Some unusual characteristics of the nucleus anterodorsali thalami: neurophysiological and ultrastructural investigation.
Single-unit activity and ultrastructural characteristics were investigated in anterodorsal nucleus of thalamus (AD) in rabbits, guinea pigs and rats. Spontaneous activity of the AD units consisted of long high-frequency trains of spikes alternating with prolonged periods of silence. The typical thalamic "inactivation bursts" were never observed in AD. The AD neurons were highly reactive to sensory stimuli of various modalities. The stimuli evoked sustained discharges with or without initial short-latency on-effects. The AD neurons in incubated slices responded to electrical stimulation of afferent inputs by high-frequency sustained discharges (up to several s). The neurons had long period of facilitation, which allowed summation of effects of repetitive stimuli following with intervals up to 20-30 s, and equally long refractory periods after tonic discharge. Ultrastructural investigation revealed highly developed Nissl bodies and extensive multilocular Golgi complex in large AD neurons. Specialized standard combinations of elements of rough and smooth endoplasmic reticulum ("doublets") were widely distributed in their cytoplasm. Large aggregates of finely granular or filamentous material (nematosomes) were present in AD neurons. The perivascular glial endfeet in some areas of the AD were very thin or absent altogether, with direct apposition of neuronal somata to the capillary basal membrane, which was characterized by high pinocytotic activity. All functional and structural features of AD listed above were absent in adjacent anteroventral nucleus. It is suggested that the AD neurons possibly have some specialized neurosecretory activity, which, regarding the role of this nucleus in relaying multimodal sensory information to the highest levels of limbic system (hippocampal formation and retrosplenial cortex), may have some special significance for memory functions.
Zhuravleva
Z N
ZN
Institute of Biological Physics, USSR Academy of Sciences, Puschino-on-Oka.
Pakhotin
P I
PI
Vinogradova
O S
OS
D000200:Action Potentials; D000344:Afferent Pathways / Q000033:anatomy & histology / Q000502:physiology; D000818:Animals; D004558:Electric Stimulation; D006168:Guinea Pigs; D009475:Neurons, Afferent / Q000502:physiology*; D011817:Rabbits; D051381:Rats; D011919:Rats, Inbred Strains; D013787:Thalamic Nuclei / Q000502:physiology* / Q000648:ultrastructure