Biomedical subjects

B J Meyerson

Publications and source records attributed to B J Meyerson.

At least 19 recordsLinked to original sources

PubMed1997

Neonatal castration and adult responsiveness to testosterone in male rats: an interstrain comparison.

We have previously demonstrated that the spontaneously hypertensive rat (SHR) has a lower central nervous responsiveness to testosterone than its normotensive counterpart the Wistar-Kyoto rat (WKY). The adult psychoendocrine response capacity depends on a neonatal testosterone surge. On that basis, we compared the effects of neonatal endocrine manipulation on the adult responsiveness to testosterone in the SHR, WKY, and yet another breed of Wistar (Wi) male rats. Interstrain differences in testosterone-induced copulatory behavior at three different doses of testosterone propionate (TP) were investigated. Neonatal treatments were as follows: TP (0.25 mg/animal) given on postnatal days (PND) 0, 2, and 4 (SHR and Wi only) or castration PND 0, 10, or 50. Neonatal TP treatment impaired copulatory performance in the adult SHR but not in the Wi. Neonatal castration improved the responsiveness to TP in the SHR but less so in WKY, whereas no evident effects were seen in the Wi. No significant interstrain differences in plasma testosterone were observed 2, 6-12, or 24 h postpartum. The demonstrated interstrain differences suggest not only that the adult responsiveness to testosterone is established on the basis of the neonatal gonadal secretion as such but that this secretion is kept to an optimal level with respect to subsequent hormone-sensitive mechanisms.

Animals↗

PubMed1996

Difference in testosterone sensitivity in male spontaneously hypertensive (SHR) and Wistar-Kyoto rats (WKY).

The effects of castration and testosterone substitution on copulatory behavior and arginine-vasopressin (AVP) concentrations in the lateral septum (LS) were compared in the male spontaneously hypertensive rat (SHR) and its normotensive counterpart, the Wistar-Kyoto rat (WKY). The copulatory behavior was attenuated in the intact SHR and remained for a shorter time after castration than in the WKY males. A higher dose (1 mg/kg) of testosterone propionate (TP) was required in the castrated SHR to reestablish the copulatory behavior compared to the WKY (0.5 mg/kg). Following castration the main decline of AVP concentrations occurred over a period of 28 days. On postcastrational day 14, a time when approximately 50% of the initial AVP concentration remained, the decrease in the LS AVP content of the SHR surpassed that of the WKY. A dose-dependent increase of the AVP concentrations was achieved after 3 weeks of TP treatment (0.5 and 1.0 mg/kg, SC), which commenced 28 and 56 days after castration. The increase of AVP concentrations in the LS after a submaximal dose of TP (0.5 mg/kg) was less in the SHR than in the WKY. It is concluded that the gonadal hormone control of the copulatory behavior and AVP content in the terminal fields of the LS is characterised by a lower sensitivity in the SHR compared to the WKY. The data suggest that the low responsiveness to testosterone in the SHR comprises hypothalamic as well as extrahypothalamic neurons.

Animals↗

PubMed1996

Evidence for regulatory mechanisms maintaining testosterone-dependent AVP concentrations in terminal regions.

The dose and time relationships of testosterone treatment on arginine-vasopressin (AVP) concentrations of steroid-dependent vasopressinergic extrahypothalamic neurons were studied in the castrated male rat. The rate of AVP increase and the extent and limits of accumulation of AVP in the terminal regions were explored. Testosterone propionate (TP) treatment (0.25, 0.50, and 1.00 mg/kg SC given three times a week) started 15 weeks after castration. The periods of treatment lasted for 20, 40, and 80 days. AVP concentrations in the lateral septum (LS) and the lateral habenula (LH), determined by radioimmunoassay, increased dose and time dependently. A significant effect was achieved by 0.25 mg/kg and a maximum level obtained by 0.50 mg/kg after a 40-day period of treatment. The maximum concentration reached corresponded to the level of the intact animal. Increasing the dose or period of treatment did not raise the AVP concentration above that particular level. The data suggest regulatory mechanisms that maintain the AVP concentration in the terminal regions at a precastrational level.

Animals↗

PubMed1996

Strain, age and sex differences in the release of vasopressin from the pituitary: a study in the spontaneously hypertensive (SHR) and Wistar-Kyoto (WKY) rat.

