Piriform cortex anterior interneuron deep layer GABA cell

- - - OLFcx - OCant - INT - - - gaba
Properties are:  Present   Absent 
Input Receptors
Intrinsic Currents
Output Transmitters
Distal equivalent dendrite
Piriform cortex anterior pyramidal layer II GLU cell
 -Axon terminal.Glutamate
AMPA
Inhibitory interneurons, recorded mostly in the deeper part of layer II of piriform cortex, mediate fast IPSPs in principal cells and are activated at least partly through the axon collaterals of the principal cells (Satou M et al, 19831 ). Evidence of spatial and temporal facilitation of fast IPSPs, interpretated as the convergence of excitatory input onto the inhititory interneurons from different olfactory structures (Satou M et al, 19832 ). Morphological evidence of local contact by pyramidal neurons (Haberly LB and Presto S, 19863 ).
5-HT2
A subpopulation of interneurons in layer III of the rat piriform cortex are excited by 5-hydroxytryptamine (5-HT) via 5-HT2A receptors and by norepinephrine via alpha 1-adrenoceptors. (Marek GJ and Aghajanian GK, 19966 ). 5-HT excites 5-HT2 receptors in interneurons and 5-HT1C receptors in pyramidal neurons (Sheldon PW and Aghajanian GK, 19917 ). (Sheldon PW and Aghajanian GK, 19908 ). PKC may have a negative feedback role in modulating excitation by 5-HT in piriform cortical interneurons (Marek GJ and Aghajanian GK, 19959 ).
Alpha1
A subpopulation of interneurons in layer III of the rat piriform cortex are excited by 5-hydroxytryptamine (5-HT) via 5-HT2A receptors and by norepinephrine via alpha 1-adrenoceptors. (Marek GJ and Aghajanian GK, 19966 ).
Monoamine Receptors
IPSPs elicited by monoamines in pyramidal cells result from a convergence of inputs from populations of layer II/III interneurons that are activated by one, two or all three of the following monoamines 5-HT, NE, and DA. (Gellman RL and Aghajanian GK, 199310 ).
Piriform cortex anterior pyramidal layer II GLU cell
 -Axon terminal.Glutamate
NMDA
Middle equivalent dendrite
Proximal equivalent dendrite
GABAergic input? Gaba
GABAergic interneurons in deeper layers of piriform cortex receive symmetric synapses as well as asymmetric synapses (Haberly LB et al, 198711 ).
Soma
Acetylcholine action: pre- or post-synaptic? Cholinergic Receptors
Cholinergic agonist carbachol caused a significant suppression of inhibitory postsynaptic potentials (IPSPs) in the pyramidal neurons that were induced by stimulation of layer Ib, with a weaker effect on IPSPs induced by stimulation of layer Ia (Patil MM and Hasselmo ME, 19995 ).
GABAergic input? Gaba
GABAergic interneurons in deeper layers of piriform cortex receive symmetric synapses as well as asymmetric synapses (Haberly LB et al, 198711 ).
I T low threshold
Low threshold inactivating Ca2+ current (Tseng GF and Haberly LB, 198914 ). (Magistretti J and de Curtis M, 199815 ).
I Na,t
TTX-sensitive sodium current (possibly of the transient type?) may also be present (Tseng GF and Haberly LB, 198914 ).
I M
I M may contribute to a sag and rebound of voltage response to hyperpolarizing current steps (Tseng GF and Haberly LB, 198914 ).
I A
Some diferences in the neurons in the deeper layers (v.s. those in the superficial layers) can be accounted for by differences in the IA channel in the cells (Banks MI et al, 1996 [rat]16 ).
Axon hillock
Axon fiber
Axon terminal
Ach action: pre- or postsynaptic? Cholinergic Receptors
Cholinergic agonist carbachol selectively suppresses intrinsic fiber synaptic potentials but not afferent fiber synaptic potentials. A presynaptic mechanism of cholinergic suppression is suggested (Hasselmo ME and Bower JM, 19924 ). Cholinergic agonist carbachol caused a significant suppression of inhibitory postsynaptic potentials (IPSPs) in the pyramidal neurons that were induced by stimulation of layer Ib, with a weaker effect on IPSPs induced by stimulation of layer Ia (Patil MM and Hasselmo ME, 19995 ).
GABAB presynaptic mechanism? GabaB
Baclofen suppresses field potentials at the intrinsic fiber synapses proximal to the pyramidal cell bodies (layer Ib) but not field potential at distal dendrites (layer Ia). afferent and intrinsic synaptic inputs may be differentially modulated by the activation of GABAB receptors and that this selective suppression is at least partially mediated via a presynaptic mechanism (at the interneuron terminals?) (Tang AC and Hasselmo ME, 199412 ). Although both the soma and distal dendrites have both the fast and slow GABAA-mediated IPSCs, there is a greater proportion of slow component in the dendrites. Slow GABAA mediated IPSC component is regulated by presynaptic GABAB inhibition (at the interneuron terminals?) whereas the fast is not (Kapur A et al, 199713 ).
