Adaptive changes of beta-adrenergic receptors after neonatal locus coeruleus lesion: regulation of serotoninergic unit activity.

Spontaneous activity of 5-hydroxytryptamine (5-HT) neurons in the dorsal raphe nucleus (DRN) was recorded in adult rats that had undergone a bilateral locus coeruleus (LC) lesion during the neonatal period. The susceptibility of this neuronal firing to beta-adrenergic manipulation was tested. Microiontophoretic application of the beta-blockers d,l-propranolol and acebutolol inhibited the firing of DRN cells in lesioned rats but not in control animals. This effect was specific to beta-receptors since the effects of pharmacological manipulation of other receptors--5-HT, gamma-aminobutyric acid (GABA), alpha-adrenoceptors--were identical in lesioned and control animals. The present data demonstrate that a neonatal noradrenergic lesion allowed the persistence of a beta-regulation of DRN neuronal firing, which in young rats is normally only transient.