Numerous studies have examined receptor
expression in neural transplants and their
possible role in transplant-induced functional
recovery from lesion-induced deficits. Herein we
attempt to summarize the results of these
studies, especially those from studies involving
striatal transplants. Autoradiographic studies
indicate that dopamine D1
and D2, muscarinic,
cholinergic, 5-HT2, opiate μ, β
adrenergic and
cholecystokinin (CCK) receptors are present in
striatal transplants. Many of these receptors are
present regardless of the transplant location and
surrounding environment. This suggests that the
expression of these receptors is determined by
intrinsic properties of transplanted tissue, and is
independent of transplant location and
environment. Some transplant receptors, such as
dopamine D1 and D2 and muscarinic receptors
in striatal transplants, or 5-HT2 receptors in
cortical transplants, display a patchy
distribution which is dissimilar to that in the
corresponding adult host tissue. This
manuscript discusses this “abnormal” receptor
distribution and possible explanations. Electrophysiological
studies have indicated that some of
the transplant receptors respond to physiological
and pharmacological stimulation, suggesting
that they are functional. However, the
association of receptor expression with
behavioral recovery is uncertain. The expression
of neurotransmitter receptors in neural
transplants may not be essential for the functional recovery associated with trophic
mechanisms. However, neurotrammitter
receptors may play an important role when
functional recovery requires neur0anatomical
integration between the host brain and the
transplanted tissue.