Glutamatergic hippocampal formation projections to prefrontal cortex in the rat are regulated by GABAergic inhibition and show convergence with glutamatergic projections from the limbic thalamus
✍ Scribed by John Gigg; Aiko M. Tan; David M. Finch
- Publisher
- John Wiley and Sons
- Year
- 1994
- Tongue
- English
- Weight
- 825 KB
- Volume
- 4
- Category
- Article
- ISSN
- 1050-9631
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✦ Synopsis
Anatomic and physiologic studies in the rat have shown projections from the hippocampal formation (HF) and mediodorsal (MD) thalamic nucleus to the medial prefrontal cortex (mPFC). The authors used multi-barrel iontophoresis to: confirm the neurotransmitter used in the projection from H F to mPFC; investigate the role of GABAergic inhibition in the regulation of this projection; and examine the functional convergence of projections from H F and MD onto single mPFC neurons. During H F stimulation, nine cells (6%) showed excitation followed by prolonged inhibition, 39 cells (26%) showed prolonged inhibition alone and 100 cells (68%) showed no clear response. In a further 12 cells that showed no predrug excitation to H F stimulation (representing 16% of the cells in this category), iontophoresis of the GABAa antagonist bicuculline methiodide (BMI) revealed excitatory responses. A total of six mPFC cells (38% of the cells showing excitatory responses to H F stimulation) showed convergent excitation to H F and MD thalamic (or adjacent paratenial nucleus) stimulation. Five out of eight (63%) of the predrug or BMI-revealed excitatory responses of mPFC neurons to H F stimulation were selectively decreased after AMPA antagonist iontophoresis (either CNQX or DNQX). These data confirm that the H F projection to prefrontal cortex is, at least in part, glutamatergic; suggest that the responses of mPFC neurons to activity in this H F pathway are regulated by GABAergic inhibition; and indicate that projections from H F and MD converge onto single mPFC neurons. 01994 Wiley-Liss, Inc.