Gonadal hormones and sex differences in nonreproductive behaviors in rodents: organizational and activational influences

Sex differences in vasopressin neurons in the bed nucleus of the stria terminalis by in situ hybridization

To determine whether a sex difference exists in the biosynthetic capacity of vasopressingergic (AVP) neurons in the bed nucleus of the stria terminalis (BNST), we have used in situ hybridization and quantitative autoradiography to measure propressophysin messenger RNA levels in these cells from adult male and female rats. We have found that significantly more (p less than 0.01) neurons are labeled in male rats than in female rats and that these labeled cells averaged more grains/cell (p less than 0.05) in males than in females. Therefore, the sexual dimorphism of AVP pathways in the BNST and lateral septum recently shown by immunohistochemistry results from a sex difference in the biosynthetic capacity of these AVP neurons.

Sex-dependent effects of inescapable shock administration on behavior and subsequent escape performance in rats

Stress-induced behavioral disturbances have widely been used as animal models of depression. Sex differences, however, have rarely been studied, even though evidence is available to show that males and females react differently after presentation of aversive stimuli. The present experiment investigated the behavioral effects of inescapable shocks on subsequent shuttlebox-escape performance in male and female rats. Exposure to inescapable shocks resulted in suppression of activity during shock administration, which was more severe when shock duration was increased. Females showed less behavioral suppression and they were also more active than males during the adaptation phase, prior to shuttlebox-escape training. Shuttlebox-escape performance was less affected in females than in males compared to that of nonshocked control subjects. Shock duration as a factor only affected efficiency of shuttlebox-escape performance in males.

Operant conditioning of response variability in male and female Wistar rats

It has previously been suggested that some of the behavioral differences between the sexes in food motivated operant procedures may be a function of the fact that males are more likely than females to exhibit stereotyped behavior. If such is the case, then it might be expected that behavioral variability is more easily conditioned in females than in males. The present experiment was designed to investigate this notion. Male and female Wistar rats were trained to respond in a procedure in which response variability was explicitly reinforced. In this procedure subjects had continuous access to two response levers in the experimental chamber. In the first experimental condition, each sequence of four responses was followed by the presentation of a food pellet, if the sequence differed from the two sequences which preceded it (Lag 2). Time-out was presented when such was not the case. During time-out the levers were retracted from the chamber and all stimulus lights were extinguished for 4 sec. In subsequent experimental conditions, subjects had to produce four-response sequences which differed from the preceding four, eight and sixteen sequences respectively (Lag 4, 8, 16). Response sequences were classified by the number of switches between levers. Behavioral variability increased as the lag requirement was increased, showing that variability is a conditionable dimension of behavior. Differences between males and females were however not observed. These results thus contradict the previously reported finding that males exhibit more behavioral stereotypy than females. It is suggested that procedural variables may account for these seemingly contradictory findings.

Perseverative responding in male and female Wistar rats: effects of gonadal hormones

Response perseveration was investigated in an experimental procedure which has previously been shown to be sensitive to pharmacologically induced behavioral perseveration and response stereotypy. Different groups of intact, gonadectomized, and gonadectomized plus chronically testosterone-treated male and female Wistar rats were exposed to this procedure in which reinforcers were randomly assigned to one of two levers in an operant chamber. One response on the lever to which the reinforcer was assigned was sufficient to produce a food pellet. Response perseveration, defined as the percentage of trials on which more than one response on the lever not selected for reinforcement was made prior to switching to the selected lever was highest in testosterone-treated subjects. Females made more responses on the lever which had been selected for food on the preceding trial, suggesting that females may be more sensitive than males to the consequences of their behavior. This behavioral difference between the sexes may be mediated by the male hormone testosterone.

Perinatal aromatase activity in male and female rats: effect of prenatal alcohol exposure

Fetal alcohol exposure has been shown to produce long-term feminizing and demasculinizing effects on male rat behaviors which are organizationally dependent upon perinatal androgen levels. Such exposure has previously been shown to suppress the normal surge of testosterone during the critical prenatal period. Since defeminization of male rat behavior is dependent upon estrogen derived from the aromatization of testosterone in brain, brain aromatase activity was measured during the perinatal period in males and females exposed to alcohol beginning on Day 14 of gestation. Aromatase activity was measured in whole hypothalamus of fetuses from Day 16 through 20 of gestation and in the hypothalamic preoptic area and amygdala of animals 6-12 hr postparturition. Hypothalamic aromatase activity was elevated in fetal alcohol exposed males compared to controls on Days 18 and 19 of gestation and on postnatal Day 1. No effect of prenatal alcohol exposure was found in females. A sex effect in aromatase activity in the amygdala was evident on Day 1 when activity was found to be greater in males than females. Overall, these findings indicate that fetal alcohol exposure will elevate regional brain aromatase activity in males, but not females during the perinatal period of neurobehavioral sexual differentiation.

