, 1996 and Jankowska et al., 1979). Consistent with this idea, PSDCs also receive inputs from nonprimary sensory neuron sources, which include GABA and glycinergic interneurons as well as inputs from corticospinal and spinocervical tracts,

providing opportunities for presynaptic and postsynaptic modulation of LTMR inputs onto PSDCs (Bannatyne et al., 1987, Maxwell, 1988 and Maxwell Caspase pathway et al., 1995). Therefore, we speculate that PSDC output neurons are main carriers of integrated information emanating from both glabrous and hairy skin and pertaining to a variety of stimulus modalities. While PSDC neurons respond to a wide variety of sensory stimuli, SCT projection neurons are mainly concerned with hair follicle movement and therefore represent a main dorsal horn output for hairy skin innervating LTMRs. Nearly everything that we know about CP-673451 research buy the morphological and physiological characteristics of SCT neurons come from studies performed in the cat. In comparison to PSDC neurons, we know considerably more about the physiological properties of SCT neurons, due in part to the fact that SCT neuron somata are larger and therefore easier to identify and record. Like PSDC neurons, SCT neurons can also be easily identified in physiological

recording experiments by antidromic activation of their axonal tracts, in this case, the dorsal lateral funiculus or the LCN (Taub and Bishop, 1965). SCT neurons respond maximally to hair follicle deflection, with a single impulse in a hair follicle afferent capable of evoking a large excitatory postsynaptic potential. Furthermore, SCT response properties are similar to primary hair follicle afferents, suggesting direct

excitatory inputs from hairy skin LTMRs (Brown et al., 1987). Unlike PSDCs, SCT neurons do not receive SA-LTMR input from hairy skin, any LTMR input from glabrous skin, or Pacinian corpuscle (RAII-LTMR) inputs (Brown, 1981b and Hongo and Koike, 1975). Based on their response Vasopressin Receptor properties to electrical and natural stimulations, SCT neurons can be categorized into three main groups: low-threshold, wide-dynamic range, and high-threshold SCT neurons, presumably reflecting the types of LTMR inputs that they receive. Low-threshold SCTs make up 30% of the total population and are excited solely by hair movement. Wide-dynamic range SCT neurons respond to both hair movement as well as pressure or pinch stimuli and receive inputs from axons with varied conduction velocities. This subgroup represents about 70% of the total SCT population and it is thought to receive monosynaptic input from both hairy skin Aβ- as well as Aδ-LTMRs.