| Cell type (class) | Nomenclature (Acronym) |
Definition | Relation of BNSTAL-5HT neuron |
| Annotation | Reference |
Collator |
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| beaded neuron | Larriva-Sahd (Larriva-Sahd) | A seventh type of interneuron consists of a cell located within the core of the nucleus that is termed a beaded neuron (BN) because of its rounded soma and numerous spherules along both dendrites and axon (Fig. 11). The soma measures from 12 to 17 micrometers in its widest axis and is nearly spherical, having a rather smooth profile. The soma issues two or three short primary dendrites, which usually run horizontally. After a short distance (10–40 micrometers), these proximal branches give
rise to sets of two to five long, secondary dendrites. The occurrence of third-order dendrites is variable, as is their length (20–150 micrometers). A defining characteristic of BN dendrites is the presence of distinct varicosities that are virtually devoid of dendritic spines, similar to those described by Belenky et al. (2003) for certain retinal ganglion cells.The axon of BNs arises from the soma and runs transversally or diagonally with respect to the fibers of the StT, reaching the neuropil of the Ov or adjacent
nuclei (Table 2), where it resolves. In about two-thirds of the sampled neurons, the axon provides multiple straight collaterals leaving the parent fiber orthogonally (Fig. 11). In the rest of the cases, no axonal collaterals were observed. The BN axon and its collaterals also exhibit a series of small spherules (i.e., 0.3–0.5 micrometers) united by thin axonal bridges. | is included | | In agreement with McDonald (1983), neurons of the BNSTAL had a characteristic oval soma (approximately 22 X 15 micrometers) from which emanated two to four primary spine-sparse dendrites. The length of the primary dendrites ranged from 126
to 50 micrometers. Unfortunately, full morphometric reconstruction on several of the recovered cells was not possible due to the loss of some of the dendritic arbor during tissue processing. Collator note: the morphological identity is not fully described in terms of dendritic arbor. It is safer to assume the 5HT-BNSTAL population is just a chemical phenotype of the BST lateral neurons of McDonald. | Levita L., Hammack S.E., Mania I., Li X.-Y., Davis M. & Rainnie D.G. | Mihail Bota |
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| BNSTALG Type I neuron | Hammack et al. (Hammack) | Type I neurons accounted for 29% of all recorded BNSTALG neurons, had a resting membrane potential (Vm) of -60.0 ± 0.6 mV, and a mean input resistance (Rm) of 452.6 ± 30.0 MOhms. In response to transient (750-ms) hyperpolarizing current injection, Type I neurons exhibited a characteristic depolarizing sag (rectification) in their voltage response that was both time dependent and voltage dependent, such that the amplitude and rate of onset of the rectification increased with increasing membrane hyperpolarization (see Fig. 2B, Type I). Type I neurons also exhibited a transient depolarizing rebound potential on termination of the hyperpolarizing current injection, the amplitude and rate of onset of which also increased with increasing levels of initial membrane hyperpolarization. | partially corresponds | | Collator note: see Figure 8 page 1796. Each physiological type BNSTALG is related to several types of the electro-chemical 5HT types. | Guo J.-D., Hammack S.E., Hazra R., Levita L.& Rainnie D.G. | Mihail Bota |
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| BNSTALG Type II neuron | Hammack et al. (Hammack) | Type II neurons were the most abundant of BNSTALG neurons, accounting for 55% of all recorded cells. These neurons had a Vm of -58.0 &plusm; 0.5 mV and an Rm of 377.4 & 15.7 MOhms.. Type II neurons also exhibited a depolarizing sag in response to hyperpolarizing current injection that was similar to that described for Type I neurons. However, in contrast to Type I neurons, the amplitude and rate of onset of the rebound depolarization observed at the termination of the hyperpolarizing current
injection were always much larger than the degree of depolarizing rectification observed. Significantly, the amplitude of the rebound depolarization often surpassed action potential threshold and triggered a rebound burst of action potentials (see Fig. 2B, Type II), suggesting that Type II neurons express additional active currents that could be modulated by prior membrane hyperpolarization. After the initial burst of action potentials, Type II neurons either fire in a regular pattern (Fig. 2A, Type II), fire in bursts, or stop firing altogether (accommodate). The variability of this second response is likely explained by the differential expression of outward rectifying currents and calcium-dependent potassium currents, and/or differences in the properties of the calcium currents that generate the initial burst. These differences suggest that even within Type II neurons there is heterogeneity in their physiological responses. | partially corresponds | | Collator note: see Figure 8 page 1796. Each physiological type BNSTALG is related to several types of the electro-chemical 5HT types. | Guo J.-D., Hammack S.E., Hazra R., Levita L.& Rainnie D.G. | Mihail Bota |
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| BNSTALG Type III neuron | Hammack et al. (Hammack) | Type III neurons made up 16% of recorded BNSTALG neurons, had a Vm of -64 ± 1.1 mV, and an Rm of 357.8 ± 38.1 MOhms. Unlike Type I and Type II neurons, Type III neurons did not show a prominent time-dependent depolarizing sag in response to hyperpolarizing current injection. Instead, Type III neurons exhibited a fast time-independent rectification that became more pronounced with increased amplitude of current injection (Fig. 2B, Type III). Unlike the time-dependent rectification observed in Type I and Type II neurons, no rebound depolarization was observed in Type III neurons on the termination of the hyperpolarizing current injection. These properties are similar to those previously reported in other brain regions after activation of an inwardly rectifying potassium current KIR (De Jeu et al. 2002; Nisenbaum and Wilson 1995), which suggested that Type III neurons may preferentially express this current. | partially corresponds | | Collator note: see Figure 8 page 1796. Each physiological type BNSTALG is related to several types of the electro-chemical 5HT types. | Guo J.-D., Hammack S.E., Hazra R., Levita L.& Rainnie D.G. | Mihail Bota |
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