CAD cells (derived from a cathecolaminergic region of mouse brain) represent a useful system to study elongation and retraction of neurites since: 1) rounded cells proliferate in standard culture medium; 2) when deprived of serum, cells stop proliferation and emit long processes similar in many aspects to normal neurons; 3) neurites rapidly retract when serum is re-added and cells resume growth. We previously found that microtubules (MTs) in these cells are highly dynamic (t ½ = 3 min, nocodazol treatment; t ½ = 6 min, FRAP), many of the major MAPs are absent, tubulin is mainly tyrosinated (Glu-tubulin is scarce and Delta 2-tubulin is absent), and acetylated tubulin is practically not detected. Herein, we investigated several possible factors that could influence elongation and/or retraction of neurites. Integrity and disassembly of MTs was required for neurite elongation and retraction, respectively. Transient increase of acetylated tubulin neither increased stability of MTs nor impeded retraction of neurites. Expression of Delta 2-tubulin did not alter elongation or retraction. Conditions that favour the interaction of MTs with plasma membrane Na,K-ATPase did not alter elongation or retraction. Treatment of cells with Lysophosphatidic acid (LPA) or with adenosine deaminase (ADA), in the absence of serum, induced neurite retraction.  ATP and/or microfilaments depletion prevented retraction suggesting that the actomyosin system is important in the retraction mechanism.