We examine the extent to which practices of language use may be diffused through language contact and areally shared, using data on spatial reference frame use by speakers of eight indigenous languages from in and around the Mesoamerican linguistic area and three varieties of Spanish. Regression models show that the frequency of L2-Spanish use by speakers of the indigenous languages predicts the use of relative reference frames in the L1 even when literacy and education levels are accounted for. A significant difference in frame use between the Mesoamerican and non-Mesoamerican indigenous languages further supports the contact diffusion analysis.

Dopamine receptors include the D1- (D1 and D5 subtypes) and D2-like (D2, D3, and D4 subtypes) families. D1-like receptors are positively and D2-like receptors negatively coupled to the adenylyl cyclase. Dopamine D2-like (D4 subtype) receptors have been identified in human and rat hearts. However the presence of D2 and D3 receptor subtypes is unclear. Furthermore, their role in cardiac functions is unknown. By autoradiographic studies of guinea pig hearts, we identified D3 and D4 receptors, using the selective radioligands [3H]-7-OH-DPAT and [3H]emonapride (YM-09151-2 plus raclopride). Western blot analysis confirmed D3 and D4 receptors in the right and left ventricle of the same species. Selective agonists of D3 and D4 receptors (+/-)-7-OH-DPAT and PD 168 077 (10(-9) to 10(-5) M, respectively) induced a significant negative chronotropic and inotropic effect in the isolated guinea pig heart preparation. Negative inotropic effect induced by PD 168 077 was associated with an inhibition in cyclase activity. No changes in cyclase activity were found with (+/-)-7-OH-DPAT. The aim of this study is to support the presence of D3 and D4 receptors in the heart. Although our results suggest that D3 and D4 receptors are functionally active in the heart, we need additional information with an antagonist and an agonist of improved potency and selectivity to understand the respective roles of D3 and D4 receptors in the cardiac functions.

1 Differences in vascular responses to phenylephrine, acetylcholine (ACh) and potassium chloride (KCl) were studied in rabbit aorta from female and male rabbits, in the absence and presence of an inhibitor of nitric oxide (NO) production, N0-nitro-L-arginine methyl ester (L-NAME, 100 yM).2 Phenylephrine and KCl-induced contractions, were significantly reduced in amplitude (P<0.01) in the rings from female rabbits compared to those from male rabbits. 3 ACh-induced relaxation was greater (P<0.01) in aortic rings from females than from males. 4 Incubation of the rings with L-NAME abolished the phenylephrine-induced contraction differences between rings from male and female rabbits. 5 Ovariectomy eliminated the differences in vascular responses to phenylephrine, KCl and ACh of aortic rings from the female rabbits. 6 Both basal and ACh-stimulated release of nitrites from aortic rings was greater (P<0.01) in vascular tissue from female than male rabbits. 7 These results indicate that differences in vascular reactivity in aortic rings from male and female rabbits may be associated with a higher release of NO, resulting in an increased vasodilator response in the female rabbits.

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