Pineal serotonin metabolism in non-innervated perinatal glands before and after intraocular maturation: supersensitivity of adrenoceptors that have never been innervated.

Transplantations were made of fetal pineal glands (crown-rump length, CRL, 19-30 mm) or pineal glands from adult male rats to the anterior chamber of the eye of the rat. Studies were performed with regard to the importance of the age of the donor animal (and thereby the degree of maturation and innervation of the gland to be transplanted) for the possible development of denervation supersensitivity. The transplants were cultured in a medium containing 14C-serotonin. Increased production of 14C-N-acetylserotonin (NAcS) was used as the main criterion for beta-adrenergic stimulation. 4 experimental groups were obtained by transplanting fetal or adult pineals to intact or sympathetically denervated eyes. In all 4 groups beta1-stimulation (KWD 2033 10(-6) M) increased 14C-NAcS formation. The response to beta-stimulation was significantly higher in denervated fetal pineal transplants than in innervated fetal transplants and thus demonstrating beta-receptor supersensitivity. It was concluded that a) the ability to respond to beta-adrenoreceptor stimulation with increased 14C-NAcS formation develops between the 18th and 20th day of gestation, b) transplants derived from fetal as well as from adult rats can respond to beta-adrenergic stimulation, c) this sensitivity also develops in oculo in transplants that at the time of transplantation lacked the capacity to increase their 14C-NAcS formation in response to treatment with beta-agonist, d) denervation supersensitivity occurs in fetal transplants that became mature in sympathetically denervated eyes.