The kappa receptor k

The k receptor is directly associated with a calcium channel (Fig. 12.42). When an agonist binds to the k receptor, the receptor changes conformation and the calcium channel (normally open when the nerve is firing and passing on pain messages) is closed. Calcium is required for the production of the nerves neurotransmitters and therefore the nerve is shut down and cannot pass on pain messages. 

The nerves affected by the k mechanism are those related to pain induced by non-thermal stimuli. This is not the case with the jjl receptor where all pain messages are inhibited. This suggests a different distribution of k receptors from x receptors. 

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