Issue Archive

Response of neurons in cat parafascicular nucleus of thalamus to noxious stimulation of peripheral nerves and intra-arterial injection of bradykinin

Yang Huanqiao, Yang Zhenquan

Shanghai Medical College for staff；Shanghai Brain Research Institute, Academia Sinica

Abstract

Responses of neurons in parafascicular nucleus of thalamus (Pf) to noxious
stimulation of cutaneous (sural) nerve and deep (gastrocnemius) nerve as well as
to injection of Bradykinin (BK) into gastrocnemius artery were studied in 36 cats anesthetized with chloralose.162 units were studied, among which 143 units (88.3%)were found to respond to both sural and gastrocnemius nerve stimulation, while the other 19 units (11.7%)l only to gastrocnemius stimulation. According to the pattern of discharges and latencies of the responses, Pf neurons could be classified into 4 types: (1) 69 units.responded to nerve stimulation with short latlency(usually 20-40 ms) discharges. Administration of Fentanyl (30#mu#g/kg, i.v.) did not affect the responses and BK (20#mu#g/kg, i. v.) did not evoke discharges in all 7 units tested. (2) 15 units had latencies longer than 100 ms. (3) The responses of 37 units started with an early short burst of discharges followed by a late long and lasting firing with long latency.(4) The spontaneous discharges of 41 units were inhibited by stimulation of the peripheral nerves. Fentanyl (30u#mu#/kg, i.v.) remarkably suppressed the long latency discharges of type 3 neurons and abolished the inhibitory responses of the spontaneous discharges of type 4 neurons evoked by noxious stimulation. BK
(20#mu#g/kg, i.a.) could excite both type 2 and 3 neurons and inhibited the
spontaneous discharges of type 4 neurons. It is concluded that all types of the Pf neurons, except type 1, might be regarded as nociceptive, in which either excitatory or inhibitory responses could be produced by noxious stimulation.

Key words: Parafascicular neuron;Peripheral nerve;Bradyldnin;Nociceptive discharges

Received: 　　Accepted:

Corresponding author: 　　E-mail:

Citing This Article：

Yang Huanqiao, Yang Zhenquan. Response of neurons in cat parafascicular nucleus of thalamus to noxious stimulation of peripheral nerves and intra-arterial injection of bradykinin. Acta Physiol Sin 1987; 39 (5): (in Chinese with English abstract).