The basal and depolarization-induced arginine-vasopressin (AVP) release from intact pituitaries of SHR and WKY rats was studied in vitro in a perfusion chamber. Differences associated to strain, sex and two age periods (pre-adult: 25-30 days of age; adult: 60-70 days of age) were assessed. The results show an enhanced AVP release in the adult male as well as female SHR compared to the WKY rat. The stimulated AVP release was also significantly higher in the preadult male SHR and indicated in preadult females SHR. No differences associated to strain in basal AVP release were detected at the age interval 25-30 days. The response to muscimol was increased in preadult female and male SHR rats compared to the WKY animals. It is concluded that the augmented depolarization-induced AVP release and sensitivity to muscimol in the SHR is not related to sex, and no apparent change in this pattern was associated to the transition between the juvenile and adult condition.

Age Factors↗

PubMed1993

The effects of long-term treatment with the 5-HT1A receptor agonist 8-OH-DPAT and the 5-HT2/1C receptor agonist DOI in the neonatal rat.

The rat pup ultrasonic call was used to study the effects of acute and long-term treatment with the 5-HT1A receptor agonist 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) and the 5-HT2/1C receptor agonist 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI) during the neonatal period. Acute administration of 8-OH-DPAT and DOI reduced the number of ultrasonic calls. The reduction induced by 8-OH-DPAT and DOI was antagonized by the 5-HT1A antagonist (S)-5-fluoro-8-hydroxy-2-(di-n-propylamino)tetralin ((S)-UH-301) and the 5-HT2 antagonist ketanserin, respectively. The long-term treatments were started on postnatal day 1. On postnatal day 7, the response of the long-term DOI-treated group was clearly attenuated in comparison to that of the acute DOI-treated group. In contrast, no tolerance to the effect of 8-OH-DPAT was achieved after an analogous treatment. The data indicate that there is a diversity in the ontogeny of the ability to develop tolerance to 5-HT1A agonists in comparison to 5-HT2/1C agonists.

8-Hydroxy-2-(di-n-propylamino)tetralin↗

PubMed1993

The influences of androgen on sociosexual behavior: a comparison between the spontaneously hypertensive (SHR) and the Wistar-Kyoto rat (WKY).

Differences in androgen-dependent forms of behavior and plasma testosterone levels in the spontaneously hypertensive rat (SHR) and its normotensive counterpart the Wistar-Kyoto rat (WKY) are described here. Copulatory behavior (solitary test to avoid influence of experience) and certain androgen-dependent elements of sociosexual orientation were significantly attenuated in the SHR compared to the WKY male rat. After castration, the differences in sociosexual orientation were no longer apparent. In contrast, differences in other behavioral elements, such as locomotion, were unchanged after castration. Plasma testosterone levels were significantly higher in the SHR than in the WKY male rats. Taken together, the behavioral and hormonal data suggest a decreased central nervous responsiveness to androgens in the SHR rats. This could lead to reduced androgen-dependent behavior, and possibly also to a decreased testosterone feedback control.

Animals↗

PubMed1993

GABA-A agonist muscimol inhibits stimulated vasopressin release in the posterior pituitary of Sprague-Dawley, Wistar, Wistar-Kyoto and spontaneously hypertensive rats.

Vasopressin-containing neurosecretory cells are partly regulated by GABAergic neurons present both at the hypothalamic and the pituitary level. In the present work, we compared GABA effects on vasopressin release from posterior pituitaries of Sprague-Dawley (SPD), Wistar (W), Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR). Release of vasopressin was studied in vitro by placing neurointermediate lobes in perfusion chambers. It was stimulated twice by 50 mM KCl (S1 and S2) and the ratio between the first and the second stimulation was calculated (S2/S1). The basal and stimulated release of vasopressin was enhanced in the SHR. There was no difference in vasopressin content in the pituitary between the WKY and the SHR but the levels were lower compared to the SPD rat. Muscimol, a GABA-A receptor agonist, was added during S2. Muscimol inhibited in a dose-dependent manner the stimulated release of vasopressin, with an ED50 about 3 microM. The effect of muscimol was not statistically different between the strains expressed in ratios. The actual inhibition was apparently greater in the SHR, as both basal and stimulated vasopressin release was larger.

Animals↗

PubMed1991

The novel 5-HT1A receptor antagonist (S)-UH-301 antagonizes 8-OH-DPAT-induced effects on male as well as female rat copulatory behaviour.

