[Absence of dopaminergic receptor sites identified with (H3)-spiroperidol in the intermediate lobe of the rabbit pituitary gland].

Dopaminergic receptors were sought in the intermediate lobe of the pituitary gland by measuring specific 3H-spiroperidol binding. This approach enabled the identification of specific sites in the Mouse neurointermediate lobe. In contrast, no such sites seem to exist in the Rabbit intermediate lobe. However, in the latter species, numerous 3H-spiroperidol binding sites were detected in the anterior lobe. These observations tally with immunocytochemical data showing the absence of catecholaminergic innervation from the Rabbit intermediate lobe and explain why dopamine has no effect on alpha MSH release from the perifused gland. A new mode of regulation of melanotrophic function, not based on inhibitory dopaminergic control, must be envisaged in Leporidae.