A pharmacologic investigation of the 'transport response' in the white rat

In a series of six experiments, the ability of specific neurotransmitter antagonists to alter the 'transport response' was investigated in 19-day-old rat pups. The serotonergic blocker, methysergide, and the cholinergic blocker, scopolamine, did not produce any consistent changes in the intensity of the response. Likewise, the opiate receptor blocker, naloxone, was without effect. Large, dose-dependent decreases in transport response intensity were seen with administration of the beta-noradrenergic receptor blocker, propranolol, and with administration of the dopaminergic blocker, haloperidol. The alphanoradrenergic receptor blocker, phentolamine, produced inconsistent changes in the response. These results indicate a central catecholaminergic involvement in the transport response.