Adaptation of female rats to stress: shift to male pattern by inhibition of corticosterone synthesis

In a previous study, male rats showed behavioural deficits after a single restraint stress but not after 5 daily restraint periods (i.e. adaptation had developed): female rats although less affected by single restraint failed to adapt over the same time course. This sex difference was associated with the male but not the female rats showing enhanced behavioural responses to the 5-HT agonist 5-methoxy-N,N-dimethyltryptamine (5-MeODMT) after 5 restraint periods. In the present study, the role of the greater increases of plasma corticosterone in stressed females in these sex differences was studied. The corticosterone synthesis inhibitor metyrapone (75 mg/kg i.p.) was given to attenuate the rise of corticosterone to a level typical of stressed males. This resulted in the behavioural deficits of the female rats being shifted in the direction of the male pattern. Thus, their deficits in open field activity and food intake after single and repeated stresses were potentiated and opposed respectively. The latter effect was associated with increased responses to 5-MeODMT. Metyrapone alone was without significant effect. Brain regional 5-HT metabolism was unaffected. The results are consistent with corticosterone facilitating adaptation to single restraint but impairing adaptation to repeated restraint. As failure to adapt to repeated stress is an animal model of depression, results as a whole suggest that increased corticoid levels and decreased 5-HT functional activity may have a role in the development of the illness and its greater incidence in women.

Medroxyprogesterone acetate and tamoxifen do not decrease aggressive behavior in CF-1 male mice

Intact CF-1 male mice were given daily injections of either medroxyprogesterone acetate (MPA, an antiandrogen), tamoxifen (TAM, an antiestrogen), or the two drugs in combination and tested for aggressive behavior toward bulbectomized stimulus males. None of the treatments decreased fighting behavior over a 20-day test period and the presence of TAM led to increased aggression even in the presence of MPA. Testis weight was reduced by MPA while both compounds decreased seminal vesicle weight. The mechanisms involved in the observed effects are considered as well as the implications of the results for the clinical use of these compounds as modulators of testosterone-facilitated behaviors.

Testosterone alters the behavioral response of the medial preoptic-anterior hypothalamus to microinjection of arginine vasopressin in the hamster

The medial preoptic-anterior hypothalamus (MPOA-AH) is necessary for expression of several testosterone-dependent behaviors including a form of hamster scent marking, called flank marking. Since arginine vasopressin (AVP) plays a critical role in the control of flank marking by the MPOA-AH the present study examined whether testosterone can influence the amount of flank marking produced by AVP microinjected into the MPOA-AH. The dose-dependent induction of flank marking by AVP was found to be reduced by approximately 50% in castrated male hamsters when compared to intact or testosterone-treated castrates. These data demonstrate that testosterone influences the amount of flank marking produced by AVP within the MPOA-AH.

Memory in male and female Wistar rats: effects of gonadectomy, and stimulus presentations during the delay interval

The present experiment was designed to investigate the effects of gonadectomy on the response accuracy of male and female Wistar rats in an operant delayed spatial response alternation procedure. Subjects were exposed to 3 randomly presented delay intervals during each experimental session (15, 30 and 60 s). Response accuracy decreased as a function of the duration of the delay interval. Prolonged exposure to the experimental procedure differentially affected the behavior of intact and gonadectomized males and females. Intact males showed a more rapid increase in response accuracy as compared to any of the other groups of subjects, but differences in steady-state behavior were not observed. The effect of stimulus presentations during the delay interval on the alternation accuracy of intact and gonadectomized male and female Wistar rats was studied in a second experimental condition. The presentation of stimuli during the delay interval equally affected response accuracy of intact and gonadectomized subjects at all delay interval durations. Differences between the sexes, or between intact and gonadectomized subjects were not observed in the second experimental condition. The results of the present experiments thus suggest that intact and gonadectomized male and female Wistar rats do not differ with respect to memory as measured in operant delayed spatial alternation tasks, since both males and females were equally susceptible to the presentation of stimuli meant to disrupt ongoing memory processes.

