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D W Pfaff

Publications and source records attributed to D W Pfaff.

At least 397 records · Page 22Linked to original sources
PubMed1979

Triggering of lordosis reflex in female rats with somatosensory stimulation: quantitative determination of stimulus parameters.

1. Pressure on the skin of the tail base and perineum of female rats in the range of 40--440 millibars, following bilateral contact with the flanks, was adequate to elicit the lordosis reflex. Hair deflection alone or noxious stimulation was neither sufficient nor necessary for lordosis behavior to occur. 2. For a given pressure, increasing the area of stimulation increased the effectiveness for evoking lordosis; inputs from mechanoreceptors at different skin locations can be summated to trigger the behavioral response. 3. During mating behavior, increased pressure from the male rat on the skin of the female, in the range of 50--450 millibars, was associated with increased probability and strength of lordosis. 4. Increasing the dose of estrogen increased the probability of lordosis to a given pressure stimulus. The hormone effect can be characterized as a facilitation of the throughput from low-threshold pressure receptors on tail base and perineum to motoneurons for the lumbar vertebral dorsiflexion of lordosis.

Animals↗
PubMed1979

Responses of single units in sixth lumbar dorsal root ganglion of female rats to mechanostimulation relevant for lordosis reflex.

1. The activity of single units (n = 312) was recorded from dorsal root ganglion L6 in female rats; 84% received input from cutaneous mechanoreceptors. 2. Among cutaneous mechanoreceptive units (n = 263), 22% responded to individual guard hair movement, 18% to down hair, 11% to clitoral hair, and 14% to stimulation of tylotrich hair-haarscheibe (type I) receptors, 5% responded to punctate skin deformation, but not hair movement of pressure, and 18% responded to pressure. 3. No significant differences between estrogen-treated and untreated ovariectomized rats were observed in receptive-field size, or von Frey hair, or pressure threshold of any given type of unit. 4. The lordosis reflex of female rats is triggered by pressure, but not hair deflection, on skin regions innervated by dorsal root L6 (10). Stimulation from the male rat mounting would cause a barrage of action potentials from most of the unit types identified here, but only pressure units and type I units gave sustained responses to a lordosis-triggering type of pressure stimulation.

Animals↗
PubMed1979

Facilitation of the lordosis reflex of female rats from the ventromedial nucleus of the hypothalamus.

1. Effects of electrical stimulation of hypothalamic ventromedial nucleus (v.m.n.) on the lordosis reflex of female rats were examined in ovariectomized and oestrogen-primed animals with chronically implanted electrodes. 2. Lordosis triggered either by manual cutaneous stimulation or by male mounting, was facilitated by electrical stimulation of the v.m.n. 3 A gradual increase in lordosis performance followed a relatively long period of stimulation; never less than 15 min and usually about 1 hr of stimulation was necessary for maximum facilitation. Following the termination of stimulation, the performance returned gradually to the control level during a 5--8 hr period. 4. The optimal frequency of stimulation was between 10 and 30 Hz. Threshold for effective facilitation was, on the average, 12.5 microA. 5. Stimulation tended to induce larger facilitation when applied to the lateral side of v.m.n. 6. Pre-treatment with oestrogen was necessary to obtain facilitation by v.m.n. stimulation. The threshold dosage of oestrogen was 2.5 microgram per animal. 7. Stimulation was effective in adrenalectomized rats, in dexamethasone-primed animals, and in rats pre-treated with exogenous progesterone. Thus, adrenal prodesterone release is not required for the v.m.n. facilitation of lordosis. 8. Medial preoptic stimulation with the same parameters suppressed the lordosis reflex. 9. The v.m.n. participates in the control of lordosis by a facilitatory output. The delay before facilitation implies that the v.m.n. is not in the direct reflex-arc for the execution of lordosis. Rather, a summation or interaction process with an unusually long time course is involved.

Animals↗
PubMed1979

Deficit in the lordosis reflex of female rats caused by lesions in the ventromedial nucleus of the hypothalamus.

1. The effect of electrolytic lesions of the ventromedial nucleus of the hypothalamus (v.m.n.) on the lordosis reflex has been investigated on ovariectomized female rats. Lesions were made through chronically implanted platinum-iridium electrodes. 2. V.m.n. lesions did not disrupt lordosis immediately, but induced a gradual decline in the reflex. Lordosis performance reached it minimum no less than 12 hr after the lesion, and typically after 36--60 hr. 3. The magnitude of the lordosis deficit was related to the amount of v.m.n. damage. Destruction of other hypothalamic regions was without appreciable relation to the deficit. Within v.m.n., lesion size in the lateral, but not medial portion was significantly correlated with lordosis deficit. 4. Because of the slow time courses of v.m.n. lesions and stimulation (Pfaff & Sakuma, 1978) effects, it is postulated that the v.m.n. is not part of the direct reflex-arc for lordosis. Rather, neurones in v.m.n. are likely to exert a tonic hormone-dependent bias on brain stem reflex paths for this behaviour.

Animals↗
PubMed1979

Descending tracts of the lateral columns of the rat spinal cord: a study using the horseradish peroxidase and silver impregnation techniques.

