T-type channels are weakly or unexpressed in adult rat chromaffin cells (RCCs) and there is contrasting evidence as to whether they play a functional role in catecholamine secretion. Here we show that 3-5 days after application of pCPT-cAMP, most RCCs grown in serum- free medium expressed a high density of low-voltage- activated T-type channels without altering the expression and characteristics of high-voltage-activated channels. The density of cAMP-recruited T-type channels increased with time and displayed the typical biophysical and pharmacological properties of low- voltage-activated Ca²⁺ channels: 1) steep voltage-dependent activation from -50 mV in 10 mM Ca²⁺, 2) slow deactivation but fast and complete inactivation, 3) full inactivation following short conditioning pre-pulses to -30 mV, 4) effective block of Ca²⁺ influx with 50 µM Ni²⁺, 5) comparable permeability to Ca²⁺ and Ba²⁺, 6) insensitivity to common Ca²⁺-channel antagonists. The action of exogenous pCPT-cAMP (200 µM) was prevented by the protein synthesis inhibitor anisomycin and mimicked in most cells by exposures to forskolin and IBMX or isoprenaline. The PKA inhibitor H89 (0.3 µM) and the competitive antagonist of cAMP binding to PKA, Rp-cAMPS, had weak or no effects on the action of pCPT- cAMP. In line with this, the selective Epac agonist 8CPT- 2Me-cAMP, nicely mimicked the action of pCPT-cAMP and isoprenaline, suggesting the existence of a dominant Epac-dependent recruitment of T-type channels in RCCs that may originate from the activation of - adrenoceptors. Stimulation of -adrenoceptors occurs autocrinally in RCCs and thus, the neosynthesis of low-voltage-activated channels may represent a new form of "chromaffin cell plasticity", which contributes, by lowering the threshold of action potential firing, to increasing cell excitability and secretory activity during sustained sympathetic stimulation and/or increased catecholamine circulation.