Lack of prenatal testosterone surge in fetal rats exposed to alcohol: alterations in testicular morphology and physiology

Pregnant Sprague-Dawley rats were administered a liquid alcohol diet (35% ethanol-derived calories), a pair-fed isocaloric diet, or dry food pellets beginning on Day 14 of gestation and continuing until parturition. Testosterone levels in male fetuses were measured on Days 17 through 20 of gestation. The normal surge of testosterone on Days 18 and 19 was present in controls, but notably absent in male fetuses exposed to alcohol. Light microscopic examination of the testes at birth revealed a reduction in the number of leydig cells in the alcohol exposed group and the presence of a large number of vacuoles in the seminiferous tubules. In vitro studies of fetal testes at 18 and 22 days of gestation revealed that this in utero alcohol exposure regimen produced a marked insensitivity to rat LH (10 ng/ml) stimulation of testosterone secretion compared to controls. The response to ethanol (160 mg/dl) in alcohol exposed testes was characterized by a long-lasting suppression of testosterone compared to a large increase observed in control testes. No differences in anogenital distance were observed among the groups. Together, these data may explain some of the long-term feminizing and demasculinizing effects on reproductive and nonreproductive sexually dimorphic behaviors observed in adult males prenatally exposed to alcohol.

The behavior of male and female Wistar rats pressing a lever for food is not affected by sex differences in food motivation

Male rats both eat more and weigh more than females. Differences in food intake and body weight result, at least partly, from differences in gonadal hormone secretions. The present experiments were designed to investigate whether sex differences in food motivation might contribute to the behavioral differences observed when food-deprived male and female rats are exposed to appetitively motivated operant learning tasks. Male and female Wistar rats were exposed to different progressive ratio schedules of reinforcement which have been shown to generate reliable indices of 'motivational' conditions. In progressive ratio schedules, subjects are required to make a systematically increasing number of responses for each successive reinforcer, until the requirement becomes so large that the subjects stop responding. Expt. Ia was designed to investigate whether or not food-deprived males would be more motivated than food-deprived females to obtain food. Expt. Ib investigated whether gonadectomy might differentially affect food motivation of male and female rats exposed to a progressive ratio schedule of reinforcement. Motivational differences between males and females were not observed. Males and females obtained an equal number of reinforcers, while differences in the total number of responses and response rate were not observed. Gonadectomy did not affect the total number of responses in the final completed ratio. The results of the present experiments do therefore not support the hypothesis that sex differences in food motivation might underlie sex differences in behavior when food-deprived male and female rats are exposed to operant schedules of positive reinforcement.

Effects of estradiol on cerebral cortical neurons and their responses to adenosine

The effects of iontophoretically applied 17 alpha- and 17 beta-estradiol on the spontaneous firing of, and actions of purines (adenosine, adenosine 5'-N-ethylcarboxamide) on, neurons in the rat cerebral cortex have been determined. Both steroids, applied as acetate, sulphate or hemisuccinate esters, depressed the spontaneous firing of approximately half of the neurons tested. 17 beta-Estradiol potentiated the inhibitory actions of adenosine on some neurons (26%) and antagonized the effects of adenosine on others (42%). 17 beta-Estradiol antagonized the inhibitory actions of adenosine 5'-N-ethylcarboxamide on 76% of the neurons tested, but did not enhance the actions of this uptake resistant adenosine analog. 17 alpha-Estradiol potentiated the actions of adenosine and adenosine 5'-N-ethylcarboxamide but failed to antagonize either purine. It is suggested that the potentiating effects of both stereoisomers on adenosine are a result of their ability to block adenosine uptake and that 17 beta-estradiol is also able to antagonize the actions of these purines. Antagonism of the effects of endogenously released adenosine may account for the excitant actions of 17 beta-estradiol on the central nervous system.

Role of gender in the behavioral effects of peripheral sympathetic ingrowth

Following cholinergic denervation of the hippocampal formation, peripheral sympathetic nerves originating from the superior cervical ganglia grow into the hippocampus. As gender is known to alter the anatomy of hippocampal sympathetic ingrowth, we assessed the effect of this variable on the behavioral recovery following ingrowth. Adult male or female rats were trained on a standard version of a radial-8-arm maze task until they reached a specific learning criterion. Animals from each sex then underwent one of three surgical procedures: sham surgery, medial septal lesions plus superior cervical ganglionectomy, or medial septal lesion plus sham ganglionectomy. Reacquisition of the maze was then assessed. Prior to surgery, male animals acquired the task significantly faster than female animals. Following surgery male and female rats recovered overall performance at similar rates. However, marked group differences were observed. In males, the control group recovered faster than the group with medial septal lesion plus ganglionectomy, which recovered faster than the medial septal lesion group. In females, the control group recovered faster than the medial septal lesion group, which in turn recovered faster than the medial septal ganglionectomy group. The results of this study clearly demonstrate that gender can influence the behavioral effects of hippocampal sympathetic ingrowth. We believe that this is the first report in which gender has been shown to alter the behavioral effect of a neuronal reorganization.

