Effect of denervation on ?synaptic? ribbon populations in the rat pineal gland

Abstract

The formation of pineal 'synaptic' ribbons (SR) may be directly related to the adrenergic innervation of the gland. In order to clarify this relationship, SR populations at various times from 12 h to 14 days after pineal denervation were morphometrically analysed by electron microscopy. Pineal denervation was accomplished by bilateral superior cervical ganglionectomy. A decrease in nocturnal pineal SR numbers, indicating a reduction in SR formation, was demonstrated 12 to 24 h after pineal denervation. Seventy-two hours after ganglionectomy SR numbers were comparable with those in nocturnal intact and sham-operated controls. Thereafter, 7 and 14 days after ganglionectomy, SR numbers exceeded nocturnal intact and sham-operated controls. Administration of isoproterenol, a beta-adrenergic receptor agonist, 24 h after denervation significantly increased SR numbers over those in untreated rats denervated 24 h earlier. Thus SR formation remained responsive to adrenergic receptor stimulation in the absence of an intact adrenergic innervation. Further, the increase in SR numbers following subacute (7 to 14 days) denervation indicated that SR formation was not dependent on an intact innervation or the presence of endogenous (pineal) norepinephrine. On the basis of these results, we suggest that SR formation may be related structurally as well as functionally to adrenergic receptors on the rat pinealocyte.

‘Synaptic’ Bodies in the Pineal Glands of the Cow, Sheep and Pig

“…Recent investigations have shown that SB are a heteroge neous population of organelles: 'synaptic' ribbons (SR) are rod-like structures surrounded by clear vesicles [ 1). In the pineal gland they are thought to play an important role in the communication between adjacent cells [2,3] or to regulate the number of (^-adrenergic receptors (4). Sev eral studies suggest that SR are influenced by (1-adrcncrgic mechanisms [5][6][7], SR have been extensively studied in the rat [8][9][10], guinea pig [3, 11.…”

Pinealocyte synaptic ribbons and neuroendocrine function

“…The plane of section is depicted by a n arrow in a. The section b was Karasek and Vollrath, 1982Kurumado and Mori, 1977Kurumado and Mori, 1980Maitra et al, 1986McNulty et al, 1985McNulty et al, 1987McNulty et al, 1989Reuss et al, 1989Vollrath et al, 1985Vollrath and Maitra, 1986Vollrath and Welker, 1984Net0 et al, 1990Saidapur et al, 1991bKing and Dougherty, 1980King and Dougherty, 1982aKing and Dougherty, 1982b McNulty, this study Saidapur et al, 1991bKosaras et al, 1983aKosaras et al, 1983bSaidapur et al, 1991bSaidapur et al, 1991bSaidapur et al, 1991bRiemann et al, 1990Seidel et al, 1990aKarasek et al, 198313 Karasek et al, 1983cKarasek et al, 1982aHewing, 1981 Karasek et al, 1983bKarasek et al, 1983aVollrath, 1973Vollrath and Huss, 1973Vollrath and Howe, 1976Vollrath, 1986Vollrath et al, 1983Khaledpour and Vollrath, 1987 Fechner, 1986Karasek et al, 1982cKarasek et al, 1983bHewing, 1979Hewing, 1980Vollrath and Maitra, 1986Diaz et al, 1990Heinzeller, 1985 tories may...…”

Ultrastructure of the mammalian pinealocyte under natural and experimental conditions: Quantitative aspects

“…These structures were believed to be Sakai et al, 1986Hewing, 1980Kurumado and Mori, 1980Kurumado and Mori, 1980Karasek, 1976Vollrath and Howe, 1976Vollrath and Howe, 1976Vollrath and Howe, 1976Vollrath and Howe, 1976Vollrath and Howe, 1976Matsushima and Morisawa, 1981King and Dougherty, 1982Karasek et al, 1982dKarasek et al, 1983dKosaras et al, 1983Matsushima et al, 1983bVollrath et al, 1985Vollrath et al, 1985Vollrath et al, 1985Maitra et al, 1986Karasek et al, 1988b t , increase; L , decrease, 0 , no effect.…”

“…involved in intercellular communication Vollrath, 1982, 1989;Vollrath, 1973;Vollrath and Huss, 1973), to be functioning as receptors for the sympathetic neurotransmitter, norepinephrine (Romijn, 1975), to be involved in the synthesis andlor storage of melatonin (Theron et al, 1979), or t o be involved in the regulation of beta-receptor density along the plasmalemma of the pinealocyte (King and Dougherty, 1982). An inverse correlation has been observed between the number of SR and the density of adrenergic nerve terminals in a variety of species (Karasek et al, 1983~).…”