The location of the cells of origin and the projection areas of descending fibre tracts of the spinal cord lateral columns were examined in rats. Unilateral micro-transections of subpopulations of lateral column fibres, at C2 or T10, with subsequent application of horseradish peroxidase to the severed axons, allowed identification, by retrograde labelling, of those cell groups projecting to the spinal cord through the lateral columns. Additionally, the pattern of fibre and preterminal degeneration below the level of transection was examined using the Fink-Heimer silver impregnation technique. The largest number of labelled cells was observed in the ventral portion of nucleus gigantocellularis, projecting ipsilaterally through both the anterolateral (AL) and dorsolateral (DL) columns. Labelled cells were observed in the dorsal portion of the lateral vestibular nucleus (lv) following a T10 transection, and throughout the necleus following a C2 transection. Protein marker was observed in the large Deiters' cells of the lv, ipsilaterally. Also following an AL, but not a DL, column transection, retrograde labelled cells occurred throughout necleus reticularis pontis oralis (rpoo), bilaterally. At the border of rpoo and the lateral lemniscus, a discrete group of labelled cells was observed bilaterally following a DL column transection. This group of reticulospinal cells was located in a position similar to that of the A7 cell group reported in histofluorescence studies. The most extensive group of labelled cells following a DL column transection occurred in the magnocellular portion of the contralateral red nucleus. Although lavelled cells were observed in the red nucleus following either a C2 or T10 DL column transection, labelled cells were more numbeous and extended further rostrally and dorsally, following a high cervical transection. Labelled cells in nucleus raphe magnus were also more numerous following a DL column transection. Additional groups of labelled cells were seen following both an AL or DL column transection. These groups included necleus subcoeruleus ipsilaterally, and nucleus reticularis ventralis and the nucleus of the tract of spinal V, bilaterally. Labelled cells were observed as far forwards as the hypothalamus, occurring predominantly in the paraventricular nucleus, ipsilaterally. A few labelled cells were observed in the lateral hypothalamus. Some cell groups were labelled only after a C2 transection. These included the interstitial nucleus of Cajal, ipsilaterally, the descending vestibular necleus and the deep layers of the superior colliculus, contralaterally, and the central grey matter and nucleus raphe pallidus. Fibre and preterminal degeneration resulting from unilateral AL or DL column transection was examined. Following an AL column transection degeneration was most intense in the ipsilateral laminae V, VI and VII...

Animals↗
PubMed1978

Autoradiographic localization of androgen-concentrating cells in the brain of the male domestic fowl.

Cells in the male fowl brain which accumulate radioactivity following 3H testosterone (T) administration were identified by autoradiography. Labelled cells were found principally in hypothalamic, limbic and midbrain structures. Marked uptake was observed in the preoptic area (POA) and in the anterior and posterior hypothalamus. There was also a significant amount of labelling in the archistriatum (ARCH), particularly in the nucleus taeniae (Tn), and in the lateral septum. In the midbrain, substantial uptake of labelled hormone was found in the nucleus intercollicularis (ICo). The pattern of accumulation of T in the male fowl was comparable to that for sex hormone uptake in vertebrates in general. Furthermore, accumulation was generally found in areas known to be concerned with sex hormone-dependent functions.

Animals↗
PubMed1977

Facilitation of the lordosis reflex in female rats by electrical stimulation of the lateral vestibular nucleus.

(1) Electrical stimulation of the lateral vestibular nucleus (LVN) facilitated lordosis reflex responses to somatosensory stimulation, in estrogen-primed female rats. (2) Unilateral LVN stimulation was sufficient for this effect. Currents as low as 10muA could be used. (3) With the stimulus parameters used, the effect develops within 5 min of LVN stimulation and decays within 10 min following cessation of stimulation. (4) Together with previous evidence that LVN lesions disrupt lordosis, these results suggest LVN facilitation of spinal reflex mechanisms for lordosis.

Animals↗
PubMed1977

Effects of spinal cord transections on lordosis reflex in female rats.

(1) Female rats with complete transections of spinal cord at low thoracic levels were not able to perform the lordosis reflex. (2) Females with bilateral transections of dorsal columns, dorsolateral columns or entire dorsal half of spinal cord performed lordosis in a normal way. (3) Bilateral transection of fibers in the ventromedial columns, added to transection of dorsal columns or entire dorsal half of the cord still allowed lordosis to be performed. (4) Large bilateral transections of the anterolateran columns caused severe loss in the strength and frequency of the lordosis reflex. Effective transections often included some ventromedial or dorsolateral column fibers, and were accompanied by abnormalities of locomotion. (5) We conclude that supraspinal control is required for the normal lordosis reflex, and that fibers necessary and sufficient for lordosis run in the anterolateral columns. These fibers are likely to be dispersed throughout the anterolateral columns, since large transections were required to eliminate lordosis, and also to be involved in (or interspersed with other fibers involved in) other aspects of motor control. Candidate ascending systems are the anterolateral fibers of Mehler. Candidate descending systems are the lateral vestibulospinal and reticulospinal tracts.

Animals↗
PubMed1977

Aggressive behavior in female hamsters: the hormonal basis for fluctuations in female aggressiveness correlated with estrous state.

The frequency and sequencing of aggressive behaviors by naive female hamsters change during series of brief encounters, probably because of the lack of stable dominance relations. Such initial encounters seem most representative of interactions likely in free-ranging hamsters and have been emphasized in studies of the hormonal mediation of female aggression. Nonestrous females exhibit intense aggression toward conspecifics of either sex. Estrous females are not aggressive and spend much time in lordosis, indicative of sexual receptivity. The inhibition of fighting on estrous day depends on estrogen and progesterone. Whereas oil-injected adrenalectomized-ovariectomized females fight at high levels, comparable with intact nonestrous females, the combination of 17 beta-estradiol benzoate and progeterone suppresses fighting completely. In contrast, replacement of estradiol, progesterone, or testosterone propionate individually has on consistent effect. Hypophysectomized females also fight at high levels, indicating that pituitary hormones are not required for vigorous aggression. Further, individual anterior pituitary hormones did not produce marked changes in fighting. These results emphasize the roles of estrogen and progesterone in synchronizing aggression with current reproductive state.

Adolescent↗