Piriform cortex

Fig. 35.1 Simplified diagram of chemosensory circuit in amygdala. Vomeronasal input via accessory olfactory bulb (VNO/ AOB) is analyzed in anterior and posterior medial amygdala (MeA, MeP). MeP appears to be inhibited by intercalated nucleus (ICNc) for heterospecific and artificial stimuli. MOE/ MOB Main olfactory epithelium/Main olfactory bulb. ACN Anterior Cortical Nucleus. PC Piriform Cortex. BLA Basolateral amygdala. ICNr rostral part of medial intercalated nucleus. ICNc caudal part of ICN. MPOA Medial Preoptic Area. VMH Ventro-medial hypothalamus...

Intracerebral injections of ibotenic acid produce cell loss in several cerebral areas, including the striatum, the hippocampus, substantia nigra, and piriform cortex (Schwarcz et al. 1979). This degeneration is limited to the site of injection and does not affect axons, passage, or synaptic terminals originating in other areas. 

Marek GJ, Aghajanian GK. (1996). LSD and the phenethyiamine haiiucinogen DOI are potent partial agonists at 5-HT2A receptors on interneurons in rat piriform cortex. J Pharmacol Exp Then 278(3) 1373-82. 

Found by IHC in amygdaloid structures, supraoptic nucleus, reticular thalamic nucleus, olfactory tract and piriform cortex, less so in the paraventricular and arcuate nuclei and hippocampus of rat (Sanghera et al., 1991). 

The long length fibres link the ventral tegmental and substantia nigra dopamine-containing cells with the neostriatum (mainly the caudate and the putamen), the limbic cortex (the medial prefrontal, cingulate and entorhinal areas) and with limbic structures such as the septum, nucleus accumbens, amygdaloid complex and piriform cortex. These projections are... 

Marek GJ, Aghajanian GK. Protein kinase C inhibitors enhance the 5-HT2A receptor-mediated excitatory effects of serotonin on intemeurons in rat piriform cortex. Synapse 1995 21(2) 123—130. 

The 5-HT7 receptors are also positively coupled to adenylate cyclase. Since their discovery in 1993 (229-233), they have been identified in numerous mammalian species, including human. Different splice variants have been detected in the rat compared to the human, but do not seem to differ in functional properties (234-236). Early and recent in situ hybridization studies in the guinea pig and rat have demonstrated 5-HT7 mRNAs to be most abundant in the tenia tecta and piriform cortex, hippocampus, thalamus, and hypothalamus, including the suprachiasmatic nucleus (230,237-239). 

The mRNA coding for 5-HT6 receptor has been localized in the rat brain by Northern blot, PCR, and in situ hybridization (206,207,213,214) (see also Fig. 10) and the protein by immunohistochemistry (213). The first and more detailed description on the localization of mRNA coding for 5-HT6 receptor was published by Ward and co-workers (215), reporting that the main rat brain regions where this receptor is expressed is the pyramidal layer of the olfactory tubercle, islands of Calleja, nucleus accumbens, striatum, hippocampus, and piriform cortex. At moderate levels, it is expressed in other cortical areas, the olfactory bulb, some nuclei of the hypothalamus and amygdale, the habenula, and the cerebellum. No mRNA expression is found in the raphe nucleus. These results were confirmed later (204). 

The D4 receptor has been described in layers II-VI of both the frontal and the piriform cortex of the mouse brain, with the highest concentration in layer II. D4 receptors are distributed in somata and proximal processes of pyramidal neurons. In cortical regions, the levels of D4 receptors were found to be higher than those of D2 and D3 receptors (Ariano et al., 1997 Mauger et al., 1998). 

Heimer L, Wilson RD (1975) The subcortical projections of the alocortex similarities in the neural associations of the hippocampus, the piriform cortex and the neocortex. In Santorini M (Ed), Golgi Centennial Symposium Proceedings, pp. 177-183. Raven Press, New York. 

Wahnschaffe U, Ebert U, Loscher W. The effects of lesions of the posterior piriform cortex on amygdala kindling in the rat. Brain Res 1993 615 295-303. 

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