Noradrenaline induces IPSCs in rat medial septal/diagonal band neurons: involvement of septohippocampal GABAergic neurons

J Physiol. 1996 Jul 1;494 ( Pt 1)(Pt 1):201-15. doi: 10.1113/jphysiol.1996.sp021485.


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.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Bicuculline / pharmacology
  • Hippocampus / drug effects*
  • Male
  • Membrane Potentials / drug effects*
  • Norepinephrine / pharmacology*
  • Presynaptic Terminals / drug effects
  • Rats
  • Rats, Sprague-Dawley
  • Receptors, GABA / drug effects
  • Septal Nuclei / drug effects*


  • Receptors, GABA
  • Norepinephrine
  • Bicuculline