Neuropeptide content and physiological properties of rat cartilage-projecting sensory neurones co-cultured with perichondrial cells

In young rats the cartilaginous epiphyses forming the knee joint are supplied with blood vessels and peptidergic sensory nerve fibres through the perichondrium and cartilage canals. In the present study we show that cartilage-related dorsal root ganglion neurones co-cultured with perichondrial cells develop extensive neurite trees and express calcitonin gene-related peptide (CGRP) and substance P (SP) in in vivo-like proportions using retrograde tracing and immunohistochemistry. Moreover, whole cell patch clamp recordings from these cells showed that the majority is depolarised by application of H + -ions. These results are compatible with the hypothesis that a local imbalance of blood flow and metabolism during normal skeletal maturation may cause tissue acidosis eliciting release of CGRP/SP from sensory nerve endings.