Biomedical subjects

N E van de Poll

Publications and source records attributed to N E van de Poll.

At least 37 records · Page 2Linked to original sources

PubMed1988

Effects of progesterone on open field behavior of food deprived ovariectomized female rats.

The effects of intraperitoneal progesterone administration on the open field behavior of ovariectomized female Wistar rats were studied in two experiments. Subjects were challenged with 5 different doses of progesterone (0, 10, 20, 40, 80 mg/kg body weight) during 5 successive days of open field testing (5 min a day) in the first experiment. Progesterone dose-dependently decreased rearing and object inspection, but did not affect total ambulation. In the second experiment food pellets were presented in the open field and subjects were repeatedly tested at regular intervals after progesterone administration on each of 5 consecutive testing days. Three doses of progesterone (0, 40, 80 mg/kg body weight) were administered during the final 3 days of the second experiment. Eighty mg/kg progesterone decreased rearing activity, but increased ambulation; motivation to retrieve food pellets was not affected. These effects of 80 mg/kg progesterone were observed at least as long as 2 hours after injection. Forty mg/kg progesterone did not produce such effects. These results, in conjunction with those of other experiments show that progesterone affects open field behavior in a way similar to central depressant drugs.

Animals↗

PubMed1988

Haloperidol, but not apomorphine, differentially affects low response rates of male and female Wistar rats.

Amphetamine-induced behavioral differences between male and female rats have been observed in tests for stereotyped behavior, locomotor activity and rotational behavior. It has also been shown that amphetamine differentially affects schedule-controlled behavior of male and female rats. The present experiments were designed to further investigate sex differences in sensitivity to agents which act upon the dopaminergic system. In the first experiment, male and female rats responding on a schedule which maintained low response rates were challenged with different low (less than 0.5 mg/kg) doses of apomorphine. Low doses of apomorphine act on the dopamine receptors on the dopaminergic terminals themselves to inhibit the release of endogenous dopamine. In the second experiment, the same subjects were given different doses of haloperidol, which selectively blocks the post-synaptic dopamine receptors. The results of the present experiments showed that haloperidol, but not apomorphine, differentially affected the behavior of male and female subjects. A behavioral difference between the sexes was thus observed when post-synaptic dopamine receptors were blocked by a dopamine antagonist, but not when dopaminergic stimulation of post-synaptic dopamine receptors was reduced by pre-synaptic inhibition of dopamine release. These results suggest a role for post-synaptic receptor mechanisms in mediating sex differences in sensitivity to dopaminergic agents, although other possible mechanisms remain to be investigated.

Animals↗

PubMed1988

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.

Animals↗

PubMed1988

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.

Animals↗

PubMed1988

Effects of lesions of the sexually dimorphic nucleus on sexual behavior of testosterone-treated female Wistar rats.

Discrete bilateral lesions were placed into the sexually dimorphic nucleus (SDN) of the medial preoptic area (MPOA) of ovariectomized female Wistar rats, chronically treated with testosterone (T). Effects of these lesions upon masculine and feminine sexual behavior were studied by comparing the results of pre- and postoperative tests, using sham-operated and unoperated females as controls. Bilaterally-lesioned and, to a lesser extent, unilaterally-lesioned females, showed a marked and significant reduction of masculine sexual behavior (i.e., mounting), especially in the first postoperative tests. Feminine sexual responses, i.e., receptive and proceptive behavior, although slightly lower in bilaterally-lesioned females, did not change significantly. Sexual partner preference, operationalized as the choice between a receptive female and a sexually active male, remained unaffected by the lesions. Plasma levels of testosterone were similar in the various groups. It is concluded that the SDN may be functionally implicated in the control of masculine sexual behavior in T-treated females.

Animals↗

PubMed1988

Acquisition of conditional associations and operant delayed spatial response alternation: effects of lesions in the medial prefrontal cortex.