Investigation into sex-related differences in locomotor activity, place learning and passive avoidance responding in NMRI mice

Learning abilities of young adult (5-6 weeks) male and female NMRI mice were compared in two tasks involving cognitive functions, namely spatial learning in a water maze and passive avoidance responding. Locomotor activity was also monitored as a putative bias for the results obtained in these learning tests. No sex-related difference was observed either in avoidance responding or in spatial learning using a procedure with the same point of departure throughout testing in the water maze. However, in this test, using a procedure with 3 different points of departure in randomized order day after day, female mice performed better than male mice. The difference was statistically significant on the last acquisition day but was not sustained during a retention trial 72 hr later. Since no sex differences in locomotor activity were observed, the learning effects cannot be attributed to a difference in general activity level.

Effects of early postnatal gonadal steroids on acquisition and extinction of a single alternation response in discrete-trials lever pressing

The present report studies the effect of sex on the acquisition and extinction of a single alternation schedule of reinforced (R) and nonreinforced (N) trials in a Skinner box. In addition to the investigation of the basic sex differences in Experiment 1, the effects of early gonadal steroids treatment and postpubertal gonadectomy of male and female rats were examined in Experiments 2 and 3, respectively. Both acquisition and extinction performances were evaluated by means of latency. In Experiment 1, males showed higher latencies on N trials and extinguished faster than female rats. In Experiment 2, female androgenization and male orchidectomy on day one after birth reversed the direction of the sex differences found in the previous experiment. However, postpubertal gonadectomy (Experiment 3) does not affect the performance of male and female rats.

Estrogen formation in the mammalian brain: possible role of aromatase in sexual differentiation of the hippocampus and neocortex

Recent studies suggest that sex differences in cognitive function may involve effects of circulating androgens on the developing cerebral cortex and hippocampus. The mechanism of these effects is not understood. In rhesus monkeys, aromatase activity is present in the hippocampus and several areas of the cerebral cortex during late fetal and early postnatal life. Similarly, work in rats and mice indicates that the hippocampus and cerebral cortex may be capable of estrogen biosynthesis during early development. These results are consistent with the hypothesis that the actions of androgens on the developing cerebral cortex and hippocampus may involve local estrogen-mediated effects similar to those responsible for differentiation of the hypothalamic mechanisms controlling reproductive function.

Sex steroid effects on extrahypothalamic CNS. I. Estrogen augments neuronal responsiveness to iontophoretically applied glutamate in the cerebellum

The purpose of this study was to test whether 17 beta-estradiol (E2) could alter neuronal activity or responsiveness to iontophoretically applied amino acid neurotransmitters in an area not reported to contain classical E2 receptors. Such a region is the cerebellum, which was selected as a model system for these studies because it has been well characterized electrophysiologically. Extracellular activity of cerebellar Purkinje neurons was recorded from urethane-anesthetized, adult, ovariectomized rats using multibarrel glass micropipets. Spontaneous firing rate and responses of single units to microiontophoretic pulses (10 s pulses every 40 s) of GABA (10-50 nA) or glutamate (GLUT, 3-40 nA) were examined before, during and after iontophoretic (0.25 mM 17 beta-estradiol hemisuccinate) or jugular i.v. (100, 300 or 1000 ng/kg 17 beta-estradiol) administration of E2. Both modes of E2 administration resulted in a significant increase in Purkinje cell excitatory responses to GLUT, independent of the direction of change in spontaneous firing rate. This effect was seen as early as one minute after iontophoretic application of E2 and 10-40 min following i.v. E2. In all cases, recovery to the control level of response was not observed by 2 h following E2 administration. 17 alpha-E2 (300 ng/kg) resulted in a less pronounced, transient increase in GLUT response, while a lower dose (100 ng/kg) did not have any effect. Prior administration of the anti-estrogen tamoxifen did not prevent any of the observed E2 effects. In addition, estrogen-priming did not alter E2-induced potentiation of GLUT responses. In contrast to the effect of E2 on GLUT responsiveness, GABA-mediated inhibition of Purkinje cells was either increased, antagonized or unchanged following E2 application. In summary, this study suggests the hypothesis that circulating levels of E2 may alter neuronal sensitivity to specific neurotransmitter substances within the cerebellar circuitry.

