Physiological properties of sensory trigeminal neurons projecting to mesencephalic parabrachial area in the cat.

Abstract

1. One hundred forty-one trigeminomesencephalic neurons in the sensory trigeminal nucleus of cats anesthetized with alpha-chloralose were identified by antidromic stimulation of the mesencephalic parabrachial area (PBA) which includes the nucleus cuneiformis, lateral periaqueductal gray matter, and the region between the inferior colliculus and brachium conjunctivum. 2. Neurons were categorized based on their responses to non-noxious and noxious mechanical and heat stimuli delivered to their peripheral receptive fields (RFs) including skin, mucosa, guard hairs, vibrissae, cornea, and tooth pulps. They were classified into three types: 48 nociceptive-specific (NS) neurons which responded to heavy pressure and/or noxious mechanical stimuli, and/or noxious radiant heat; 19 wide dynamic range (WDR) neurons which had a graded response to light tactile stimuli, noxious pinch, and/or noxious radiant heat; and 36 low-threshold mechanoreceptive (LTM) neurons which responded maximally to innocuous tactile stimuli. In subnucleus caudalis (Vc), NS and WDR neurons were the majority (75%) among the three types, while in the rostral subnuclei they were about one-half (54%) of the population. 3. The RFs were distributed over the orofacial and head region but mainly in the facial region. Twelve neurons (33% of the LTM neurons) responded to deflection of vibrissae and only 1 NS neuron out of 52 NS and WDR neurons tested responded to electrical stimulation of a tooth pulp. 4. A contralateral projection was dominant (57%), 30% projected ipsilaterally and 13% projected bilaterally.(ABSTRACT TRUNCATED AT 250 WORDS)