Antinociceptive effect of Aristolochia trilobata stem essential oil and 6-methyl-5-hepten-2yl acetate, its main compound, in rodents.

Aristolochia trilobata L. is an aromatic plant, popularly known as "mil-homens", and its essential oil (EO) is generally used to treat colic, diarrhea and dysentery disorders. We evaluated the antinociceptive effect of A. trilobata stem EO and of its major compound, the (R)-(-)-6-methyl-5-hepten-2-yl acetate (sulcatyl acetate: SA), using acetic acid (0.85%)-induced writhing response and formalin-induced (20 µL of 1%) nociceptive behavior in mice. We also evaluated the EO and SA effect on motor coordination, using the rota-rod apparatus. EO (25, 50 and 100 mg/kg) or SA (25 and 50 mg/kg) reduced nociceptive behavior in the writhing test (p<0.001). EO (100 mg/kg) and SA (25 and 50 mg/kg) decreased the nociception on the first phase of the formalin test (p<0.05). On the second phase, EO (25: p<0.01; 50: p<0.05 and 100 mg/kg: p<0.001) and SA (25 and 50 mg/kg; p<0.001) reduced the nociceptive response induced by formalin. EO and SA were not able to cause changes in the motor coordination of animals. Together, our results suggest that EO has an analgesic profile and SA seems to be one of the active compounds in this effect.

The effects of gap junction modulators on the rhythmic contractions in aortas isolated from rats subjected with sinoaortic denervation.

Following sinoaortic denervation (SAD) rats present intense arterial pressure lability without sustained hypertension. This study aimed to verify the effects of heptanol (a putative gap-junction blocker) and tetraethylammonium (TEA, a putative gap-junction activator) on rhythmic contractions (RCs) and vascular reactivity in the aortas isolated from SAD and Sham-operated (SO) rats. Rhythmic contractions were observed with phenylephrine in endothelium-removed aortic rings from SAD rats. We evaluated the effects of the gap-junction modulators heptanol or TEA on the frequency and amplitude of these oscillations. Additionally, concentration-response curves were constructed to TEA and KCl and in pre-contracted arteries (with phenylephrine or KCl) to heptanol in order to verify the effects of those gap-junction modulators. Comparatively, rhythmic contractions were observed in 10/10 SAD rat aortas vs. 2/10 controls. Heptanol decreased the frequency of oscillations in a concentration-dependent manner. TEA increased the amplitude and frequency of RCs. In the experiments of concentration-response curves to TEA, the maximal contractile effect was similar in both groups, although the potency was lower in SAD than in SO rat aortas. The relaxation to heptanol was different between the groups only after pre-contraction induced by phenylephrine. Heptanol showed higher potency in SAD as compared to SO rat aortas. In conclusion, arterial pressure lability occurs only in SAD rats, and their isolated aortas exhibit intense RCs. These RCs seem to be dependent of the gap-junction communication, since these oscillations are intensified by TEA and inhibited by heptanol. After SAD, aortas are more sensitive to heptanol and less sensitive to TEA.

Increased dilator response to heptanol and octanol in aorta from DOCA-salt-hypertensive rats.

This study tests the hypothesis that contractile responses in aortae of hypertensive rats are more dependent on gap junctional communication compared to those from normotensive rats. The experimental approach was pharmacological, using inhibitors of gap junctional activity (heptanol and octanol). Two models of experimental hypertension were characterized: (1) mineralocorticoid (DOCA)-hypertensive rats and (2) stroke-prone spontaneous hypertensive rats (SHRSP). Vessels from DOCA-hypertensive rats showed a greater relaxation to heptanol and octanol, particularly when precontracted with phenylephrine, compared to sham-operated animals. Octanol-induced relaxation in aortic segments from SHRSP did not differ from normotensive values regardless of the agonist used to cause contraction. These results suggest that in DOCA hypertension, gap junctional communication and voltage-operated calcium channels are differentially regulated, which could explain in part the changes in vascular reactivity observed in mineralocorticoid hypertension.

