Biomedical subjects

J G Kohlert

Publications and source records attributed to J G Kohlert.

6 recordsLinked to original sources

PubMed1999

Sexual experience sensitizes mating-related nucleus accumbens dopamine responses of female Syrian hamsters.

We examined the effects of prior sexual experience on extracellular concentrations of dopamine in the nucleus accumbens of female hamsters. Nucleus accumbens dopamine was measured by in vivo microdialysis during mating in female Syrian hamsters that had previously been given six prior sexual encounters with a male, three prior encounters, or were sexually naive. High levels of sexual behavior were observed in all three groups, which were accompanied by increases in dialysate dopamine during periods when the male was present. However, females that received six prior sexual encounters had significantly elevated and prolonged increases in dialysate dopamine compared with those of the sexually naive females or females with only three prior sexual encounters with a male. The data indicate that the mesolimbic system can be sensitized by repeated experiences associated with a motivated behavior.

Animals↗

PubMed1997

Intromissive stimulation from the male increases extracellular dopamine release from fluoro-gold-identified neurons within the midbrain of female hamsters.

Extracellular concentrations of dopamine in the nucleus accumbens were monitored using microdialysis in ovariectomized female Syrian hamsters hormonally primed with estradiol and progesterone or with a similar regimen of oil injections. Some females in each of these groups had their vaginas occluded with tape, whereas the remaining females' vaginas stayed unoccluded. When exposed to a male, both groups of hormonally primed females showed high levels of lordosis. However, only in the hormone-primed, unoccluded females were there significant elevations of dialysate dopamine during the sexual interactions with the male. There were no significant elevations in dopamine levels in the oil-treated females during interactions with the male. These data suggest that nucleus accumbens dopamine is responsive to stimuli associated with the vaginocervical stimulation received by the female during intromissions by the male. Histological analyses were based on Fluoro-Gold efflux through the probes combined with immunocytochemistry for tyrosine hydroxylase. Probe placements in the rostral accumbens, caudal accumbens, or rostral bed nucleus of the stria terminalis were not distinguishable based on analyses of basal dopamine levels, volume of Fluoro-Gold injection sites, or Fluoro-Gold labeling of midbrain, tyrosine hydroxylase-stained neurons. The number of midbrain neurons containing Fluoro-Gold was positively related to basal dopamine levels, indicating that the amount of dopamine recovered from the nucleus accumbens in microdialysis studies is a function of the number of neurons contributing to the terminal field in the region of the probe.

Animals↗

PubMed1996

Hyperactivity in hyposexual male rats.

It is widely accepted that some male rats fail to copulate because of a decrease in arousability, measured as decreased general locomotor activity (hypoactivity). This relationship, however, failed to explain an observation made in our laboratory that rats that failed to copulate exhibited increased general locomotor behavior. To directly address this issue, we quantified open-field and male sexual behaviors in 360 rats from two different strains. Twenty-two out of 49 hyposexual males were also hyperactive; this was a significantly greater number than would be expected by chance (p < 0.002, binomial test). Interestingly, only 6 of the 49 hyposexual males were hypoactive; this number was actually significantly smaller than would be expected by chance (p < 0.02). There was no correlation between behavioral measures and plasma levels of testosterone or progesterone. A decrease in selective attention and a failure to be stimulated by amphetamine was apparent in all hyperactive rats--those normal-sexual as well as hyposexual. The hyperactive rats were not hypertensive. We conclude that a significant percentage of hyposexual rats are hyperactive, and that hypoactive rats generally exhibit normal levels of sexual behavior. Decreased selective attention and decreased responsiveness to amphetamine do not explain this result, which is also not related to blood pressure or androgen levels.

Amphetamine↗

PubMed1996

Galanin microinjected into the medial preoptic nucleus facilitates female- and male-typical sexual behaviors in the female rat.

Galanin (GAL) microinjected within the sexually dimorphic medial preoptic nucleus (MPN) facilitates male-typical sexual behaviors in the male rat, a response that requires the presence of testosterone. As in the male, GAL-immunoreactive cells located within the MPN of the female also concentrate gonadal steroids and become less immunoreactive after gonadectomy. Thus, to investigate sexual behaviors in the female and to determine whether effects are comparable to those obtained in the male, GAL was microinjected unilaterally within the MPN of female rats. We report that GAL stimulated female-typical lordosis behavior after estrogen priming, and that the effect was not due to general arousal as measured by nonspecific locomotor activities. In a separate experiment, GAL microinjected within the MPN dose-responsively increased mount frequencies and decreased mount latencies in testosterone-primed females. A higher dose of testosterone was required in females for this stimulation of male-typical sexual behavior than required in a previous experiment in males.

Animals↗

PubMed1993

Microinjection of galanin into the medial preoptic nucleus facilitates copulatory behavior in the male rat.

The medial preoptic area (MPOA) is an important region for masculine sexual behavior. Because galanin (GAL) immunoreactive cells within the MPOA are affected by the gonadal steroid environment and GAL binding is apparent, GAL was microinjected site specifically in 0, 10, 50, 100, and 500 ng doses in order to determine effects on copulatory behavior. Unilateral microinjection of GAL within the medial preoptic nucleus facilitated copulatory behavior in a dose-responsive fashion, evidenced by an increase in the percentage of males that displayed sexual behaviors and a decrease in mount and intromission latencies. These effects required the presence of gonadal steroids, and were not due to general arousal as measured in open field testing. The techniques of survival analysis were used to display data and for statistical analysis of intromission and mount latencies; these approaches revealed significant effects that were not evident with more commonly used procedures. The results support the suggestion that sexually dimorphic galaninergic cell groups within the MPOA are involved in gonadal steroid-induced masculine sexual behavior.

Animals↗

PubMed1993

A rat model for attention deficit-hyperactivity disorder.

A number of animal models for attention deficient-hyperactivity disorder (ADHD), a common childhood disorder, have been developed. However, none of these models are truly representative of naturally occurring developmental ADHD. In such models, hyperactivity is induced by electrical or chemical brain lesions, by pharmacological manipulation, or by genetic breeding that is coupled with hypertension. Based on the observation that some hyposexual rats also are hyperactive, we have studied these rats in order to determine whether they portray characteristics representative of ADHD. Results of open field testing, response to stimulant medication challenge, and measurement of the rat's ability to block irrelevant information in a conditioned avoidance response demonstrate three properties characteristic of ADHD: a) a high level of spontaneous motor activity; b) an attenuation of motor activity in response to amphetamine; and c) a deficit in selective attention. These data indicate that these rats may be a model for the study of ADHD.

Animals↗