The high endogenous serotonin levels resulting from monoamine oxidase A (MAOA) deficiency in the Tg8 mouse (Cases et al. 1995) alter the prenatal maturation of the respiratory network and induce respiratory deficits in adults (Bou-Flores et al. 2000; Burnet et al. 2001). As the ventral respiratory group (VRG) contains structures necessary for respiratory rhythm generation, we wondered whether the VRG network was different in mutant Tg8 and normal albino Swiss strains (ASS).

Four adult male from both strains were deeply anaesthetised (chloral hydrate, 300 mg kg^-1 I.P.). Their VRG was first localised by recording inspiratory multiunit activity with a glass micropipette (30-70 µm tip diameter, 4-8 MV) filled with a mixture of 2 % Fast Blue (FB, Sigma) and 10 % Fluororuby (FR, Molecular Probes). Then, pressure injections were made unilaterally at VRG sites (Picospritzer, General Valve). The animals were killed (under deep anaesthesia) 10 days after the injection. Histological sections were studied with a standardised procedure to evaluate quantitative differences (means ± S.E.M.; P ²le³ 0.05, Student’s unpaired t test).

In conclusion, the VRG is interconnected with different cerebellar, midbrain, diencephalic and telencephalic areas related to autonomic functions in both mouse strains, as well as in rats (Gaytán & Pásaro, 1998; Gaytán et al. 2002) but the adult VRG connectivity is altered by prenatal serotonin excess.

This work was supported by P.A.I. Junta de Andalucía and D.G.I. BFI2002-02055