In this article 8 male Wistar rats received bilateral lesions of the medial prefrontal cortex, whereas another 8 rats were control operated. Three weeks after surgery, they were exposed to an autoshaping procedure in which the insertion of a lever into the experimental chamber (conditioned stimulus) always preceded the delivery of a response-independent food pellet (unconditioned stimulus). Subjects with lesions acquired this conditional association faster than control-operated subjects as evidenced by the fact that they were more likely than control-operated subjects to contact the conditioned stimulus at higher rates. Locomotor activity, observed in a standard open-field preceding autoshaping sessions, decreased for both groups of subjects with repeated exposure to the open-field, whereas differences between groups were not observed. The same subjects were also exposed to an operant delayed spatial response alternation procedure in which they were required to alternate responding between two levers that were inserted into the experimental chamber after delay intervals of either 5, 10, or 20 s had elapsed. Alternation response accuracy of both subjects with lesions and control subjects decreased as a function of the duration of the delay interval, but control-operated subjects responded more accurately than did lesion subjects at each interval duration. Response accuracy increased with prolonged training for both groups of subjects, but faster for control-operated than for subjects with lesions.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1987

Effects of pentobarbital and progesterone on random ratio responding in male and female rats.

Intact male and ovariectomized female rats were trained to lever press under a random ratio (RR) schedule of food reinforcement. Effects of different doses of pentobarbital (1-16 mg/kg) and progesterone (10-80 mg/kg) on response output were studied. Low doses of pentobarbital increased responding, high doses decreased responding. Sex differences were observed in the rate-decreasing effects of high doses of pentobarbital. Progesterone increased the response rate of ovariectomized females, but did not affect responding in intact males.

Animals↗

PubMed1987

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.

Animals↗

PubMed1987

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.

Animals↗

PubMed1987

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.

Animals↗

PubMed1987

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.

Analysis of Variance↗

PubMed1987

Discriminative stimulus properties of pentobarbital and progesterone in male and female rats.

Intact male and ovariectomized female rats were trained to discriminate 12 mg/kg pentobarbital from physiological saline. Generalization tests with different doses of pentobarbital did not reveal significant sex differences in the pentobarbital generalization gradient. Different doses of progesterone produced a generalization gradient to pentobarbital in ovariectomized females, but not in intact males. The results of the present experiment thus suggests that systemic administration of progesterone produces a "pentobarbital-like" stimulus in ovariectomized female rats, but not in intact males.

Animals↗

PubMed1987

Sexual experience and preference for males or females in the female rat.

The influence of sexual experience on preference behavior was investigated in adult female rats. In the first experiment, preference behavior for sexually active males versus estrous females was investigated in female rats who were experienced with mounting behavior. Preference of these mount experienced females was compared to preference of females who were naive in this respect. Mount experience with estrous females induced a female-directed preference in ovariectomized female rats, irrespective of whether the females were treated with OIL or with testosterone-propionate (500 micrograms TP, injected once 48 h prior to testing). Sexually naive, OIL-treated females did not show a preference for males or females, but TP induced a preference for a male. Individual differences in mount frequency were not correlated with preference behavior. In the second experiment, the influence of experience with feminine sexual responses on preference behavior was investigated. OIL-treated and TP-treated females oriented equally toward males and females when they had been given the opportunity to copulate with males prior to the preference tests. The results strongly suggest that prior sexual experience is an important determinant of preference behavior. The female's behavior during sexual interactions was, however, not predictive of later preference.

Animals↗

PubMed1986

Vasopressin has general rate-decreasing effects on schedules maintaining either high or low response rates.

Male and female Wistar rats were treated with different doses of vasopressin (0.05, 0.25, 1.25, 3.75 and 6.25 micrograms/kg) after responding had stabilized on either a differential reinforcement of low rate 15 s (DRL 15 s) or a differential reinforcement of high rate 0.75 s (DRH 0.75 s) schedule of reinforcement. Low to moderate doses of vasopressin did not affect response rates, response efficiency or the number of reinforcers obtained during vasopressin sessions on both the DRL and DRH schedules. Administration of 6.25 micrograms/kg vasopressin reduced low response rates and the number of reinforcers obtained during vasopressin sessions, but increased response efficiency. High response rates and response efficiency were reduced after administration of 3.75 and 6.25 micrograms/kg vasopressin, while the number of reinforcers obtained during vasopressin sessions was reduced at 6.25 micrograms/kg. Sex differences in the effects of vasopressin were not observed on either schedule.

Animals↗

PubMed1986

d-Amphetamine differentially affects low, but not high response rates of male and female Wistar rats.

