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S Shimamune

Publications and source records attributed to S Shimamune.

6 recordsLinked to original sources
PubMed1997

Ascending pathways from the nucleus of the solitary tract to the subfornical organ in the rat.

Electrical stimulation of the nucleus of the solitary tract (NTS) produced orthodromic excitation (n = 28, 15%) and inhibition (n = 6, 4%) of the activity of neurons in the subfornical organ (SFO) in male rats under urethane anesthesia. Almost all (n = 26) of the excitatory responses (n = 28) were blocked by microiontophoretically applied phentolamine, an alpha-adrenergic antagonist, but not by timolol, a beta-adrenergic antagonist. In contrast, the inhibitory response of all the neurons (n = 6) tested was not affected by either phentolamine or timolol. Approximately two-third (n = 19) of SFO neurons that demonstrated the excitatory response to NTS stimulation exhibited an increase in neuronal activity in response to hemorrhage (10 ml/kg b.w.t.). Hemorrhage did not cause any change in the activity of all the neurons that demonstrated the inhibitory response to NTS stimulation. These results suggest that the excitatory pathways from the NTS to the SFO may transmit the peripheral baroreceptor information through alpha-adrenoreceptor mechanisms.

Afferent Pathways↗
PubMed1997

A1 noradrenergic modulation of AV3V inputs to PVN neurosecretory cells.

Phasically active neurosecretory neurons in the paraventricular nucleus (PVN) of urethane-anesthetized rats displayed orthodromic excitation, inhibition or no response following electrical stimulation of the anteroventral third ventricle (AV3V) region, and exhibited orthodromic excitation or no response following electrical stimulation of the A1 noradrenergic region of the ventrolateral medulla. Of the 14 neurons that responded to both the stimuli, A1 region stimulation at the subthreshold current significantly enhanced the excitation induced by AV3V region stimulation, and the enhancement was abolished by iontophoretically applied phentolamine, an alpha-adrenoceptor antagonist, but not by timolol, a beta-adrenoceptor antagonist. These results suggest that A1 noradrenergic projections may act to potentiate the excitatory inputs from the AV3V region to vasopressinergic PVN neurons through alpha-adrenoceptor mechanisms.

Adrenergic alpha-Antagonists↗
PubMed1997

Angiotensinergic modulation of osmotic activation of neurosecretory neurons.

Extracellular recordings were obtained from 34 phasically active neurosecretory cells in the hypothalamic paraventricular nucleus (PVN) of male rats under urethane anesthesia. Intracarotid injections of hypertonic saline (0.2 M NaCl solution, 0.05 ml) caused an increase in neuronal activity of 27 PVN cells. Pretreatment with saralasin (Sar, 10(-10) M), a specific angiotensin II (ANG II) antagonist, into the median preoptic nucleus (MnPO) diminished the excitatory response to the osmotic stimulation in 13 of 17 cells tested. Pretreatment with Sar in the vicinity of the MnPO or the third ventricle did not cause a marked change. These results suggest that the ANGergic system in the MnPO could contribute to the mechanism of osmotic activation of PVN neurosecretory cells.

Angiotensin II↗
PubMed1997

Subfornical organ efferents enhance extracellular noradrenaline concentrations in the median preoptic area in rats.

The present study was carried out to examine whether angiotensinergic pathways from the subfornical organ (SFO) regulate the noradrenergic system in the median preoptic nucleus (MnPO). Intracerebral microdialysis techniques were used to quantify the extracellular concentration of noradrenaline (NA) in the MnPO area. In urethane-anesthetized male rats, electrical stimulation (5-20 Hz, 0.6 mA) of the SFO significantly increased the NA concentration in the MnPO area, and the increase was significantly diminished by pretreatment with the angiotensin II (ANG II) antagonist saralasin (Sar; 5 microg), into the third ventricle (3V). Injections of ANG II (5 microg) into the 3V significantly enhanced NA release in the MnPO area. The data imply that the angiotensinergic pathways from the SFO to the MnPO may act to enhance NA release in the MnPO area.

Angiotensin II↗
PubMed1989

[Schedule sensitivity in human operant behavior: instructed versus shaped verbal behavior].

Presses on left and right buttons by undergraduate students occasionally produced points exchangeable for money, according to a multiple random-ratio random-interval schedule. During interruptions in the schedule, the subjects were required to fill out sentence-completion guess sheets about how they should press the buttons to gain the points available. Three of six subjects were instructed about the rules of button pressing (the instructed group), whereas the others received no instructions but their guesses were shaped with differential points also worth money (the shaped group). The schedule was changed so that button pressing relying on the instructed or shaped rules substantially decreased the available points in the contact condition but not in the no-contact condition. A schedule change in the no-contact condition produced no performance change in either groups. In the contact condition, shaped group subjects showed a performance change, whereas instructed group subjects did not until they temporarily encountered an extinction schedule. When the no-contact condition was reintroduced, sensitive responding occurred in the shaped group but not in the instructed group suggesting that prior experience in the contact condition increased the schedule sensitivity of the shaped group. The findings clearly demonstrated that responding was more sensitive to schedule changes when the rules were shaped than when they were instructed.

Adult↗