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Biomedical subjects

R J Barfield

Publications and source records attributed to R J Barfield.

At least 55 records · Page 3Linked to original sources
PubMed1984

Brain monoaminergic control of male reproductive behavior. II. Dopamine and the post-ejaculatory refractory period.

This study was designed to examine the role of central dopaminergic mechanisms in the control of copulation and the subsequent post-ejaculatory refractory period in the male rat. Disruption of central dopaminergic pathways was achieved in two separate groups of animals by: (1) selective electrolytic lesions of the substantia nigra (the major locus for dopamine cell bodies in the brain); or (2) localized intracerebral injection of 6-hydroxydopamine, a specific neurotoxin for catecholaminergic pathways. A third group of animals was tested for sexual behavior following administration of the dopamine receptor blocker pimozide. Both electrolytic and neurochemical lesions localized in the substantia nigra produced a significant increase in the length of the post-ejaculatory refractory period. Dopamine receptor blockade following administration of pimozide also caused a significant increase in refractory period duration. These results support the hypothesis that central dopaminergic pathways are involved in the motivational or arousal component of copulation and may be integral to the maintenance of a normal post-ejaculatory refractory period.

Amygdala↗
PubMed1984

Brain monoaminergic control of male reproductive behavior. III. Norepinephrine and the post-ejaculatory refractory period.

The present study was performed to examine the role of brain norepinephrine in the control of copulation and the post-ejaculatory refractory period in the male rat. Disruption of central noradrenergic systems was achieved by (1) selective electrolytic lesion of noradrenergic cell bodies in the locus coeruleus or (2) administration of specific inhibitors of norepinephrine synthesis, sodium diethyldithiocarbamate (DDC) or 1-phenyl-3-(2-thiazolyl)-2 thiourea (U-14, 624). Electrolytic lesions of the locus coeruleus produced a significant increase in the duration of the post-ejaculatory refractory period and its concomitant 22-kHz ultrasonic vocalization. Administration of norepinephrine synthesis inhibitors significantly increased both mount and intromission latencies and caused a dramatic increase in the length of the post-ejaculatory refractory period. These findings support the hypothesis that norepinephrine-containing neural pathways are involved in the control of sexual arousal and suggest that a functional noradrenergic system is essential to the integrity of normal masculine copulatory behavior.

Animals↗
PubMed1984

Behavioral effects of progestin in the brain.

In this article we review research on the role of progestins in the regulation of estrous responsiveness in female rats. Estrous responsiveness normally results from a synergistic action of estradiol (E2) and progesterone (P). E2 primes the system but normally does not result in estrous behavior. The full expression of estrous responsiveness results from the action of P on the E2-primed system. It has been demonstrated with implants of dilute E2 (1 part E2: 250 parts cholesterol) that the site of E2 priming is the ventromedial nucleus of the hypothalamus (VMN). In females primed with systemically administered E2, P also acts on the VMN to facilitate full estrous responsiveness. It has been shown in addition that estrous responsiveness results from sequential application of E2 and P to the VMN but not to other areas of the brain. The VMN is also the site at which P produces sequential inhibition of estrous responsiveness. The time course of P action in facilitating full estrous responsiveness is about two hours, regardless of whether the hormone is administered intracerebrally or intravenously. The duration of estrous responsiveness is directly correlated with the length of time P is in contact with brain tissue. Experiments with the protein synthesis inhibitor anisomycin are consistent with the view that P acts in the VMN by way of a protein synthetic mechanism to facilitate estrous behavior; however, other mechanisms must be considered as alternatives. Finally, we address the question of whether estrogenic priming depends upon induction of progestin receptors in the VMN. Results indicate that estrogenic priming of estrous responsiveness may occur without concomitant induction of progestin receptors.

Animals↗
PubMed1984

Electrophysiological and ultrasonic correlates of reproductive behavior in the male rat.

The purpose of the present study was to examine the electrophysiological correlates of copulatory behavior in the rat and correlate brain electroencephalographic (EEG) activity with the ultrasonic vocalizations that have been shown to play a major role in the integration of mating behavior. Ultrasonic vocalizations of male rats with chronically implanted hippocampal and cortical electrodes were monitored during mating with a female rat. Hippocampal theta rhythms were significantly correlated with high activity, mounting, intromissions, and preejaculatory excitatory behavior and were also significantly associated with 50-kHz short ultrasonic vocalizations. Postmount or postintromission behaviors (grooming, exploration) were closely correlated with an absence of ultrasonic vocalizations and the onset of irregular low-amplitude hippocampal EEG recordings. Long 22-kHz vocalizations occurred in all tests during the postejaculatory refractory period. Shorter 22-kHz vocalizations occurred during mating and were associated with unsuccessful intromissions or mounting attempts. Postejaculatory long 22-kHz vocalizations were significantly associated with irregular high-amplitude hippocampal EEG tracings, and preejaculatory short 22-kHz vocalizations were also accompanied by sleep-like irregular high-amplitude hippocampal EEG tracings with cortical spindling. The correlation of ultrasonic vocalizations with electroencephalographic and behavioral manifestations of central arousal and inhibitory processes suggests that these vocalizations are indicators of the sexual arousal of the mating pair.

