accessory olfactory receptor
Acronym:
OLRa
The term accessory olfactory receptor (OLRa) refers to one of two kinds of olfactory receptor (OLR). The other is the main olfactory receptor (OLRm). OLRa's are less numerous than OLRm's. Their cell bodies are located in the vomeronasal organ (VNO), a small circumscribed depression in the olfactory epithelium (OLE) of the nasal septum rostral and ventral to the OLRm's ( Barral-2009 ). They detect pheromones, 'social' oderants, which are sex- and age-specific chemicals secreted by other individuals of the same species. The VNO locus of OLRa's is quite prominent in the rodent ( Wirsig-Wiechmann-2001 ), less so in the human ( Barral-2009 ) and may be absent in the macaque ( Zhang-2003 Francia-2014 ).
The specialized receptor dendrite of an OLRa neuron transduces chemical oderant signals into electrochemical spikes. The spike signal is transmitted by axon in the vomeronasal nerve (vn) component of the vomeronasal-terminal nerve complex (vtnc) through the cribriform plate, the bony roof of the nasal cavity, to the accessory olfactory bulb (OLBa) ( Barral-2009 Wirsig-Wiechmann-2001 ). OLRa neurons also receive reciprocal input from the OLBa. Axons from OLBa are embedded in the terminal nerve (tn) component of the same vtnc. They release gonadotrophin-releasing hormone (GnRH) to OLRa neurons.
GnRH in other parts of the brain has different physiological and behavioral effects in males and females .( Wirsig-Wiechmann-2001 ). The presence of information as to the sexual category of both the stimulus individual and the perceiving individual at the entry to the olfactory system (OLS) suggests that the unique sensorimotor pathway from oderant stimulus to the adaptive behavioral response begins at the very first level of olfactory sensory processing.
In animals, pheromones play an essential role in marking, mate selection and other aspects of territorial and reproductive behavior. In humans they are known to be involved in physiological synchronization of menstrual cycles of women living in close residential contact, such as a convent or boarding school ( Barral-2009 ).
Some authors consider OLRa's to be vestigial in primates and, by implication, of minimal if any causal significance in the human ( Witt-2002 Zhang-2003 Francia-2014 ). Others note the physiological synchronizing effect in humans and tentative evidence of behavioral and psychological effects as potentially important clinical significance in humans ( Grammer-2005 Barral-2009 Buck-2013 ).
Experimental evidence for behavioral significance of an accessory system operating subconsciously in primates includes findings that: 1) humans and macaques are able to make accurate discriminations between visual stimuli without conscious awareness (blindsight, subliminal perception)...an effect mediated by the amygdala ( Weiskrantz-2004 ), and, 2) whereas OLRm neurons responsive to consciously perceived oderants project to multiple cortical structures, the accessory pathway from OLRa projects exclusively to the amygdala,( Buck-2013 ). Updated 13 Sep 2024.
Also known as: No other name for this structure has appeared in PubMed.NeuroNames ID : 5718
|
|