overall, the results suggest that olfactory-mediated behaviors related to reproduction appear more sensitive to age-related declines, while behavior related to food procurement is more minimally affected.     

Modeling behavioral recovery following lesion induction in the rat dentate gyrus

Unilateral entorhinal lesions have enjoyed immense popularity as a model of recovery from damage. In part, the popularity has been supported the laminar organization of the hippocampal formation, which allows for the dissection of the contribution of individual afferent pathways to the recovery process. The commissural/associational pathway is of particular interest, since electrophysiological and gross anatomical data, although limited, have correlated sprouting in this pathway with behavioral recovery. Unfortunately, information relating recovery to synaptic structure is lacking. Addressing this issue, two analyses were conducted. Initially, a quantitative review of the literature reporting behavioral recovery following this type of lesion was conducted using meta-analytic techniques. Using this detailed information across decades of research, multiple linear regression analysis was conducted to address whether the morphological correlates of recovery could predict behavioral recovery. This resulted in an equation relating morphology and recovery that stood up well to several diagnostic tests. Moreover, this model suggests that synapse structure (in particular, synapse size and curvature, as well as terminal compartmentalization and the density of multi-synaptic terminals) holds a greater potential to predict behavioral recovery than increases in synapse number, which is typically seen as the optimal anatomical measure of recovery. This initial attempt to identify, quantify, and validate a model of lesion recovery is an important initial step in understanding how synaptic morphology may help mediate recovery of function.     

Mesencephalic participation in the control of sexual behavior in the female rat

Electric stimuli applied to both pudendal nerves evoked field potentials, unit responses, and multiunit responses in the ventrolateral midbrain, in and around the peripeduncular nucleus. Bilateral lesions placed in this region suppressed sexual behavioral responses (lordosis and courting behavior) of ovariectomized rats primed with 5, 10, 100, and 1,000 microgram of estradiol benzoate and 2 mg of progesterone per kilogram of body weight. It is proposed that the region in question represents a relay station for the integration of sensory and endocrine information concerned in the control of receptive sexual behavior in the female rat.     

The role of neuropeptide Y in the amygdala on corticotropin-releasing factor receptor-mediated behavioral stress responses in the rat

Neuropeptide Y (NPY) is one of the most abundant peptides in the brain and has been shown to be a critical regulator of emotionality, most notably for its effect in decreasing anxiety-like behaviors. The stress response in both humans and animals has been shown to involve a cascade of biological events initiated by corticotropin releasing factor (CRF), another centrally acting peptide. Interestingly, NPY and CRF are present in similar brain regions mediating stress responses and may act in an opposing fashion. The basolateral nucleus of the amygdala (BLA) is a distinct division of the amygdala and contains CRF receptors and the highest concentration of NPY neurons. The current study investigates the behavioral effects in rodents when NPY is injected directly into the BLA prior to the pharmacological stressor, urocortin I (Ucn; a CRF receptor agonist) or the emotional stressor, restraint. The animals that underwent restraint were evaluated in the social interaction (SI) test, while those injected with Ucn into the BLA were assessed in the two floor choice test, a modified version of the conditioned-place avoidance paradigm. The results showed that injections of NPY into the BLA prior to Ucn significantly blocked the development of the avoidance behavior in the two floor choice test and the decrease in SI time that is usually seen following restraint stress. These results provide further support that an interaction between NPY and CRF within the BLA may be critical for maintaining a normal homeostatic emotional state.     

Acute stress persistently enhances estrogen levels in the female rat

Here we tested whether exposure to either tailshock or swim stress alters ovarian hormone levels, estrogen and progesterone, in females and whether the effects are persistent. Adrenal hormone levels were also measured in males and females. Estradiol levels were elevated in unstressed females during proestrus relative to females in other stages of estrous, and exposure to the stressors enhanced estradiol beyond basal levels. For females stressed during diestrus 2, estradiol levels were elevated immediately after stressor cessation and up to 24 hrs. Exposure to tailshock, but not swim-stress, transiently enhanced progesterone in females stressed during the stage of proestrus and estrus. Glucocorticoid levels were elevated in response to both stressors and were supraelevated in females under both basal and stress conditions relative to males, particularly in blood from females exposed to acute swim stress. These results indicate that exposure to a relatively acute stressful event immediately and persistently enhances serum estradiol and are discussed in the context of reports that exposure to the same stressors immediately and persistently impairs associative learning in the female rat.