, 2012), and in responses of hypothalamic neurons to leptin to control energy homeostasis (Liao et al., 2012). What function would a dendritically

released neuropeptide play? The most probable role would be that the neuropeptide acts to signal other nearby neurons to either increase or decrease activity. In the olfactory CP 868596 bulb, most of the neurons, including mitral, periglomerular, and granule cells possess dendrites that release either GABA or glutamate at presynaptic specializations (Shepherd et al., 2004). Many of the presynaptic dendrites are organized in a reciprocal manner; for instance, mitral cell dendritic release of glutamate activates a presynaptic granule cell dendrite that releases GABA back onto the mitral cell, resulting in feedback inhibition. In contrast, most dendrites in the brain are not presynaptic to other cells, and dendritic release of peptides appears to be independent of synaptic specializations. Nonsynaptic release of oxytocin or vasopressin could serve to recruit or inhibit click here neighboring cells, or to synchronize activity. Oxytocin receptors are expressed by oxytocin neurons (Freund-Mercier et al., 1994), and vasopressin receptors by vasopressin cells (Hurbin et al., 2002). During

lactation, oxytocin is released in an orchestrated burst where many or most oxytocin neurons fire rapidly for a brief period of about a second (Armstrong and Hatton, 2006; Leng et al., 2008). Intermittent bursts of oxytocin release

may prevent oxytocin receptors in the mammary gland from desensitizing if oxytocin levels were to remain at statically raised L-NAME HCl levels. The burst of oxytocin potentially appears to be dependent on dendritic release of oxytocin that primes the cells for subsequent massive oxytocin release induced by an increase in spike frequency, as described above. Dendritically released peptides can act to initiate retrograde signals to modulate subsequent release of fast amino acid neurotransmitters from local axons. Oxytocin released by magnocellular cell bodies and dendrites reduces presynaptic glutamate and GABA release; although this was initially thought to be mediated by presynaptic peptide receptors, it appears more likely that oxytocin release activates receptors on oxytocin cells, resulting in release of an endocannabinoid that diffuses in a retrograde direction to activate CB1 receptors on presynaptic axons and thereby reducing fast transmitter release (Kombian et al., 1997, 2002; Hirasawa et al., 2001, 2004; Leng et al., 2008). Oxytocin release appears to be obligatory to achieve this presynaptic inhibition after depolarization of oxytocin neurons ( Hirasawa et al., 2004). Blockade of synaptic activity transiently isolates oxytocin cells from external influences, potentially amplifying local cellular interactions.