title: Noradrenaline induces IPSCs in rat medial septal/diagonal band neurons: involvement of septohippocampal GABAergic neurons.
abstract: 1. The physiological and pharmacological actions of noradrenaline (NA) on neurons of the medial septum and diagonal band of Broca (MSDB) were examined using extracellular, intracellular and whole-cell patch-clamp recordings in an in vitro rat brain slice preparation. 2. In current- and voltage-clamp recordings with KCl- or potassium gluconate-containing electrodes, bath-applied NA increased the number of tetrodoxin- and bicuculline-sensitive synaptic events in > 80% of cholinergic- and GABA-type neurons tested. The NA-induced synaptic activity originated from GABAergic neurons located within the MSDB itself, as a similar effect occurred in brain slices in which the MSDB had been surgically isolated from neighbouring structures. 3. In antidromic studies, NA dose-dependently increased firing in a subpopulation of septohippocampal neurons with fast conducting fibres (mean conduction velocity, 1.78 +/- 0.10 m s-1; presumably GABAergic). The NA excitation was mimicked by the alpha 1-agonist phenylephrine (PE) and blocked by the alpha 1-antagonists prazosin and WB-4101, suggesting the presence of alpha 1-receptors on septohippocampal GABAergic neurons. 4. Similarly, in whole-cell recordings in both cholinergic- and non-cholinergic-type MSDB neurons, prazosin blocked the effects of NA and PE mimicked the effects of NA by inducing IPSCs with a similar amplitude distribution. 5. Consistent with the above findings, GABA-type neurons that responded directly to NA and PE with a prazosin-sensitive inward current were found within the MSDB. 6. In conclusion, NA, via alpha 1-adrenoceptors, excites MSDB septohippocampal GABAergic neurons and influences both septal and septohippocampal circuitry.
authors.affiliation: Department of Psychiatry, Yale University School of Medicine, New Haven, CT 06508, USA. Meenakshi.Alreja@yale.edu
authors.forename: M
authors.initials: M
authors.lastname: Alreja
authors.forename: W
authors.initials: W
authors.lastname: Liu
mesh_terms: D000818:Animals; D001640:Bicuculline / Q000494:pharmacology; D006624:Hippocampus / Q000187:drug effects*; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects*; D009638:Norepinephrine / Q000494:pharmacology*; D017729:Presynaptic Terminals / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D018079:Receptors, GABA / Q000187:drug effects; D012686:Septal Nuclei / Q000187:drug effects*
chemical_list: D018079:Receptors, GABA; D009638:Norepinephrine; D001640:Bicuculline