Animals↗
PubMed1984

Blockade of progesterone-activated estrous behavior in rats by intracerebral anisomycin is site specific.

The hypothesis that progesterone (P) activates estrous behavior in estrogen-primed female rats via a protein synthetic mechanism was examined. The protein synthesis inhibitor anisomycin was applied intracerebrally via 28-gauge bilateral implants to neural sites implicated in the mediation of estrous responsiveness. Results showed that anisomycin blockade of P-activated estrous behavior was neural site specific. Animals with anisomycin placed in the ventromedial hypothalamus (VMH) (n = 27) showed low levels of lordosis and solicitation behavior 4 h after the subcutaneous administration of 500 micrograms P, whereas animals with anisomycin implants in the preoptic area (n = 11) or the midbrain area in the region of the interpeduncular nucleus (n = 11) displayed high levels of estrous behavior. No deficits in open-field activity were observed following localized anisomycin treatment, and all animals appeared to be healthy. Results of the present study are consistent with the hypothesis that P acts to promote estrous behavior via a receptor-mediated genomic protein synthetic mechanism, and provide additional evidence that the VMH is the primary site of P action.

Animals↗
PubMed1983

Onset of the receptive and proceptive components of feminine sexual behavior in rats following the intravenous administration of progesterone.

The present study was carried out in order to assess the time course of action of progesterone (P) in the facilitation of complete feminine sexual behavior. Female rats (estrogen primed via 5% E2 Silastic capsules) were given 200 micrograms of P either intravenously (iv) or subcutaneously (sc), and tested for estrous behavior at 1/4, 1/2, 1, 2, and 4 hr after treatment. Among iv-treated animals, significant amounts of lordosis behavior were seen as early as 1/2 hr, and a dramatic rise in solicitation behavior was observed at 2 hr. Although sc-treated animals displayed significant amounts of lordosis and solicitation behavior at 2 hr, the behavior was not maximal until 4 hr. Intravenous administration of 400 micrograms P was equipotent to 200 micrograms P, whereas 50 micrograms of iv P was relatively ineffective. A dual mechanism hypothesis pertaining to progesterone's actions in the facilitation of both the receptive and proceptive components of feminine sexual behavior in rats is discussed.

Animals↗
PubMed1983

Influence of androgen on the development of sexual behavior in the rat. II. Time and dosage of androgen administration during the neonatal period and masculine and feminine copulatory behavior in females.

The objective of the present study was to delineate the period of sensitivity to a single androgen exposure during the initial neonatal hours on the development of masculine and feminine copulatory behavior in female rats. Female rats were injected once with either 500, 50, or 5 micrograms testosterone propionate (TP) at either 1 or 24 hr after birth. Following castration in adulthood and TP replacement, the females were tested four times at weekly intervals in prolonged sessions for masculine copulatory behavior. One month following the masculine copulatory tests the females were tested for 3 weeks for feminine copulatory behavior with weekly increasing levels of estradiol benzoate (2.5, 10, and 25 micrograms) and progesterone (200 micrograms). The results demonstrate that a single injection of TP administered at either 1 or 24 hr after birth can significantly increase the capacity of female rats to exhibit ejaculation patterns and that the amount of androgen that is administered is critical in determining the levels of ejaculatory responding. Similarly, the females given high doses (50 and 500 micrograms) of TP at either 1 or 24 hr neonatally were almost completely defeminized. In contrast, however, the females treated with 5 micrograms TP at 1 and 24 hr showed different levels of lordotic performance indicating a greater sensitivity to androgen immediately after birth than at 24 hr in female rats as has been shown in male rats.

Age Factors↗
PubMed1983

Effects of prenatal exposure to morphine sulfate on reproductive function of female rats.

The purpose of this study was to investigate the effect of prenatal exposure to morphine sulfate on the development of reproductive function in female rats. Female rats exposed to morphine sulfate in utero (5-10 mg/kg on days 5-12 of gestation) exhibited varying dates of vaginal opening and a partial inhibition in adult feminine sexual behavior when compared to controls. However, the estrogen binding capacity of hypothalamic cytosols from morphine- and saline-treated females was identical. While we cannot rule out the possibility that the observed changes in reproductive function were an indirect result of morphine-induced alterations in maternal physiology or behavior, these results suggest that the development of feminine sexual behavior can be influenced during the early prenatal period and that morphine sulfate can affect the process of feminization.

Animals↗
PubMed1983

Induction of estrous behavior in ovariectomized rats by sequential replacement of estrogen and progesterone to the ventromedial hypothalamus.