The 5-HT1A receptor agonist 8-hydroxy-2-(dipropylamino)tetralin (8-OH-DPAT) facilitates male rat copulatory behaviour but inhibits female rat copulatory behaviour. The effect of the novel 5-HT1A receptor antagonist (S)-5-fluoro-8-hydroxy-2-(dipropylamino)tetralin [S)-UH-301) on these 8-OH-DPAT-induced responses was tested. 8-OH-DPAT was given s.c. in a dose of 0.176 mumol/kg (50 micrograms/kg). The doses of (S)-UH-301 given s.c. were 1.76 mumol/kg (0.53 mg/kg) and 5.28 mumol/kg (1.60 mg/kg). The administration of (S)-UH-301 10 min before 8-OH-DPAT antagonized the 8-OH-DPAT-induced effects on both male and female rat copulatory behaviour. The results presented strongly support the classification of (S)-UH-301 as a 5-HT1A receptor antagonist. In addition, the effect of the enantiomer of (S)-UH-301, (R)-5-fluoro-8-hydroxy-2-(dipropylamino)tetralin [R)-UH-301), on male rat copulatory behaviour was tested. This enantiomer was found to facilitate male rat copulatory behaviour in a 8-OH-DPAT-like manner, supporting a 5-HT1A agonistic action of (R)-UH-301.

8-Hydroxy-2-(di-n-propylamino)tetralin↗

PubMed1991

Neonatal exposure to substance P alters behavioral and substance P levels in the central nervous system of the adult rat.

Substance P (SP) administered subcutaneously to male and female rats during a neonatal period (days 1-7 after birth), produced long-term effects. Thermal/pain perception and elements of both male and female copulatory behavior were altered. A significant increase in the SP level in the dorsal part of the spinal cord was demonstrated by radioimmunoassay and by micro-fluorescence. The present study indicates that exposure to SP during the neonatal period, when the role of SP in transmission is likely to be established, has biochemical and functional consequences for SP systems in the adult.

Animals↗

PubMed1991

The effects of long-term treatment with 8-OH-DPAT on the lordosis response and hypothermia in female rats.

The effects of long-term treatment with a low dose of the 5-HT1A agonist 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) on steroid hormone-dependent copulatory behaviour in female rats, the lordosis response, and on the hypothermic response of female rats were studied. Female rats were treated for 15 days, once daily, and tested on days 1 and 15 of treatment. They received 25 micrograms/kg on test days and 50 micrograms/kg on all other days. Subsensitivity was not induced to the inhibitory effect of 8-OH-DPAT on the lordosis response. In contrast, however, the acute effect of 8-OH-DPAT on body temperature was abolished by the long-term treatment. The results presented indicate that the induction of subsensitivity to the effects of 8-OH-DPAT is not primarily dependent on the pre- or post synaptic locus of action. Our data suggest that hormonal mechanisms are involved.

8-Hydroxy-2-(di-n-propylamino)tetralin↗

PubMed1990

The long-term effects of 8-hydroxy-2-(di-n-propyl-amino)tetralin (8-OH-DPAT) on copulatory and exploratory behaviour in male rats.

The long-term effects of low doses of the 5-HT1A-agonist, 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT), were studied to assess differences in the development of subsensitivity in 8-OH-DPAT-induced behavioural responses. Male rats received 33 or 100 micrograms/kg per day s.c. for 8 or 15 days. The chronic treatment did not alter the facilitatory effects of 8-OH-DPAT on male copulatory behaviour. In contrast, the effects on exploratory activity and the induction of flat body posture observed after the acute treatment were attenuated by prolonged administration of 8-OH-DPAT. The results presented indicate that gonadal hormones are involved in 5-HT receptor regulatory mechanisms.

8-Hydroxy-2-(di-n-propylamino)tetralin↗

PubMed1989

Aging and sociosexual behavior in the male rat.

Senescent and young rats have been studied in a copulatory test and sociosexual approach test. The copulatory test was applied to investigate age-dependent changes in the copulatory capacity in the rat. The sociosexual approach test was used to describe motivational aspects of this behavior. Latencies, frequencies and durations of copulatory behaviors in the copulatory test and visits to various incentive animals in the approach test have been measured. Senescent rats had longer latencies and less frequencies of copulatory behaviors. In the approach test they showed less visits to the estrous female. Data were also subjected to a correlational analysis in order to relate the findings of the two tests. It is concluded that aged male rats differ from young ones in organizing their behavior in relation to time, are less social and have a less pronounced social preference pattern. In addition, the coherence between various elements of copulatory behavior was less in the senescent rat than in the young male rat, whereas the social approach patterns are more coherent in the aged male.

Aging↗

PubMed1988

Neonatal vasopressin antagonist treatment facilitates adult copulatory behavior in female rats and increases hypothalamic vasopressin content.