Gap junctions in isolated rat aorta: evidence for contractile responses that exhibit a differential dependence on intercellular communication.

Connexin43 (Cx43) is a major gap junction protein present in the Fischer-344 rat aorta. Previous studies have identified conditions under which selective disruption of intercellular communication with heptanol caused a significant, readily reversible and time-dependent diminution in the magnitude of alpha1-adrenergic contractions in isolated rat aorta. These observations have indentified a significant role for gap junctions in modulating vascular smooth muscle tone. The goal of these steady-state studies was to utilize isolated rat aortic rings to further evaluate the contribution of intercellular junctions to contractions elicited by cellular activation in response to several other vascular spasmogens. The effects of heptanol were examined (0.2-2.0 mM) on equivalent submaximal ( approximately 75% of the phenylephrine maximum) aortic contractions elicited by 5-hydroxytryptamine (5-HT; 1-2 microM), prostaglandin F2alpha (PGF2alpha; 1 microM) and endothelin-1 (ET-1; 20 nM). Statistical analysis revealed that 200 microM and 500 microM heptanol diminished the maximal amplitude of the steady-state contractile responses for 5-HT from a control response of 75 +/- 6% (N = 26 rings) to 57 +/- 7% (N = 26 rings) and 34.9 +/- 6% (N = 13 rings), respectively (P<0.05), and for PGF2alpha from a control response of 75 +/- 10% (N = 16 rings) to 52 +/- 8% (N = 19 rings) and 25.9 +/- 6% (N = 18 rings), respectively (P<0.05). In contrast, 200 microM and 500 microM heptanol had no detectable effect on the magnitude of ET-1-induced contractile responses, which were 76 +/- 5. 0% for the control response (N = 38 rings), 59 +/- 6.0% in the presence of 200 microM heptanol (N = 17 rings), and 70 +/- 6.0% in the presence of 500 microM heptanol (N = 23 rings) (P<0.13). Increasing the heptanol concentration to 1 mM was associated with a significant decrease in the magnitude of the steady-state ET-1-induced contractile response to 32 +/- 5% (21 rings; P<0.01); further increasing the heptanol concentration to 2 mM had no additional effect. In rat aorta then, junctional modulation of tissue contractility appears to be agonist-dependent.

Calcium waves between astrocytes from Cx43 knockout mice.

Gap junctions are regarded as the primary pathway underlying propagation of Ca2+ waves between astrocytes, although signaling through extracellular space may also contribute. Results obtained from astrocytes cultured from sibling Cx43 knockout (KO) and wild-type (WT) mice in six litters showed that Ca2+ waves propagated more slowly in Cx43 KO than in WT astrocytes; however, because this difference in velocity was only seen in conditions where cell confluence was higher in WT than KO astrocytes, it is attributable to differences in plating density. By contrast, density-independent differences were observed in the amplitudes of the Ca2+ responses (15% smaller in KO astrocytes) and efficacy of spread (to 14% fewer cells in KO astrocytes). Blockade of purinergic receptors with suramin reduced the velocities of the waves by 40% in WT and KO astrocytes and reduced the amplitudes by 20% and 6%, respectively. In the presence of heptanol, Ca2+ waves spread to only 30% of the cells, with a 70% reduced velocity and 30% reduced amplitude. It is concluded that the propagation of Ca2+ waves between astrocytes from Cx43 KO mice is not so greatly affected as expected by deletion of the major gap junction protein between these cells. The residual 5% coupling contributed by the additional connexins (Cx40, Cx45, and Cx46) expressed in KO astrocytes still suffices to provide a more substantial portion of Ca2+ wave propagation than does signaling through extracellular purinergic pathways. These studies demonstrate that, even with severely reduced junctional conductance, Cx43 KO astrocytes are capable of performing long-range Ca2+ wave signaling, perhaps preserving one mechanism critical to neural function.