The influence of estrous cycle and intrastriatal estradiol on sensorimotor performance in the female rat

The influence of estrous cycle and intrastriatal implants of 17 beta-estradiol (17 beta-estradiol). 17 alpha-estradiol (17 alpha-estradiol) or cholesterol on the number of footfaults made by female rats traversing a narrow suspended beam was investigated. Female rats made fewer footfaults on estrus than on other days of the cycle. This was true when testing occurred during either the light or dark phase of the light:dark cycle. Intrastriatal implants of 30% 17 beta-estradiol for 6 hours resulted in a significant improvement in sensorimotor performance as soon as 4 hours after hormone implant and persisting for days. In contrast, intrastriatal implants of either 30% 17 alpha-estradiol or cholesterol had no influence on performance. The extent of hormone diffusion away from the implant cannula was minimal, and the resulting concentration of 17 beta-estradiol in the striatum was less than 10 pg/mg. It is concluded that estradiol has a direct, stereospecific effect in the striatum that influences performance of a skilled motor act in the female rat.

Age- and sex-related induction of excessive grooming and "wet-dog" shakes by the codeinone RX 336-M in the rat

Peripheral administration of the dihydrocodeinone RX 336-M (6 mg/kg) stimulated vigorous "wet-dog" shakes and excessive grooming in young drug-naive rats. The effects of RX 336-M were greater in younger than in older animals of both sexes, and were greater in 39-day-old male rats than in female rats of the same age. In a second experiment, female rats were pretreated with testosterone benzoate (1 mg/kg/day) for 1 week prior to testing the effects of RX 336-M at 39 days of age. The sex hormone pretreatment enhanced the ability to RX 336-M to induce "wet-dog" shakes and excessive grooming in female rats. The results suggest that both sex- and hormone-dependent developmental status are critical in the display of the so-called "quasi-morphine withdrawal syndrome." The results imply, and are consistent with previous studies which suggest, that different neural mechanisms underlie the behavioral responses induced by ACTH and RX 336-M.

Activation of male-typical aggression by testosterone but not its metabolites in C57BL/6J female mice

Ovariectomized adult C57BL/6J mice were exposed to androgens, estrogens, or combined androgen-estrogen treatments and tested for the display of male-typical aggressive behavior toward olfactory bulbectomized stimulus males. Among the androgenic treatments (testosterone, dihydrotestosterone, or methyltrienolone) only testosterone, which, in contrast to the other androgens, can be aromatized, activated fighting behavior. In the second experiment, estradiol benzoate (EB) was totally ineffective as an aggression-promoting compound. Lastly, combined EB+dihydrotestosterone also did not induce male-like aggression. These data suggest that T itself may be capable of promoting aggression without undergoing aromatization or 5 alpha-reduction.

Sex differences in the sensitivity of CBA mice to convulsions induced by GABA antagonists are age-dependent

The administration of the GABA-blocking agents picrotoxin and bicuculline to adult (2.5-3 months old) CBA/HZgr mice resulted in the appearance of convulsions, the occurrence and/or lethality of which was greater in males than in females. The latency of picrotoxin-induced convulsions was also shorter in male mice. Strychnine, a drug which induces convulsions by blocking glycine receptors was equally effective in producing convulsions in both male and female adult mice. Unlike adult mice, young (20 days old) or old (2 years old) mice fail to display sex differences following the picrotoxin administration. Accordingly, the observed sex differences in the sensitivity of CBA mice to administration of convulsive agents are specific for the GABA system and present only in sexually mature, but not in immature or old animals.

Oxytocin stress responses are dependent upon emotionality

Comparison of posterior pituitary responses to stress in rat strains with contrasting emotionality has revealed an inverse relationship between oxytocin (OT) responses and emotional reactivity. The plasma OT and arginine-vasopressin (AVP) responses to stress were determined in two psychogenetically selected strains of rat, Roman high avoidance (RHA) and Roman low avoidance (RLA), RLA's being more emotionally reactive than RHA's. Following 1 min immobilisation stress, plasma levels of OT were significantly higher in RHA's compared to RLA's. This finding correlates with the previous demonstration of a sex difference in the OT stress response, females having a higher response than males. Plasma levels of AVP were not significantly modified by immobilization in either strain of rat. However, control levels of AVP were markedly raised in both male and female RHA's.