The present experiment was designed to determine whether sequential replacement of estrogen and progesterone to the ventromedial hypothalamus (VMH) would be sufficient to induce estrous behavior in ovariectomized rats. Bilateral cannulae containing 17 beta-estradiol (E2) diluted with cholesterol (1:250) were lowered into the VMH, preoptic area or midbrain and left in place for 4 days. On day 5, the E2 inserts were removed and P-filled cannulae were lowered into half of the subjects. The remaining females received systemic progesterone (500 micrograms). This steroid regimen was repeated 2 weeks later with the mode of progesterone administration reversed. All subjects were tested for estrous behavior twice after progesterone treatment. In a second experiment, 3H-P:P-filled cannulae were lowered into the VMH of estrogen-primed females in order to estimate the extent of hormone spread from full-strength P-filled cannulae. Results indicated that estrogen and progesterone stimulation of the VMH is sufficient to activate estrous behavior in spayed female rats, however, precise localization of the hormone implants within the VMH is essential. 9 of the 11 females with both cannulae located within or at the border of the ventromedial nucleus (VMN) exhibited estrous behavior whereas only half of the females with only one implant resting in the VMN exhibited estrous responsiveness. Subjects with neither cannula located within or at the border of the VMN did not exhibit the behavior. The facilitative effects of P appeared to result from hormonal stimulation of the VMH and not from leakage of the steroid into other brain regions or into the systemic circulation. Following placement of tritiated progesterone implants into the VMH, high levels of radioactivity were recovered only from the mediobasal hypothalamus. The low levels of radioactivity measured in other brain regions, pituitary, uterus and blood indicate that relatively little if any hormone reached these tissues.

Animals↗
PubMed1983

Progesterone in the ventromedial hypothalamus facilitates estrous behavior in ovariectomized, estrogen-primed rats.

The putative neural target sites of progesterone (P) action for the facilitation of estrous behavior in female rats were reexamined using the hormone implant technique. Subjects were ovariectomized, estrogen-primed Long-Evans females. All were outfitted with bilateral double barreled cannulae assemblies consisting of 23-gauge guide cannulae and 28-gauge inserts. Subjects in Exp 1 received sc injections of individually determined threshold priming doses of estradiol benzoate. Estrogenic priming for subjects in Exp 2 was provided by sc placed Silastic capsules (5 mm) filled with 17 beta-estradiol-cholesterol (1:20). Each subject was tested for estrous behavior with a male after P-filled cannulae and after blank inserts were lowered into the brain. Behavioral tests were conducted 1 and 4.5 h postcannulae placement. Thirty-five of 40 females with P in the ventromedial hypothalamus exhibited high levels of lordosis behavior during the 4.5-h test. Moreover, 29 of the 35 exhibited solicitation behavior as well. Estrous behavior was not exhibited by these animals during the 1-h test. Implants in other regions of the brain (i.e. mesencephalic reticular formation, preoptic area, central grey, caudate putamen, and hippocampus; n = 80) did not consistently facilitate estrous responsiveness. In Exp 3, levels of estrous responsiveness were similar before and after adrenalectomy (n = 10); thus, facilitation of estrous behavior by P-filled implants in the ventromedial hypothalamus was not dependent upon activation of the hypothalamic-pituitary-adrenal axis.

Adrenalectomy↗
PubMed1983

Analysis of ultrasonic vocalizations emitted by intruders during aggressive encounters among rats (Rattus norvegicus).

This investigation was concerned with the identification of the ultrasonic vocalizations produced by intruders during aggressive interactions and the role of these signals in agonistic behavior of rats. In the first experiment, experienced resident males were paired with both devocalized and intact vocalizing naive intruder males. Devocalization of the intruder males resulted in a drastic decrease in 50-kHz vocalizations and the elimination of all 22-kHz vocalizations. This almost total absence of ultrasonic vocalizations was not accompanied by any change in resident aggressive behavior or intruder defensive and submissive behavior. In a second experiment, naive intruders were tested with either deafened or intact resident males. Similarly, preventing residents from hearing intruder ultrasounds had no detectable effect on any aggressive behavior. These experiments are not consistent with the correlative evidence that intruder-produced 22-kHz vocalizations inhibit the aggressive behavior of the resident. The results also show that most of the ultrasonic vocalizations emitted during aggressive encounters are probably produced by the intruder.

Aggression↗
PubMed1983

Analysis of ultrasonic vocalizations emitted by residents during aggressive encounters among rats (Rattus norvegicus).

This investigation was concerned with the extent to which aggressive resident rats emit 40-70-kHz vocalizations and the effect of these signals on intruders. In Experiment 1, deafened and intact intruder males were given two encounters with resident animals. Deafened intruders engaged in a higher duration of immobile or freezing postures than intact animals. Experiment 2 indicated that the augmentation of freezing found among deafened intruders was not due to an inability to detect ultrasounds made by residents since intruders encountering devocalized resident males showed no reliable differences in specific motor patterns from intruders paired with intact residents. The results further demonstrated that 40-70-kHz vocalizations are produced almost entirely by intruding animals since there were no significant changes in occurrence of these calls when resident males were devocalized. Under the constraints of the testing procedures employed, the role of ultrasonic communication during the initial formation of agonistic relations could not be determined experimentally.

Aggression↗