Unitary activity in the bed nucleus of the stria terminalis after homo- and contralateral stria terminalis stimulation.

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.