Gaba
Piriform cortex anterior pyramidal layer II GLU cell
 -Proximal apical dendrite.GabaA
 -Proximal apical dendrite.GabaB
 -Soma.GabaA
 -Soma.GabaB
onto pyramidal neuron
Inhibition of deep neurons (pyramidal and multipolar) by (presumed?) deep layer interneurons involves a fast Chloride and a slow potassium-mediated IPSP (Tseng GF and Haberly LB, 198917 ). Different GABAergic receptors are localized to specific layers, and may mediate feedforward and feedback inhibitions (Princivalle A et al, 200018 ). Cholinergic agonist carbachol caused a significant suppression of inhibitory postsynaptic potentials (IPSPs) in the pyramidal neurons that were induced by stimulation of layer Ib, with a weaker effect on IPSPs induced by stimulation of layer Ia (Patil MM and Hasselmo ME, 19995 ). Dendritic GABAA-mediated IPSPs act largely independent of somatic IPSPs and may regulate facilitation of MNDA-mediated respnses (Kanter ED et al, 199619 ).
Classical References: first publications on each compartmental property; search PubMed for complete list
1.  Satou M, Mori K, Tazawa Y and Takagi SF. (1983) Interneurons mediating fast postsynaptic inhibition in pyriform cortex of the rabbit. J Neurophysiol 50:89-101 [Journal] .
2.  Satou M, Mori K, Tazawa Y and Takagi SF. (1983) Neuronal pathways for activation of inhibitory interneurons in pyriform cortex of the rabbit. J Neurophysiol 50:74-88 [Journal] .
3.  Haberly LB and Presto S. (1986) Ultrastructural analysis of synaptic relationships of intracellularly stained pyramidal cell axons in piriform cortex. J Comp Neurol 248:464-74 [Journal] .
4.  Hasselmo ME and Bower JM. (1992) Cholinergic suppression specific to intrinsic not afferent fiber synapses in rat piriform (olfactory) cortex. J Neurophysiol 67:1222-9 [Journal] .
5.  Patil MM and Hasselmo ME. (1999) Modulation of inhibitory synaptic potentials in the piriform cortex. J Neurophysiol 81:2103-18 [Journal] .
6.  Marek GJ and Aghajanian GK. (1996) Alpha 1B-adrenoceptor-mediated excitation of piriform cortical interneurons. Eur J Pharmacol 305:95-100.
7.  Sheldon PW and Aghajanian GK. (1991) Excitatory responses to serotonin (5-HT) in neurons of the rat piriform cortex: evidence for mediation by 5-HT1C receptors in pyramidal cells and 5-HT2 receptors in interneurons. Synapse 9:208-18 [Journal] .
8.  Sheldon PW and Aghajanian GK. (1990) Serotonin (5-HT) induces IPSPs in pyramidal layer cells of rat piriform cortex: evidence for the involvement of a 5-HT2-activated interneuron. Brain Res 506:62-9.
9.  Marek GJ and Aghajanian GK. (1995) Protein kinase C inhibitors enhance the 5-HT2A receptor-mediated excitatory effects of serotonin on interneurons in rat piriform cortex. Synapse 21:123-30 [Journal] .
10.  Gellman RL and Aghajanian GK. (1993) Pyramidal cells in piriform cortex receive a convergence of inputs from monoamine activated GABAergic interneurons. Brain Res 600:63-73.
11.  Haberly LB, Hansen DJ, Feig SL and Presto S. (1987) Distribution and ultrastructure of neurons in opossum piriform cortex displaying immunoreactivity to GABA and GAD and high-affinity tritiated GABA uptake. J Comp Neurol 266:269-90 [Journal] .
12.  Tang AC and Hasselmo ME. (1994) Selective suppression of intrinsic but not afferent fiber synaptic transmission by baclofen in the piriform (olfactory) cortex. Brain Res 659:75-81.
13.  Kapur A, Pearce RA, Lytton WW and Haberly LB. (1997) GABAA-mediated IPSCs in piriform cortex have fast and slow components with different properties and locations on pyramidal cells. J Neurophysiol 78:2531-45 [Journal] .
14.  Tseng GF and Haberly LB. (1989) Deep neurons in piriform cortex. II. Membrane properties that underlie unusual synaptic responses. J Neurophysiol 62:386-400 [Journal] .
15.  Magistretti J and de Curtis M. (1998) Low-voltage activated T-type calcium currents are differently expressed in superficial and deep layers of guinea pig piriform cortex. J Neurophysiol 79:808-16 [Journal] .
16.  Banks MI, Haberly LB and Jackson MB. (1996) Layer-specific properties of the transient K current (IA) in piriform cortex. J Neurosci 16:3862-76.
17.  Tseng GF and Haberly LB. (1989) Deep neurons in piriform cortex. I. Morphology and synaptically evoked responses including a unique high-amplitude paired shock facilitation. J Neurophysiol 62:369-85 [Journal] .
18.  Princivalle A, Spreafico R, Bowery N and De Curtis M. (2000) Layer-specific immunocytochemical localization of GABA(B)R1a and GABA(B)R1b receptors in the rat piriform cortex. Eur J Neurosci 12:1516-20.
19.  Kanter ED, Kapur A and Haberly LB. (1996) A dendritic GABAA-mediated IPSP regulates facilitation of NMDA-mediated responses to burst stimulation of afferent fibers in piriform cortex. J Neurosci 16:307-12.