Properties of large conductance calcium-activated potassium channels in pyramidal neurons from the hippocampal CA1 region of adult rats.

The properties of large-conductance Ca(2+)-activated K(+) (BK(Ca)) channels were studied in rat hippocampal CA1 pyramidal neurons by using the patch-clamp technique in the excised-inside-out-patch configuration. The lowest [Ca(2+)](i) in which BK(Ca) channel activities were observed was 0.01 microM with the membrane potential of +20 mV and the [Ca(2+)](i) at which P(O) of the channel is equal to 0.5 was 2 microM. The unitary conductance of the single BK(Ca) channel was 245.4 pS with symmetrical 140 mM K(+) on both sides of the excised membrane. With a fixed [Ca(2+)](i) of 2 microM, P(O) increased e-fold with a 17.0 mV positive change in the membrane potential. Two exponentials, with time constants of 2.8 ms and 19.2 ms at the membrane potential of +120 mV with 2 microM [Ca(2+)](i), were required to describe the observed open time distribution of BK(Ca) channel, suggesting the existence of two distinct open channel states with apparently normal conductance. A BK(Ca) channel occasionally entered an apparent third open channel state with the single channel current amplitude about 45% of the normal amplitude. The properties of BK(Ca) channel, which were found in this study to be more steeply dependent on voltage and more sensitive to [Ca(2+)](i) in adult hippocampal neurons than in cultured or immature hippocampal neurons, may be responsible for the shortened duration of action potential in hippocampal CA1 pyramidal neurons of adult rat.

The distribution of substance P receptor (NK1)-like immunoreactive neurons in the newborn and adult human spinal cord.

Substance P receptor (i.e. NK1)-like immunoreactive (SPR-LI) neurons were observed in the newborn and adult human spinal cord. Substance P receptor-like immunoreactive neuronal cell bodies were seen most frequently in lamina I, and were scattered throughout the remaining laminae of the dorsal horn and the area around the central canal. Some neurons in the intermediolateral nucleus also showed weak immunoreactivity. The pattern of distribution of SPR-LI neurons in the adult spinal cord was essentially the same as that in the newborn spinal cord. However, SPR-LI neurons cell bodies were seen much more frequently in the newborn than in the adult dorsal horn, especially in lamina II.

Direct projections from the lumbosacral spinal cord to Barrington's nucleus in the rat: a special reference to micturition reflex.

In the present study, direct projections from the lumbosacral cord to Barrington's nucleus in the rat were investigated by using retrograde and anterograde tracing techniques. After injection of cholera toxin B subunit (CTb) into Barrington's nucleus, a number of moderately CTb-labeled neurons were observed in the lumbosacral cord, with a slight ipsilateral dominance; most were located in the spinal parasympathetic and dorsal commissural nuclei of the lumbosacral cord. In addition, some retrogradely labeled neurons were found in the periaqueductal gray (PAG). These findings were confirmed by an anterograde labeling experiment. After biotinylated dextran amine (BDA) was injected into the lumbosacral cord, dense BDA-labeled axon terminals were found in Barrington's nucleus as well as in the PAG. Injection of BDA into the PAG resulted in many BDA-labeled terminals in Barrington's nucleus. The present results provided clear evidence for a direct projection from the spinal parasympathetic and dorsal commissural nuclei to Barrington's nucleus that could subserve conveying bladder-filling information from the lumbosacral cord to Barrington's nucleus in the micturition reflex of the rat.

GABAergic synapses on mu-opioid receptor-expressing neurons in the superficial dorsal horn: an electron microscope study in the cat spinal cord.

A double-immunocytochemical electron microscope study was performed in the cat to examine whether GABAergic axons might be in synaptic contact with spinal neurons expressing mu-opioid receptor (MOR) in laminae I and II of the spinal dorsal horn at the lumbar cord segments. Structures showing MOR-like immunoreactivity (-LI) and those showing GABA-LI were labeled, respectively, with diaminobenzidine/peroxidase-reaction products and immunogold particles. Approximately one-third of dendritic profiles with MOR-LI in laminae I and II were postsynaptic to axon terminals with GABA-LI; about one-fourth of somatic profiles with MOR-LI were also postsynaptic to axon terminals with GABA-LI. The results suggest that activation of MOR on postsynaptic neurons may modulate effects which are induced by GABA released from presynaptic neurons.

Coexistence of mu-opioid receptor-like and substance P-like immunoreactivities in the cat dorsal root ganglionic neurons.

Coexistence of mu-opioid receptor (MOR)-like immunoreactivity (LI) and substance P (SP)-LI in the neurons of the cat dorsal root ganglia (DRG) was examined by a double immunofluorescence histochemical method. Approximately 91% of SP-LI neurons in the DRG showed MOR-LI. However, SP-LI was exhibited in approximately 28% of the neurons labeled with MOR-LI. These morphological findings indicated that the MOR exist on most of the primary afferent SP-containing terminals, and suggest that MOR may regulate SP release from the primary afferent terminals in the cat dorsal horn.