Synaptic profile of nucleus tractus solitarius neurons involved with the peripheral chemoreflex pathways.

The glomus cells in the carotid bodies (CB) detect alterations in pH and pCO2 and low pO2 level in arterial blood. The carotid sinus nerve conveys the information related to the oxygen level to 2nd-order neurons in the nucleus tractus solitarius (NTS) via tractus solitarius (TS), which is part of the chemoreflex pathways. It has been demonstrated that in 2nd-order NTS neurons receiving inputs from the aortic depressor nerve (ADN), the TS stimulation presents high temporal fidelity. However, the temporal properties of synaptic activity in NTS neurons receiving inputs from CB were not yet fully investigated. Herein using patch-clamp recordings in NTS brainstem slices, we studied TS-evoked excitatory postsynaptic currents (TS-eEPSCs) on morphologically identified 2nd-order NTS neurons that receive afferent inputs from the CB and compared with 2nd-order ADN-NTS neurons recorded in the same experimental conditions. The amplitudes of TS-eEPSCs were similar in both groups, but the latencies and standard deviation (SD) of latency were significantly higher in the CB-NTS neurons (latency: 4±0.2 ms, SD: 0.49±0.03 ms) than in ADN-NTS neurons (latency: 3.3±0.3 ms, SD: 0.19±0.02 ms; P=0.049 for latency and P<0.001 for SD of latency). In a series of double-labeling experiments, we confirmed that some CB-NTS 2nd-order neurons send direct projections to the rostral ventrolateral medulla (RVLM). We conclude that: (a) CB-NTS 2nd-order neurons present temporally distinct postsynaptic currents when compared with ADN-NTS 2nd-order neurons; (b) low SD of latency of TS-eEPSCs is not necessarily a characteristic of all 2nd-order neurons in the NTS; and (c) the presence of direct connections between these 2nd-order neurons in the NTS and RVLM is indicative that these synaptic properties of CB-NTS neurons are relevant for the processing of respiratory and autonomic responses to chemoreflex activation.

The balloon catheter induces an increase in contralateral carotid artery reactivity to angiotensin II and phenylephrine.

1. The effects of balloon injury on the reactivity of ipsilateral and contralateral carotid arteries were compared to those observed in arteries from intact animals (control arteries). 2. Carotid arteries were obtained from Wistar rats 2, 4, 7, 15, 30 or 45 days after injury and mounted in an isolated organ bath. Reactivity to angiotensin II (Ang II), phenylephrine (Phe) and bradykinin (BK) was studied. Curves were constructed in the absence or presence of endothelium or after incubation with 10 microm indomethacin, 500 microm valeryl salicylate or 0.1 microm celecoxib. 3. Phe, Ang II and BK maximum effects (Emax) were decreased in ipsilateral arteries when compared to control arteries. No differences were observed among pD2 or Hill coefficient. 4. Emax to Phe (4 and 7 days) and to Ang II (15 and 30 days) increased in the contralateral artery. In addition, Phe or Ang II reactivity was not significantly different in aorta rings from control or carotid-injured animals. 5. The increased responsiveness of contralateral artery was not due to changes in carotid blood flow or resting membrane potential. The endothelium-dependent inhibitory component is not present in the contraction of contralateral arteries and it is not related to superoxide anion production. 6. Indomethacin decreased contralateral artery responsiveness to Phe and Ang II. Valeryl salicylate reduced the Ang II response in contralateral and control arteries. Celecoxib decreased the Phe Emax of contralateral artery. 7. In conclusion, decreased endothelium-derived factors and increased prostanoids appear to be responsible for the increased reactivity of contralateral arteries after injury.

Angiotensin actions on the isolated rat uterus during the estrous cycle: influence of resting membrane potential and uterine morphology.

The involvement of AT1 and AT2 receptor subtypes in the response of the isolated rat uterus to angiotensin II (AngII) was studied throughout the estrous cycle. The AngII potency varied during the different estrous cycle phases, as indicated by significantly different pD2 values. No significant differences were observed in AngII metabolism among different estrous phases. Morphological analysis indicated that external and internal myometrium layers were thicker during estrus. In addition, the highest resting membrane potential was also observed during this phase, when compared with the proestrus and diestrus phases. The AngII-induced uterine contractions were blocked by losartan. Different losartan pD2 values were observed. PD123319 had no effect on the contractile response to AngII. The results also indicate that estrous cycle-dependent changes in AngII potency are correlated with uterine morphological and/or membrane potential changes.

Influence of estrogen and/or progesterone on isolated ovariectomized rat uterus. Responsiveness to Ang II.

Steroids hormones can influence several functions of the uterus, including agonist-induced contractions. The aim of this work is to study the influence of hormonal replacement on angiotensin II (Ang II) and losartan responsiveness on the isolated rat uterus. The Ang II pD(2) values are: 9.69 +/- 0.07 for vehicle-treated animals, 8.85 +/- 0.06 for estrogen-treated animals, 10.12 +/- 0.03 for progesterone-treated animals and 8.90 +/- 0.03 for estrogen-and-progesterone-treated animals. The losartan pD(2)' values are: 8.43 +/- 0.03 for vehicle-treated animals, 8.21 +/- 0.03 for estrogen-treated animals, 7.83 +/- 0.05 for progesterone-treated animals and 8.70 +/- 0.09 for estrogen-and-progesterone-treated animals. There is not a correlation between Ang II pD(2) and losartan pD(2)' values, suggesting that the hormones affect Ang II and losartan binding by different mechanisms in rat uterus.