Behavioral differences between male and female Wistar rats on DRL schedules: effect of stimuli promoting collateral activities

Female rats are more active than males in open-field procedures. They also make fewer unreinforced responses than males on schedules which maintain low rates of responding (differential reinforcement of low rate responding, DRL). The addition of objects to promote collateral activities facilitates the acquisition of efficient DRL behavior. It was hypothesized that differences in activity levels might underlie the observed sex differences in DRL learning. If females are more likely than males to engage in activities other than lever pressing, the addition of objects to the experimental environment should not as much influence the behavior of females than that of males. Male and female rats were exposed to a DRL 15 sec or a DRL 30 sec schedule, either with or without objects to promote collateral activities. General activity was tested twice in an open-field procedure. Females showed higher activity levels than males in the open-field. They also acquired a DRL task more efficiently than males. The addition of objects facilitated the acquisition of efficient DRL performance in males, but not in females. The results of the present experiments, therefore, suggest that differences in general activity between male and female rats may underlie sex differences in some experimental paradigms.

Sex differences in response rates during random ratio acquisition: effects of gonadectomy

Sex differences in response rates were observed during acquisition of behavior on different random ratio schedules of reinforcement. Intact male rats responded at higher rates than intact female rats. Response rates of castrated males were found to be lower than response rates of intact males. Differences were not observed between intact and ovariectomized females.

Absence of behavioral differences between male and female rats in different radial-maze procedures

Male and female Wistar rats were exposed to different radial-maze procedures to determine whether or not behavioral differences would be observed. They were allowed free access to all arms of the maze in the first experimental condition, while they were confined between choices to the central platform for 1 and 15 sec during the second and third experimental conditions. In addition, separate, experimentally naive groups of males and females were exposed to the 15 sec confinement procedure. Female and male Wistar rats required an equal number of choices and equal amounts of time to successfully complete visits to eight different arms in all experimental conditions, whether they were experienced or not. Performance improved as training progressed. The results of the present experiments suggest that the previously observed behavioral differences between the sexes in different complex maze procedures, may not be a function of differences in visuospatial abilities, but of activity differences, which interact with the behavioral requirements of different experimental procedures.

Behavioral differences between male and female Wistar rats in food rewarded lever holding

Female rats are more active and explore more than males. In addition, females make fewer unreinforced responses on schedules which maintain low rates of responding (DRL). When general activity is high, subjects are more likely to engage in activities other than lever pressing. To test this hypothesis, male and female Wistar rats were trained to hold a response lever depressed for a minimum duration of 10 seconds. Reinforcement was delivered upon release of the lever. Females spent a significant smaller proportion of the total session time depressing the response lever than males. Differences between males and females in the number of unreinforced responses were not observed. Providing subjects with objects to promote collateral activities decreased the proportion of total session time subjects spent depressing the response lever for females, but not for males. An effect on the number of unreinforced responses was not observed.

Effects of prenatal testosterone propionate treatment on saccharin preference of adult rats exposed to ethanol in utero

Prenatal exposure to alcohol feminizes saccharin consumption patterns in adult male rats. To study the involvement of testosterone in this effect, testosterone propionate (TP) was administered to pregnant dams in an attempt to reverse that feminized saccharin consumption pattern in the male offspring. Female offspring were also studied to determine the effect of TP on saccharin preference in normal males and females. During the last week of gestation, dams were administered a liquid diet containing 35% ethanol derived calories, an isocaloric liquid diet containing no ethanol, or Purina Lab Chow. Half of the dams in each group received twice daily injections of TP, the other half were injected with the oil vehicle. Saccharin consumption of adult fetal alcohol exposed (FAE) males from dams administered oil or TP was significantly greater than controls, indicating that the feminized pattern of saccharin consumption of FAE males cannot be overcome with TP administration during the prenatal period. In controls, prenatal TP exposure alone was found to increase adult saccharin consumption in both sexes. Prenatal administration of TP was also found to markedly depress body weight of offspring of dams receiving the liquid diets compared to offspring from dams receiving the same diets plus oil injections. Body weights of offspring from TP or oil injected dams receiving the chow fed diets during pregnancy did not differ.