This study confirms that i.c.v. administration of Arg-vasopressin (AVP, 20 ng) inhibits copulatory behavior in female rats (lordosis response, LR) and demonstrates that this inhibitory effect is blocked by the vasopressin antagonist (3-mercapto-3-methylbutyryl-Tyr-[Me])arginine vasopressin (dPTyr(Me)AVP, 20 ng, i.c.v.). The effects of neonatal AVP antagonist treatment on adult female copulatory behavior, hypothalamic content of AVP and AVP-like immunoreactive (AVP-ir) neurons were examined. dPTyr(Me)AVP was given to female rats 1 microgram/animal/day s.c. from day 1 through to day 7 (day 0 = day of birth). The females were ovariectomized as adults and sexual receptivity activated by submaximal doses of estradiol plus progesterone. The LR was significantly facilitated in the neonatally dPTyr(Me)AVP treated females who also showed a higher content and an increased number of AVP-ir neurons in the suprachiasmatic nucleus compared to saline controls. Functional, biochemical and immunocytochemical evidence is provided that neonatal exposure to an AVP antagonist induces persistent changes in central vasopressinergic neuronal mechanisms.

Animals↗

PubMed1988

Neonatal naltrexone treatment: effects on sexual and exploratory behavior in male and female rats.

The effect of neonatal naltrexone treatment (100 micrograms SC from day 1 to day 10) on copulatory and exploratory behavior in male and female rats was studied. In the female, neonatal naltrexone treatment enhanced copulatory (lordosis response) and exploratory behavior. An altered response to morphine was obtained; the effect of morphine on copulatory behavior was diminished while morphine's effect on exploratory activity was potentiated. The neonatal naltrexone treatment did not cause analogous effects in copulatory or exploratory behavior in the male rat. These data suggest that opioid mechanisms involved in the female copulatory and exploratory activity are established perinatally and can be influenced by early exposure to an opioid antagonist. It is concluded that there exist sex differences in this respect, both as to the sex-typical copulatory behavior and as to exploratory activity.

Animals↗

PubMed1988

Influence of ACTH1-24 on grooming and sociosexual behavior in the rat.

The effects of intraventricular administration of ACTH 1-24 on grooming, exploratory and socio-sexual behaviors in male rats were studied. The various behavioral elements were analyzed in terms of latency, frequency, and duration, which provided a multivariate behavioral profile. Behaviors that occur early during the test procedure had decreased, whereas behaviors displayed after the animal had spent some time in the test situation increased. Sociability, sexual approaches, and sexual preference in a sociosexual test situation were not altered by this treatment. The extinction of the response after removal of the incentive animals was delayed, however. It is concluded that ACTH1-24 did not specifically influence goal-directed behaviors. The obtained change in the behavioral profile, including the grooming pattern, rather suggest that ACTH1-24 affects mechanisms associated with attention and habituation.

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

Ethology in animal quarters.

This contribution will be concerned with the interaction between environment, adaptability optimization and behaviour. Animal laboratory experiments demand repeated measurements under identical environmental conditions. This is a prerequisite for the conventional statistical methodology used in order to clarify causal relationships involved in various biological functions. The understanding of biological functions is a necessary fundament for knowledge to prevent illness and to achieve a palliative or specific therapy. It is reasonable to assume that the routines in the quarters are very artificial, considering an animal's normal living conditions. The experimental situation as well as animal maintenance involves a process of adaptation. Adaptability depends on type of animal, degree of domestification etc. However, even with respect to choice of suitable species, strain and genetic manipulation, the process of adaptation becomes an important variable for ethical and practical points of view. The more emphasis on constancy, the more do we run the risk of increasing the span between normal and laboratory conditions and subsequently increase the factor and problem of adaptation. This vicious circle should be broken rather by finding optimal conditions than by a middle course determined by experimental requirements, economical frames and general notions about what may be good for the animal. Optimization must involve an understanding of how the experiment and the way of maintenance of the animal in the animal quarters influence adaptability. This understanding requires a systematic exploring of what physio-chemical and psychological factors are of importance. We will probably never be able to control the variability in the degree of adaptation.(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptation, Psychological↗

PubMed1985

Neonatal exposure to naltrexone affects morphine sensitivity and facilitates sexual behaviour in female rats.

The female copulatory behaviour (lordotic response) is inhibited by morphine. Female rats treated neonatally with naltrexone displayed enhanced copulatory behaviour as adults, and the morphine-induced lordosis inhibitory effect was diminished. The present data suggest that in the female rat the opioid mechanisms involved in the copulatory behaviour are established neonatally and can be influenced by early manipulation of the opioid system.

Animals↗