AJP - Cell Physiology, Vol 252, Issue 4 C369-C377, Copyright © 1987 by American Physiological Society
Two types of cells with central innervation in pineal gland of guinea pigs
H. C. Parkington, I. McCance and H. A. Coleman
Cells within pineal glands isolated from young, male guinea pigs were
impaled with intracellular microelectrodes and their responses to stimulate
the nerve supply to the gland were studied. Two types of cells were
identified. The response of cells of type I was a depolarization on which
spikes were superimposed. Blockers of alpha-adrenoceptors abolished the
spikes while beta-adrenoceptor blockers reduced the depolarization to 27%,
leaving a small tetrodotoxin-sensitive depolarization. After bilateral
removal of the superior cervical ganglia (SCG) the beta-mediated
depolarization was not observed while the spikes and the smaller
depolarization persisted. The response of cells of type II was an initial
large, transient depolarization followed by a smaller depolarization. Both
components were reversibly blocked by tetrodotoxin. The only agents found
to have any effect on these cells were oxytocin, vasopressin, and
vasotocin. These peptides caused depolarization similar in amplitude to the
larger response to nerve stimulation, although more prolonged. The large
depolarization was not observed following ganglionectomy, but the smaller
one persisted. It is concluded that cells of type I and II both receive
inputs from nerves whose cell bodies lie in the SCG. Cells of both types
are also innervated through another pathway.
