Year: 1981
Type: article
Abstract: I Fridoy Introduction:B-endorphin derives from a 31K dalton gly~oprotein termed pro-opiocortin.Other products of pro-opiocortin include one or more ACTH related peptides and a 16K dalton fragment which is under investigation.The discovery that these cells produce and package several biologically active peptides raises many new questions about the nature of synaptic transmission.We previously showed the ACrH and ~-MSH are potent analgesics following PAG administration, suggesting homolgous actions of $-endorphin and the ACTH-Iike connterparts.We now suggest that y-MSH 1-12, a portion of the N-terminal fragment of pro-opiocortin does not produce analgesia.However, it promotes the analgesic effects of ACTH 1-24.Methods: Permanent indwelling cannulas aimed for the periaqueductal gray were implanted in 14 male rats (250-350 gr) under deep barbituate anesthesia.After one week of recovery the animals were given four tests to measure the analgesic effects of ACTH 1-24 and y-MSH 1-12 alone and in combination.Analgesia was measured using tail-flick test.Half the animals received 17nm y-MSH, the other half received 32nm.Results and Discussion: As in a previous report ACTH 1-24 was found to produce a significant rise in tail-flick latency after micro-injection in the PAG (ANOVA).7-MSH alone produced no statistically reliable change in tail-flick latency but when administered in combination with ACTH the combined effect was nearly twice that of ACTH alone.At 17nm similar effects were observed but as expected the degree of potentiation was smaller.It thus appears that one function of dual release may be to modulate the efficacy of the synaptic junction.If so the effectiveness of ~-endorphin in modulating pain sensitivity might also depend on the rate of synthesis or release of other pro-opiocortin products.
Source: Pain
Authors: J. M. Walker, H. Akil, S. J. Watson
Institution: University of Michigan
Language: English
Subfield: Physiology (medical)
Field: Medicine
Domain: Health Sciences
Open Access status: green
OpenAlex ID: W2123436140