Asunto(s)

RESUMEN

Acute experiments were performed on anaesthetized rats using standard techniques of electrical stimulation and single-unit recording in order to study the responses of the bed nucleus of the stria terminalis (BNST) neurons to homo- and contralateral stria terminalis (ST) inputs. Satisfactory records were obtained from 174 BNST neurons. The majority of these fired spontaneously at variable rates, with single random-occurring spikes. The stria terminalis inputs are able to influence the discharges of many BNST neurons. Homolaterally the response patterns consisted of: (a) an excitatory-inhibitory sequence with variable latency in 61% of the cells; (b) a pure inhibitory period in 23% of the cells; (c) an inhibitory period followed by excitation in 2%; (d) no changes in 13% of the cells. The most frequent response to contralateral ST stimulation was excitation followed by inhibition (46%) and pure inhibition (28%). A high proportion of the cells (27%) did not show any change. These results correlate well with neuro-anatomical studies of ST distribution on the BNST nucleus. Our finding of the high proportion of BNST cells affected in their discharge frequency by ST stimulation together with the variability of the observed responses is an indication of the close amygdala-BNST relationship and also of the diverse functions in which both structures are involved.

Asunto(s)

RESUMEN

Electrical stimulation of the lateral amygdala nucleus was found to evoke field potentials and influence unitary activity in the suprarhinal cortex of anesthetized rats. Laminar distributions of the field responses consisted of positive waves in superficial layers, that reversed to electronegatives from a depth of 0.4-0.5 mm. This response was followed by a shallow electropositive wave deeper than 0.7-0.8 mm. Extracellularly recorded units were studied in the posterior agranular insular area of the suprarhinal cortex. The data revealed that stimulation of the lateral amygdala produced a train of small amplitude spikes in association with a negative slow potential. Furthermore, such stimulation invariably elicited an inhibition of the spontaneous firing of large amplitude spikes, in association with a positive slow potential. The onset of this inhibitory response always occurred at longer latency than the excitatory one. The small amplitude spikes may well represent the firing of inhibitory interneurons after lateral amygdala stimulation. The study suggests that a feed-forward system of inhibition appears to be present in the connection between lateral amygdala and posterior agranular insular area of the suprarhinal cortex.

Asunto(s)

RESUMEN

Unitary responses in the suprarhinal cortex were studied in anesthetized rats. Lateral amygdala stimulation gave rise to two types of cortical responses: (i) an excitatory response (59%) characterized either by a single spike discharge, or by a burst of two to four spikes, or (ii) an inhibitory response (41%) affecting cortical neurons which exhibited spontaneous discharge. The duration of inhibition appeared to be related to the intensity of stimulation and the spontaneous discharge frequency.

Asunto(s)

RESUMEN

The commissural component of the stria terminalis (S. T.) was studied in Equi-Thesin (92.7 mg/kg) anesthetized rats after their exposure in the caudothalamic surface of both hemispheres. Two types of connection between right and left S. T. across the anterior commissure are described: A "direct" connection set up by fibres that run through the S. T. and join the contralateral S. T., and another "indirect" component, formed by cell axons that receive excitatory synaptic contacts from fibres running in the S. T.

Asunto(s)

RESUMEN

Evoked field potentials and extracellular unitary activity were recorded from entorhinal lateral and subicular ventral cortices under conditions of amygdala stimulation in equithesin-anesthetized rats. The stimulation of the lateral and basolateral nuclei of the amygdaloid complex evoked field potentials consisting of negative-positive waves in layers III-VI and positive-negative deflections in the superficial layers of the ventral subdivision of the entorhinal cortex. The stimulation of the lateral nucleus evoked similar potentials in the dorsal subdivision of this cortex. And the stimulation of the lateral and basolateral nuclei of the amygdala evoked negative-positive field potentials in layer III of the subicular cortex. Cellular activity of the entorhinal and subicular cells evoked by stimulation of the lateral and basolateral nuclei consisted of an excitatory response followed by a prolonged suppression period. This activation coincided with the negative potential recorded in the deeper layers of these cortices. Such observations provide support for amygdaloid projection to the entorhinal and subicular cortices as recent anatomical findings suggested. The functional significance of these observations indicate an amygdaloid influence on entorhinal-hippocampal neurotransmission as well as on the ventral subiculum which provides the major output from the hippocampus.

Asunto(s)

RESUMEN

The present study concerns an electrophysiological investigation of the responses of entorhinal and subicular neurons to electrical stimulation of the lateral and basolateral amygdaloid nuclei. All the neurons exhibited suppression of cell firing after the stimulation of these amygdaloid nuclei. Initial excitation following by the suppression characterized 91% of the units and 9% showed initial inhibition. The suppression effect was observed in association with an extracellularly recorded positive deflection. These data suggest that this inhibitory response is mediated by an interneuron.

Asunto(s)

Asunto(s)

Asunto(s)

Asunto(s)

Asunto(s)

Asunto(s)

Asunto(s)

Asunto(s)

Asunto(s)

Asunto(s)

Asunto(s)

Asunto(s)

Asunto(s)

Asunto(s)