The present experiments investigated sex differences in the effects of d-amphetamine on schedule-controlled behavior. Male and female Wistar rats were exposed to either a differential reinforcement of low rate 15 s schedule, or a differential reinforcement of high rate 0.75 s schedule and challenged with different doses of d-amphetamine (0.2, 0.4, 0.8, 1.6 and 3.2 mg/kg). d-Amphetamine in low to moderate doses increased low response rates. High doses of d-amphetamine decreased low and high response rates in both males and females. The response rate increasing effects of d-amphetamine on low baseline rates were significantly higher for females than for males. Sex differences for high baseline rates were not observed. The results of these experiments show not only that hormonal and neurochemical variables influence the effects of d-amphetamine administration on schedule-controlled behavior, but also that environmental contingencies maintaining the behavior can modify these effects.

Animals↗

PubMed1986

Attractivity of male and female rats which are hormonally manipulated during early development and in adulthood.

Attractivity is one aspect of female sexuality relevant for the understanding of male-female sexual interactions. In a previous study, it was shown that intact males were equally attracted to early androgenized, gonadally intact females as to normally developed, estrous females. The present study was designed to investigate in what way hormones given in adulthood might influence attractivity of early androgenized females in adulthood. Specifically, we compared the attractivity of neonatally androgenized females (NeoTP) to the attractivity of normally developed females (NeoOIL), neonatally castrated males (NeoCASTR), and neonatally sham-castrated males (NeoSHAM) when different groups received either OIL, estradiol benzoate (EB) or testosterone propionate (TP) in adulthood. The male's preference to stay in the vicinity of one incentive in favor of the other was taken as an index of attractivity. The results show that, under the present hormonal conditions, NeoTP-females are generally less attractive than NeoOIL-females, more attractive than NeoSHAM-males, and equally attractive as NeoCASTR-males. TP-treated androgenized females were found to be equally attractive as TP-treated NeoSHAM-males. It is concluded that, relative to normally developed females, androgenized females become less attractive when the endogenous secretion of sex steroids is artifically controlled by gonadectomy and/or by administration of fixed amounts of sex steroids.

Animals↗

PubMed1986

Effects of testosterone, estrogen, and dihydrotestosterone upon aggressive and sexual behavior of female rats.

Groups of female TMD rats were treated either with estradiol benzoate (EB), dihydrotestosterone propionate (DHTP), testosterone propionate (TP), EB + DHTP (EB/DHTP), or with oil. These groups of females were tested for social aggression and for masculine and feminine sexual behavior. In addition, patterns of masculine and feminine sexual responses during the aggressive encounters, were investigated. TP-treated females of the same strain were used as opponents in the tests for aggression. In accordance with previous results, EB did not activate aggression whereas TP treatment resulted in a significant increase in aggression in females. Aggressive responses were activated by adding DHTP to EB, up to levels equal to those activated by TP. Sexual responses were observed in the tests for aggression as well as in tests for sexual behavior. The results indicated that feminine and masculine sexual responses were affected significantly by hormonal treatment. Mounting behavior in the test for aggression was activated by TP and by EB/DHTP. Lordosis and proceptive responses were inhibited in these groups as compared to EB-treated females, both in tests for aggression and in tests for sexual behavior. The results are consistent with the idea that dihydrotestosterone inhibits feminine and activates masculine sexual activity. The results also indicate that EB and DHTP synergistically activate aggression.

Aggression↗

PubMed1986

Sex-specific interactions between aggressive and sexual behavior in the rat: effects of testosterone and progesterone.

The influence of progesterone on sexual and aggressive behaviors during aggressive encounters was investigated in pairs of TP-treated male and female rats. Gonadectomized females, chronically injected with testosterone propionate (TP), showed low but consistent levels of feminine sexual behavior which alternated with aggression. Progesterone when given in addition to TP facilitated receptive and proceptive behaviors, but reduced levels of aggression. In TP-treated males, levels of aggression were the same as observed in TP-treated females. However, TP-treated males seldomly showed sexual behavior during aggressive encounters and additional treatment with progesterone did not affect their behavior. After the aggression tests, animals were tested in a social preference test in which an ovariectomized female cage mate and the opponent from the aggressive encounter served as incentives. Positive correlations between levels of aggression and social preference for an opponent were found in both sexes, although correlations only reached statistical significance when progesterone was given in addition to TP. These correlations were found in both sexes, despite the fact that group analysis revealed pronounced sex differences in social preference: males preferred to spend their time near ovariectomized female cage mates, whereas females divided their time equally among female cage mates and opponents.

Aggression↗