Dopamine modulates cardiovascular function by actions in the central and peripheral nervous system, by altering the secretion/release of prolactin, pro-opiomelanocortin, vasopressin, aldosterone, and renin, and by directly affecting renal function. Dopamine produced by the renal proximal tubule exerts an autocrine/paracrine action via two classes of dopamine receptors, D1-like (D1 and D5) and D2-like (D2, D3, and D4), that are differentially expressed along the nephron. The autocrine/paracrine function of dopamine, manifested by tubular rather than by haemodynamic mechanisms, becomes most evident during extracellular fluid volume expansion. This renal autocrine/paracrine function is lost in essential hypertension and in some animal models of genetic hypertension. The molecular basis for the dopaminergic dysfunction in hypertension may involve an abnormal post-translational modification of dopamine receptors.

A sub-2Ops silicon bipolar technology has been developed using Selective Epitaxial Growth (SEG) for the active base and collector regions. This transistor concept allows the simultaneous reduction of base width and base/collector capacitance while maintaining low extrinsic base resistance.At a current of 0.8 mA a record CML gate delay time of 18ps is achieved with devices showing a cut-off frequency of 44 GHz. The high-speed capability of this technology has also been shown by a static 2:l frequency divider operating up to 25 GHz.

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This paper describes a high performance bipolar process based on bonded SO1 wafers featuring deep trench isolation, double polysilicon self-alignment, and a substrate-erosion free composite spacer scheme. The process provides transistors with excellent dc and ac parameters. Gate delay times of 19.6 ps, powerdelay products of 8.6 fJ, and 2:l frequency dividers operating up to 22.4 GHz are prominent performance data which are -to the authors knowledge -best values ever reported for SOI-based bipolar technologies.

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