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Biomedical subjects

J W Gunnet

Publications and source records attributed to J W Gunnet.

23 records · Page 2Linked to original sources
PubMed1985

The interaction of the medial preoptic area and the dorsomedial-ventromedial nuclei of the hypothalamus in the regulation of the mating-induced release of prolactin.

The medial preoptic area (MPOA) and the dorsomedial-ventromedial nuclei (DMN-VMN) of the hypothalamus regulate the mating-induced nocturnal and diurnal surges of prolactin in rats. The neural mechanisms governing the release of the two surges differ. For the nocturnal surge the MPOA serves an inhibitory role while the DMN-VMN serves a stimulatory role. The diurnal surge is controlled by both areas functioning as stimulatory centers. The goal of the present study was to explore the possibility of functional interactions between the MPOA and the DMN-VMN in control of mating-induced prolactin secretion. Stimulation of the MPOA in conscious, cervically stimulated (CS) females suppresses the nocturnal surge of prolactin. To determine if the inhibitory effects of the MPOA operate through the DMN-VMN, electrical stimulation was applied to the MPOA of conscious ovariectomized female rats bearing bilateral electrolytic lesions of the DMN-VMN. In the first experiment, control (sham-stimulated, sham-lesioned) CS females exhibited normal nocturnal surges which peaked at 03.00 h. MPOA stimulation (01.00-05.00 h) of both sham-lesioned and DMN-VMN lesioned CS females inhibited the release of their nocturnal surges. This suggests that the inhibitory function of the MPOA is independent of the DMN-VMN. MPOA stimulation can induce the release of a diurnal surge if the females are anesthetized with pentobarbital. In the second experiment, MPOA stimulation (15.00-19.00 h) of sham-lesioned anesthetized females produced elevated prolactin levels with significant peaks at 15.30 and 19.00 h. Anesthetized females with DMN-VMN lesions did not respond to MPOA stimulation with any change in prolactin secretion.(ABSTRACT TRUNCATED AT 250 WORDS)

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PubMed1984

Hypothalamic regulation of mating-induced prolactin release. Effect of electrical stimulation of the medial preoptic area in conscious female rats.

Lesions of the medial preoptic area (MPOA) induce nocturnal prolactin surges similar to those initiated by cervical stimulation (CS). These same lesions can abolish diurnal prolactin surges previously initiated by CS. Based on these results the MPOA has been suggested to contain two functionally dissimilar sets of neurons, one inhibitory for the nocturnal surge and the other stimulatory for the diurnal surge. The present study sought to demonstrate the existence of these neural elements by electrically stimulating the MPOA of conscious ovariectomized female rats during those times of day when these neurons would be most active. Serial blood samples were collected via cannula before, during and after the stimulation. Stimulation of the MPOA (01.00-05.00 h) on day 2 after CS inhibited the nocturnal surge of prolactin while sham MPOA stimulation of CS females did not disturb the nocturnal surge. MPOA stimulation in non-CS females had no effect upon prolactin secretion. Application of MPOA stimulation (15.00-19.00 h) to CS females also suppressed the diurnal surge of prolactin. Sham-stimulated CS females, however, secreted a diurnal surge peaking at 17.00 h. Basal prolactin levels were unaffected by MPOA stimulation (15.00-19.00 h) in non-CS females. The results from these experiments suggest that the MPOA contains neurons inhibitory for both the nocturnal and diurnal prolactin surges. In a further attempt to show a stimulatory role for the MPOA in prolactin regulation, MPOA stimulation was applied (15.00-19.00 h) to pentobarbital anesthetized non-CS females. Pentobarbital treatment allowed the MPOA stimulation to trigger two prolactin peaks, one at 16.00 h and the other at 19.00 h.(ABSTRACT TRUNCATED AT 250 WORDS)

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PubMed1981

The role of the dorsomedial-ventromedial area of the hypothalamus in the control of prolactin secretion induced by cervical stimulation.

Cervical stimulation (CS) initiates daily nocturnal (N) and diurnal (D) surges of PRL, which persist for at least 10 days, in intact and ovariectomized (OVX) rats. To affect pituitary PRL release, CS probably acts through several areas of the hypothalamus. PRL regulation by one hypothalamic area, the dorsomedial-ventromedial nuclei (DMN-VMN), was investigated in the present study. Electrical stimulation of the DMN-VMN of rats with intact ovaries produces both N and D PRL surges of the same magnitude, timing, and persistence as those initiated by CS. However, in long term OVX rats, stimulation of the DMN-VMN results in N surges which last only until day 6 and D surges present only through day 2. OVX rats receiving sc Silastic implants containing progesterone on the day after DMN-VMN stimulation had larger N surges, which persisted only as long as those secreted by long term OVX untreated rats. The D surge was unaffected. Rats OVX immediately after DMN-VMN stimulation secreted N surges through day 10, but D surges only through day 6. CS of long term OVX rats bearing lesions or sham lesions within the DMN-VMN results in N surges persisting through day 10. However, D surges could not be initiated by CS in rats bearing DMN-VMN lesions. These results suggest that the DMN-VMN is one area which responds to CS by initiating N and D surges of PRL. Excitation of this area is a requirement for the initiation of D, but not N, surges of PRL. However, continuation of the N surge probably involves the excitation of other areas within the central nervous system.

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